Interatrial Communication and Left Atrial Hypertension

The combination of left atrial hypertension and a small atrial septal defect was observed in three patients and was found to be responsible for a continuous heart murmur. Mitral stenosis was present in two patients, and mitral atresia in the third. The continuous murmurs were loudest over the lower sternum, were augmented by inspiration, and were reduced or abolished by the Valsalva maneuver. Cardiac catheterization studies demonstrated the presence of a left-to-right shunt at the atrial level in each instance. The continuous murmurs were localized to the right atrium by intracardiac phonocardiography in two patients, and alterations in the interatrial pressure gradient during respiratory maneuvers were documented.