Mumps (epidemic parotitis) is generally regarded today as an acute systemic disease of virus origin, having a special predilection for the parotid glands. Among the complications most familiar to the physician are acute orchitis, pancreatitis, meningitis and meningoencephalitis. Cardiac involvement has been considered rare and when observed has been described as either acute pericarditis or acute endocarditis. That the virus of mumps may also produce myocarditis was originally suspected by Pujol1 and by Barbato2 from their clinical observations, but no satisfactory evidence to support their contention was presented. Later, Manca3 reported the histologic changes in an instance of acute interstitial fibrinous myocarditis which occurred in a fatal case of mumps. He regarded this as a characteristic reaction to the mumps virus.
In January 1943, I had the unique opportunity of observing an instance of complete heart block in a patient convalescing from epidemic parotitis. From the electrocardiographic