Influence of acute stress on cardiac electrophysiological stability in male goats

Stress plays an important role in the pathogenesis of ventricular arrhythmias. This study was designed to examine the effect of acute stress and metoprolol, a beta adrenergic receptor blocker, on cardiac electrophysiological stability of male goats.

Fifteen male goats were randomly divided into three groups: (i) control animals (n=5), (ii) a compound stimuli group including noise and red flash (n=5), (iii) and a compound stimuli group with metoprolol treatment (n=5). Plasma catecholamines were determined by using high performance chromatography with electrochemical detection. Heart rate turbulence (HRT) and heart rate variability (HRV) were analysed with the MGY-H12L analysis system. Also, the ventricular fibrillation threshold (VFT) and the ventricular vulnerable period (VVP) were determined by programmed S1S2 stimulus with bipolar electrodes at the apex of the goat hearts.

Compound stimuli increased plasma catecholamine levels progressively and decreased the negative value of turbulence onset (TO), turbulence slope (TS), SDNN, PNN50. Moreover, compound stimuli broadened VVP and decreased VFT significantly. Although metoprolol treatment failed to affect plasma catecholamine levels, TS and PNN50 value of the compound stimuli group, it significantly increased the negative value of TO, SDNN, VFT and narrowed VVP.

Our data demonstrates that compound stimuli can induce acute stressful reactions, and decrease the cardiac electrophysiological stability of male goats, which can be counteracted by metoprolol treatment.