APOPTOTIC MYOCARDIAL DEGENERATION IN THROMBOTIC THROMBOCYTOPENIC PURPURA

The objective of this study was to determine whether the known myocard ial degeneration in TTP is due to apoptosis. In TTP the heart is often involved, including the cardiac conduction system. Despite many plate let occlusions of small coronary arteries, there is little myocardial necrosis. Why the intermittent clinical episodes begin or end is unkno wn. Six hearts of patients dying with TTP were examined with routine a nd immuno-histochemical stains. In addition to ventricular and atrial myocardium we examined the cardiac conduction system and coronary chem oreceptor. Numerous small coronary arteries were occluded with platele t thrombi in all these sites, including especially the sinus node, AV node and His bundle. The myocardial degeneration we found was conspicu ously devoid of inflammation and the myocytes were relatively intact. These characteristics combined with TUNEL-positivity in the degenerati ng cells are typical of apoptosis. The focal degeneration in TTP is pr imarily apoptotic. Because circulating serotonin is carried by platele ts and is released during aggregation, and because serotonin can cause a powerful cardiogenic hypertensive chemoreflex, we suggest that such a response may dislodge early platelet aggregations. Lessons from TTP may have special relevance for better understanding of myocardial rep erfusion problems associated with angioplasty, thrombolysis and ischem ic preconditioning.