MYOCARDIAL INSULIN-RESISTANCE IN PATIENTS WITH SYNDROME-X

Insulin resistance is common in patients with angina pectoris, a posit ive exercise electrocardiogram, and normal coronary angiograms (syndro me X). It is still not known whether insulin resistance affects the ca rdiac muscle itself and, if so, whether insulin resistance involves my ocardial hemodynamics and energy metabolism, We investigated hemodynam ics as well as metabolite exchanges across the heart and the forearm i n eight patients with syndrome X and eight control subjects during a b aseline period after an overnight fast and during a hyperinsulinemic-e uglycemic clamp. Myocardial hemodynamics and metabolism were studied a t rest, during pace stress, and in the recovery period after pacing, N either coronary sinus blood flow nor forearm blood flow differed betwe en the groups before and during the clamp, Whole body insulin-stimulat ed glucose uptake was decreased in the patients (15.6+/-2.1 vs. 23.1+/ -2.0 mu mol x kg(-1) x min(-1)). Insulin-stimulated glucose uptake in the forearm and the cardiac muscle was equally reduced in the patients (46+/-5 and 48+/-5%). Myocardial glucose uptake correlated with total arterial delivery in the control subjects (r = 0.63, P < 0.01), but n ot in patients (r = 0.22, P = 0.13). Carbohydrate and lipid oxidation was similar in the two groups at rest, and changes during the clamp we re not different in control subjects and patients either at rest, duri ng pacing, or in the recovery period. Patients with syndrome X exhibit myocardial insulin resistance, but cardiac energy metabolism remains unaffected, In patients with syndrome X, insulin-stimulated glucose up take is independent from myocardial blood flow.