10-50: Acute Inflammatory Pericarditis

ESSENTIALS OF DIAGNOSIS

GENERAL CONSIDERATIONS

Acute (less than 2 weeks) inflammation of the pericardium may be infectious in origin or may be due to systemic diseases (autoimmune syndromes, uremia), neoplasm, radiation, drug toxicity, hemopericardium, postcardiac surgery, or contiguous inflammatory processes in the myocardium or lung. In many of these conditions, the pathologic process involves both the pericardium and the myocardium. Overall pericarditis accounts for 0.2% of hospital admissions and about 5% of patients with nonischemic chest pain seen in the emergency department. The ESC in 2015 proposed four categories of pericarditis: acute, incessant, current, and chronic. Each category has its own diagnostic criteria. In acute pericarditis, there are four criteria: (1) pericardial chest pain, (2) pericardial rub, (3) new widespread ST-elevation or PR depression, and (4) new or worsening pericardial effusion. To establish the diagnosis of acute pericarditis, at least two of these four criteria must be present. Incessant pericarditis is defined by its duration; it lasts longer than 4–6 weeks but less than 3 months without remission. Recurrent pericarditis can be diagnosed in a patient with one reported episode of pericarditis who has been symptom free for at least 4–6 weeks. Finally, chronic pericarditis is diagnosed when it persists for more than 3 months.

Viral infections (especially infections with coxsackieviruses and echoviruses but also influenza, Epstein-Barr, varicella, hepatitis, mumps, and HIV viruses) are the most common cause of acute pericarditis and probably are responsible for many cases classified as idiopathic. COVID-19 has been associated with both acute pericarditis and even cardiac tamponade. Males—usually under age 50 years—are most commonly affected. The differential diagnosis primarily requires exclusion of acute MI. Tuberculous pericarditis is rare in developed countries but remains common in certain areas of the world. It results from direct lymphatic or hematogenous spread; clinical pulmonary involvement may be absent or minor, although associated pleural effusions are common. Bacterial pericarditis is equally rare and usually results from direct extension from pulmonary infections. Pneumococci, though, can cause a primary pericardial infection. Borrelia burgdorferi, the organism responsible for Lyme disease, can also cause myopericarditis (and occasionally heart block). Uremic pericarditis is a common complication of CKD. The pathogenesis is uncertain; it occurs both with untreated uremia and in otherwise stable dialysis patients. Spread of adjacent lung cancer as well as invasion by breast cancer, renal cell carcinoma, Hodgkin disease, and lymphomas are the most common neoplastic processes involving the pericardium and have become the most frequent causes of pericardial tamponade in many countries. Pericarditis may occur 2–5 days after infarction due to an inflammatory reaction to transmural myocardial necrosis (post-MI or postcardiotomy pericarditis [Dressler syndrome]). Radiation can initiate a fibrinous and fibrotic process in the pericardium, presenting as subacute pericarditis or ...