Back to CARDIOLOGYThe pericardium is a two-layered sac that encircles the heart, the inner serosal layer ( visceral pericardium ) adhering to the outer wall of the heart and being reflected back upon itself, at the level of the great vessels, to join the though fibrous outer layer ( parietal pericardium ). A thin film of fluid ( about 50 ml )slightly separates the two layers and decreases friction between them.
The pericardium appears to serve three functions : it fixes the heart within the mediastinum and limits its motion; it prevents extreme dilatation of the heart during sudden rises of intracardiac volume; and it may function as a barrier to limit the spread of infection from the adjacent lungs. However, patients with complete absence of the pericardium ( either congenital or surgically removed ) generally do fine without it, casting doubt on its actual physiologic importance.
Constrictive Pericarditis is present when a fibrotic, thickened, and adherent pericardium restricts diastolic filling of the heart. It usually begins with an initial episode of acute pericarditis, which may not be detected clinically. This then slowly progresses to a subacute stage of organization and resorption of effusion, follwed by a chronic stage consisting of fibrous scarring and thickening of the pericardium with obliteration of the pericardial space, producing uniform restriction of the filling of all heart chambers. In this stage, calcium deposition may contribute to stiffening of the pericardium. The possible etiologies of constrictive pericarditis are shown in Table 1
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. Idiopathic - nearly half of cases . Post Viral Pericarditis . Tuberculosis - 15 % of cases in developed nations . Postsurgical . Prior Mediastinal Radiation Therapy . Chronic Renal Failure Treated with Hemodialysis . Connective Tissue Disorders . Neoplastic Pericardial Infiltration . Incomplete Drainage of Purulent pericarditis . Fungal and Parasitic Infections . Following Pericarditis Associated with Acute Myocardial Infarction . Following Postmyocardial Infarction ( Dressler ) Syndrome . In Association with Pulmonary Asbestosis |
The symmetrical constricting effect of the pericardium results in elevation and equilibrium of diastolic in all four cardiac chambers, as well as of pulmonary capillary wedge pressure. In early diastole, when intracardiac volume is less than that defined by the stiff pericardium, diastolic filling is unimpeded and early diastolic filling abnormally rapidly because venous pressure is elevated. Rapid early diastolic filling is abruptly halted when the intracardiac volume reaches the limit set by the noncompliant pericardium.
As virtually all filling of the ventricles occur very early in diastole, this abnormal pattern of filling is reflected in the characteristic dip-and-plateau waveforms in ventricular volume - time plots. The early diatolic dip corresponds to the period of excessively rapid filling, while the plateau corresponds to the period of mid and late diastole when there is little aditional ventricular volume expansion. Because the atria are equilibrated with the ventricles in early diastole, the jugular venous waveform and right and left atrial waveforms show a prominent and deep y descent. The systolic x descent is usually also present, and the venous waveform may therefore exhibit a characteristic M or W configuration. This pattern of venous return contrasts with that in cardiac tamponade, in which cardiac compression is present throughout diastole, so that the diastolic surge is blunted or abolished such that the atria fill during ventricular ejection in early systole and the venous pressure tracing shows absence of or blunted diastolic y descent.
Another striking abnormality of constrictive pericarditis is the failure of intrathoracic pressure changes during respiration to be transmited to the pericardium and intracardiac chambers. As a consequence, during inspiration, systemic venous and right arterial pressures do not fall and venous flow into the right ventricle does not increase, in contrast to the situation in normal subjects and patients with cardiac tamponade. In some patients, systemic venous pressure may actually increase with inspiration, i.e., Kussmauls’s sign. This finding may occur in other disorders such as chronic right ventricular failure and restrictive cardiomyopathy. However, it does not occur in acute cardiac tamponade, in which the inspiratory fall in intrathoracic pressure to the fluid-filled pericardial space. Pulsus paradoxus ( the inspiratory fall of aortic systolic pressure greater than 10 mm Hg ) is also less common in constrictive pericarditis than in cardiac tamponade, in which the exagerated increase in right ventricular filling during inspiration at the expense of left ventricular filling is more prominent. Table 2 resumes the differential features of tamponade and constrictive pericarditis.
The symptoms and signs of constrictive pericarditis result from (1 ) reduced cardiac output ( fatigue, hypotension, reflex tachycardia ), (2 ) elevated systemic venous pressure ( jugular venous distension, hepatomegaly with marked ascites and peripheral edema ) and (3 ) pulmonary venous congestion ( exertional dyspnea, cough and orthopnea ). Chest pain typical of angina may be related to underperfusion of the coronary arteries or compression of an epicardial coronary artery by the thickned pericardium. Because the most impressive physical findings are often the insidious development of ascites of hepatomegaly and ascites, such patients are often mistakenly tought to suffer from hepatic cirrhosis or an intraabdominal tumor. It is only after a careful inspection of the jugular veins that a cardiac source is identified.
Beside those signs discussed earlier ( Kussmaul’s sign and prominent y waves in the jugular pulse ), the most impressive abnormality is during auscultation, in which a characteristic diastolic pericardial “ Knock “ ( an early diastolic sound that is often heard along the left sternal border following S2 ) occurs. It represents the sudden cessation of ventricular diastolic filling imposed by the rigid pericardial sac. It tends to occur earlier than and to have a higher acoustic frequency than the typical S3 gallop sound, and therefore it may be confused with the opening snap of mitral stenosis.
The chest radiograph in constrictive pericarditis shows a normal or mildly enlarged cardiac silhouette. Calcification of the pericardium is detected in up to 50 % of patients. However, this finding is not specific for constrictive pericarditis in that a calcified pericardium is not necessarily a constricted one. The lateral chest film is particularly useful for its detection in the atrioventricular groove or along the anterior and diaphragmatic surfaces of the right ventricle. Pleural effusions are present in about 60 % of patients, and persistent unexplained pleural effusions can be the presenting manifestation.
The EKG findings include low QRS voltage, generalized T wave inversion or flattening, and left atrial abnormalities suggestive of P mitrale (left atrial enlargment ). Atrial fibrillation occurs in less than half of patients. An unusual pattern that simulates right ventricular hypertrophy with right axis deviation may be present in about 5 % of patients.
Echocardiographic evidence of constriction is subtle; the pericardium, if well imaged, is thickened; the ventricular cavities are small and contract vigorously, and diastolic filling terminates abruptly in early diastole ( best documented by doppler flow analysis ).
CT or MRI are superior in the assessment of pericardial anatomy and thickness. In assessing the role of this expensive imaging modalities, it must be emphasized that severe constrictive physiology can occur in the presence of a diseased but minimally thickened pericardium, whereas pericardial thickening or calcification alone are not diagnostic of hemodynamically significant constrictive pericarditis.
The diagnosis is confirmed by cardiac catheterization. There are three key features : (1) elevation and equalization of the diastolic pressures in each of the cardiac chambers, (2) the right and left ventricular tracings show an early diastolic “ dip-and-plateau “ configuration, and (3) the right atrial pressure tracing shows a prominent Y descent. The hemodynamic findings in constrictive pericarditis can be similar to those of restrictive cardiomyopathies, the last being suggested by finding a marked right ventricular systolic hypertension ( pressure > 60 mm Hg ) and left ventricular diastolic pressure exceding right ventricular diastolic pressure by more than 5 mm Hg. Distinguishing these conditions is important because pericardial constriction is fully treatable, whereas most cases of restrictive cardiomyopathies are not. An edomyocardial biopsy is somethimes necessary to distinguish between these, as it is abnormal in the latter.
Chronic constrictive pericarditis is a progressive disease without spontaneous reversal of either pericardial abnormalities, symptoms or hemodynamics. A minority of patients may survive for many years with modest jugular venous distension and peripheral edema that is controlled by the judicious use of diet and diuretics. Drugs that slow the heart rate, such as beta blockers and calcium channel blockers should usually be avoided because mild sinus tachycardia is a compensatory mechanism. The majority of patients become progressively more disabled and subsequently suffer the complications of severe cardiac cachexia.
Treatment for constrictive pericarditis is complete resection of the pericardium. Attention must also be paid to th presence of associated right atrial thrombosis, which can partly obstruct the tricuspid valve and should be managed with thrombectomy at the time of pericardiectomy. Changes in technique have included the use of median sternotomy rather than left thoracotomy cadiopulmonary bypass to permit greater mobilization of the heart, and performance of pericardiectomy earlier in the course of the disease prior to the cardiac cachexia and dense pericardial calcifications ( which carries a higher surgical mortality ).
The operative mortality is reported to be between 5 and 20 % in highly experienced centers, a low output syndrome occuring in up to 30 % of patients in the immediate postoperative period. Among the patients who survive the operation, symptomatic improvement can be expexted in about 90 % and complete relief of symptoms in 50 %. Five year survival ranges from 75-85 %, depending on how early surgery is performed.
Pericardiectomy probably should not be routinely attempted in very elderly patients with severe liver dysfunction, cachexia, densely calcified pericardium and massive cardiac enlargment indicative of underlying myocardial damage or in patients with limited life expectancy. In some patients, improved hemodynamics may be delayed for weeks to months after surgery, in can be attributed to imcomplete pericardial resection ( sometimes the visceral pericardium must also be resected ), myocardial atrophy or fibrosis caused by the inflamatory process and the development of recurrent cardiac compression by mediastinal inflamation and fibrosis.
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