ABSTRACT
OBJECTIVE: Myocarditis has been described as a complication of influenza. Patients with influenza may have symptoms and abnormal laboratory data (including chest X-ray, electrocardiogram, etc.) suggestive of myocarditis, although few observations have been made regarding the prevalence of asymptomatic myocardial injury. We investigated whether influenza can produce myocardial injury without cardiac symptoms. METHODS: During the epidemic of influenza A (H3N2) from 1998 to 1999 in Japan, we examined possible cardiac muscle damage associated with influenza in patients without apparent clinical myocardial injury by measuring serum myosin light chain concentrations. PATIENTS: Ninety-six influenza-positive patients (46 males and 50 females, average age 43.4 years) without impaired renal function were studied. RESULTS: Of these patients, 11 (11.4%) had elevated serum myosin light chain I concentrations. CONCLUSION: Asymptomatic myocardial injury may be present in patients with influenza even when they have no symptoms suggestive of myocardial injury.
