A topic in the Open Knowledge Graph — a free, open map of 15,290 topics and the order to learn them in.
Pericardial inflammation from viral infection, autoimmunity, or uremia causes fibrinous pericarditis and serous effusion. Large or rapidly accumulating effusions restrict ventricular filling, causing equalization of diastolic pressures and shock (tamponade). Constrictive pericarditis from chronic inflammation impairs diastolic function.
Your study of cardiac anatomy established that the pericardium is a two-layered fibrous sac surrounding the heart, normally containing only 15–50 mL of lubricating fluid. Its inner layer (visceral pericardium) is adherent to the epicardium; its outer layer (parietal pericardium) is tough and inextensible. This anatomical detail is the key to understanding every pericardial disease: the rigid outer layer means any pressure increase within the pericardial space is transmitted directly to the cardiac chambers, compressing them from outside.
From your study of acute inflammation, you know that any inflammatory stimulus causes vascular permeability changes, exudation of protein-rich fluid, and fibrin deposition. When this process involves the pericardium—typically from viral infection (coxsackievirus, echovirus), autoimmune disease, or uremia—the visceral and parietal layers become roughened with fibrin deposits. Patients classically experience pleuritic chest pain that worsens with lying flat and improves leaning forward—a positional pattern explained by the pericardial friction rub that occurs when inflamed surfaces move against each other, and by the fact that leaning forward reduces pericardial contact. The ECG hallmark is diffuse ST elevation in a saddle-shaped pattern across multiple leads, reflecting widespread pericardial inflammation rather than the focal ischemic ST elevation of myocardial infarction.
The transition to pericardial effusion occurs when inflammatory exudate accumulates faster than it can be reabsorbed. Here, the key physiological variable is not the volume of fluid but the *rate* of accumulation. The pericardium can slowly accommodate 1,000 mL or more if the effusion develops over weeks, because the fibrous outer layer gradually stretches. But rapid accumulation of even 150–200 mL can be fatal—the inextensible pericardium has no time to accommodate, and intrapericardial pressure rises sharply. This is cardiac tamponade: rising pericardial pressure compresses all four chambers during diastole, equalizing their filling pressures. When right atrial, right ventricular, and pulmonary capillary wedge pressures all converge at the same elevated level, ventricular filling is severely impaired. Cardiac output collapses, triggering the compensatory tachycardia and hypotension of obstructive shock. The clinical triad—hypotension, distended neck veins, and muffled heart sounds—is called Beck's triad. The treatment is immediate pericardiocentesis: needle drainage of the sac reduces intrapericardial pressure and immediately restores ventricular filling.
Constrictive pericarditis is the chronic endpoint of recurrent or tuberculosis-related pericarditis: the pericardial sac becomes fibrotic, calcified, and adherent, forming a rigid shell that permanently impairs diastolic filling. Unlike tamponade (a fluid pressure problem), constriction is a structural encasement problem—the heart beats within a shell it cannot expand against. The hemodynamic signature—equalized diastolic pressures, prominent venous waveforms, and respiratory variation in ventricular filling—can mimic restrictive cardiomyopathy, but correct identification matters enormously because pericardiectomy (surgical removal of the pericardium) can be curative in constriction.