Angiocardiography of obstructing muscular bands of the right ventricle

Two types of obstructing anomalous muscle bundle are described on the basis of right ventricular angiocardiographic analysis in 28 patients. In the low type the anomalous muscle bundle is located in the midsinus of the right ventricle; in the high type it lies at the subinfundibular level. Ocassionally, both forms of obstruction exist in the same individual. A ventricular septal defect was present in 24 of the 28 patients (85%). Serial catheterizations at a mean interval of 6.6 years demonstrated progession of the obstruction in eight of 15 patients. Differentiation of anomalous muscle bundle from tetralogy of Fallot is facilitated by clear angiographic delineation of the anomalous muscle and the position of the parietal band in most cases, but may not be possible when both anomalies occur together.