| Objective:To investigate the possibility of optical pacing and defibrillation in vivo of rat heart allowing for the photoelectric conversion characteristics of optogenetics.Furthermore,explore the effects of light intensity,pulse duration and illumination sites on the efficiency of optical pacing and defibrillation.Methods:According to the random number table,twenty-seven juvenile SD rats were randomized into Ch R2,non-Ch R2 and normal group,(n=9 each).Rats was injected via right jugular vein with 60μl adeno-associated virus carrying the gene encoding the light-sensitive ion channel protein channelrhodopsin-2(H134R),[AAV9-CAG-h Ch R2(H134R)-m Cherry],non-Ch R2 virus(AAV9-CAG-m Cherry),PBS in each group separately.Raised in clean environment for 8 weeks,the adult rats were anesthetized and their hearts were fully exposed.Then the Labchart parameters were set and the 473nm laser was adjusted.The blue light pulse above the heart’s autonomous rhythm was applied to the right ventricle of the heart.Meanwhile,the light power density(0.03～1.97mw/mm~2),pulse duration(2,5,10,20,50ms)and illumination sites(right atrium,left ventricle,right ventricle,ventricular septum,apex)were changed.Light output signals and surface electrocardiogram were simultaneously recorded to observe the capture rate of the right ventricle with blue light.After that,an acute myocardial infarction model was prepared via the ligation of the left anterior descending coronary artery,and ventricular fibrillation was induced using a burst stimulation protocol.When ventricular fibrillation had been lasting for 5s,a light pulse of 2 times the pacing intensity threshold for 1s was given on non-infarcted left ventricle,right ventricle or apex respectively,and all of above procedure were conducted twice.Successful defibrillation was defined as ventricular fibrillation termination within 2s after light-off.The defibrillation rate at each site was recorded and counted.Results:All SD rats survived and completed the optical pacing process in 8 weeks after jugular injection.Ch R2(H134R)was efficiently expressed in the hearts of all SD rats,and no obvious abnormalities of growth and electrocardiogram parameters were observed and all rats finished the optical pacing experiment.Five rats selected in random complemented the rest experiment process,including the preparation of acute myocardial infarction model,ventricular fibrillation/ventricular tachycardia induction and optical defibrillation.(1)When the parameter of 473nm blue light pulse was set as 0.64mw/mm~2 light intensity,20ms pulse duration,5Hz frequency,illumination on each heart region achieved 1:1 pacing,including the right atrium,left ventricle,right ventricle,ventricular septum,and apex.(2)When illumination parameter was fixed as 20ms pulse duration,8Hz frequency on the right ventricle,heart capture rate increases until 100%with light intensity raising in range of 0.03～0.64 mw/mm~2.(3)8Hz blue light illumination on the right ventricle with different pulse duration(2,5,10,20,50ms),the minimum light intensity required for completely heart pacing in oder is 0.46±0.33,0.26±0.10,0.18±0.04,0.13±0.04,0.16±0.07mw/mm~2.The rats in Ch R2 group received a light with power intensity of 2 times the threshold.Before and after that,the heart rate(HR),QT interval,and QRS duration showed no statistically different(P>0.05).(4)Setting light intensity as 2 times the pacing threshold,1s pulse duration,the defibrillation rate on the non-infarct zone of left ventricular,right ventricle and apex were 60±22.36%,70±27.39%,100%orderly.Conclusion:473nm blue light is feasible for pacing and defibrillation in vivo,and the right ventricular pacing rate is related to the light intensity and pulse duration.The defibrillation rate is related to the illumination zone. |
PDF Full Text Request