Histologic findings in the conduction system after cardiac transplantation and correlation with electrocardiographic findings.

The study of the sinus node and the specialized atrioventricular junction by serial sections in cardiac transplantation revealed that acute rejection involving the conduction system was equally severe as the working myocardium, with the exception of the His bundle. During acute rejection, the sudden appearance of a first-degree atrioventricular block may suggest severe involvement of the conduction system with impending cardiac arrest.