Aortic Valve Disease

Calcific Aortic Stenosis (Congenital)

Calcific aortic stenosis implies stenosis secondary to heavy dystrophic calcification of a congenitally abnormal valve ( Fig. 12-1, A and B ). Calcification is rarely present before age 20; thereafter it is slowly progressive and results in important stenosis, most often in the fifth and sixth decades of life, earlier in unicommissural than bicuspid valves, and earlier in men than women. The calcification presents as a bulky cauliflower-like mass within the cusps, maximal at sites of commissural fusion or congenital buttress formation, often extending into the anulus (left ventricular [LV]-aortic junction) and adjacent aorta. Retrograde extension of calcification into the region beneath the right noncoronary cusp commissure adjacent to the membranous septum may lead to complete heart block. The valvar orifice is slitlike, often eccentrically located and oriented in a sagittal (most often) or transverse plane, and fixed, which often results in trivial or mild aortic regurgitation. (For description of critical congenital aortic stenosis, see Morphology in Chapter 47 , Section I.)

Bicuspid Aortic Valve

Bicuspid aortic valve is considered the most common congenital heart anomaly, reported in 0.5% to 2% of the general population. The valve has two cusps of unequal size, the larger one containing a central raphe. The raphe results from commissural fusion (type 1). The most common pattern involves fusion of the right and left cusps and is associated with coarctation of the aorta. Rarely, the cusps are symmetric without residual commissure or raphe (type O). Even less common is two raphes (type 2), usually with a well-developed commissure between the left and noncoronary sinuses.

Among patients with a bicuspid aortic valve, structural abnormalities exist at the cellular level that are independent of hemodynamic effects. The thoracic aorta typically shows reduced fibrillin-1, and increased matrix metalloproteinases are associated with smooth muscle cell detachment, matrix disruption, and cell death. The genetics of bicuspid aortic valve is complex and likely involves multiple pathways. Mutations in the signaling and transcriptional regulator NOTCH1 and in the ACTA2 gene (which encodes vascular smooth muscle cell B-actin) are linked with bicuspid aortic valve and familial thoracic aortic aneurysms. Numerous cardiac malformations are associated with bicuspid aortic valve: coarctation, Shone syndrome, William syndrome, Turner syndrome, and hypoplastic left heart syndrome. Abnormalities of the aorta (aortopathy) are the most frequent cardiac anomalies (with a male predominance of 3 : 1). Although ascending aortic dilatation is most common, aortic root and arch involvement are also frequent.

Controversy exists regarding the contribution of genetic mutations vs. flow characteristics in the genesis of the aortopathy. Using magnetic resonance imaging (MRI), Hope and colleagues demonstrated two distinct flow patterns specific to the two most common cusp fusion types and related these to location of thinning and dilatation of the ascending aorta. Asymmetric distribution of wall stress in patients with a bicuspid aortic valve (likely superimposed on genetically conferred aortic wall weakness) has been linked with asymmetric aortic smooth muscle cell apoptosis that could be flow mediated.

Degenerative Aortic Stenosis

Degenerative disease is often present in stenotic aortic valves of patients older than 65 years of age, and its prevalence increases with age. In a series of patients whose mean age was older than 70, prevalence of degenerative aortic valve stenosis exceeded 70%. The valve is tricuspid, without commissural fusion; the cusps are held in a closed position by deposits of diffuse nodular or eggshell calcification ( Fig. 12-1, D ). These deposits are not bulky and may also involve the sinuses of Valsalva and ascending aorta. Although degenerative (senile) aortic stenosis is presumed to be arteriosclerosis, Hoagland and colleagues found no correlation between aortic stenosis in adults over age 50 and systemic hypertension, elevated serum cholesterol, smoking, or diabetes. A more recent study of 5201 subjects older than 65, however, found that clinical factors associated with aortic sclerosis and stenosis are similar to risk factors for arteriosclerosis. Aortic valve sclerosis was present in 26% and aortic valve stenosis in 2% of the entire study cohort. In patients over age 75 the prevalence of aortic sclerosis was 37% and stenosis 2.6%. Smoking increased the risk by 35% and hypertension by 20%. Other factors associated with increased risk of aortic valve disease were high lipoproteins, elevated low-density cholesterol levels, and diabetes mellitus. Older age was directly associated with risk, with a twofold increase in risk for each 10-year increase in age.

Mitral anular calcification is common in elderly patients with calcific aortic stenosis. Presumably, both are degenerative in origin.

Rheumatic Aortic Stenosis

Rheumatic aortic stenosis is characterized primarily by diffuse, prominent fibrous cusp thickening of a tricuspid valve ( Fig. 12-1, C ), with fusion to a variable extent of one or two commissures (rarely all three). The orifice is approximately central and irregular in shape. Calcification other than a mild form is rarely present except in elderly patients, but is bulkiest at sites of commissural fusion. Rheumatic aortic stenosis is seldom if ever isolated, although at the patient's first operation this may appear to be the case. In surgical series of apparently isolated aortic stenosis, prevalence of rheumatic etiology is low compared with that when patients with important mitral valve stenosis are included.

About half of patients with so-called rheumatic aortic stenosis fail to report a history of rheumatic fever, suggesting other unrecognized inflammatory processes as the cause. However, with the decline in incidence of rheumatic fever in the United States and other developed countries, rheumatic aortic stenosis decreased from a prevalence of 30% to 18% by the 1980s (and senile degenerative disease increased from 30% to 46%).

Relevant Aortic Root Anatomy

Basic anatomy of the aortic root is detailed in Chapter 1 . This section provides additional details about aortic root anatomy and relationships that are relevant to aortic root reconstruction and valve-sparing aortic root replacement (discussed later in this chapter). The aortic root is that part of the aorta bounded proximally by the bases of the aortic valve cusps and distally by the sinutubular junction. McAlpine conceptualizes a continuous membrane covering the ostium or opening of the LV (called the aortoventricular membrane ) that contains the anulus of the mitral valve and the aortic anulus and adjacent fibrous components. The left anterior fibrous trigone is a membrane between the left and right cusps and the ostium of the LV. The remaining structures related to the aortic root result from thickening of the aortoventricular membrane ( Fig. 12-2 ), and these are the right anterior fibrous trigone, the ventricular and atrial segments of the membranous septum, intervalvar trigone, right fibrous trigone, and fila coronaria (the portion of the aortoventricular membrane between the ostium of the LV and the left atrial attachment, which comprises about 75% of the mitral anulus). The region where the aortic valve cusps are in fibrous continuity with the anterior leaflet of the mitral valve (aortomitral anulus) is thickened at each end to form a left and right fibrous trigone. The right fibrous trigone is in continuity with the membranous portion of the septum, and these two structures form the central fibrous body. The left anterior fibrous trigone, right anterior fibrous trigone, and intervalvar trigone are also termed intercusp triangles . The membranous septum is divided into the ventricular membranous septum and atrial membranous septum by attachment of the tricuspid valve septal leaflet to the aortoventricular membrane ( Fig. 12-3 ). Attachment of the right ventricle (RV) to the aortoventricular membrane is in close relationship to the left and right anterior fibrous trigones ( Fig. 12-4 ).

The aortic root forms the outflow tract from the LV and contains the aortic valve cusps, sinuses of Valsalva, and intercusp triangles (trigones). Morphology of the aortic valve cusps reflects their exposure to the mechanical stress of diastolic pressure. They have three distinct layers. The outflow surface is the fibrosa , comprising bundles and sheets of collagen aligned in the circumferential direction. The cusp has a coaptional portion (where the collagen bundles are discontinuous) and a noncoaptional surface or cusp belly (where the collagen bundles are continuous). The ventricular surface of the cusp is composed of the ventricularis , which is another fibrous layer. It is a mixture of both collagen and elastin (although the elastin is not as important as the collagen from a biomechanical standpoint). The fibers are arranged randomly, and therefore when the ventricularis is under load, the fibers realign in the direction of the applied load and only then resist further extension. The spongiosa layer between the fibrosa and ventricularis is composed principally of glycosaminoglycans, which are responsible for energy dissipation and lubrication of the movements between fibrosa and ventricularis. The biomechanical properties of the fibrosa and ventricularis allow radial extension of the cusp to form a large coaptional area.

The sinuses of Valsalva are the bulging portions of the aortic root from which the coronary arteries arise. They accommodate the open cusps of the aortic valve and generate vortices that are important for aortic cusp closure. The base of the aortic cusp attachment forms a coronet-like structure ( Fig. 12-5 ). The tissue inbetween the attachment of the aortic valve cusps to the aortic wall is the intercusp triangle , a layer composed of circularly oriented collagen fibers. The base of two of the intercusp triangles is LV muscle, and the intercusp triangle beneath the commissure of the left and right cusps is fibrous (left anterior fibrous trigone). Attachment of the base of the aortic root is approximately 55% fibrous and 45% muscular. The intercusp triangles are exposed to ventricular hemodynamics, and they may function in part to allow each of the sinuses to act independently. An important surgical point regarding the ventricular-aortic junction is the site of attachment of prosthetic valves, which are largely circular structures. Prosthetic valves are actually attached to the anatomic ventricular-aortic junction and do not follow the cusp attachment, although this is usually regarded as the “anulus.”

Aortic Regurgitation Related to Aortic Root Pathology

A spectrum of aortic pathology may result in aortic regurgitation due to alterations in the geometry of the sinutubular junction, sinuses, and the ventricular-aortic junction. Ascending aortic aneurysms and aortic root disease may be distinct processes, or they may coexist as a blending of morphologic manifestations.

Many different pathologies may result in ascending aortic aneurysms (see Chapter 26 ). These include long-standing hypertension, arteriosclerosis, aneurysms associated with bicuspid aortic valves, and extreme forms of post-stenotic dilatation of a stenotic aortic valve. Ascending aortic aneurysms may also result from inflammatory processes causing aortitis, including rheumatoid arthritis, ankylosing spondylitis, and Reiter syndrome. Ascending aortic aneurysms and aortic root disease may arise from clearly defined genetic syndromes, including Marfan syndrome, Loeys-Dietz syndrome, Ehlers-Danlos syndrome, and filamin A mutations. Most patients with thoracic aorta disease and aortic dissections do not have a clearly defined genetic disorder, but many have an inherited predisposition to the process.

Marfan syndrome , one of the most common connective tissue disorders, is an autosomal dominant condition affecting about 1 in 3000 to 5000 people. Most patients with the typical Marfan phenotype have mutations involving the FBN1 gene that codes for fibrillin-1, an extracellular matrix glycoprotein that contributes to structural integrity of connective tissue. In a minority of cases, an FBN1 mutation is not found. Fibrillin-1 is an important component of both elastic and nonelastic connective tissue. In about 10% of Marfan phenotypes, mutations have been noted in transforming growth factor (TGF)-β receptor genes. Criteria for diagnosis of Marfan syndrome involve genetic studies, family history, and major and minor clinical manifestations. Because of the linkage between these genetic mutations and phenotypes that overlap with typical Marfan syndromes, the clinical diagnosis requires specific combinations of criteria. Histologic features of the ascending aorta media in Marfan patients include fragmentation of elastic lamellae, loss of smooth muscle cells, fibrosis, and cystic medial necrosis (a misleading term coined to describe the lacunar appearance of medial degeneration when, in fact, cystic changes and necrosis are absent).

Other connective tissue disorders that predispose to aortic aneurysmal disease and dissection include Loeys-Dietz syndrome and the vascular type of Ehlers-Danlos syndrome. Loeys-Dietz syndrome is an autosomal dominant aortic syndrome resulting from mutations in genes for the cytokine (TGF)-β receptor (TGFBR) type I or II. Arterial tortuosity and aneurysms, hypertelorism, and bifid uvula or cleft palate characterize the disease phenotype. Skeletal features are similar to those of Marfan syndrome. The aortic disease in this syndrome is particularly aggressive, and 98% of patients develop aortic root aneurysms that have a high propensity for dissection. Mean age of death with this syndrome is 26 years. In children affected with Loeys-Dietz syndrome, prominent craniofacial features are associated with more severe aortic disease. Because these patients are prone to aneurysm development in other locations, yearly MRI or computed tomography (CT) is advisable from the pelvis to the brain.

The vascular form (type IV) of Ehlers-Danlos syndrome is a rare autosomal dominant disease caused by a defect in type III collagen, encoded by the COL3A1 gene. Prominent clinical features include easy bruising, thin skin, characteristic facial features, and tendency for rupture of arteries, uterus, or intestines. The role of prophylactic aortic replacement surgery to prevent aortic rupture or dissection is less clear than for Marfan or Loeys-Dietz syndromes. Of importance, these patients typically have extreme tissue fragility, so if aortic aneurysms or aortic regurgitation require cardiac surgery, reinforcement of suture lines with felt pledgets or strips is recommended.

Anuloaortic ectasia can produce aortic regurgitation of varying but sometimes severe degree even though the cusps are normal. It is most often caused by cystic medial degeneration of the aorta and may be associated with Marfan syndrome. Even in the absence of Marfan syndrome, anuloaortic ectasia appears to be a genetic disease. It begins in the sinuses of Valsalva; at this stage, regurgitation is usually not present. With time, the process extends to involve the proximal ascending aorta, producing a symmetric, pear-shaped aneurysmal enlargement. Regurgitation now appears and progresses because dilatation of the aortic wall at the sinutubular junction separates the commissures and tightens the free cusp edges, preventing coaptation during diastole. As dilatation of the aorta progresses, central aortic valve regurgitation increases. The LV-aortic junction usually does not increase in size, even in patients with large aneurysms associated with anuloaortic ectasia. Size of the aortic valve prosthesis used in these patients (if indicated) is generally similar to that used for replacement in patients with rheumatic or other disease.

The aneurysmal process eventually involves the entire ascending aorta, but usually stops just before the level at which the brachiocephalic artery originates, although the remainder of the arch may show cystic medial degeneration. The aneurysms are thin walled with a smooth lining. Dissection may begin within the aneurysms, extending proximally and distally or remaining localized (although most acute aortic dissections occur in the absence of an aortic root aneurysm). In patients with Marfan syndrome, about 30% of those operated on for anuloaortic ectasia and aneurysm of the ascending aorta have an aortic dissection. It is limited to the ascending aorta in about half the patients and extends into the transverse and descending aorta in the rest. Frequently, dissection is unexpectedly found at operation. With proximal extension of this dissection, the commissural attachment of the valve becomes separated from the outer aortic wall such that the valve prolapses centrally, and regurgitation may abruptly increase (see Chapter 25 ).

Arteriosclerotic and Syphilitic Ascending Aortic Aneurysms

Ascending aortic aneurysms also produce valvar regurgitation because of tightening of the free edges of the cusps that results from aortic dilatation. In syphilitic ascending aortic aneurysm, aortic regurgitation is exacerbated by a valvulitis that produces thickening and retraction of the cusp edge. Neither condition, however, is generally associated with aortic dissection.

Aortitis

In some patients with rheumatoid arthritis, ankylosing spondylitis, or Reiter disease, an aortitis occurs that may lead to aneurysmal dilatation of the ascending aorta and aortic valvar regurgitation. The aortitis is characterized by dense adventitial inflammatory fibrosis involving the sinuses of Valsalva and proximal aorta, especially adjacent to the commissures. The process may extend below the base of the aortic valve to form a characteristic subvalvar ridge and may involve the base of the anterior mitral leaflet or even the adjacent ventricular septum, causing conduction disturbances. Particularly in rheumatoid arthritis, the cusps may be thickened and shortened and show rheumatoid nodules histologically.

Rheumatic Aortic Regurgitation

Rheumatic aortic regurgitation results from a different response of the valve to the rheumatic process than occurs when stenosis develops. Commissural fusion is minimal or absent, and the cusps are only slightly thickened. Minor calcification is present in about 10% of affected valves. The major pathologic process is cicatricial shortening of the cusps between their free edge and their anular attachment, with rolling of the free edge. As time passes, the aortic root widens in response to the regurgitation, further increasing central valvar regurgitation.

Native Valve Endocarditis

Native valve endocarditis, which may occur on a structurally normal valve or on congenitally or rheumatically deformed valves, is a common cause of aortic regurgitation. The regurgitation may result from a destroyed commissure and consequent cusp prolapse or from a perforation in the belly of the cusp. An infected pannus may appear below the cusps, or extensive destruction of the aortic root may occur, with a periaortic root abscess sometimes extending into the mitral anulus and anterior mitral leaflet. Mitral regurgitation may also develop because of perforation of the anterior leaflet by a “drop lesion” caused by the infected regurgitant stream from the diseased aortic valve.

Congenital Aortic Valve Disease

A congenitally bicuspid or unicuspid valve can produce regurgitation from prolapse of the free edge of a redundant cusp. In such patients, the regurgitation may be aggravated by infective endocarditis or an improper valvotomy (see Chapter 47 ). Lack of support of the aortic anulus in association with ventricular septal defect may result in aortic valve prolapse and regurgitation (see Chapter 35 ).

Floppy Aortic Valve

Occasionally, aortic regurgitation may be caused by prolapse of redundant aortic cusps that are mildly thickened and myxomatous. The aortic root may be normal or dilated, usually with cystic medial necrosis, and mitral valve prolapse may also occur.

Iatrogenic Aortic Valve Disease

Aortic valve regurgitation may be caused by a number of physician-related interventions. Perforation of the aortic valve cusps may result from diagnostic or balloon dilatation catheters. Even with newer methods and lower doses of mediastinal irradiation, occasional cases of mediastinal fibrosis occur, with injury to the pericardium, cardiac valves, coronary arteries, and myocardium. Cardiac valve disease has also been associated with migraine medications (ergotamine, methysergide) and appetite suppressants (fenfluramine, with or without phentermine) ( Fig. 12-6 ).

Other Types of Aortic Regurgitation

Other causes of aortic valve regurgitation include spontaneous cusp rupture, rupture caused by severe closed-chest trauma, and severe long-standing systemic hypertension with aortic root dilatation. In patients with long-standing hypertension, regurgitation may result from typical myxoid degeneration of the valve. Some instances of regurgitation are probably related to arthropathies with minimal joint involvement or to hypertension, psoriasis, giant cell aortitis, or Takayasu disease. Occasionally the etiology of regurgitation is not apparent.

Survival

Grant reported that 35% of unoperated patients with usual symptoms of aortic stenosis are alive at 10 years. Wood stated that 46% of such patients were alive 1 to 7 years later. Frank and Ross reported that of 12 unoperated patients with severe aortic stenosis, only 18% were alive 5 years later. Based on their data, Ross and Braunwald concluded that average survival after onset of angina or syncope is 3 years and after onset of heart failure about 1.5 years. ACC/AHA guidelines suggest that after onset of symptoms, average survival is less than 2 to 3 years, with a high risk of sudden death. Thus, development of symptoms identifies a critical point in the natural history of aortic stenosis. O’Keefe and colleagues followed 50 symptomatic patients with severe aortic stenosis in whom operation was declined or deferred. Average age of these patients was 77 (60-89) years. Survival was 55%, 37%, and 25% at 1, 2, and 3 years, respectively, compared with a matched general population of 93%, 85%, and 77%. Death was from cardiac causes in all cases except one. Of 179 patients aged 83 ± 8.3 years deemed inoperable in the PARTNER IB cohort, 1-year survival was 49%.

Although it is impossible to rigorously assemble such disparate data, a likely survival curve for adult patients with severe, unoperated aortic stenosis is estimated in Fig. 12-8 . Deaths within the first 1 or 2 years are likely to be sudden, presumably associated with ventricular fibrillation (15%-20% of all deaths in aortic stenosis are sudden ) or, after a few hours or days of acute pulmonary edema, from sudden LV failure. Most unoperated patients die in the latter mode within about 5 years of diagnosis. Beyond 5 years of follow-up, some die of gradually worsening cardiac failure, with low cardiac output and gradually worsening symptoms of pulmonary venous hypertension. Moderate pulmonary artery hypertension develops in some patients who exhibit these findings; in a few, typical symptoms and signs of RV failure become prominent.

Asymptomatic patients with severe aortic stenosis usually develop symptoms within a few years of diagnosis. Otto and colleagues showed that about one fourth of initially asymptomatic patients with aortic valve stenosis had developed symptoms, half by 3 years and three fourths by 4 years. When the Doppler outflow velocities were initially 4.0 m · s ⁻¹ or greater, progression was more rapid, with three fourths of patients symptomatic by 2 years. Thus, even in initially asymptomatic patients with aortic stenosis, progression to symptoms may be rapid, and patients should be monitored closely for progressive disease. Sudden death is uncommon in asymptomatic patients with aortic stenosis, occurring in less than 1% per year. However, as noted by Freed and colleagues, failure to identify subtle symptoms of severe aortic stenosis is common, and the subsequent mortality without surgery may exceed 10% in the ensuing 1 to 1.5 years.

Left Ventricular Structure and Function

The LV hypertrophies progressively in the presence of important aortic stenosis, which usually develops over decades. The increase in wall thickness is usually enough to counter the high intraventricular systolic pressure and maintain normal ventricular volume. In this circumstance, LV wall stress (afterload) remains within normal range, and EF remains preserved (given the inverse relationship between systolic wall stress and EF). However, when the hypertrophic response is not adequate for progressively higher intracavitary pressures, the increased afterload can cause a decrease in EF, which is generally reversible with valve replacement.

Myocardial hypertrophy in aortic valve stenosis is caused by new myofibrils added in parallel to myocytes. No new myocytes are added, but existing myocytes become thicker, not longer, compared with normal myocytes. The hypertrophy of myocardial cells (increased myocardial cell diameter) is a determinant of both increased systolic load stress and decreased LV diastolic function found in aortic stenosis, and is also related to reduction in EF. Myocardial fibrosis exerts little effect.

Schwartz and colleagues found good systolic function and only hypertrophic myocardial cells when LV mass was less than 200 g · m ⁻² . When it was 200 to 300 g · m ⁻² , degenerative changes were present but mild. When LV mass was greater than 300 g · m ⁻² , systolic function was greatly depressed and multiple degenerative changes in ultrastructure were present (mitochondrial changes, disruption of sarcomeric units, nonoriented growth of fiber components, disappearance of organelles). Maron and colleagues also described these degenerative changes in detail. Krayenbuehl and colleagues found degenerative changes in the form of increased interstitial nonmuscular tissue in association with myocardial cellular hypertrophy. These changes are probably the morphologic basis for loss of inotropic (contractile) strength and irreversibility.

Thus, during the compensated phase, thickening of the LV wall keeps LV afterload (systolic wall stress) more or less normal (see “Ventricular Afterload” under Cardiac Output and Its Determinants in Section I of Chapter 5 ), preserving LV systolic function. LV compliance and diastolic function are gradually impaired, to a degree primarily related to extent of LV hypertrophy. At a more advanced stage, hypertrophy and wall thickness may increase less than LV systolic pressure (afterload mismatch ); the resulting increase in afterload impairs LV systolic function. The degree of LV hypertrophy and decrease in contractility that ultimately develop are more often the cause of declining cardiac function. As indices of systolic function (EF, end-systolic volume, LV fractional shortening, velocity of circumferential shortening) decline, cardiac output decreases gradually or acutely, and LV diastolic function decreases with a consequent increase in LV end-diastolic pressure. By this time the condition is advanced, and chronic heart failure is present.

The atrial contribution to ventricular filling is of great importance with a thickened noncompliant ventricle. As long as sinus rhythm is maintained, left atrial and pulmonary venous pressure can remain near normal. However, loss of atrial contraction with the onset of atrial fibrillation can induce rapid clinical decompensation.

The hypertrophied ventricle may have reduced coronary perfusion per gram of muscle with diminished coronary vasodilator reserve. Added myocardial oxygen demands with exercise or tachycardia may induce subendocardial ischemia and angina in the absence of coronary artery disease.

Occasionally, complete heart block develops in patients with extensive calcification of the stenotic aortic valve. It may be the result of gradually increasing pressure on the bundle of His by calcific deposits beneath the commissural area between the noncoronary and right coronary cusps. However, complete heart block sometimes occurs without calcific pressure on the bundle of His. Pressure in the LV is hypothesized to play a role. Rarely, relief of aortic stenosis relieves the heart block.

Survival

Even when aortic regurgitation becomes severe, there may be a long latent period (3-10 years), during which LV enlargement is only mild, symptoms are absent or mild, and the prognosis is good as long as the findings remain unchanged. Bonow and colleagues followed patients with chronic aortic regurgitation and normal EF. They found that 81% were alive and without need of aortic valve replacement 5 years later. Less than 6% per year required aortic valve replacement because of symptoms or LV dysfunction at rest, less than 3.5% per year developed asymptomatic LV systolic dysfunction, and less than 0.2% per year died suddenly. Vasodilator therapy using nifedipine may benefit such patients and delay surgical intervention. When important symptoms develop, however, prognosis becomes severely limited (see Fig. 12-8 ).

The probability of death increases with development of specific risk factors. Symptoms of cardiac failure, development of ventricular premature beats, marked cardiomegaly (cardiothoracic ratio > 0.6), and ECG evidence of severe LV hypertrophy all increased the risk of death in a group of 180 surgically untreated patients with isolated severe aortic regurgitation of rheumatic etiology.

When severe aortic regurgitation develops acutely, as from infective endocarditis, the natural history is much less favorable. Only 10% to 30% survive more than 1 year after onset.

Left Ventricular Structure and Function

Cardiac size gradually increases in the presence of important aortic regurgitation. Quantitative angiography has shown that increased LV end-diastolic volume is directly related to the magnitude of aortic regurgitant flow.

Bonow and colleagues found a higher-risk subgroup within patients who are asymptomatic and have normal LV systolic function. Progressive enlargement (dilatation) of the LV or reduction in resting EF identified by serial echocardiography heralds onset of symptoms. Patients at risk for sudden death are those with extreme LV dilatation or an LV cavity dimension of 75 mm or more at end-diastole and 55 mm or more at end-systole (normal values are ≤55 mm and ≤35 mm, respectively). As LV size and end-diastolic volume steadily increase, eventually there is loss of LV reserve, and LV end-diastolic pressure then rises rapidly.

As the LV enlarges, LV hypertrophy begins to develop. In addition, the LV undergoes an increase in mass and wall thickness, and its shape and ultrastructure change. The myocardial cell hypertrophy and increase in interstitial nonmuscular tissue found in the pressure-overloaded LV of aortic stenosis are similar in the volume-overloaded LV of aortic regurgitation. Concomitant with hypertrophy, LV compliance decreases, compromising diastolic function. Finally, LV end-diastolic and left atrial pressures become elevated, with further increases during exercise.

At some point, LV stroke work fails to respond to increased wall stress (e.g., afterload increase by infusion of angiotensin). As LV systolic function decreases, LV end-systolic dimension steadily increases, and even in asymptomatic patients the rate of increase is about 7 mm per year.

Despite these changes and because of the complex interaction between aortic regurgitation and decreasing systemic vascular resistance, LVEF response to exercise is favorable for a considerable time. Eventually, however, it declines, and systolic function may even decrease during stress. Symptoms then worsen, and the decline in LV function accelerates.

Initial Steps

After the usual preparations and median sternotomy, cardiopulmonary bypass (CPB) is established at 34°C using a single two-stage venous cannula. A cardioplegia infusion catheter is positioned in the ascending aorta, and a coronary sinus perfusion catheter may be passed through a purse-string stitch in the right atrium and positioned in the coronary sinus. The cardioplegic infusion catheter, on one arm of a Y assembly on the cardioplegic infusion tubing filled with cardioplegic solution, is positioned in the ascending aorta. The other arm of the Y assembly, now clamped, also has two arms. One is connected to a second Y assembly, on each arm of which is an O-ring cannula to be used for direct cardioplegic infusion into the coronary ostia. The other arm can be attached to the coronary sinus retrograde perfusion catheter (see Technique of Retrograde Infusion in Chapter 3 ).

Perfusate temperature is lowered and adjusted to 25°C to 28°C. The ascending aorta is occluded, promptly if ventricular fibrillation occurs, to prevent LV distention. The operation may be performed without a vent; alternatively, a vent may be introduced into the left atrium from the right side through the right superior pulmonary vein and advanced into the LV. The vent catheter may be introduced before aortic occlusion if ventricular fibrillation occurs or aortic regurgitation produces ventricular distension during cooling. Following aortic clamping, antegrade cold blood cardioplegia may be infused into the aortic root provided there is no aortic regurgitation. Even the slightest leak at the aortic valve will cause ventricular filling, although a properly functioning LV vent may prevent ventricular distention. Subsequent to cardiac electromechanical arrest, cold cardioplegia may be infused into the coronary sinus. Cardioplegic arrest may be accomplished by exclusive perfusion of the coronary sinus in the presence of important aortic regurgitation. A small aortotomy should be made or the aortic root vented when coronary sinus perfusion is performed. Alternatively, in the presence of aortic regurgitation, topical and systemic cooling of the vented LV may intentionally induce ventricular fibrillation, after which the aorta is promptly clamped, an aortotomy made, and direct coronary artery cardioplegia administered.

An initial aortotomy is made about 15 mm downstream from the origin of the right coronary artery. Its precise location is very important not only for surgical exposure but also because of space for intraaortic positioning of an allograft, autograft, or prosthetic valve, ease and security of closure, avoiding damage to the right coronary artery or its ostium, and facilitating aortic root enlargement if necessary. Exposure for this incision is facilitated by the first assistant's retraction of the fat pad along the right atrioventricular groove over the aortic root. The pulmonary trunk may also need to be partially dissected from the aorta to avoid incising it. The initial incision is made directly anteriorly with scissors, facilitated by the collapsed state of the aorta. Once this small incision is made, the inside of the aortic root is visualized and a decision made as to whether an allograft valve, a pulmonary autograft valve, or a prosthesis will be used or repair performed (see “Nonreplacement Aortic Valve Operations in Adults” under Special Situations and Controversies later in this chapter).

The incision is extended. The surgeon has a choice depending on the operation to be performed:

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  Extend the incision transversely ( Fig. 12-9, A ). This is the most common approach and has the advantage of providing good exposure of the aortic root without distorting it. The sinutubular junction is not disturbed. Exposure at the level of the aortic valve and below into the left ventricular outflow tract (LVOT) is usually very good.

  

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  Extend the incision into the posterior commissure between the left and noncoronary cusps if posterior enlargement of the aortic root is required.

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  Extend the incision obliquely ( Fig. 12-9, B ) into the noncoronary sinus to a point near the aortic anulus, to provide maximal exposure at the level of the aortic valve and below into the LVOT. This incision, which divides the sinutubular junction, can be extended into the anterior leaflet of the mitral valve for posterior aortic root enlargement.

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  Extend the incision to divide the aorta ( Fig. 12-9, C ). This incision provides optimal exposure of the aortic root because the proximal aortic structures can be easily moved and displaced inferiorly and anteriorly so that the surgeon may visualize the intact aortic root and look directly into it. This incision is best for placing aortic allografts and stentless porcine bioprostheses inside the aortic root, as well as for aortic valve replacement with a pulmonary autograft or other procedures requiring replacement of the complete aortic root. It also provides excellent exposure for routine prosthetic valve implantation. Traction stitches are placed just above the aortic valve commissures for optimal exposure of the aortic root structures, regardless of type of incision.

The aortic valve is removed ( Fig. 12-10, A ). Unless the aortic valve disease is noncalcific, a short strip of narrow packing gauze can be inserted through the valve orifice into the LV (and some foolproof system is used to ensure its removal) to trap all calcific fragments that may escape during valvectomy. Neat, complete removal of the valve, particularly when heavily calcified, without damage to the LV-aortic junction, ventricular septum, or aortic wall, is one of the operation's critical aspects. Usually an area exists in about the midportion of the right coronary cusp where an initial scissors cut can be made from the free edge to the point of cusp attachment. This incision allows entry of a knife blade to incise precisely along the attachment of the right coronary cusp toward the commissure between left and right coronary cusps. This commissure may also be calcified, but the incision can usually be carried between it and the aortic wall, often with scissors. The incision is then carried along the attachment of the left coronary cusp, stopping at a point about two thirds of the distance to the left coronary–noncoronary cusp commissure, because beyond that point, there is a tendency to carry the incision into the aortic wall or LV-aortic junction.

Returning to the right coronary cusp, the incision is extended toward the right coronary-noncoronary cusp commissure. In this area and in this commissure the calcification is often especially abundant, sometimes extending onto the underlying ventricular septum or, especially at the commissure, onto the aortic wall or underlying membranous septum. Thus, in dissecting this area, great care must be taken in deciding whether to cut through the calcific cusp attachment to the aortic wall or to go around some of the calcific material and leave it for later piece-by-piece removal. To the extent possible, one-piece removal is preferable, but perforation of the septum, LV-aortic junction, or aortic wall should not become a risk.

When the aortic valve is completely replaced by calcium deposits, or when the deposits extend into the sinus aorta or anterior leaflet of the mitral valve, it is useful to mobilize the calcified tissues by the endarterectomy technique. Using a scalpel, a shallow incision is made in the aortic intima alongside the calcific deposit. This allows insertion of an endarterectomy spatula (Freer septum elevator) to lift the intact hard deposit away from the soft underlying aortic or mitral valve tissues without fragmenting the calcified material. The incision is carried down along the attachment of the noncoronary cusp, stopping about two thirds of the distance to the commissure between the noncoronary and left coronary cusps. The latter commissural area, which is at particular risk of junctional or aortic wall perforation during valvectomy, can then be approached with excellent visibility from both sides; the incision is carried through this area with firm upward traction on the valve.

After the valve is excised, the bed is examined and any loose calcific particles removed. Any remaining fragments are grasped with forceps or small rongeur and gently enucleated with a twisting motion ( Fig. 12-10, B ).

The downstream area of aorta is irrigated and examined for any loose calcific fragments, and the valve bed is wiped with gauze and irrigated with cold saline solution to remove any tiny fragments. The LV vent is turned off so that it will not suck fragments into the inaccessible depths of the ventricle, and the gauze strip is carefully removed from the LV cavity, most likely having trapped a few small calcific fragments. The LV cavity is then vigorously irrigated and aspirated with high suction and inspected for fragments. Generally, no fragments are found. With the precautionary measures against calcific embolization complete, the LV vent is again activated.

Prosthetic Aortic Valve

Insertion of a prosthetic aortic valve is the most common operation for replacing the aortic valve. The anulus is sized and an appropriate-size prosthesis selected. There is no advantage in choosing an oversized prosthesis that will erode the aortic anulus. Instead, if the aortic anulus is too small to accommodate a prosthesis that will provide adequate hemodynamic performance, a supraanular device may be chosen or the anulus enlarged (see “Managing the Small Aortic Root” under Special Situations and Controversies later in this chapter).

Interrupted Suture Technique

Synthetic suture material is used, with a compressed PTFE pledget placed centrally and needles at each end. Alternating suture colors (green, white) simplifies sorting so that sutures may be held together as a group for each aortic sinus. Mattress stitches are taken through the aortic valve anulus beginning at the commissure between the left and right coronary cusps. The suture is placed through the sewing ring of the prosthesis after completing each anular pass. Stitches are placed in the right coronary anulus working clockwise toward the commissure between the right and noncoronary sinus ( Fig. 12-11, A ). Separate stitches are placed close to one another, and the space along the aortic anulus is taken beneath the pledget of the mattress stitch. The prosthesis is held away from the aortic anulus until all stitches have been placed.

The anulus of the left coronary sinus of Valsalva is then approximated to the sewing ring of the aortic valve prosthesis, working counterclockwise from the commissure between the left and right coronary cusps ( Fig. 12-11, B ). The anulus of the noncoronary sinus of Valsalva is then approximated to the valve prosthesis, working clockwise from the commissure between the right and noncoronary cusp toward the commissure between the left and noncoronary cusp ( Fig. 12-11, C ). Needles are passed through the anulus in a backhand manner. The three groups of sutures are then strongly retracted so that the prosthesis may be slid over the suture loops into the aortic anulus. Position of the occluder mechanism may be adjusted before the valve holder is removed.

Sutures are sorted and tied down in order, working first in the noncoronary sinus in a counterclockwise approach. The first suture in the left coronary sinus closest to the commissure between the left and right coronary cusps is tied to secure seating of the prosthesis directly across the anulus from those sutures already tied in the noncoronary sinus. The sutures of the left coronary sinus are tied down counterclockwise. Sutures are tied in the right sinus, working clockwise to complete the procedure ( Fig. 12-11, D ). For valve prostheses that have any part of the device projecting below the sewing ring, such that it is positioned partially below the anulus in the LVOT, the order of tying should be altered so that the prosthesis is first secured adjacent to the portions of the device below the anulus.

An alternative technique for placing the pledget stitches is used for the small aortic anulus ( Fig. 12-11, E ). Pledgets are placed below the anulus in the LVOT by passing a double-needle suture with center pledget as a mattress stitch from below the anulus and up through the prosthesis. A larger prosthesis is thereby secured above the anulus as the anulus is compressed between the pledget and device.

Continuous Suture Technique

Continuous suture technique provides the advantage of tight approximation of the prosthesis to the aortic valve anulus, because the suture loops can slip through the tissues so that tension is equalized with heart motion. Inserting a slightly larger prosthesis may also be possible because an interrupted mattress suture technique may bunch tissues together.

The aortic anulus is divided into three segments by the commissures. During valve replacement, the anulus is further subdivided into six subsegments at the midpoint on the anulus between the commissures. Polypropylene suture (2-0) is used, with needles at each end and a compressed PTFE pledget in the center of the suture. An initial mattress stitch is placed at the center of the sinus of Valsalva through the anulus of the aortic valve and brought through the sewing ring of the prosthesis ( Fig. 12-12, A ). The prosthetic valve is held away from the anulus and positioned and retracted for added exposure. Exactly three stitches are placed between the initial pledgeted stitch and the commissure on each side of the sinus. The final stitch at each end is secured to the wound drapes by a hemostat. A loop of size 0 suture is placed around the polypropylene suture as the first suture loop is completed through the prosthesis in each subsegment. This suture loop is held by a hemostat to be used to adjust tension on the suture line.

Sutures in the right coronary anulus are placed from the center toward the commissures in the first and second subsegments. The initial stitch in the left coronary sinus passes through the sewing ring of the prosthesis opposite the last stitch of the second subsegment. Working from the center to the commissures in the left coronary sinus, the third and fourth subsegments are approximated to the prosthesis, and then the fifth and sixth subsegments are completed in the noncoronary sinus.

Traction is placed on the six size 0 silk loop sutures to pull the prosthesis into the anulus of the aortic valve ( Fig. 12-12, B ). The occluder of the prosthesis is opened, and the area below the prosthesis is checked to ensure that no loose suture loops exist in the LVOT beneath the prosthesis.

The tension suture loops are removed sequentially and the ends of the polypropylene suture pulled up tightly to approximate the sewing ring of the prosthesis to the anulus. A final check of this approximation should be made with special attention to placement of the pledget, which should be above the anulus at the point of maximal stress deep in the center of the sinus of Valsalva. The suture ends are then joined by a knot at the three commissures (see Fig. 12-12 , B ).

Allograft Aortic Valve

Replacing the aortic valve with a transplanted human aortic valve became more feasible and available to surgeons because of improved commercial cryopreservation techniques.

Subcoronary Technique

Because with this technique the graft is to be sewn in “freehand” using the natural aorta for support, a clear understanding of the anatomy and spatial relationships of the aortic root is essential. Important deformity of the aortic sinuses should be appreciated and corrected or the procedure abandoned in favor of conventional valve replacement or aortic root replacement techniques.

A transverse aortotomy is made initially. After assessing aortic valve morphology and anatomy of the aortic root, the incision is extended to transect the aorta (see Fig. 12-9, C ). The aortic valve is excised and anulus débrided by usual techniques. Diameter of the aortic root at the level of the ventricular-aortic junction (anulus) is determined using standard sizing devices. This dimension must be accurately measured and clearly visualized. The aortic valve allograft to be placed inside the aortic root will consume space simply because of the thickness of its wall. Therefore, it must be 1 to 2 mm smaller in internal diameter than the measured aortic anulus. This will allow some redundant aortic valve cusp to provide a larger than normal coaptation surface to accommodate the expected tissue shrinkage for several weeks after implantation.

The aortic allograft is removed from the liquid nitrogen freezer valve bank and thawed by protocol. The septal muscle is excised, with a finger placed inside the aorta to stabilize the graft, gauge the thickness of the trimmed graft, and remove endothelial cells that are antigenic.

Excess aorta is trimmed from the valve cusps, leaving a 3- to 4-mm rim of aorta beyond attachment of the cusps. Most of the sinus aorta is removed from the right and left coronary sinuses, leaving the noncoronary sinus intact ( Fig. 12-13, A ). This technique was described by Ross and colleagues in London and has been used successfully for many years.

The allograft is implanted in anatomic position. Three stitches are used to attach it to the outflow tract. The first suture is 3-0 or 4-0 polypropylene, placed using two small (17-mm) strong half-circle needles. This suture is chosen for high needle strength and low tissue drag. The suture is placed through the patient's aortic outflow tract below the medial commissure between the right and left coronary sinuses and through the septal myocardium below the corresponding commissure in the graft; the stitch is placed below the anulus of the aortic valve. The other two stitches are simply stay sutures placed to assist in aligning the allograft to the patient's aortic root. These sutures will be removed because the primary suture line includes their position. They are placed beneath the appropriate commissure of the allograft and directly below the anterior and posterior commissures of the patient's aorta.

The allograft valve is lowered into position in the patient's aortic root. Commissures of the allograft are inverted through its anulus into the patient's LV so as to expose the subvalvar edge of the allograft. A knot is placed in the primary suture, and the stay sutures are tightened to align the allograft with the LVOT. Stitches are placed between the allograft and the LVOT at or below the level of the anulus, attempting to make a level suture line ( Fig. 12-13, B ). Because the aortic anulus is not circular but crescent shaped, the stitches are well below the fibrous anulus in the subcommissural region and through this fibrous tissue of the anulus at the midpoint of the aortic sinus (see “Cardiac Valves” in Chapter 1 ). The stitches below the left coronary sinus are placed first. The suture line is taken to a point below the posterior commissure. Using the opposite needle, the stitches between the allograft and LVOT are placed below the right coronary sinus and completed below the noncoronary sinus ( Fig. 12-13, B ). Alternative suture techniques are equally effective, such as using three separate polypropylene sutures to facilitate placing multiple suture bites without “snugging” the suture line to improve exposure, after which the sutures are tightened with a blunt nerve hook prior to tying. In the small aortic root, simple sutures of 4-0 polypropylene are also effective.

The commissures of the allograft are pulled out of the LV so that the allograft assumes its normal position and configuration. The allograft commissures are attached to the patient's sinus aorta using continuous 4-0 or 5-0 polypropylene sutures. Separate sutures are used for each aortic sinus. The first stitch is taken deep in the sinus aorta at midposition in the sinus slightly above the aortic anulus and then passed through the allograft. Suturing proceeds along the sinus aorta toward the commissure, so as to place the allograft flat against the patient's aortic wall. The final stitch is placed at the top of the commissure, leaving the suture to be secured later ( Fig. 12-13, C ). Suturing proceeds in each aortic sinus until the allograft is completely attached. Either the right or left coronary sinus is completed first, sewing from the center point of the sinus to each of the commissures using opposite ends of the suture. The repair is completed in the noncoronary sinus by shortening the allograft aorta to approximate the height of the patient's intact noncoronary sinus. The two edges of the aorta are simply oversewn by continuous suture so that the intact noncoronary sinus of the allograft is completely enclosed within the aorta. Optionally, the space between the allograft noncoronary sinus and the underlying native aortic wall can be partially obliterated with mattress sutures that are tied outside the native aorta. The ends of the patient's aorta are then reanastomosed by continuous suture.

Intraoperative echocardiography is used to confirm aortic valve competence.

Root-Enlarging Technique

An aortic allograft may be used for valve replacement as part of a root-enlarging operation. A transverse incision is made in the patient's aorta. The incision is extended to the posterior aspect of the aorta and into the posterior commissure between the left and noncoronary sinuses. Incision into the triangular space of the commissure between the fibrous attachment of the native aortic valve opens the aortic root where there is little fibrous support so that the edges of the aortotomy will separate widely. The incision is taken to the upper edge of the anterior leaflet of the mitral valve, but it does not need to enter the leaflet tissue to provide the desired separation of the edges of the incision. The increased diameter of the patient's aortic root is measured and an appropriately sized aortic allograft chosen. The allograft is trimmed, leaving the noncoronary sinus intact. The sinus aorta is removed from the left and right sinuses, leaving a few millimeters attached to the fibrous support of the cusps. The allograft is attached to the rim of the aortic-mitral anulus (without entering the actual anterior leaflet of the mitral valve) and superior aspect of the left atrium with interrupted 3-0 or 4-0 polypropylene sutures. The stitches are placed in the corresponding mitral valve and left atrium of the allograft's noncoronary sinus. A PTFE felt strip is fashioned to slightly more than the length of the unsupported area of the separated aortotomy. The sutures of the noncoronary sinus are then tied down over the felt strip so as to incorporate it and fill in any potential defects in the suture line. The commissures of the valve are inverted into the LVOT, and the rest of the repair is completed according to the approach previously described under “Subcoronary Technique.” The allograft's intact noncoronary sinus is used to close the aortotomy and widen the aortic root.

When greater enlargement of the LVOT is required, or when there is infective endocarditis with extension of anular abscess into the anterior leaflet of the mitral valve, the incision in the aorta is extended across the mitral valve anulus into the middle of the valve's anterior leaflet. Anular abscesses are thoroughly débrided and much of the anterior leaflet of the mitral valve removed ( Fig. 12-14, A ). The anterior leaflet of the mitral valve is left attached to the aortic allograft and used to widen the LVOT or repair defects in the patient's mitral valve ( Fig. 12-14, B ). The defect in the roof of the left atrium is closed with a patch taken from the aorta of the allograft or with bovine pericardium.

Aortic Root Replacement Technique

An aortic allograft may be used to replace the patient's aortic root completely when gross deformity is caused by infection or congenital anomaly, or it may be used to enlarge the root. Many surgeons use this technique routinely because aortic valve competence is virtually assured due to retention of the valve relationships within the intact aortic root of the allograft.

An initial transverse aortotomy is made ( Fig. 12-15, A ). After decision to proceed with aortic root replacement, the patient's aorta is transected ( Fig. 12-15, B ). The sinus aorta is removed except for a rim surrounding the ostia of the coronary arteries. The aortic valve is removed and an appropriately sized aortic allograft selected. The allograft is used intact and in natural anatomic orientation, with only the excess of septal myocardium and the anterior leaflet of the mitral valve removed. Size match is not nearly as important as it is for freehand subcoronary valve replacement, but if the aortic anulus is more than 3 mm larger in diameter than the largest available aortic allograft, the patient's aortic root should be narrowed to approximate the size of the allograft. This can be done conveniently by placing a pledgeted mattress stitch through the aortic anulus alongside the commissures so that when tied, the intercusp triangle below the commissure is obliterated (see “Method for Reducing Diameter of Dilated Aortic Anulus” later in this chapter).

The allograft is attached to the LVOT at the aortic anulus and below the commissures by simple interrupted stitches of 3-0 or 4-0 polypropylene ( Fig. 12-15, C ). The key to a hemostatic proximal suture line is use of a PTFE felt collar. The felt is approximately 5 mm wide and long enough to encircle the allograft. The allograft is slipped over the sutures into the desired position in the LVOT. The sutures are then tied down, incorporating the felt strip within the suture loops ( Fig. 12-15, D ).

An alternative hemostatic method is to incorporate a double-suture-line technique in which the first suture line uses three separate polypropylene continuous sutures (one for each sinus), placing the sutures as in the interrupted technique. They are gently tightened with a nerve hook and tied. A second suture line incorporates the cut edge of the aortic wall adjacent to the anulus and the adventitia of the allograft immediately above the prior suture line.

The coronary ostia on the allograft are removed to create openings 5 to 10 mm in diameter ( Fig. 12-15, E and F ). The coronary arteries are anastomosed to the allograft by continuous 4-0 or 5-0 polypropylene suture using a small needle (exact size depends on thickness of the tissues). The left coronary anastomosis is created first ( Fig. 12-15, E ), followed by the right coronary anastomosis ( Fig. 12-15, F ). Repair is completed by end-to-end anastomosis of the distal end of the allograft to the patient's aorta ( Fig. 12-15, G ). Continuous stitches of 3-0 or 4-0 polypropylene are used.

Porcine Xenograft Stentless Bioprosthesis

Several manufacturers supply porcine xenograft stentless aortic valves. The devices most frequently used are manufactured by St. Jude Medical and Medtronic ( Fig. 12-16, A ). The St. Jude Medical device (Toronto SPV) is supplied for subcoronary valve replacement with the sinus aorta removed from all three sinuses of Valsalva. The device is covered with a thin polyester mesh. Proper insertion depends on near-normal diameter relationships of the aortic anulus and the sinutubular junction. The Medtronic device (Freestyle) is presented as the entire untrimmed aortic root.

Autograft Pulmonary Valve

The aortic valve may be replaced with the patient's own pulmonary valve (pulmonary autograft) and a pulmonary allograft used to replace the pulmonary valve. This operation was devised by Ross and carries his name. The operation has the advantage of placing autogenous tissue in the high-pressure aortic position that theoretically should last indefinitely, assuming the procedure is technically correct. (See “Selection of Technique and Choice of Device for Isolated Aortic Valve Replacement” later in this chapter). The allograft tissue is placed in the low-pressure pulmonary position, where even if it should fail, valve regurgitation is tolerated for a long time.

CPB is established using two cannulae for venous drainage. A right-angle cannula is placed directly into the superior vena cava at the pericardial reflection. The other is placed in the inferior vena cava through the right atrium at the diaphragm (see “Preparation for Cardiopulmonary Bypass” in Section III of Chapter 2 ). Alternatively, a single two-stage venous uptake cannula may be used, placing the second-stage opening low in the right atrium near the inferior vena cava orifice. Vacuum-assisted venous return provides more safety and reserve when the single-cannula technique is used, reducing the risk and consequences of air lock, which may occur in a gravity drainage system when the RV is opened (see “Vacuum-Assisted Venous Return” in Section I of Chapter 2 ). Oxygenated blood is returned to the ascending aorta.

Pulmonary Autograft Technique

The aortic root is explored through the usual transverse incision. Once it is determined to proceed with the pulmonary autograft operation, the ascending aorta is divided, the aortic valve removed, and the entire sinus aorta excised except for a generous rim around the coronary ostia ( Fig. 12-17, A ). Traction stitches on the aorta above the coronary arteries are helpful. Only the fibrous connection of the aortic cusps remains for attachment of the pulmonary autograft. Traction stitches are placed above each commissure. Diameter of the aortic anulus is measured using Hegar dilator sizers.

The pulmonary trunk is separated from the aorta up to its bifurcation. It is divided at the bifurcation, taking care not to shorten the right pulmonary artery ( Fig. 12-17, B ). The pulmonary valve is inspected from above. If it is normal, operation may proceed. If it is abnormal, the pulmonary artery is reanastomosed and an aortic allograft used to replace the aortic root.

Dissection between the medial commissure of the aorta and the pulmonary trunk comes down onto the muscle of the right ventricular outflow tract (RVOT; Fig. 12-17, C ). Thorough dissection between the aorta and pulmonary trunk, especially low onto the RV in the plane between the RVOT and the infundibular septum, makes removing the pulmonary trunk much easier.

The anterior intercusp triangle below the anterior commissure is identified as a reference point for opening the RVOT. A small right-angle clamp is placed precisely in the anterior intercusp triangle and pushed through the anterior wall of the RV. The small opening is carefully enlarged. The pulmonary trunk is separated from the RV, looking inside frequently to maintain appropriate length of the ventricle below the pulmonary valve ( Fig. 12-17, D ). Incision of the RVOT continues on the right side and posterior to the extent of previous dissection ( Fig. 12-17, E ).

The critical and unique part of the Ross operation is separating the pulmonary trunk from the RVOT above the infundibular septum. When done correctly, this part of the procedure makes the entire operation safe. Anatomy of the subpulmonary infundibulum is described in “Right Ventricle” under Cardiac Chambers and Major Vessels in Chapter 1 . Injury to the underlying first septal branch of the left anterior descending coronary artery during dissection of the pulmonary trunk is a major source of morbidity in this operation. A shallow incision of the endocardial surface is made to join both ends of the partly excised pulmonary trunk ( Fig. 12-17, F ). The incision extends completely across the remaining undivided RVOT. The angle of the scalpel is immediately changed to shave off the ventricular myocardium almost parallel to the endocardial surface. This shaves off the pulmonary trunk without injuring the underlying first septal branch. This part of the operation should be performed deliberately and under precise control. The septal excision eventually separates the pulmonary trunk completely, leaving the left main coronary artery and the first septal branch behind and protected by a generous layer of tissue. The septal artery is occasionally seen in the myocardium.

The separated pulmonary trunk is placed in the pericardial sac for immediate use. The trunk is not removed from the operating field, to prevent its misplacement or inadvertent mixture with the allograft. At this point it is convenient to measure the dimensions of the pulmonary anulus using standard prosthetic valve sizers and to choose a pulmonary allograft for preparation for later use.

The pulmonary autograft is attached to the unmodified LVOT, using interrupted stitches of 3-0 polypropylene ( Fig. 12-17, G ). Size discrepancy between the pulmonary autograft anulus and aortic anulus should not exceed 2 mm. A larger discrepancy indicates the need to adjust the anulus of the aorta to match that of the pulmonary autograft (see “Method for Reducing Diameter of Dilated Aortic Anulus” later in this chapter). The autograft is marked below each of the commissures for orientation. The anterior commissure of the autograft is oriented to approximate the commissure between the right and noncoronary sinuses. Suturing proceeds below each sinus, separating the stitches into three groups. Stitches are placed through the strong fibrous tissue of the aortic anulus, keeping the plane of repair as level as possible. A strip of PTFE felt about 5 mm wide is used to fix the diameter of the proximal suture line and to ensure hemostasis between the sutures ( Fig. 12-17, H ). A strip of autogenous pericardium may also be used. A “supported” repair is favored to prevent dilatation of the pulmonary autograft at the proximal suture line. Some surgeons prefer a continuous suture line using absorbable stitches without prosthetic material, especially for children in whom growth of the pulmonary autograft is desired. However, the accuracy of carefully spaced individual stitches and fixation support of the anulus seem best in adult patients. The felt or pericardial strip is placed within the suture loops so that it is incorporated as the sutures are tied down. The pulmonary autograft is partially inverted into the LVOT as the sutures are tied to ensure that tissue approximation is accurate and that the support ring is to the outside rather than interposed between the tissues of the autograft and the aortic anulus.

An opening is made into the left coronary sinus of the autograft using a scalpel ( Fig. 12-17, I ). Only minimal sinus tissue is excised, because the delicate pulmonary artery dilates and separates readily. The sinutubular junction of the autograft is preserved to maintain proper relationships of the commissures and cusps.

The left coronary anastomosis proceeds, working on the outside of the pulmonary autograft ( Fig. 12-17, J ). Continuous stitches of 5-0 polypropylene are used. As a practical matter, it is best to perform the right coronary anastomosis after completing the aortic anastomosis so that the pulmonary trunk can be distended by temporarily removing the aortic clamp ( Fig. 12-17, K ). The right coronary anastomosis typically fits high in the right sinus or even above the sinutubular junction on the anterior wall of the pulmonary trunk. It may also be advisable to anastomose the pulmonary allograft to the bifurcation of the pulmonary trunk before the aortic anastomosis if the medial aspect of the pulmonary anastomosis might be obscured by the overlying aorta ( Fig. 12-17, L ). Often the diameter of the aorta is larger than that of the pulmonary trunk, but the pulmonary trunk is usually sufficiently long that a bevel can be created to take up any size discrepancy. With gross aortic enlargement or aneurysm, the entire ascending aorta may be removed and the pulmonary trunk extended with a prosthetic graft (see “Method for Extending Pulmonary Autograft” later in this chapter).

Method for Lengthening Pulmonary Allograft

The pulmonary allograft may be tailored to achieve greater length, reducing the chance that the graft will be too tight between the RVOT and pulmonary artery bifurcation. The entire left pulmonary artery may be retained on the graft. The right pulmonary artery is removed and closed by direct suture using 5-0 polypropylene to lengthen the graft ( Fig. 12-18, A ). The left pulmonary artery is cut back to the bifurcation to create a large circumference for anastomosis. Making the pulmonary allograft long or even slightly redundant may be important in maintaining proper allograft length, because myocardium below the pulmonary allograft valve is resorbed and replaced with contracting scar.

Initial Steps

The early steps of the en bloc operation differ somewhat from those of simple aortic valve replacement. The arterial cannula may need to be placed in the common femoral artery (see “Cardiopulmonary Bypass Established by Peripheral Cannulation” in Section III of Chapter 2 ). When the ascending aortic aneurysm stops short of the brachiocephalic artery origin, the distal ascending or proximal transverse arch can be cannulated in the usual manner.

A limited dissection is done, separating the right and contiguous portion of the pulmonary trunk from the back of the aorta and the aneurysm. This approach affords safe placement of the aortic occlusion clamp just proximal to the brachiocephalic artery. The procedure involves clean surgical separation of the right and contiguous portion of the pulmonary trunk from the back of the aorta and from the aneurysm, if possible.

CPB is established at 34°C using a single two-stage venous cannula and left atrial vent. The perfusate temperature is lowered to bring body temperature to 28°C. The aorta is occluded just proximal to the brachiocephalic artery. The ascending aorta is opened transversely in its midportion, stay sutures are applied, and cardioplegia is given.

The patient's aortic root is disconnected from the LVOT and left atrium–mitral valve complex. The sinus aorta surrounding the coronary arteries is retained. The remaining sinus aorta is excised, leaving only fibrous aortic valve attachments, which are normal and uninvolved with the disease process being treated. The ascending aorta is divided by extension of the transverse aortotomy.

Allograft Aortic Valve Cylinder

When the ascending aorta is replaced along with the valve, sizing of the allograft valve is less critical than in the case of isolated aortic valve replacement. Aorta is usually sufficient on the allograft to replace the ascending aorta. Length of the retained ascending aorta and arch are considered when choosing the graft (see Fig. 12-14 ). The distal aorta is tailored to fit the native aorta. The distal anastomosis is performed directly or under circulatory arrest with the patient's body temperature at 18°C.

Autograft Pulmonary Valve Cylinder

In young patients it may be desirable to use a pulmonary autograft as part of the en bloc operation. The pulmonary autograft is used as an intact pulmonary trunk to replace the aortic root as described earlier for isolated aortic valve replacement (see Fig. 12-18, C ). The abnormal dilated or aneurysmal ascending aorta is excised. A crimped polyester tubular graft, collagen coated and of the same diameter as the distal end of the pulmonary autograft, is selected for replacing the ascending aorta. This graft is anastomosed to the distal end of the pulmonary trunk. The graft is shortened and beveled appropriately for end-to-end anastomosis to the distal ascending aorta.

Composite Valve Conduit

Replacing the aortic valve and ascending aorta as an en bloc procedure is most often done with a composite prosthesis containing a mechanical or bioprosthetic cardiac valve enclosed within a slightly larger tubular polyester graft. This operation is frequently referred to as the Bentall procedure. These grafts have a collagen or gel coating that makes them impervious to blood.

The patient is placed on CPB using a single venous two-stage cannula, with oxygenated blood returned to the femoral artery in most cases. Occasionally, the amount of ascending aorta is sufficient to allow it or the transverse portion of the aortic arch to be perfused. The ascending aorta is occluded by a vascular clamp, and a vent catheter is placed through the right superior pulmonary vein to the left atrium and LV. A vertical incision is made in the ascending aorta aneurysm. Cold cardioplegic solution is administered to the coronary sinus by a retrograde coronary perfusion cannula. Traction stitches are placed above each aortic valve commissure to expose the aortic root ( Fig. 12-19, A ). The aortic valve is excised. The coronary arteries are mobilized, retaining a generous button of sinus aorta. A limited dissection of the coronary artery is sufficient to ensure that excision of the coronary artery is complete and that the coronary button will move easily up to the composite prosthesis without kinking or creating undue tension on the artery. The remaining sinus aorta is removed.

Diameter of the anulus is calibrated, and an appropriately sized composite prosthesis, including the prosthetic aortic valve and attached crimped polyester tubular prosthesis, is selected. Stitches are placed through the anulus of the aortic valve and brought up through the sewing ring of the prosthesis using mattress stitches of 2-0 braided polyester with PTFE felt pledgets ( Fig. 12-19, B ). Suture placement is started in the right coronary sinus, working clockwise, as for typical aortic valve replacement. Repair of the left coronary sinus follows, working counterclockwise. The repair is completed in the noncoronary sinus, working clockwise.

Sutures are tied down to approximate the sewing ring of the prosthetic valve firmly to the aortic anulus ( Fig. 12-19, C ). A running suture technique is an acceptable method provided the anulus is strong and able to support the repair.

A decision is then made regarding the method of reimplanting the coronary arteries to the graft. A direct anastomosis of the coronary ostia to the graft is usually made ( Fig. 12-19, D and E ). When aortic dissection involves the coronary ostia, it is necessary to repair the dissected aorta with biological glue or reapproximate the dissected layers of aorta between PTFE felt washers ( Fig. 12-19, F ). In unusual circumstances when the coronary ostia are displaced far laterally by a large-diameter aneurysm, it may be advisable to interpose a second graft between the coronary ostia and aortic graft to prevent tension on the coronary anastomosis, which is the most frequent point of hemorrhage after repair. Irreparable coronary ostial obstruction may require a bypass graft between the aortic graft and the affected coronary artery ( Fig. 12-19, G ). The primary ostium of the affected coronary artery is closed by suture.

The graft may be shortened appropriately to facilitate anastomosis of the coronary arteries to its side. Openings are made into the side of the graft exactly opposite the coronary artery ostia using scissors or battery-operated cautery. Appropriately sized openings assist in creating the anastomosis. An adequate amount of graft should be left between the sewing ring of the prosthesis and the new coronary artery opening. The left coronary anastomosis is made first (see Fig. 12-19, D ). The coronary ostium is approximated to the side of the graft by continuous stitches of 5-0, 4-0, or 3-0 polypropylene, depending on thickness of the aortic tissues. All the suture loops around the inferior rim of the coronary ostium are placed before pulling them up so that this difficult area may be accurately approximated to the graft (see Fig. 12-19, D ). Stitches are placed in cartwheel fashion around the coronary artery ostium, with deep bites into the aorta.

The right coronary anastomosis is performed after completing the left coronary anastomosis (see Fig. 12-19, E ). Both coronary ostia are approximated to the side of the graft in a similar manner.

The distal end of the graft is then shortened to approximate the distal end of the aorta. The aorta is completely divided to allow a direct end-to-end anastomosis. A short segment of graft is cut and placed as a collar over the main portion of the graft. The anastomosis is constructed using continuous stitches of 3-0 or 4-0 polypropylene, depending on the thickness and strength of the aorta. It is convenient to bring the first stitch from the outside of the aorta so that the stitching may continue from the inside surface of the graft. Several suture loops may be placed posteriorly before pulling the graft tightly against the aorta, to ensure accurate closure of the posterior wall of the anastomosis ( Fig. 12-19, H ).

The anastomosis is continued anteriorly and is completed by including all layers of the aorta in the graft. The graft collar is used to cover the completed anastomosis for hemostasis ( Fig. 12-19, I ).

Modifications are required when coronary artery ostia are either close to the anulus or widely separated laterally by an aortic aneurysm. When coronary artery ostia are bound tightly to the aortic anulus, usually by prior operation or valve replacement, it is impossible to create an accurate anastomosis to the tubular portion of a composite graft because the valve sewing ring may impinge on the coronary ostia. In this situation, a composite valve prosthesis is constructed by placing a prosthetic valve within a tubular polyester graft so that there is a short length of tubular graft extending below and a longer length of graft extending above the sewing ring of the valve ( Fig. 12-19, J ). The graft and sewing ring of the prosthetic valve are attached by continuous suture. The extension of the tubular graft below the prosthetic valve is attached to the aortic anulus, displacing the level of the prosthetic valve cephalad above the bound down coronary ostia. Obstruction of the coronary ostia from contiguous placement of the thick sewing ring of the prosthetic valve is avoided. Ten-millimeter extension grafts from the aortic graft above the prosthetic valve to the coronary ostia complete the repair.

When the coronary artery ostia have been carried laterally and superiorly from the usual location relative to the aortic anulus by aneurysm or dilatation of the aortic root, it is necessary to create an extension from the composite prosthesis to the coronary arteries. Ten-millimeter tubular polyester grafts are attached to the coronary arteries and brought up to the anterior aspect of the composite prosthesis ( Fig. 12-19, K ).

Remodeling versus Reimplantation Procedures

Technique of Operation

After induction of anesthesia and before incision, intraoperative transesophageal echocardiography (TEE) is used to measure aortic root dimensions at the sinutubular junction and ventricular-aortic junction. Operations are performed on CPB using a single two-stage cannula for venous uptake, with oxygenated blood returned to a cannula placed high in the ascending aorta or arch or in the femoral artery. Hypothermic circulatory arrest is used when the aneurysm extends beyond the ascending aorta.

The aorta is divided above the sinutubular junction and the aortic valve thoroughly examined. Normal aortic valve cusps suggest the possibility of a valve-sparing operation. Diameters of the sinutubular junction and ventricular-aortic junction are measured using Hegar dilators or accurate valve sizers. Alterations of aortic root dimensions are noted and will guide the steps taken to restore dimensions to normal.

Aortic Anulus Normal, Normal Sinuses of Valsalva, Sinutubular Junction Enlarged

A normal aortic anulus with enlarged sinutubular junction is found in patients with aortic ectasia and aneurysm of the ascending aorta not involving the aortic sinuses. The coronary arteries are not displaced from their usual location in relation to the anulus.

A vascular graft the same diameter as the aortic anulus is selected. A 4- to 5-mm segment of the graft is prepared for placement on the outside of the aorta at the sinutubular junction ( Fig. 12-21 ). The thickness of the aortic wall when compressed within the graft will reduce the inside diameter of the aorta to restore the normal dimension, which is 15% less than the diameter of the aortic anulus. Using this short segment of graft is easier and more accurate than attempting to attach a longer graft directly to the sinutubular junction.

Remodeling Procedure

In the remodeling procedure, the aortic sinuses are removed. The aortic anulus is reduced to a diameter appropriate for the patient's body size ( Fig. 12-22 ), generally 25 mm for the average adult male, 27 mm for a large male, and 23 mm for an adult female. A vascular graft 10% to 15% smaller than that diameter is selected; thus, for a 25-mm anulus, a 22-mm graft is chosen. Two 4- to 5-mm segments (rings) of the graft are prepared to adjust the anulus diameter. The remaining graft is tailored by making three incisions and trimming the flaps for sinus reconstruction and replacing the ascending aorta. To achieve an LVOT 25 mm in diameter at the ventricular-aortic junction, the circumference of the aorta must be reduced to 78 mm (25 · π = 78). This reduction is accomplished by anuloplasty, using the short segments of graft to size the anulus accurately and to support the repair. Anuloplasty mattress stitches are placed in the LVOT at a level plane just below the hinge point of the aortic valve. The stitches are placed beginning below the nadir or midpoint of the right coronary cusp of the aortic valve and working counterclockwise to the commissure between the noncoronary and right coronary cusps. This places the stitches on five sixths of the circumference, avoiding stitches in the one sixth of the ventricular septum that contains the conduction system. A strip of fabric to cover five sixths of the circumference and achieve a diameter of 25 mm is 65 mm in length (78 · = 65). It is convenient that a 22-mm crimped tubular polyester graft provides a strip of fabric 75 mm in length when the 4- to 5-mm segment is cut, opened, and stretched to length. From the strip of the graft, 10 mm of length is removed. The anuloplasty stitches are placed through the fabric strip and passed through the LVOT to the outside. Thickness of tissue through which the needles pass is about 3 mm. Thus, the outside diameter to be supported will be about 28 mm in diameter. The length of fabric needed to support this diameter is, conveniently, about 75 mm (28 · π · = 73). The anuloplasty stitches are passed through the outside fabric strip. A 25-mm-diameter Hegar dilator is placed in the LVOT while the sutures are tied down. This narrows the LVOT to a calculated diameter while distributing the tension equally over five sixths of its circumference.

The sinus aorta is reconstructed to the flap graft. Diameter of the sinutubular junction is accurately restored by the diameter of the graft chosen for the repair. Relationships just described should hold for the various graft sizes that might be chosen for reconstructing the aortic root. Intraoperative TEE is performed with the heart contracting and ejecting at normal pressure to determine adequacy of the repair.