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 exercise, 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 x kg(-1) x min(-1); glucose = 6 mg x kg(-1)min(-1)) (test B) infusions on systolic and diastolic functions at rest and during dynamic exercise were examined by radionuclide ventriculography. Twenty-two noninsulin-dependent diabetic patients and 22 gender, age and body mass index matched healthy 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 filling 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 test B than it was in test A only in diabetic subjects (p < 0.01). Stress-LVEF 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-peak filling rate in either group. No difference in left ventricular end diastolic 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 patients.

CONCLUSIONS

In both normal and diabetic humans, insulin induces a very important rise in LVEF after submaximal work. However, the rise is significantly lower in diabetic than in nondiabetic subjects. The increase in exercise-LVEF on insulin is likely due to an enhancement of ventricular contractility. Insulin resistance could justify the lower angioscintigraphic indexes in diabetic subjects.