Cellular And Ionic Of Ventricular Arrhythmias In Rabbit Heart During Long-term Myocardial Infarction And The Effect Of Bisoprolol

BackgroundMost severe ventricular arrhythmias result from coronary heart disease and previous myocardial infarction. About half all deaths of patients are due to arrhythmias during recovery period of acute myocardial infarction. The severe ventricular arrhythmias may result in incomplete complication and high mortality. And researchers continuously paid close attention to it. The electrophysiological studies declared that there were abnormal myocardial electrical activity and conduction in after myocardial infarction. Animal experiments showed that 3 blocker could prevent ventricular fibrillation after coronary occlusion. Clinic research also showed that prophylactic P blocker could significant reduce the risk of ventricular fibrillation, total mortality and sudden cardiac death. Recent years, with the development of clinic electrophysiologic study and whole-cell patch-clamp, the electrophysiologic study in myocytes went more deeply after myocardial infarction. And the electrophysiologic study offered a foundation on mechanism of ventricular arrhythmias after myocardial infarction.Present study made myocardial infarction model in rabbit. Methods used in the study included observation with light microscopy, electrophysiologic test, patch-clamp technique and laser scanning confocal microscopy. WE investigated changes in ionic channel currents and intracellular calcium of ventricular myocytes after myocardial infarction. The purpose of this study was to elucidate abnormal electrophysiologic changes and effect of bisoprolol after myocardial infarction.Methods and resultsPART I Rabbits were undergone coronary occlusion, and were randomly assigned-9-into MI group, 3 -B group(administer bisoprolol within 24h after myocardial infarction for 3 weeks),and sham group(without coronary occlusion). Result: 1 Under light microscopy, necrosis and scar were showed in myocardium in MI group. With epicardial electrogram, Q waves and normal electrogram showed from central to surround region of infarction. These results showed successful animal model. 2 Heart rate in 3 -B group was significant lower than in MI group and sham group. LVEDP in MI group and 3 -B group were significant higher than sham group, but 3 -B group was significant lower than MI group(p<0.05). 3 Ventricular fibrillation (VF) could be induced by programmed electrical stimulation in 9/19 MI rabbits, and among the 9 rabbits, 2 rabbits could be induced ventricular tachycardia (VT). VF could only be induced in 2/20 3 -B group rabbits. No sustained VT/VF could be induced by 81-84 stimulation protocol in sham group. 4 Heart rate variability indexes: SDNN was significant lower in VT/VF group than no VT/VF group (p<0.05). CV in MI group was significant lower than sham group(p<0.01) and 3 -B group(p<0.05).CV in VT/VF group was significant lower than sham group(PO.OOl). LF/HF in MI group was significant higher than sham group(p<0.01) and & -B group(p<0.05). LF/HF in VT/VF group was significant higher than sham group (p<0.01). 5 ERP-D in MI group was significant higher than sham group (p<0.01). ERP-D in 3 -B group was lower than MI group(P<0.05). There was no significant different between sham group and 3 -B group. 6 APDso and APD90 from noninfarcted region in MI group were significant high than sham group (p<0.05). There was no significant different between sham group and 3 -B group. PART II Single ventricular myocytes from rabbit hearts were isolated by using modification langendoff perfusion and soak with collagenase. Rod-shaped rabbit ventricular myocytes with clear cross-striation and intact membrane were obtained in this experiment. Contraction of the myocytes was observed and ionic channel currents were recorded by path-clamp recording technique. 30-70% of the rod-shaped cells did not take up the vital stain of Typan. Vitality of the myocytes maintained 24 hours.PART HI Ionic channel currents of isolated rabbit ventricular myocytes were investigated by using whole-cell path-clamp technique. Results: 1 Membrane capacitance of MI group was signifi...