Pericardial Disease

Pathophysiology of Cardiac Compression

Cardiac compression occurs in chronic constrictive pericarditis, but is also a feature of acute cardiac tamponade and effusive constrictive pericardial disease, a condition characterized by pericardial thickening and variable amounts of fluid in the pericardial space.

Chronic Constrictive Pericarditis

Basic pathophysiology of chronic constrictive pericarditis has been debated for more than half a century. By 1949, Holman and Willett concluded that constriction of the caval orifices and atria was important in its pathogenesis and for this reason adopted the median sternotomy approach for its surgical correction. In 1951, Burwell concluded from cardiac catheterization study that both right and left ventricular function were impaired and constriction of caval orifices or atria played no role. In 1952, Isaacs and colleagues showed in dogs that a change in the pressure-volume curves of the two ventricles resulted from experimentally produced constrictive pericarditis, and this was the fundamental pathophysiologic change associated with the disease ( Fig. 23-1 ). These investigators also demonstrated during development of the constriction an increase in right and left ventricular diastolic pressure and a decrease in stroke volume. In their experimental animals, a small increase in volume resulted in a considerable increase in end-diastolic pressure. These studies indicated that lack of ventricular diastolic distensibility, and thus inability to generate an adequate preload (see “ Ventricular Preload ” under Cardiac Output and Its Determinants in Section I of Chapter 5 ), was a characteristic of hearts with chronic constrictive pericarditis. These considerations influenced Scannell and colleagues to adopt a left anterolateral thoracotomy as their surgical approach of choice by 1952.

A number of features of clinical cases of chronic constrictive pericarditis derive from these basic abnormalities of diastolic function. Ventricular filling is impaired and ventricular stroke volume reduced as a result of decreased compliance of the fused cardiac and pericardial mass. Phasic aspects of ventricular filling are also altered. For a brief period in early diastole, ventricular filling is rapid. However, the limit of ventricular distensibility is reached rapidly, and the right ventricular pressure pulse displays an early diastolic dip and then a high diastolic plateau (square root sign) . There is nearly complete diastolic ventricular filling during the first 50 milliseconds of diastole.

Systemic venous pressures are correspondingly abnormal; mean venous pressure is elevated. The x descent is steep and deep, corresponding to the beginning of ejection. The y descent is also steep and deep, corresponding to the early diastolic dip of right ventricular pressure. This differs from events during acute cardiac tamponade, in which the y descent is absent. The normal inspiratory increase in vena caval flow and decrease in pressure is diminished and often absent.

Pulsus paradoxus is said to be infrequent in chronic constrictive pericarditis, in contrast to the situation with acute cardiac tamponade. However, frequency of its recognition is influenced by cardiac rhythm; it is usually present when there is sinus rhythm, but impossible to detect when there is atrial fibrillation (a frequent accompaniment of chronic constrictive pericarditis).

Ventricular end-diastolic volumes are small in this disease, as are end-systolic volumes and stroke index. Rate of increase of left ventricular systolic pressure and ejection fraction are not altered. Thus, systolic left ventricular function under these circumstances is normal, but this does not necessarily indicate normal contractility.

Etiology

In most patients the etiology of chronic constrictive pericarditis is not known. McCaughan and colleagues were able to identify a specific etiologic factor in only 27% of their patients, and Blake and colleagues in only 34%.

In about 10% of cases, documented acute pericarditis precedes development of chronic constrictive pericarditis. Prior to its effective treatment, tuberculosis was the etiology of chronic constrictive pericarditis in up to 17% of cases. Currently, a prominent cause is mediastinal radiation for malignant disease. Rheumatoid disease and sarcoidosis occasionally are causes. Trauma is another uncommon cause, with hemopericardium usually present as the precursor of pericardial thickening and constriction.

Cardiac surgery can be followed by constrictive pericarditis, but this is uncommon, probably occurring in less than 5% of patients. It may be more common after coronary artery bypass grafting than after other operations. The interval between the original cardiac operation and development of evidence of pericardial constriction is highly variable, ranging from 1 month to nearly 10 years. Mean interval is about 2 years.

Clinical Presentation

Classically, symptoms of chronic constrictive pericarditis are delayed for several years after the clinical or subclinical episode of acute pericarditis. The interval may, however, be as short as 3 to 4 weeks in those rare instances in which pericarditis develops after cardiac surgery, or 4 to 12 months after trauma or acute nonspecific pericarditis.

Initial symptoms may be only fatigue with or without modest effort breathlessness, and neck vein distention may be noticed. Insidiously, however, hepatomegaly and ascites develop, initially with or without peripheral edema. Even within the context of such evidence of appreciable fluid retention, breathlessness may occur only on exertion and not at rest; although in severe cases there may be orthopnea. Paroxysmal nocturnal dyspnea occurs infrequently.

Clinical Findings

When constriction is not severe, clinical findings may be limited to modest but persistent elevation of jugular venous pressure and slight liver enlargement with or without intermittent ankle edema. As constriction increases, there is a progressive increase in venous pressure and hepatomegaly, with eventual development of persistent peripheral edema, ascites, and pleural effusion. Venous pressure fails to decline during inspiration (Kussmaul sign), but this is not specific, in that the same findings may accompany right ventricular failure, restrictive myocardial disease, or tricuspid valve stenosis. By this stage, pulsus paradoxus is to be expected if sinus rhythm persists, and pulse pressure often is reduced. The apex beat is usually not palpable, but there is often systolic retraction in the left parasternal region. This retraction may be followed by a visible and palpable forward thrust extending toward the expected site of the cardiac apex. This impulse, which results from forceful ventricular filling with the onset of diastole, may be mistaken for the apex beat and used to argue against the existence of pericardial constriction. Rapid ventricular filling in early diastole is also associated with an unusually early, often loud, third heart sound that is sometimes referred to as a pericardial knock, but usually there are no murmurs.

As in other forms of heart failure, salt and water retention are present. Anand and colleagues found important increases of total body water, extracellular volume, plasma volume, and exchangeable sodium in their study of patients with proven constrictive pericarditis. However, renal plasma flow was only moderately decreased, and glomerular filtration rate was normal. Norepinephrine, renin activity, aldosterone, and cortisol were also increased, as was plasma atrial natriuretic hormone, although not to levels usually seen in other heart failure syndromes. The ratio of left atrial to aortic diameter measured by echocardiography was only minimally increased, indicating that in constrictive pericarditis, the atria are prevented from expanding. The restricted distensibility of the atria may limit secretion of atrial natriuretic hormone, thus reducing natriuretic and diuretic effects, resulting in retention of sodium and water greater than that occurring in patients with edema from myocardial disease.

Laboratory Investigation

Protein-losing enteropathy occurs in some patients with chronic constrictive pericarditis who develop ascites and hepatomegaly. They may have severe hypoproteinemia, with depression of albumin and gamma globulin, and an increased rate of leakage of plasma protein into the gastrointestinal tract. This syndrome also develops after other conditions that chronically elevate inferior or superior vena caval pressure, such as the Fontan operation and atrial switch operations with inferior vena caval obstruction (see “ Protein-Losing Enteropathy ” under Results in Section IV of Chapter 41 , and “ Superior Vena Caval Obstruction ” and “ Inferior Vena Caval Obstruction ” under Special Situations and Controversies in Chapter 52 ).

Chest Radiography

The chest radiograph may be unremarkable, although about one third of patients show moderate to marked enlargement of the cardiac silhouette. Pericardial calcification is evident in about 40%, and radiologic evidence of compression in about 60%.

Electrocardiography

The electrocardiogram (ECG) is usually abnormal, with nonspecific ST-segment and T-wave changes in 90% of cases. In about 40% of patients with surgically verified chronic constrictive pericarditis, the QRS complexes have low voltage, and an atrial arrhythmia is present in 30%.

Imaging Studies

Cardiac Catheterization

Characteristically, end-diastolic pressures are elevated and equal in the right atrium, pulmonary artery, and left atrium; this is the hallmark of chronic constrictive pericardial disease. In the report by McCaughan and colleagues, such findings were obtained in all patients coming to catheterization. Intraventricular pressure pulse contours characteristically demonstrate an early rapid fall in diastolic pressure in the right ventricle, followed by a rapid rise to an elevated diastolic plateau (square root sign). Left ventricular pressure pulse usually has a similar contour.

Mean right atrial pressure fails to decrease normally during inspiration, or it may actually rise slightly. There is a transient increase in pulmonary blood volume and a slight reduction in right ventricular afterload, resulting in a fall in pulmonary arterial and right ventricular systolic pressure and a decline in pulmonary venous pressure and left ventricular diastolic pressure as well.

Vaitkus and Kussmaul identified the predictive accuracy of three different hemodynamic criteria for differentiating constrictive from restrictive disease ( Table 23-1 ): (1) equalization of right and left ventricular end-diastolic pressure favors constriction; (2) constriction is associated with more modest elevation of right ventricular systolic pressure (≤50 mmHg); in restriction, it exceeds that amount; (3) in constriction, right and left ventricular end-diastolic pressure usually is greater than one third of right ventricular systolic pressure; in restriction, the ratio is characteristically less than one third.

When hemodynamic studies are equivocal, rapid infusion (in 6 to 8 minutes) of 1000 mL of normal saline solution produces diagnostic features of occult chronic constrictive pericardial disease. These features include not only striking elevations of filling pressures but also development of typical pressure pulse morphologic characteristics of constriction, loss or reversal of the respiratory variation of right atrial pressure, and precise diastolic equilibration of cardiac pressures.

Endomyocardial Biopsy

When diagnosis is unclear, myocardial biopsy may be useful. Normal myocardium, nonspecific changes (e.g., from irradiation), or myocarditis on biopsy must be considered nondiagnostic, because they may be present with either restrictive or constrictive disease. Finding amyloid disease is diagnostic of a restrictive etiology.

Minor Thoracotomy

Despite the studies mentioned previously, distinguishing between chronic constrictive pericarditis and restrictive cardiomyopathy can remain difficult, and a minor thoracotomy may be useful in a few circumstances. A small left anterior thoracotomy incision placed in the line of the formal anterolateral incision that would be used for pericardectomy is made, and the pericardium is exposed through the interspace and biopsied. If the pathologic diagnosis is chronic constrictive pericarditis, the incision is extended and a formal pericardectomy performed. If no pericardial pathologic condition is found, diagnosis favors restrictive cardiomyopathy, and operation is terminated as a minor procedure. If recurring pericardial effusion is found with a more or less normal pericardium, wide removal of the pericardium can be easily accomplished with slight extension of the incision.

Left Anterolateral Thoracotomy Approach

The patient is positioned supine, with a roll beneath the left scapula. The left hand is secured beneath the left buttock, with the elbow padded and positioned on the left side of the table ( Fig. 23-2, A ). A curving left anterolateral skin incision is made beneath the breast anteriorly and more laterally over the fifth interspace. Incision is carried through the pectoralis major anteriorly, and the fifth interspace is opened. The interspace incision is extended well anteriorly. The internal thoracic vessels can be ligated and divided and the fifth costal cartilage disconnected from the sternum if exposure is inadequate. The rib spreader is inserted and the interspace incision extended laterally with scissors as the spreader is gradually opened.

The left phrenic nerve is identified and freed from the pericardium if possible. Occasionally the nerve is mobilized with a narrow strip of pericardium to avoid injury. The pericardium is incised through an area of minimal calcification posterolaterally if possible, over what is presumed to be left ventricle ( Fig. 23-2, B ). On occasion, this initial incision through the abnormal pericardium takes the dissection immediately onto the myocardium; in other cases, it enters a fluid-filled space (see “ Morphology ” earlier in this section).

When a space is entered, the initial longitudinal incision is carried anteriorly and posteriorly from its superior and inferior extremities. The anterior pericardial flap is dissected as far as the right atrioventricular groove, beneath the elevated thymus and prepericardial fat, and resected ( Fig. 23-2, C ). The posterior flap is dissected far posteriorly and excised. Dissection must be carried superiorly onto the pulmonary trunk, because failure to relieve pericardial bands across it can result in postoperative gradients and severe right ventricular hypertension. The piece of pericardium left inferiorly is dissected off the diaphragm except in the area of the central fibrous tendon, from which it often cannot be removed. Fibrous plaques adherent to the epicardium are then dissected off through the entire area of resection. If the epicardium is thin and relatively normal, it need not be disturbed. If it is thickened, it must be removed either in its entirety or in a sufficient number of areas to allow more normal diastolic filling of the ventricles. Failure to do this severely compromises results of operation.

If no pericardial space is found, the entire longitudinal incision and its anterior and posterior extensions are made only through the fibrous pericardium. Then the incision is deepened in an area that seems to be over myocardium rather than over the interventricular or atrioventricular groove. Slowly and carefully, the posterior flap is dissected off the left ventricular myocardium. At first, this dissection is done only in areas in which it proceeds reasonably well, leaving the epicardium on the myocardium wherever it is thin and normal. When dissection in this plane is not possible, such as in an area of calcification or dense scarring, islands of calcification and scarring may be left attached to the myocardium but separated from other areas. Dissection moves to the anterior pericardial flap whenever progress ceases posteriorly and vice versa. Particular care is necessary when dissection passes across the interventricular groove containing the coronary vessels; here, islands of calcific plaque may need to be left in place. Dissection is carried just across the atrioventricular groove and onto the atria. It is important to be certain that all constrictions in the atrioventricular groove are removed, because they can result in gradients between atrium and ventricle.

No special effort is made to free the venae cavae or cavoatrial junctions, because constriction does not occur in these areas. When dissection is complete, the pericardial flaps, as well as the diaphragmatic portion of the pericardium, are excised ( Fig. 23-2, D ).

If a pulmonary arterial catheter is not placed, a polyvinyl catheter can be inserted into the left atrium via the appendage or left pulmonary veins to monitor pressure and assist in postoperative care. Two pleural drainage catheters are inserted, the tip of one being placed posteriorly and inferiorly and that of the other anteriorly and superiorly. The interspace incision is closed with heavy pericostal and perichondrial absorbable sutures, and the muscle layers are closed with continuous absorbable sutures. The skin is closed with a continuous subcuticular suture.

Median Sternotomy Approach

The median sternotomy approach may be used with or without cardiopulmonary bypass (CPB). In either event, the sternum is divided in the usual manner (see “ Incision ” in Section III of Chapter 2 ). The pericardium is opened vertically anteriorly. Often it is necessary to use a knife for this maneuver, and particular care must be taken when the plane between the thickened (visceral) pericardium and the myocardium is reached. The pericardial flaps are then dissected laterally, superiorly and inferiorly, as described in preceding text. To the right, dissection passes across the atrioventricular groove and proceeds across the anterior and lateral walls of the right atrium, as long as the cleavage plane there is readily found. If it is not, this portion of thickened pericardium can be left in situ. In the former instance, the pericardial flap is excised about 1 to 2 cm anterior to the right phrenic nerve. To the left, dissection proceeds across the front of the ventricles and then over the lateral left ventricular wall. This pericardial flap is excised about 1 cm in front of the left phrenic nerve. Dissection continues posterior to the phrenic nerve but in the plane between myocardium and epicardium until the entire left ventricle is freed (up to the atrioventricular groove posteriorly and over the diaphragm inferiorly). It is usually possible to remove the thickened, often calcified, outer pericardial layer, because there is generally a cleavage plane between this and the overlying thickened pleura containing the phrenic nerve. The same is usually true of the thickened pericardial tissue inferiorly overlying the diaphragm. Operation is completed as described earlier.

The need for CPB is debatable. However, if CPB is anticipated, the obvious approach is median sternotomy. The improved exposure afforded by CPB must be balanced against the probability of increased blood loss. When CPB is used, it may be most convenient to use the femoral vessels for both venous and arterial cannulation (see “ Cardiopulmonary Bypass Established by Peripheral Cannulation ” under Special Situations and Controversies in Section III of Chapter 2 ). Then, after CPB has been established at 34°C to 37°C, the thickened pericardium can be incised and dissection accomplished.

Choice of Surgical Approach

The main advantage of the left anterolateral approach is the excellent exposure afforded for complete liberation of the left ventricle and complete removal of the diseased pericardium over it, including its diaphragmatic surface. The main advantage of median sternotomy is the ease with which the incision is made and the improved exposure obtained for removing pericardium from the right ventricle. It is a better approach when CPB is used, although CPB can be used with the anterolateral approach by cannulating the femoral vessels (see “ Cardiopulmonary Bypass Established by Peripheral Cannulation ” under Special Situations and Controversies in Section III of Chapter 2 ). Although there are proponents of near-routine use of CPB for pericardectomy, there is no clear evidence that this improves outcomes after operation. One proposed advantage, is the ability to liberate the cavoatrial junction and to remove the pericardium over the right atrium, although the benefit of this is controversial.

Complementary Techniques

A high-speed burr or ultrasonic dissector may help to define the epicardial layer and dissect the adherent calcified pericardium away from the myocardium. Complete resection of all thickened and constrictive epicardium is as important for achieving a good result as complete removal of the parietal pericardium. However, in some patients (particularly those with postoperative or postirradiation constriction), it is impossible to develop a consistent plane of dissection. Usually that plane is apparent by encountering dark pink myocardium, the surface of which expands into the pericardial incision and contracts vigorously. In cases in which the epicardial peel is exceptionally adherent, a cross-hatching “waffle” procedure described by Heimbecker and colleagues or multiple incisions of the peel (turtle cage operation) allow myocardial expansion and restoration of adequate hemodynamics.