Pericarditis

The pericardium is a double-layered, fibroelastic sac surrounding the heart, consisting of a visceral layer over the epicardium and a richly innervated parietal layer, separated by a potential space that normally holds 15 to 50 mL of serous fluid. Pericarditis refers to inflammation of the pericardial sac surrounding the heart and is the most common pathological condition affecting the pericardium. This condition can be classified into acute, incipient or subacute, chronic, and recurrent pericarditis, which is estimated to occur in about 15% to 30% of cases. Pericarditis may also present alongside other pericardial syndromes, including pericardial effusion, cardiac tamponade, constrictive pericarditis, and effusive-constrictive pericarditis. Pericardial inflammation often leads to fluid accumulation within the pericardial sac, resulting in a pericardial effusion, which can be serous, hemorrhagic, or purulent, depending on the etiology. The fluid accumulation can become hemodynamically significant, especially if the effusion is large or accumulates rapidly, as the fluid may extrinsically compress the cardiac chambers, restrict diastolic filling, and lead to cardiac tamponade. This condition can present with obstructive shock and is considered a medical emergency that requires immediate intervention. Additionally, pericarditis may lead to pericardial thickening, which can rarely manifest as constrictive pericarditis months or even years after the initial insult. A more recently described condition known as effusive-constrictive pericarditis occurs when fluid accumulates around the heart, yet constrictive physiology, eg, respiratory-enhanced interventricular dependence, a restrictive E/A filling pattern (ratio of early [E] to late [A] diastolic velocities), and mitral annulus reversus with septal e' velocity greater than lateral e'—persists even after pericardiocentesis. This indicates the presence of constrictive pathology that is independent of the pericardial effusion. The aforementioned pericardial syndromes may occur alongside acute pericarditis but are not required for its diagnosis.