Isolated anomalous right ventricular muscle bundle in the asymptomatic adult.

Muscular obstruction to right ventricular outflow is usually at the infundibular level, but, less commonly, it can occur within the body of the ventricle due to an anomalous muscle bundle. This lesion is almost always associated with a ventricular septal defect or other cardiac lesions, and is usually discovered in infancy or childhood. Two asymptomatic adults with severe obstruction due to right ventricular muscular band as an isolated lesion are presented. The lesion can be tentatively diagnosed on clinical grounds and confirmed by angiocardiography. The advisability of surgical correction in the asymptomatic adult with such an isolated lesion is uncertain.