Ruptured aneurysm of aortic sinus of Valsalva into right atrium. Associated atrioventricular block presumable caused by aneurysmal compression of His bundle.

We have seen a case of rupture of an aneurysm of the noncoronary sinus into the right atrium. Surgery revealed an aneurysmal mass the size of the tip of an index finger extending through the inter-atrial septum down to just above the tricuspid valvular ostium. An electrocardiogram showed first-degree atrioventricular block, while the His bundle electrogram demonstrated the presence of disturbances in the intra-atrial as well as His bundle conduction. The disturbance in His bundle conduction was interpreted as being due to compression of the His bundle by the aneurysm.