48 h快速起搏对老龄犬心房病理性重构的影响

The Effect Mechanism of 48 h Rapid Pacing on Atrial Pathological Remodeling in Elder Canine

目的探讨48 h快速起搏对老龄犬心房病理性重构的影响。方法20只纯种比格犬根据年龄及是否行心内膜起搏分为成年窦性心律组、老龄窦性心律组、成年起搏组和老龄起搏组,模型构建成功后行电生理检查、心脏超声检查、心率变异性测定和透射电镜检测以明确快速起搏诱导的老龄犬心房病理性重构。结果老龄起搏组的PR间期明显延长(P<0.05),双侧心房和4条肺静脉的有效不应期显著缩短(P<0.05),心房颤动(房颤)诱发率明显提高(P<0.05),这些不稳定的心房电生理性质伴随左心房扩张、左心室收缩末期内径增大(P<0.05),以及心脏功能下降(P<0.05)。心率变异性分析显示相比于年龄增加,快速起搏将增加整体交感神经张力(P<0.05),减小副交感神经张力(P<0.05)。透射电镜显示增龄导致心房肌细胞肌节拉长,线粒体膜和嵴形态明显改变,老龄和高频起搏的双重作用加剧细胞骨架破坏和线粒体裂解。结论快速心房异位电活动显著加剧老龄犬心房电重构、结构重构表征,增加交感神经张力,加速心房肌节破坏和线粒体损伤,促进“房颤致房颤”的恶性循环。

Objective To investigate the effect of 48 h rapid pacing on atrial pathological remodeling in the ageing canines.Methods 20 purebred canines were randomized into four groups according to whether receiving the endocardial atrial pacing or the age exactly as the adult sinus rhythm group,the elder sinus rhythm group,the adult pacing group,the elder pacing group.The electrophysiological properties,the cardiac ultrasound,the heart rate variability and the transmission electron microscope were tested after the establishments of atrial fibrillation(AF)models to figure out the atrial pathological remodeling mediated by rapid pacing.Results The PR intervals were enlarged in the elder pacing group,the bilateral atrial and four pulmonary venous effective refractory period significantly shortened,as well as the elevated AF inducibility(P<0.05).Such instable electrophysiological parameters were accompanied by the expansive left atrial diameter,the increased left ventricular systolic diameter and the decreased ejection fraction(P<0.05).From the results of heart rate variability analysis,we found that rapid pacing can enhance the systemic sympathetic tone and decrease the parasympathetic tone compared to the ageing groups(P<0.05).Transmission electron microscope showed that the myotomes of atrial myocytes are elongated,and the morphology of mitochondrial membranes and ridges are significantly changed with the increase of age.In addition,aging combined with rapid pacing could aggravate the cytoskeletal destruction and mitochondrial cleavage.Conclusion Rapid ectopic activities could significantly facilitate the“AF begets AF”vicious cycle by potentially inducing the electrical and structural remodeling in the ageing canines,increasing the sympathetic tone and accelerating atrial myotome destruction and mitochondrial damage.