The Effect And Electrophysiological Mechanism Of Acute Stress On Ventricular Arrhythmias Of Goats

Objective:To explore the effect and mechanism of acute stress and metoprolol intervention on ventricular arrhythmias and electrophysiological properties of ventricular myocardium in physiological conditions,which may provide preventive methods and theoretical evidence for stress induced ventricular arrhythmias.Methods:1.Fifteen goats were randomly divided into control group,acute stress group, and metoprolol group.Noise and red flash were used as the stressor.Plasma epinephrine and norepinephrine concentration was measured by HPLC method. Serum cortisol concentration was measured by ELISA method.2.Results of DCG were automatically scanned and heart rate,ventricular arrhythmias,parameters of HRV and HRT were analyzed with MGY-H12L system.3.MAP of left ventricular myocardium and right ventricular epicardium were recorded with ablation electrode and complex electrode.VFT and VVP were measured by programmed S₁S₂ stimuli with bipolar electrodes at apex of goat hearts.Results:1.Acute stress and metoprolol intervention goats appeared irritated and displayed attacking behavior.2.Plasma epinephrine and norepinephrine levels of acute stress and metoprolol intervention goats increased progressively in contrast to control goats.Serum cortisol concentration increased significantly 6 hours after stimulation. Thereafter,they didn't increase further.3.Heart rates and premature ventricular captures of acute stress goats increased markedly,but no severe ventricular arrhythmias appeared.Metoprolol intervention could decrease heart rates and premature ventricular captures when compared with acute stress group,but still more than control group.4.SDNN,PNN₅₀,TO negative value and TS of acute stress goats were significantly lower than control goats.Metoprolol invention increased SDNN and TO negative value in contrast to acute stress goats,but had no effect on PNN₅₀and TS.5.MAP₅₀and MAP₉₀of left ventricular mid-myocardium were longer than epi-myocardium and endo-myocardium in all groups.Compared with control group,MAP₅₀and MAP₉₀of left ventricular myocardium shortened in acute stress group.Metoprolol intervention could prolong MAP₅₀and MAP₉₀of left ventricular epi-myocardium and endo-myocardium remarkably than acute stress group,but didn't affect those of mid-myocardium.6.Acute stress significantly increased left ventricular TDR,decreased VFT and broadened VVP in contrast to control goats.Compared with acute stress group, metoprolol group showed decreased left ventricular TDR,increased VFT and narrowed VVEConclusions:1.Noise and red flash can successfully induce stress in goats.Stress goats showed higher sympathetic and adrenal cortex function.2.Under acute stress condition,goats appear more ventricular arrhythmias. Metoprolol can reduce ventricular arrhythmia events.3.Acute stress decrease HRV and HRT apparently.Metoprolol can partially improve HRV and HRT.4.Repolarization time of left ventricular mid-myocardium is longer than epi-myocardium and endo-myocardium.Acute stress shortens repolarization time. Metoprolol intervention can prolong repolarization time of left ventricular epi-myocardium and endo-myocardium,but have no effect on that of mid-myocardium.5.Acute stress increases left ventricular TDR and electrical unstability,which can be counteracted by metoprolol.