Cardiac responses to insulin-induced hypoglycemia in nondiabetic and intensively treated type 1 diabetic patients

Insulin-induced hypoglycemia occurs commonly in intensively treated patient s with type 1 diabetes, but the cardiovascular consequences of hypoglycemia in these patients are not known. We studied left ventricular systolic [lef t ventricular ejection fraction (LVEF)] and diastolic [peak filling rate (P FR)] function by equilibrium radionuclide angiography during insulin infusi on (12 pmol.kg(-1).min(-1)) under either hypoglycemic (similar to2.8 mmol/l ) or euglycemic (similar to5 mmol/l) conditions in intensively treated pati ents with type 1 diabetes and healthy nondiabetic subjects (n=9 for each). During hypoglycemic hyperinsulinemia, there were significant increases in L VEF (Delta LVEF = 11 +/-2%) and PFR [Delta PFR = 0.88 +/-0.18 end diastolic volume (EDV)/s] in diabetic subjects as well as in the nondiabetic group ( Delta LVEF = 13 +/-2%; Delta PFR = 0.79 +/-0.17 EDV/s). The increases in LV EF and PFR were comparable overall but occurred earlier in the nondiabetic group. A blunted increase in plasma catecholamine, cortisol, and glucagon c oncentrations occurred in response to hypoglycemia in the diabetic subjects . During euglycemic hyperinsulinemia, LVEF also increased in both the diabe tic (Delta LVEF = 7 +/-1%) and nondiabetic (Delta LVEF = 4 +/-2%) groups, b ut PFR increased only in the diabetic group. In the comparison of the respo nses to hypoglycemic and euglycemic hyperinsulinemia, only the nondiabetic group had greater augmentation of LVEF, PFR, and cardiac output in the hypo glycemic study (P<0.05 for each). Thus intensively treated type 1 diabetic patients demonstrate delayed augmentation of ventricular function during mo derate insulin-induced hypoglycemia. Although diabetic subjects have a more pronounced cardiac response to hyperinsulinemia per se than nondiabetic su bjects, their response to hypoglycemia is blunted.