[A case of brain stem encephalitis complicated with bifascicular block caused by rubella virus].

We reported a case of a 29-year-old man who had been in good health until contracting brain stem encephalitis due to a rubella virus 5 years previously, at which time the ECG revealed complete right bundle branch block and right axis deviation. An ECG obtained 6 months earlier had been within normal limits. Since yearly health checkups continued to show the same abnormalities, the patient was admitted for closer examination. At the time of admission, physical findings and blood tests revealed no abnormalities. No cardiomegaly nor pulmonary congestion was observed on chest X-rays either at the time of the original illness or at this time. An endomyocardial biopsy specimen obtained from the right ventricle revealed size variation of cardiac myocytes, moderate disarrangement, and mild myocardial interstitial fibrosis, indicative of post-myocarditic changes. The above findings suggest that bifascicular block (right bundle branch and posterior fascicle) appeared at the time of the rubella virus infection, in the pathogenesis of which the involvement of myocarditis was strongly suspected. Some patients developing myocarditis do not manifest cardiac symptoms such as heart failure. In these cases, conduction disturbances are the sole sequelae. To differentiate pathogenesis in such cases, endomyocardial biopsy was thought to be of value.