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Chapter 63: Myocarditis

A 42-year-old man presents with two weeks of dyspnea on exertion, pedal edema, and orthopnea. One month ago, he had a mild febrile illness. Echocardiography confirms reduced left ventricular (LV) systolic dysfunction. Serologies are suggestive of a viral myocarditis secondary to coxsackievirus B3. Which of the following is not true regarding coxsackie-mediated viral myocarditis?

A. Myocardial infection is initiated by the transmembrane coxsackievirus-adenovirus receptor (CAR)

B. Cell damage is induced by direct cytotoxicity and is mediated by viral proteinases

C. Patients with defects of dystrophin and dysferlin demonstrate increased susceptibility to myocardial CV-B3 infection

D. The early innate immune response results in direct myocyte injury

E. All of the above are true

The answer is D. (Hurst’s The Heart, 14th Edition, Chap. 63) The cardiotropic coxsackievirus B3 (CV-B3) is one of the most common causes of myocarditis.1 The myocardial infection is initiated by the transmembrane CAR; the ablation of CAR blocks viral affliction of myocardial cells and inflammation in the myocardium in experimental models (option A).2 In CV-B3–infected myocytes, the cell damage is induced by direct cytotoxicity and mediated by viral proteinases (option B).3 Patients with defects of dystrophin and dysferlin demonstrate increased susceptibility to myocardial CV-B3 infection by enhancing viral propagation to adjacent cardiomyocytes and disrupting membrane repair function (option C).4-6 In viral infections, the early innate immune response provides the first defense mechanism and is mediated by cytokines. However, the late adaptive immune response contributes to the myocardial lymphocyte infiltration that must clear virus-infected cardiac myocytes in CV-B3 myocarditis and endothelial cells in parvovirus B19 myocarditis. Although this mechanism clears the virus, it also results in myocyte injury (option D).

Which of the following is not associated with a poor outcome after a diagnosis of viral myocarditis?

A. New York Heart Association (NYHA) classes III to IV symptoms at 6 months

B. Biventricular dysfunction at the time of diagnosis

C. The presence of late gadolinium enhancement (LGE)

D. High rate of cardiomyocyte apoptosis on biopsy

E. Presentation with heart failure symptoms

The answer is D. (Hurst’s The Heart, 14th Edition, Chap. 63) Predictors of outcome vary in different myocardial biopsy studies. Persistence of New York Heart Association (NYHA) classes III to IV, left atrium enlargement, and improvement in LVEF at 6 months emerged as independent predictors of long-term outcome in one study (option A).7 Biventricular dysfunction at diagnosis was the main predictor ...

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