Cardiac conduction system in hemochromatosis: Clinical and pathologic features of six patients

Abstract

Iron deposition in the heart in patients with hemochromatosis often occurs in association with congestive heart failure and electrocardiographic abnormalities including arrhythmias and conduction disturbances. Whether these disturbances are due to direct involvement of the specialized conduction tissue of the heart is uncertain. The conduction system and the walls of the four chambers in the hearts of six patients with exogenous or secondary hemochromatosis were studied at autopsy to determine if there is an association between clinically manifested myocardial dysfunction and iron storage in fibers of the specialized conduction tissue. In all cases iron deposits were present in the myocardium of all four chambers although always to a lesser extent in the atria than in the ventricles. No differences in iron deposition were demonstrated in the right, septal and left ventricular walls or within the transmural extent of the walls themselves. Two patients had myocardial muscle cell necrosis, possibly attributable to severe cardiac iron deposition. The cardiac conduction tissue revealed no iron deposition in one case, mild deposition in two cases and moderate deposition in three cases, uniformly staining less intensely for iron than the working myocardium. However, the degree of iron deposition varied in the components of the conduction system. The sinoatrial node, involved in only two cases, stained less intensely than the remaining conduction tissue. The atrioventricular (A-V) node had iron in four cases, and the bundle of His and its right and left branches usually stained with a similar intensity. Congestive heart failure was present in five of the six cases. Electrocardiographic abnormalities were present in only those cases that revealed iron involvement of the conduction system. Thus, there is a gradient of iron deposition in the heart in cases of hemochromatosis with working ventricular myocardium showing the most and the sinoatrial node the least involvement. Iron deposition in the A-V node and His bundle tissue occurs with severe myocardial iron storage and is associated with electrocardiographic abnormalities, most often supraventricular rhythm disturbances and less often conduction block.