Coxsackie B virus is the most frequent cause of viral myocarditis. There is a presumed myocardial membrane affinity for these viral particles.
Human immunodeficiency virus (HIV) infection is associated with myocardial involvement in 20-25% of infected patients, but clinical disease is noted in only 10% of HIV-infected patients. Dilated cardiomyopathy presenting as congestive heart failure is the usual presentation, although pericardial effusion is also noted with some frequency. Less commonly noted are marantic endocarditis, ventricular arrhythmia, and right ventricular dilatation or hypertrophy.
Lassa fever is caused by an arenavirus and is a major cause of death in West Africa. Involvement is usually subclinical with one-half of the patients showing ST changes and low voltage on an ECG.
Myocarditis was frequently seen in fatal cases of poliomyelitis, especially during epidemics in the past.
List the bacterial diseases often associated with myocarditis and their characteristic presentations.
Clostridium perfringens infection: These infections commonly involve the heart, with myocardial changes due to toxin produced by the bacteria. The characteristic pathologic finding is gas bubbles in the myocardium. Abscess formation with resultant rupture into the pericardium and subsequent purulent pericarditis is seen.
Diphtheria: Myocardial involvement is very common (up to 20% of cases) and is the most common cause of death from this organism. The bacteria-produced toxin, which interferes with protein synthesis, is the basis for the cardiac damage. On pathologic examination, the heart shows streaks,‚ and microscopic examination reveals fatty infiltration of the myocytes. Clinically the myocarditis usually presents a cardiomegaly and severe congestive heart failure. Antitoxin should be administered as soon as the diagnosis is made, and antibiotic therapy then instituted. Conduction disturbances are common and may require a pacemaker. Some studies indicate that early treatment with carnitine ameliorates the course of the myocarditis.
Meningococcal infection: Cardiac involvement is common in fatal infections. Congestive heart failure, pericardial effusion, tamponade, and involvement of the atrioventricular node with resultant heart block may occur.
Mycoplasma pneumonia: This infection commonly involves the heart, with subclinical findings such as ST and T-wave changes noted on ECG. Pericarditis with an audible friction rub is noted on occasion.
Psittacosis: Myocarditis is a common finding with this infection. Cardiac involvement usually presents as congestive heart failure and acute (often fibrinous) pericarditis. Immediate treatment with tetracycline is indicated.
Whipple disease: Intestinal lipodystrophy is associated with rod-like organisms in the intestine and myocardium. The organism and mechanism of damage to the myocardium have not been elucidated. Cardiac involvement includes coronary artery lesions (panarteritis) and valvular fibrosis. Antibiotic therapy is reported to be effective in the treatment of the underlying disease.
Spirochete infections: Leptospirosis (Weil’s disease), Lyme carditis, syphilis, and, in Ethiopia, relapsing fever have myocardial involvement.