Introduction: A positive chronotropic effect of beta2 stimulation is well known. Case reports of ventricular arrhythmias during beta2-inhalation therapy have been published. The aim of this study was to asses the overall electrophysiologic effects of the beta2-agonist salbutamol.
Methods and results: Electrophysiologic and hemodynamic variables were measured in 10 healthy volunteers during atrial pacing at baseline and during infusion of salbutamol at two different rates (0.1 and 0.2 microg/kg/min). To characterize beta2-agonist effects, a comparison was made with the beta1-selective agonist dobutamine. Salbutamol infusion produced significant changes in electrophysiologic properties in both myocardial and nodal tissues, with significantly greater effects on nodal properties. The proportional decreases in AV nodal parameters were more pronounced than in the sinus node (P < 0.001). An interesting result was a significant increase in the duration of the QS interval, which in the presence of an unchanged His-Purkinje conduction (HV) represents slower depolarization of the ventricle. QT dispersion also increased.
Conclusion: Infusion of salbutamol results in significant electrophysiologic effects on most heart structures, proportionally most pronounced in the AV node. Discordant effects on ventricular conduction, which slowed, and the refractoriness of the ventricular myocardium, which shortened, were seen. QT dispersion was increased.