Pericarditis

The pericardium encloses most of the heart, the ascending aorta, the pulmonary trunk, and the terminal segment of the venae cavae. Serving primarily to anchor the heart in the central thorax and reduce its contact with surrounding structures, the pericardium is composed of two layers, a serous visceral layer adherent to the heart and a fibrous parietal layer. The space between the two layers is lubricated by a small amount of clear fluid, an ultrafiltrate of plasma. The pericardium receives its blood supply from the internal mammary arteries and is innervated by the phrenic nerves.Acute pericarditis is an inflammatory condition that can arise from a wide variety of causes, most commonly infection, autoimmune disease, rheumatic fever, uremia, malignancy, as a reaction to a drug, or after cardiac surgery. Up to one third of cases have no identifiable cause and are considered idiopathic.Viral infection is the most common cause of pericarditis in children. In most cases, patients report a 10- to 14-day prodrome of respiratory or gastrointestinal illness. Coxsackievirus, echovirus, adenovirus, Epstein-Barr virus, influenza virus, and human immunodeficiency virus are some of the most common responsible agents. Patients who have viral pericarditis present with fever and chest pain, and most have a friction rub. Viral pericarditis, unlike the other infectious disorders, often is accompanied by myocarditis.Bacterial pericarditis, although less common, is associated with a higher mortality rate than viral disease. Patients appear toxic and have high temperatures, irritability, and chest pain. Cardiomegaly frequently is present on chest radiograph. The infection may be primary following thoracic surgery or secondary to spread from another site, such as pneumonia. Staphylococcus aureus and Haemophilus influenzae are the two most common bacterial pathogens.Tuberculous pericarditis, although rare, still is seen in immunocompromised patients and in areas where tuberculosis is endemic. Spread either directly from mediastinal lymph nodes or bloodborne from a distant site, tuberculous pericarditis usually presents without the typical pulmonary or extrapulmonary symptoms of tuberculosis. Affected patients often develop large pericardial effusions, and cardiac tamponade is common. Prior to the advent of antituberculous agents, this infection was fatal in most cases.Pericarditis also can develop from noninfectious mechanisms. In autoimmune disease, such as juvenile idiopathic arthritis and systemic lupus erythematosus, pericarditis can precede the rheumatologic diagnosis. Uremic pericarditis occurs with end-stage renal disease and correlates with the degree of azotemia. Drug-induced pericarditis is a lupuslike syndrome and has been particularly associated with hydralazine, isoniazid, and procainamide. Lastly, a variety of solid and hematologic malignancies can lead to pericardial metastases, causing neoplastic pericarditis.Regardless of the cause, pericarditis presents primarily with chest pain, which tends to be substernal, sharp, worse with inspiration, and relieved by sitting upright and leaning forward. The pain typically radiates to the scapular ridge due to irritation of the phrenic nerves. More specific symptoms of pericarditis depend on the cause.On physical examination, the pathognomonic finding is the pericardial friction rub, a scratchy, high-pitched, to-and-fro sound caused by the inflamed pericardial surfaces rubbing together during cardiac motion. Loudest when the patient is upright and leaning forward, the sound is heard best in the second to fourth intercostal spaces along the left sternal border or the midclavicular line.Patients who have acute pericarditis have laboratory evidence of systemic inflammation, such as elevations of the white blood cell count, erythrocyte sedimentation rate, and C-reactive protein value. The plasma troponin concentration also may be increased, reflecting myocardial involvement. To determine the specific cause, blood cultures, viral cultures, tuberculin skin testing, gastric cultures for Mycobacterium, and measurement of rheumatoid factor and antinuclear antibody may be helpful.In acute pericarditis, electrocardiography (ECG) is the most useful diagnostic test. The changes seen on ECG demonstrate the effect of the inflamed pericardium on the underlying myocardium. Classically, the ECG findings evolve through four stages: The duration of the ECG changes depends on the cause and extent of myocardial damage.In the presence of pericarditis with a pericardial effusion, the fluid in the pericardial space insulates the heart, resulting in a low-voltage QRS complex on ECG. In most cases, the amplitude of the QRS complex returns to normal after the pericardial effusion resolves or is drained. In cardiac tamponade, the ECG can reveal electrical alternans, a cyclic variation in the amplitude of the QRS complex caused by excessive motion of the heart within a fluid-filled pericardial sac.A chest radiograph usually appears normal in patients who have acute pericarditis. However, the image may reveal lung or mediastinal abnormalities responsible for the disease. When a significant pericardial effusion is present, the heart may have a triangular shape with a smooth border, known as a “water-bottle heart.”Echocardiography is a rapid, accurate, and noninvasive modality to evaluate pericardial and cardiac morphology. In acute pericarditis, results may be normal or may reveal the presence of an effusion. Although the finding of a pericardial effusion in a patient suspected of having pericarditis supports the diagnosis, the absence of an effusion or other abnormalities on echocardiography does not exclude it.Management of acute pericarditis should be aimed at identifying and treating the underlying cause. For patients who have idiopathic or viral pericarditis, therapy is directed at alleviating chest pain and inflammation. Nonsteroidal anti-inflammatory drugs (NSAIDs) are the mainstay of therapy, and symptoms resolve within days for most patients. Ibuprofen is the preferred first-line agent because it has the lowest incidence of adverse effects. Although helpful in treating acute pericarditis, NSAIDs do not prevent its complications. If chest pain persists beyond 2 weeks or recurrent pericarditis develops, colchicine can be added as another effective treatment.The use of corticosteroids in acute pericarditis remains controversial. Steroids pose the risk of significant adverse effects, including reactivating an infectious process through immunosuppression. In addition, observational studies suggest that patients treated with steroids early in the course of their disease are more likely to have a recurrence. Therefore, steroid use should be reserved for patients whose pericarditis is unresponsive to NSAIDs and colchicine and patients who have recurrent pericarditis or a rheumatologic disease.Complications of acute pericarditis include recurrence, constrictive pericarditis, and cardiac tamponade. Recurrent pericarditis is believed to be an immune-mediated process and occurs in approximately one third of patients. Constrictive pericarditis, the end stage of acute or chronic pericardial inflammation, results in a thickened, adherent pericardium that restricts filling of the ventricles. Cardiac tamponade occurs when a pericardial effusion rapidly exceeds the pericardial reserve volume, causing increased intrapericardial pressures and impaired filling. The result is decreased cardiac output, requiring emergent treatment. The hallmark finding of tamponade is pulsus paradoxus, defined as more than a 10-mm Hg drop in systolic blood pressure during inspiration.Pericardiocentesis is indicated in idiopathic pericarditis with hemodynamic compromise, cardiac tamponade, purulent pericarditis, and suspected neoplastic pericarditis. When pericardiocentesis is performed, the pericardial fluid should be evaluated for cell count and differential count, as well as sent for bacterial, fungal, and viral cultures. If malignancy is suspected, cytology of the fluid also should be performed. In resistant cases, a pericardial window (surgical incision in the pericardium) or pericardiectomy (surgical removal of part or all of the pericardium) may be necessary.Comment: Yes, a child who is suspected of having pericarditis is going to undergo echocardiography, but it's nice that in the age of magnetic resonance imaging and positron emission tomography scans, a physical examination with old-fashioned electrocardiography remains the best way to make the diagnosis and the least expensive.