The conduction system in transplanted hearts.

This is a serial section examination of the conduction system (CS) in six patients who died seven months, 11 months, two years four months, four years two months, 11 years, and 16 years eight months following cardiac transplantation. The heart was hypertrophied and enlarged in all. There was myocarditis of varying degree in all cases with arteriosclerosis and arteriolosclerosis. These findings were more dominant in the atria than in the ventricles. In the CS, myocarditis with fibrosis was found in all in the approaches to the sinoatrial (SA) node, the SA node, the atria, the atrioventricular (AV) node, and the bundle and bundle branches, to a varying degree. When compared with the endomyocardial biopsy findings, the autopsied cases revealed more myocarditis and fibrosis than those estimated to be present in the biopsy specimen. In summary, this study demonstrates that there are fibrotic changes in the CS with the persistence of inflammatory phenomena of the myocardium and the CS to a varying degree in transplanted hearts. This is accompanied by the ubiquitous coronary artery disease affecting not only the large coronaries but also the small vessels. The pathologic changes in and around the CS may be responsible for arrhythmias and sudden death in some cases of cardiac transplantation.