Effect of glucagon on cardiac conduction in man

Abstract

His bundle electrograms were obtained in 26 patients before and after intravenous administration of glucagon (50 μg/kg). The group consisted of 4 patients with normal conduction and 22 patients with conduction disease. The P-A interval, measured in all patients, was 35 ± 1.4 msec (mean ± standard error of the mean) before and 30 ± 1.5 msec after infusion of glucagon ( P < 0.001). The mean A-H interval during sinus rhythm in all patients and during pacing at 100/min in 21 patients was, respectively, 97 ± 6.0 msec and 114 ± 6.4 msec before, and 96 ± 6.0 msec and 114 ± 6.6 msec after infusion of glucagon (not significant). The mean H-V interval in 25 patients was 48 ± 2.6 msec before and 49 ± 2.0 msec after infusion of glucagon (not significant). The mean sinus rate and sinus recovery times were, respectively, 73 ± 3.0 beats/min and 1,025 ± 42.0 msec before and 81 ± 3.0 beats/min and 919 ± 27.0 msec after infusion of glucagon ( P < 0.001 and < 0.01). Functional and effective refractory periods were measured (In milliseconds) with use of the atrial extrastimulus technique. The mean atrial functional and effective refractory periods (21 patients) were, respectively, 273 ± 11.6 and 252 ± 12.0 before and 256 ± 10.0 and 238 ± 9.6 after infusion of glucagon ( P < 0.001 and < 0.01). Mean atrloventricular (A-V) nodal functional refractory period (22 patients) and effective refractory period (15 patients) were 465 ± 22.0 and 404 ± 33.0 before and 457 ± 23.0 and 395 ± 32.0 after the infusion (not significant). The mean effective refractory period of the His-Purkinje system (2 patients) was 440 ± 45.0 before and 425 ± 55.0 after infusion of glucagon (not significant). In summary, glucagon increased sinus nodal automaticity, as manifested by an increase in sinus rate and decrease of sinus nodal recovery time, and improved intraatrial conduction as manifested by a reduction of the P-A interval and atrial functional and effective refractory periods. Glucagon had no effect on A-V nodal or intraventricular conduction.