PATHOPHYSIOLOGY Constrictive pericarditis is pathologically distinct from acute pericarditis. 18 Following pericardial injury and the resultant inflammatory and reparative process, fibrous thickening of the layers of the pericardium may occur. This fibrous reparative process is most commonly encountered after cardiac trauma with intrapericardial hemorrhage, after pericardiotomy (open-heart surgery, including coronary revascularization), in fungal or tuberculous pericarditis, and in chronic renal failure (uremic pericarditis). When the fibrous and/or collagenous response prevents passive diastolic filling of the normally distensible cardiac chambers, constriction is said to be present. Intrapericardial fluid is not required to produce such a hemodynamic effect. By its nature, constrictive pericarditis is most commonly a clinically chronic process. However, clinical manifestations may occur early if fluid also accumulates within the thickened, noncompliant pericardial sac (so-called effusive constrictive pericarditis). In the vast majority of cases of constrictive pericarditis, proved by hemodynamic assessment (see below), a specific cause is never determined.
CLINICAL FEATURES The symptoms of constrictive pericarditis usually develop gradually and may mimic those of CHF and restrictive cardiomyopathy.11 If symptoms develop within months of a pericardial injury, a combination of pericardial effusion and constriction should be suspected. Exertional dyspnea and decreased exercise tolerance are common complaints; however, orthopnea, paroxysmal nocturnal dyspnea, and chest pain are unusual. Lower-extremity swelling (pedal edema) and increasing abdominal girth (ascites) are also common complaints and are the result of decreased RV diastolic compliance and the resultant increase in systemic venous pressure.
In most instances, physical findings and their correct interpretation will lead the clinician to suspect constrictive pericarditis. 18 Examination of the neck veins with the torso of the patient at a 45° angle from horizontal will reveal jugular venous distention and a rapid y descent of the cervical venous pulse. Elevated venous pressure is also seen in CHF, but a rapid y descent is infrequently encountered. The Kussmaul sign (inspiratory neck vein distention) is frequently but not invariably noted in constrictive pericarditis but rarely noted in uncompensated CHF. A paradoxical pulse is found in a minority of patients, and thus its absence does not exclude a diagnosis of constrictive pericarditis. On cardiac auscultation, an early diastolic sound, a pericardial "knock," may be heard at the apex 60 to 120 ms after the second heart sound. The pericardial knock sounds like a ventricular gallop but occurs earlier than the S 3 of CHF, which it may mimic. The knock is due to accelerated RV inflow in early diastole and early myocardial distention, followed by an abrupt slowing of further ventricular expansion. There is usually no pericardial friction rub. Hepatomegaly, ascites, and dependent edema of varying severities are usually found.
DIAGNOSIS Electrocardiogram Diagnostic ECG changes have not been described in constrictive pericarditis. However, low-voltage QRS complexes and inverted T waves are common.
Radiographic Assessment Conventional posteroanterior and lateral chest x-rays most commonly demonstrate a normal or slightly enlarged cardiac silhouette, clear lung fields, and little or no evidence of pulmonary venous congestion. Pericardial calcification, which may be evident in up to 50 percent of patients with constrictive pericarditis, is seen best on the lateral chest x-ray but is not diagnostic of constrictive pericarditis.
Echocardiographic Studies On occasion, two-dimensional echocardiography may demonstrate pericardial thickening and abnormal ventricular septal motion in a patient with suspected constrictive pericarditis. However, its diagnostic utility is much less than in a patient with acute pericarditis. Doppler echocardiography is preferred, and cardiac computed tomography and magnetic resonance imaging may also be useful.
TREATMENT AND DISPOSITION In cases of significant constriction and impaired ventricular filling, pericardiectomy is the treatment of choice. CHAPTER REFERENCES
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