A 55-year-old white man with controlled hypertension and hypercholesterolemia awoke with mild chest discomfort that he believed was mild gastroesophageal reflux. He denied radiation of pain to the shoulders, arms, back, or neck; dyspnea; palpitations; diaphoresis; nausea/vomiting; cough; or fever, during the first 30 hours of discomfort. There was no change in discomfort with deep breath, palpation of the chest, or administration of antacids. Minimal, short-lived improvement was noted with belching.
The patient had no trouble sleeping in the prone position and did not notice an increase in discomfort or unusual difficulty during his daily vigorous 30-minute aerobic workout. In fact, his symptoms seemed to improve or disappear during exercise. The patient denied any recent illness or exposure to sick people, had not traveled outside the United States, and had not been exposed to radiation of the chest wall. At the end of the second day of discomfort, the patient noted irregular palpitations with mild shortness of breath and was transported to the hospital for evaluation. He denied being a cigarette smoker or illicit drug user.
The patient had no history of MI or diabetes. The patient’s father had an MI in his 80s, and two uncles died suddenly in their 50s of “massive heart attacks.” His mother, who had died of sepsis of uncertain etiology approximately 10 days earlier, also had hypertension and hypercholesterolemia but no history of coronary artery disease (CAD). Both of the patient’s adult daughters had been diagnosed with celiac disease in the preceding three years. His elder daughter had also been diagnosed with type 1 diabetes within the past two years.
On examination, the patient was afebrile, with a blood pressure of 143/87 mm Hg; pulse, 53 beats/min; and respiratory rate, 17 breaths/min. The patient’s weight was 204 lb and his height, 75 in (BMI, 25.5). The patient was in no apparent distress. Head, eyes, ears, nose, and throat were unremarkable. There was no significant jugular venous distention. The carotid pulses were full, and no bruits were appreciated. S1 and S2 sounds were within normal limits. No murmurs or S3 or S4 gallops were appreciated. The chest was clear on auscultation. Results of the abdominal exam were negative, no edema was noted in the extremities, and pulses were symmetrical.
ECG demonstrated subtle ST-segment elevation in leads I and aVL with a prominent R wave in lead V1. This pattern was interpreted as consistent with an acute inferolateral MI. A baseline ECG, previously obtained by the patient’s internist, had been interpreted as normal.
Peak troponin level was 55 ng/mL (normal, < 0.03 ng/mL); total creatine kinase (CK), 807 U/L (reference range, 20 to 259 U/L); and mass CK-MB fraction, 44 ng/mL (0.1 to 6.6 ng/mL). Total cholesterol was 105 mg/dL, with both LDL- and HDL-cholesterol fractions at 46 mg/dL. A complete blood count without differential revealed a total white blood cell count of 53,000/µL. Hemoglobin and hematocrit were both low (12.3 g/dL and 34.5%, respectively). All indices were within normal limits, as was the platelet count. Glucose, blood urea nitrogen, creatinine, potassium chloride bicarbonate, and calcium were all within normal limits. The sodium level was slightly low (132 mEq/L). Emergency catheterization revealed an ejection fraction of 45% (reference range, 55% to 70%), with mild-to-moderate diffuse hypokinesis but normal coronary arteries.
The patient was diagnosed with myocarditis, likely of viral origin.
DISCUSSION
Although the incidence of myocarditis in the US is difficult to assess, autopsy reports implicate it in 8.6% to 12% of cases of sudden cardiac death in young adults,1,2 and a large prospective series implicated myocarditis in 9% of cases of dilated cardiomyopathy.3 Myocarditis is considered to be at one extreme of a spectrum of perimyocardial processes that result in inflammation of the myocardium (see figure), pericardium, or both.4
The underlying pathology involves an acute injury to the myocyte. This activates the innate and humoral immune systems, resulting in severe inflammation. The immune reaction eventually subsides, and the myocardium recovers. In certain patients, however, myocardial inflammation persists, resulting in ongoing myocyte damage, relentless symptomatic heart failure, or even death.5
Although a variety of diagnostic criteria have been developed and employed, the diagnosis of myocarditis is often one of exclusion. First proposed in 1986, the Dallas criteria—a histopathologic classification for myocarditis diagnosis—are based on endomyocardial biopsy, with inflammatory cellular infiltrate (with or without associated myocyte necrosis) visible on conventionally stained myocardial tissue sections.5 However, this method poses significant practical limitations, including low sensitivity (43% to 64%) and complication and death rates of 6% and 0.4%, respectively.5,6