Contributions of intramyocardial sinusoids in pulmonary atresia and intact ventricular septum to a right-sided circular shunt.

In the patient with congenital heart disease, the phenomenon termed 'circular shunt' implies that some of the right-to-left shunted blood returns to its chamber of orgin through intracardiac channels or communications, hence bypassing the systemic capillary bed. We are reporting the angiographic appearance of a right-sided 'circular shunt' in 2 patients with pulmonary atresia, diminutive, hypertensive right ventricle, and intact ventricular septum. In these patients the intramyocardial sinusoids and diverticulaform the anatomical basis for the right-sided 'circular shunt': blind, hypertensive right ventricle->intramyocardial sinusoids-1coronary artery--coronary venous system-*coronary sinus--right atrium--right ventricle. It is suggested that retrogradeflow through these intramyocardial sinusoids may impede or limit normal diastolic coronary artery perfusion and may predispose to myocardial ischaemia and dysfunction. In addition, the natural history of these intramyocardial sinusoids and diverticula is discussed.