Effect of glucose--insulin--potassium solution on the exercise performance of patients with coronary artery disease.

Treadmill exercise testing was performed in double blind fashion on nine untrained nondiabetic subjects with angiographically proven coronary artery disease and stable exercise tolerance. They were exercised on three different days in randomized sequence as follows: With infusion of 30 per cent solution of glucose in water containing 50 units of regular insulin and 80 mM. of KCl per liter, 50 ml. bolus followed by 1 ml./Kg./hr. (GIK); with infusion of normal saline, (NSS), 50 ml. bolus followed by 1 ml./Kg./hr. and without infusion (control). There were no significant differences between control and saline experiments.A decrease in work capacity (9.9 ± 3.4 to 7.0 ± 2.1 METS p < 0.005) and the product of the heart rate and systolic blood pressure (20318 ± 6068 to 17597 ± 5788 mm. Hg min.^?1, p < 0.05) at the end of exercise was observed in GIK experiments. Angina occurred at lower exercise levels in GIK studies (6.4 ± 1.4 METS) than in NSS studies (9.9 ± 3.4 METS p < 0.01). When compared at the same exercise level (5 METS), more pronounced ST depression (0.21 ± 0.11 mV.) was seen in GIK than in NSS studies (0.1 ± 0.18 mV., p < .025). In two patients, the exercise test was negative in NSS and became positive in GIK.In GIK, a decrease in serum FFA compared to resting level was noted at the end of exercise (197 ± 246 μEq/L.) and during exercise at 5 METS (272 ± 400 μEq/L.) as opposed to an increase (566 ± 853 μEq/L., p < 0.025 at 5 METS and 650 ± 996 μEq/L., p < 0.05 at the end of exercise) in NSS. An increase in blood glucose (73 ± 74 mg./100 ml., p < 0.01) at the end of exercise and (116 ± 75 mg./100 ml., p < 0.005) at 5 METS was noted in GIK but not in NSS studies. A small decrease in serum potassium (by 0.11 ± 0.23 mEq./L. at 5 METS and by 0.15 ± 0.24 mEq./L. at the end of exercise) was seen in GIK but an increase in the saline group (by 0.21 ± 0.39 mEq./L., p < 0.05 at 5 METS and by 0.43 ± 0.38 mEq./L., p < 0.001 at the end of exercise). No significant differences in serum lactate were noted.The data indicate that GIK diminishes the exercise performance and hastens the onset of angina in patients with coronary artery disease. It appears that increased availability of glucose and potassium does not have a beneficial effect in the presence of depressed FFA levels during exercise.