Low-dose intravenous glucagon has no effect on myocardial contractility in normal man. An echocardiographic study

In order to investigate the pathophysiological background for the increased cardiac performance described in short-term insulin-dependent diabetes, we infused glucagon intravenously in 8 healthy men at a dose of 5 ng/kg/min for 1 h and at a dose of 10 ng/kg/min for a further hour. Heart rate and blood pressure were measured and myocardial contractility assessed by echocardiography as the fractional shortening of the left ventricle and as the mean circumferential shortening velocity before the glucagon infusion (first base-line level), after the first glucagon infusion period, after the second glucagon infusion period and at 1 h after stopping the glucagon infusion (second base-line level). Plasma levels of glucagon were 79 +/- 15 ng/l, 123 +/- 76 ng/l, 381 +/- 179 ng/l and 77 +/- 22 ng/l, respectively. Heart rate decreased significantly during the first (8%, p less than 0.05) and second (6%, p less than 0.01) glucagon infusion period compared to the mean of the first and the second base-line value. Mean arterial blood pressure, fractional shortening of the left ventricle and mean circumferential shortening velocity were unchanged. We conclude that increments in plasma concentrations of glucagon to levels seen in poorly controlled diabetes does not change myocardial contractility in normal man.