Effects of insulin-glucose infusion on left ventricular function at rest and during dynamic exercise in healthy subjects and noninsulin dependent diabetic patients - A radionuclide ventriculographic study

OBJECTIVES The aim of this study was to evaluate: 1) the effects of insulin administration on left ventricular ejection fraction (LVEF) during exercis e, and 2) the eventual impairment of the cardiovascular response to insulin in noninsulin dependent diabetes mellitus. BACKGROUND Insulin influences the cardiovascular system, but its effect on left ventricular function has yet to be established. METHODS The effects of normal saline (test A) and insulin-glucose (insulin = 1.7 mU(.)kg(-1.)min(-1); glucose = 6 mg(.)kg(-1) min(-1)) (test B) infusi ons on systolic and diastolic functions at rest and during dynamic exercise were examined by radionuclide ventriculography. Twenty-two noninsulin-depe ndent diabetic patients and 22 gender, age and body mass index matched heal thy subjects were investigated. RESULTS Both groups had normal scintigraphic parameters at rest and during dynamic exercise. Rest-and stress-LVEF as well as rest- and stress-peak fil ling rate were significantly (p < 0.001) lower in diabetic than in healthy subjects, both in test A and B. Rest-LVEF was significantly higher during t est B than it was in test A only in diabetic subjects (p < 0.01). Stress-LV EF was significantly higher (p < 0.05) during test B than it was in test A, in both groups. Insulin-glucose infusion did not modify rest- and stress-p eak filling rate in either group. No difference in left ventricular end dia stolic volume and in mean blood pressure was found between test A and B at rest and during exercise in either group. A significant linear correlation between LVEF and the index of insulin sensitivity was found in diabetic pat ients. CONCLUSIONS In both normal and diabetic humans, insulin induces a very impo rtant rise in LVEF after submaximal work. However, the rise is significantl y lower in diabetic than in nondiabetic subjects. The increase in exercise- LVEF on insulin is likely due to an enhancement of ventricular contractilit y. Insulin resistance could justify the lower angioscintigraphic indexes in diabetic subjects. (C) 2000 by the American College of Cardiology.