Prolonged intra-myocardial growth hormone administration ameliorates post-infarction electrophysiologic remodeling in rats

Abstract

Experimental studies indicate improved ventricular function after treatment with growth hormone (GH) post-myocardial infarction, but its effect on arrhythmogenesis is unknown. Here, we assessed the medium-term electrophysiologic remodeling after intra-myocardial GH administration in (n = 33) rats. GH was released from an alginate scaffold, injected around the ischemic myocardium after coronary ligation. Two weeks thereafter, ventricular tachyarrhythmias were induced by programmed electrical stimulation. Monophasic action potentials were recorded from the infarct border, coupled with evaluation of electrical conduction and repolarization from a multi-electrode array. The arrhythmia score was lower in GH-treated rats than in alginate-treated rats or controls. The shape and the duration of the action potential at the infarct border were preserved, and repolarization–dispersion was attenuated after GH; moreover, voltage rise was higher and activation delay was shorter. GH normalized also right ventricular parameters. Intra-myocardial GH preserved electrical conduction and repolarization–dispersion at the infarct border and decreased the incidence of induced tachyarrhythmias in rats post-ligation. The long-term antiarrhythmic potential of GH merits further study.

• Myocardial infarction
• ventricular tachyarrhythmias
• electrical conduction
• repolarization–dispersion
• alginate
• growth hormone

Acknowledgements

The authors thank Professor Y. Etzion for providing the miniature pacing electrodes and Dr. M. R. Franz for his help in the interpretation of our MAP recordings.

Declaration of interest

The authors report no declarations of interest. The study was funded by the Cardiovascular Research Institute, Ioannina, Greece.