Microcirculation and microstructure of coronary beds in Kawasaki Disease

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We encountered 9 patients with Kawasaki disease with ischemic findings on exercise stress tests, but without a stenotic lesions on coronary arteriography. 8 out of these 9 patients had a reduced coronary flow reserve due to reduced dilatory capacity of the small coronary arteries that are not visualized by coronary arteriography.To clarify the pathogenesis of reduced coronary flow reserve in Kawasaki disease, in this research, we examined ultrastructually the myocardial lesions and coronary bed in 8 patients with reduced coronary flow reserve described above, in comparison with 6 patients without reduced coronary reserve. The duration of illness is from 4 months to 15 years. All patients are still alive, but the persistent damages of myocardium and vasculature are found even after 15 years. Ultrastructurally, the myocardial changes are non-specific, showing hypertrophy and degeneration with bizarre nuclei, disarranged myofibrils and aggregative mitochondria with abnormalities. The vascular lesions included microaneurysm formation, endothelial cell projection and necrosis, and platelet thrombosis in both capillary and arteriole. Interstitial edema and fibrosis are also encountered.In this study, we emphasized that the vascular lesions have a progressive potential danger, which are one of the important factors induced the reduced coronary flow reserve and the persistent myocardial lesions in Kawasaki disease, though there is no active inflammation or other evidence seen in active phase of this disease.