Y. Suwa

Small vessel pathology and coronary hemodynamics in patients with microvascular angina

We studied the ultrastructure of cardiac myocytes and small blood vessels obtained by endomyocardial biopsy from 21 patients with microvascular angina. Ischemic ST segment depression during atrial pacing was recognised in all the patients who had normal coronary arteriograms and biopsy tissues were examined by light and electron microscopy. In patients with microvascular angina, insufficient increases in coronary sinus blood flow and in myocardial oxygen consumption measured with a Websters catheter were apparent during atrial pacing. Biopsy samples under the light microscope showed evidence of myocardial hypertrophy and sclerosis of small arteries and arterioles with perivascular fibrosis in 18 of 19 (95%) patients. Electron microscopy revealed that many endothelial nuclei in capillaries were swollen and that lumina of small arteries and arterioles were irregularly narrowed with proliferated and deformed medial smooth muscle cells. These findings suggest that disturbances in the coronary microcirculation in these patients is responsible for the ischemic changes in electrocardiograms.

Electron Microscopic Cytochemical Studies on ATPase and Acid Phosphatase Activities of Cardiac Myocytes in Streptozotocin Induced Diabetic Rats

It has often been reported that a crisis of congestive heart failure is frequently observed in patients with diabetes mellitus independent of coronary artery disease or hypertension (1). In this respect, a contraction/relaxation disorder of the cardiac muscle has also been noted in animal experiments. The dysfunction of the heart observed in diabetes is known as so-called diabetic cardiomyopathy (2). However for its causes, while complex factors such as intramyocardial microangiopathy and myocardial metabolic disorder caused by diabetes are suspected, a definitive conclusion has not yet been drawn.

Biochemical and Morphologic Alterations in Cardiac Myocytes in Streptozotocin-Induced Diabetic Rats

Complication of congestive heart failure in patients with diabetes mellitus has well been known in clinical practice. Impairment of cardiac function was recognized in the absence of arteriosclerotic changes in diabetics, and the concept of “diabetic cardiomyopathy” has been proposed as the diabetes specific myocardial disorder (1,2). In the clinical practice, diabetes mellitus occurs in the mature to elder age and complication of coronary arterio- or athero-sclerosis is usual. Therefore, influence of ischemia could not be excluded in clinical cases. To elucidate effect of hyperglycemic state on cardiac myocytes without vascular changes, experimental diabetes was induced in relatively young rats by single intravenous injection of streptozotocin (STZ), and the effects of abrupt and long-standing severe hyperglycemia on the cardiac micro organs such as the sarcoplasmic reticulum (SR) and the structural proteins were investigated in comparison with the fine structures of cardiac myocytes.