Ineffectiveness of Glucose, Potassium, and Insulin Infusion During Pacing Stress in Chronic Ischemic Heart Disease

Eight patients with coronary artery disease and positive exercise electrocardiograms undergoing cardiac catheterization were subjected to periods of atrial pacing-induced tachycardia at identical rates, before and during a glucose, potassium, and insulin (GKI) infusion. Steady state elevation of glucose and insulin was obtained prior to repeating the atrial pacing test in the GKI state. With each patient serving as his own control, five developed augmented clinical signs of acute ischemia during the paced GKI state, two no change, and one subjective improvement. Left ventricular end-diastolic pressure (LVEDP) was elevated in all patients (1-8 mm Hg) at rest during GKI infusion as compared to the rest control state. LVEDP during pacing was greater during the GKI paced state as compared to the control paced state in three of the eight patients whereas after pacing LVEDP was higher in four of eight patients during GKI. ST-segment depression was less during pacing in the GKI as compared to control state in four patients. A decrease in ST-segment depression was noted in two patients after pacing in the GKI state as compared to this measure after pacing in the control state. Augmented myocardial glucose uptake was demonstrated in the paced GKI state but lactate analysis failed to demonstrate a stoichiometric relationship between enhanced glucose uptake and lactate production. It is concluded that tolerance to ischemia is not extended and in the majority of cases may be adversely affected by GKI.