Pathology of the Cardiac Conduction System in Amyloidosis

Abstract

In 5 patients with amyloidosis and documented disturbances in cardiac rhythm or conduction the heart was examined postmortem with particular attention to the sinus node, AV [atrio-ventricular] node and His bundle. Amyloid was abundantly present in all areas of the conduction system in all patients. With the exception of one heart, in which the His bundle was more involved, the sinus node was the site of major destruction by amyloid infiltration and in 2 hearts the node was almost completely replaced by amyloid. Because the sinus node is so heavily involved by this disease, physicians attempting to restore sinus rhythm in patients with known or suspected amyloidosis should be aware that the sinus node may not be available as an efficient pacemaker. Similarly, unusual sensitivity to digitalis in patients with cardiac amyloidosis may be due to the amount of amyloid infiltrating the conduction system, destroying some of it and possibly rendering the rest functionally abnormal.