DIABETES-MELLITUS AND CARDIAC-FUNCTION

Cardiovascular complications are the most common causes of morbidity a nd mortality in diabetic patients. Coronary atherosclerosis is enhance d in diabetics, whereas myocardial infarction represents 20% of deaths of diabetic subjects. Furthermore, re-infarction and heart failure ar e more common in the diabetics. Diabetic cardiomyopathy is characteriz ed by an early diastolic dysfunction and a later systolic one, with in tracellular retention of calcium and sodium and loss of potassium. In addition, diabetes mellitus accelerates the development of left ventri cular hypertrophy in hypertensive patients and increases cardiovascula r mortality and morbidity. Treating the cardiovascular problems in dia betics must be undertaken with caution. Special consideration must be given with respect to the ionic and metabolic changes associated with diabetes. For example, although ACE inhibitors and calcium channel blo ckers are suitable agents, potassium channel openers cause myocardial preconditioning and decrease the infarct size in animal models, but th ey inhibit the insulin release after glucose administration in healthy subjects. Furthermore, potassium channel blockers abolish myocardial preconditioning and increase infarct size in animal models, but they p rotect the heart from the fatal arrhytmias induced by ischemia and rep erfusion which may be important in diabetes. For example, diabetic per ipheral neuropathy usually presents with silent ischemia and infarctio n. Mechanistically, parasympathetic cardiac nerve dysfunction, express ed as increased resting heart rate and decreased respiratory variation in heart rate, is more frequent than the sympathetic cardiac nerve dy sfunction expressed as a decrease in the heart rate rise during standi ng.