The atrioventricular conduction system in dissecting aneurysm of the aorta.

In dissecting aneurysm of the ascending aorta the hemorrhage may spread into the interatrial septum and into the area of the specialized atrioventricular junctional tissue. A clinicopathologic investigation has been performed in 48 cases with classical complete dissecting aneurysm in order to evaluate whether such hemorrhage may lead to conduction disturbances. Among 42 cases with aortic dissection originating in the ascending aorta, eight hearts (19 per cent) presented with hemorrhagic infiltration of the atrial septum, extended to the coronary sinus. Histologic examination of the atrioventricular conduction tissues was performed in six of these hearts and in five without such gross evidence (“controls”). In the former the hemorrhage had spread between the transitional cell zone of the atrioventricular junctional area, but never actually penetrated the compact node. In none of the “controls” was there any histological evidence for hemorrhage. The correlation between the histologic data and the available electrocardiographic findings disclosed that atrioventricular conduction disturbances, including atrioventricular dissociation, were present only in cases with hemorrhage of the atrial septum. It is suggested that: (a) hematoma of the interatrial septum is not at all infrequent in cases with dissection of the ascending aorta, (b) this complication leads to atrioventricular conduction disturbances, (c) the hemorrhage preserves a large part of the atrioventricular junctional tissues, thus explaining the occurrence of the atrioventricular dissociation with junctional rhythm and eventual restoration of the normal conduction.