Combined Aortic and Mitral Valve Disease with or without Tricuspid Valve Disease

Definition

Acquired diseases of both the aortic and mitral valves severe enough to require simultaneous surgery (replacement, repair, or valvotomy) are considered in this chapter. Because tricuspid valve disease may form part of this spectrum and require simultaneous surgery, it is also considered, although discussed in more detail in Chapter 14 .

Historical Note

Surgical treatment of combined aortic and mitral valve disease began during the early 1950s by closed methods. In 1955, Likoff and colleagues reported 74 patients who had undergone simultaneous closed repair of aortic and mitral stenosis by Bailey and Glover in Philadelphia. In 1958, Lillehei and colleagues were the first to report simultaneous repairs of both valves by open techniques using cardiopulmonary bypass (CPB). In 1963, soon after introduction of durable mechanical prostheses, Cartwright and colleagues first reported simultaneous aortic and mitral valve replacement. In 1964, Starr and colleagues reported 13 patients who had undergone multiple valve replacements, including one who received mechanical aortic, mitral, and tricuspid prostheses.

Morphology

Morphology of diseases involving mitral, aortic, and tricuspid valves is described in Chapter 11, Chapter 12, Chapter 14 . In most patients, multivalvar disease is rheumatic in origin, but each valve may manifest a separate pathologic condition—for example, rheumatic aortic valve disease and mitral regurgitation from infective endocarditis, idiopathic chordal rupture, or ischemic papillary muscle dysfunction.

The effect of combined disease on morphology of the left ventricle (LV) is of great importance. Thus, at the extremes, combined aortic and mitral regurgitation imposes a large volume overload on the LV, and LV volume and wall thickness increase severely; combined aortic and mitral stenosis results in a small, thick-walled, noncompliant LV.

Clinical Features and Diagnostic Criteria

In general, clinical criteria and noninvasive diagnostic tests are the same for mitral and aortic valve disease whether they are combined or isolated, but additional cardiac catheterization and angiography data are more frequently needed when they are combined. In patients older than 40 years of age, coronary angiography is indicated routinely, and the valve lesions are assessed at that time.

One lesion is usually dominant and may modify the clinical signs of the less dominant one. A frequent problem is assessing severity of the less dominant lesion; if it is mild or even mild to moderate, it may not require simultaneous correction. Historically, it was sometimes possible to obtain reliable information on the second lesion during operation by palpating an atrial chamber to detect systolic pulsation, by feeling the valve directly with the finger before beginning CPB, or by exposing the valve. Today, with two-dimensional (2D) and color Doppler echocardiography, the status of the aortic, mitral, and tricuspid valves is usually known before the patient enters the operating room. Intraoperative use of transesophageal echocardiography (TEE) verifies this status if necessary.

Dominant Aortic Stenosis

Dominant aortic stenosis is diagnosed by the same techniques used in isolated aortic stenosis (see Chapter 12 ). Dominant aortic stenosis may complicate diagnosing coexisting mitral stenosis by simple methods. The auscultatory signs of moderate mitral stenosis may be masked, and transmission of the aortic systolic murmur to the apex may confuse the assessment of mitral regurgitation. However, Doppler echocardiography can render as precise a diagnosis as in isolated mitral stenosis. Severity of pure mitral stenosis associated with aortic stenosis can be verified by pressure measurements (left atrium to LV) on the operating table, although varying cardiac output sometimes makes interpretation difficult. In questionable cases, the valve may be palpated on CPB or examined directly by opening the left atrium through the superior approach (see Chapter 11 ).

A convincing sign of important mitral regurgitation associated with aortic stenosis is a right parasternal systolic lift, especially if associated with an apical third heart sound when the venous and hepatic pulses do not indicate important tricuspid regurgitation. More than modest left atrial enlargement on the posteroanterior chest radiograph and also P mitrale in the electrocardiogram strongly suggest important associated mitral valve disease. Two-dimensional echocardiography with Doppler color flow interrogation is helpful in identifying mitral regurgitation, both preoperatively and intraoperatively.

Dominant Aortic Regurgitation

In dominant aortic regurgitation, as noted in Chapter 12 , an Austin Flint murmur can mimic that of mitral stenosis, the absence of which can be confirmed by 2D echocardiography with Doppler color flow interrogation. If in addition to a mid-diastolic murmur there is an opening snap, left atrial enlargement above grade 2, and P mitrale, then important coexisting mitral stenosis is usually present.

With dominant aortic regurgitation, severity of associated mitral regurgitation requires careful assessment by 2D echocardiography, particularly because it is frequently secondary to LV enlargement or dysfunction. If it is less than grade 2 in severity, it usually regresses after the aortic regurgitation is corrected. When the LV is severely enlarged, it is likely that both aortic and mitral regurgitation are severe.

Dominant Mitral Stenosis

Dominant mitral stenosis may minimize the usual signs and symptoms of coexisting aortic regurgitation. When aortic regurgitant flow is moderate or large, its presence and severity are readily assessed clinically by character of the arterial pulse and blood pressure. At times, however, what seems to be less than grade 2 aortic regurgitation becomes clearly moderate or severe after surgical relief of the mitral stenosis. Magnitude of aortic regurgitation cannot be assessed reliably at operation. Visual inspection of the aortic valve may provide information about extent of the rheumatic condition but not about magnitude of the leakage. Thus, evaluating the aortic valve preoperatively with 2D echocardiography Doppler color flow interrogation is important before undertaking mitral valve surgery. Intraoperative TEE can be of value as well. Size of the jet visualized by color Doppler echocardiography may not represent the degree of aortic regurgitation. It is possible to measure the vena contracta, which is the size of the regurgitant jet within the regurgitant aortic valve orifice. This measurement correlates well with effective regurgitant orifice. Width of the vena contracta is measured from the parasternal view long axis, just below the flow convergence. Vena contracta greater than or equal to 7 mm uniformly indicates severe aortic valve regurgitation, whereas measurements of 5 mm or less correspond to regurgitation that is moderate or less.

Moderate (grade 2) associated aortic stenosis can usually be identified clinically by characteristic physical findings (see Chapter 12 ), and LV-aortic gradient can be measured at operation, but flow may not be known. Therefore, an estimate of aortic valve orifice size by 2D echocardiography or cardiac catheterization (see Chapter 12 ) should be available when mitral valve surgery is undertaken.

Dominant Mitral Regurgitation

The same considerations discussed for dominant mitral stenosis apply to aortic valve disease associated with dominant mitral regurgitation.

Dominant Tricuspid Valve Disease

In uncommon cases of dominant tricuspid stenosis or regurgitation, accurate clinical assessment of downstream lesions in the mitral and aortic valves is seldom possible. Preoperative 2D echocardiographic study is required, and occasionally cardiac catheterization as well.

Natural History

The natural history of combined aortic and mitral valve disease is complicated by the same variability in dominance of one lesion over the other that makes diagnosis and decision making difficult. For example, in rheumatic aortic valve disease, the mitral valve is involved almost universally, although the lesions—either stenosis or regurgitation—may be so mild that operation is not required until many years after replacement of the aortic valve. Double valve surgery in such patients is sequential. Patients with rheumatic mitral valve disease often have only mild rheumatic aortic valve disease at the time of their original mitral operation. The longer these patients survive, the more likely it is that a mild rheumatic aortic lesion will become important and require operation. Choudhary and colleagues followed 284 patients with rheumatic heart disease who had mild aortic valve involvement at the time of mitral valve surgery. After a mean interval of about 5 years, 35% of those with mild aortic valve stenosis had progressed to moderate or severe stenosis. Freedom from development of moderate or severe aortic valve stenosis was 75% ± 6%, 62% ± 9%, and 46% ± 11% at 5, 10, and 15 years, respectively. Mild aortic valve regurgitation at the time of mitral valve intervention, on the other hand, progressed slowly, with only 5% of patients developing moderate or severe aortic valve regurgitation after a mean interval of 12 years. Freedom from development of moderate or severe aortic valve regurgitation was 100%, 97% ± 2%, and 87% ± 5% at 5, 10, and 15 years, respectively.

Simultaneous development of important aortic and mitral valve disease usually results from a particularly severe and prolonged attack of rheumatic fever or from recurrent attacks, and there may be a florid myocarditis and pericarditis as well. Regurgitant combined valve lesions may mature particularly rapidly, requiring operation by the second decade of life.

When dominant aortic stenosis coexists with mitral stenosis, prognosis may be worse than that of isolated aortic stenosis. When dominant mitral stenosis coexists with important aortic stenosis, survival is shorter than for isolated mitral stenosis, with sudden death being a particular risk. When severe aortic and mitral regurgitation coexist, reduction of LV afterload by mitral regurgitation provides a protective effect (see Chapter 11 ), and patients with aortic regurgitation tend to remain asymptomatic despite advanced left ventricular dysfunction (see Chapter 12 ). Consequently, it is likely that patients with this combination will remain asymptomatic well beyond the stage when left ventricular dysfunction becomes irreversible.

Technique of Operation

After induction of general inhalation anesthesia and during appropriate preparation of the skin and draping of a sterile field, an echocardiography probe is inserted into the esophagus (see Chapter 4 ). Two-dimensional ultrasound imaging is used to evaluate valve morphology and color Doppler ultrasound to evaluate valvar hemodynamics. The plan for operation is then refined. The aortic valve is replaced in most circumstances, but it may be repaired if there is aortic valve regurgitation that is judged to be secondary to dilatation of the aortic root or to dilatation or aneurysm of the ascending aorta. The mitral valve may be repaired or replaced. The tricuspid valve may not need intervention or may be repaired. The crux of the operation usually involves the intervention judged necessary for the mitral valve; there are more options available for it than for the aortic valve, and the tricuspid valve is usually reparable.

A median sternotomy is performed. The cardiac valves lie in close proximity to each other, so an extensive incision is unnecessary. The pericardium is opened and suspended to provide optimal exposure of the heart. A systematic evaluation is made by assessing cardiac chamber size and palpating for thrills caused by turbulent blood flow. CPB is established using a single venous uptake cannula or two venous cannulae if the left atrium is small. Two venous cannulae and caval tapes with tourniquets are required for operations involving the tricuspid valve (see Chapter 2 ). Oxygenated blood is returned through a cannula placed in the ascending aorta. Multiple valve operations are enhanced by using small cannulae and vacuum-assisted venous return (see “Vacuum-Assisted Venous Return” in Chapter 2 ). The perfusate may be cooled to lower the body temperature to 28°C.

Operations involving more than one cardiac valve are most conveniently performed using intermittent retrograde administration of cardioplegic solution via the coronary sinus (see “Technique of Retrograde Infusion” in Chapter 3 ). A perfusion cannula is inserted into the coronary sinus through the right atrial wall for aortic and mitral valve operations, or directly after opening the right atrium for operations involving the tricuspid valve.

A vascular clamp occludes the ascending aorta. A vent catheter is inserted through the right superior pulmonary vein and advanced across the mitral valve into the LV. A transverse aortotomy is made and cold cardioplegia administered. For tricuspid valve operations, the right atrium is opened parallel to the atrioventricular groove, the coronary sinus cannula is inserted, and cold cardioplegia is administered.

The aortotomy is extended into the noncoronary sinus of Valsalva or extended to divide the aorta above the sinutubular junction. The aortic valve is inspected for the possibility of repair. If it is not reparable, it is excised. Calcareous deposits are removed from the aortic anulus. Diameter of the LV outflow tract at the aortoventricular junction (aortic anulus) is measured.

The operation then focuses on the mitral valve. The left atrium is opened on the right side posterior to the interatrial groove at the junction of the right pulmonary vein, and the incision is extended superiorly behind the superior vena cava and inferiorly behind the inferior vena cava. Alternatively, the superior aspect of the left atrium is opened medial to the superior vena cava and behind the aortic anulus. This superior approach is particularly useful when the aorta has been divided. When operation on the tricuspid valve is required, a transseptal approach may be convenient, extending the right atrial incision superiorly medial to the superior vena cava and onto the superior aspect of the left atrium. The atrial septum is cut back inferiorly through the fossa ovalis to the inferior wall of the left atrium. A self-retaining retractor maintains exposure of the mitral valve.

The mitral valve is inspected for the possibility of repair. If repair is not feasible, the valve is usually replaced with a mechanical prosthesis, although second- or third-generation stent-mounted bioprostheses may be used in patients older than (≈)70 years of age. This influences the choice of replacement device for the aortic valve, because it is usually replaced with the same type of valve as the mitral valve (see “Choice of Device” in Chapter 12 ). The only exception to mixing rather than matching the type of prosthesis is in the case of a very small aortic root, when a stentless bioprosthesis (allograft or xenograft) may be chosen (see “Small Aortic Root and Small Prosthesis: Prosthesis-Patient Mismatch” in Chapter 12 ). If the mitral valve is reparable, more selection options are available for the aortic valve, with weight given to a bioprosthesis to avoid anticoagulation if the cardiac rhythm is likely to be normal sinus after operation. The tricuspid valve is usually repaired regardless of choices made for the aortic and mitral positions. Occasionally the tricuspid valve is involved by rheumatic disease and requires replacement.

Coronary artery bypass grafting (CABG) may be required in combination with multiple valve procedures. It is usually performed after the valves are excised but before the prostheses are inserted, to reduce risk of atrioventricular groove disruption during cardiac retraction to expose the posterior wall of the LV. Proximal vein graft anastomoses to the aorta for left-sided grafts may be performed after completing distal anastomoses to the coronary arteries. For right-sided grafts, the proximal anastomosis is deferred until the atria and aorta are closed.

Special Features of Postoperative Care

Postoperative care of patients who have undergone combined aortic and mitral valve surgery is the same as that for other patients undergoing cardiac surgery with the aid of CPB (see Chapter 5 ). Anticoagulants are indicated in patients with atrial fibrillation or mechanical prostheses.

Results

Survival

Early (Hospital) Death

Simultaneous aortic and mitral valve replacement is often accompanied by other procedures, so complexity of the operation partly explains higher hospital mortality after multiple valve operations than after single valve surgery. In the Society of Thoracic Surgeons National Adult Cardiac Surgery Database, operative mortality during the 1990s ranged from 6.9% to 9.9%. Hannan and colleagues reported hospital mortality of 9.6% in 1418 multiple valvuloplasty or replacement operations from 1995 to 1997 in the state of New York. John and colleagues reported 9.2% hospital mortality among 456 patients having aortic and mitral valve replacements, whereas Mueller and colleagues reported 5%. When CABG was added to the multiple valve operation, operative mortality doubled to 19% in the state of New York experience.

Time-Related Survival

Time-related survival of heterogeneous groups of patients undergoing simultaneous combined aortic and mitral valve replacement, including those undergoing concomitant tricuspid valve surgery and CABG, is lower than after single valve replacement. In the UAB group's experience from an earlier era, it was 88%, 77%, 63%, 47%, and 23% at 1 month and 1, 5, 10, and 20 years after operation, respectively. The hazard function for death has a rapidly declining early phase of risk, giving way to a second slowly increasing hazard phase about 3 months postoperatively. The increasing phase of hazard may reflect an imperfect postoperative hemodynamic state dating from the time of operation.

Modes of Death

Most deaths early after primary combined aortic and mitral valve replacement are from acute or subacute cardiac failure. However, an unusually high prevalence of death with hemorrhage has occurred in this group of patients in the past. This is because of the ease with which left atrioventricular rupture can be produced at the time of double valve replacement. Currently, greater attention to this detail has considerably lessened the prevalence of this early postoperative complication.

Mode of death occurring after hospitalization discharge is most commonly due to chronic heart failure. Even when tricuspid valve regurgitation and right ventricular dysfunction have seemed to be absent before operation, a number of patients present late postoperatively with increasing evidence of tricuspid regurgitation, right atrial enlargement, and progressing hepatomegaly. The reason for the unusually high prevalence is not apparent. However, the primary feature appears to be right ventricular dysfunction, and tricuspid valve replacement at this stage generally does not improve the patient's condition.

Incremental Risk Factors for Death

Double Valve Replacement

Double valve replacement itself is an incremental risk factor for death (9.4%) compared with isolated replacement of the mitral (5.7%) or aortic valve (3.5%). This is evident early after operation, and particularly in intermediate and long-term follow-up, when many deaths occur because of increasing tricuspid regurgitation progressing to right atrial enlargement, hepatomegaly, and finally cardiac cachexia. These types of death occur much less frequently after isolated mitral valve replacement and rarely after isolated aortic valve replacement. The relative roles of decreasing LV performance, increasing pulmonary vascular resistance, and decreasing right ventricular performance in this late deterioration after double valve replacement are uncertain.

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