Intracardiac causes of superior vena cava obstruction.

Most causes of superior vena cava (SVC) obstruction are extracardiac. In rare instances, an intracardiac process may obstruct the venous return from the SVC. This is illustrated by a report of a patient with a congenital coronary artery fistula to the right atrium obstructing the SVC return. We propose a classification and clinical approach to the differential diagnosis of SVC obstruction.