Objective To investigate the cause of high cardiovascular lethality in patients with diabetics mellitus. Methods Sections from autopsied coronary arteries and myocardium of dead patients with non-insulin-dependent diabetics mellitus and 12 dead control subjects were used for histomorphometric studies. Results The coronary atherosclerotic lesion in diabetics patients was not different in severity from those in controls. Nor was there difference in number of myofibers or diameters of myocardic fibers and capillaries. But the capillary density and the ratio of capillary number to myocardic fiber number in diabetics group were significantly reduced compared with control group(P<0.01),and the capillary basement membrane in the former was significantly thicker than in the latter(P<0.01).Conclusion The decrease in number of capillaries and the thickening of basement membrane enhance myocardiac vulnerability to further ischemia and
hypoxia, which may undelie high lethality of myocardiopathy in diabetic patients.