Elevated serum myosin light chain I in influenza patients

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.

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.

Ninety-six influenza-positive patients (46 males and 50 females, average age 43.4 years) without impaired renal function were studied.

Of these patients, 11 (11.4%) had elevated serum myosin light chain I concentrations.

Asymptomatic myocardial injury may be present in patients with influenza even when they have no symptoms suggestive of myocardial injury.