经心外膜行窦房结改良的实验研究

Modification of sinus node function by epicardial radiofrequency ablation in rabbits

目的探讨经心外膜行窦房结改良的可行性及安全性。方法选用日本大耳白兔17只,全麻下开胸,经颈内静脉穿刺送入4 F 起搏电极至高右房。静脉推注美多心安和阿托品,测固有心率、行窦房结功能检查;采用消融电极沿界沟处由上至下移动放电,以窦性心率下降30%±5%或出现异位性心律为消融终点。在达到消融终点后即刻及2 h 分别测定窦房结功能。达到消融终点后2 h,沿界沟进一步消融,观察在过度消融时可能出现的反应。消融术结束,采用前固定技术留取标本,供病理学研究。结果在达消融终点后即刻有12只动物(70.59%)的心律达到了靶心律,有5只(29.41%)出现了房性节律;2h 后均恢复了窦性心律,但有3只(17.65%)动物心率未达到靶心率。进一步消融后,有12只仍为窦性节律,其中6只出现了房室阻滞,4例出现了房性节律、1例出现了房室交界性心律。在窦房结改良前后测定的窦房结功能指标(CSNRT、SACT)差异无显著性(P>0.05),窦房结改良前后心率差异有显著性(P<0.0001),而消融终点即刻心率与2 h 时相比较,差异无显著性(P>0.05)。病理学研究未见心房壁穿孔,窦房结改良成功者只有部分窦房结细胞发生了凝固性坏死;而最后表现为异位节律者则见窦房结区域遭到了广泛性破坏。结论经心外膜行窦房结改良,可以有效地控制窦性心律,且对窦房结功能无严重影响;并为经心内膜改良窦房结奠定了实验基础。临床上可用于有症状的窦性心率异常加速或不适当窦性心动过速(inappropriate sinus tachycardia,IST)

Objective To investigate the feasibility and safety of modification of sinus pacemaker function by epicardial radiofrueqency ablation in rabbits to control sinus rate.Methods Epicardial radiofre- quency ablation along the suleus terminalis was pedormed in 17 thoracotomized rabbits.The instrinsic heart rate(IHR)and the sinoatrial node function were examined before and 2h after ablation.The ablation end- point is 30±5% reduction in the sinus heart rate or development of a low ectopic rhythm.2 hurther abla- tion was performed in order to observe the possible complications.At the end of the procedure,samples were reserved for histological studies using premortal fixation technique.Results 12 animals(70.59%)that attained the targeted sinus rhythm,5 rabbits(29.41%)that developed ectopic atrial rhythm.Two hours later,all eases returned sinus rhythm,whereas 3 rabbits didnot obtain the targeted heart rate.After modifi- cation of sinus node function,the corrected sinus node recovery time(CSNRT)and sinoatrial conduction time(SACT)had no remarkable difference(P>0.05);sinus heart rate decreased significantly(P<0. 0001).After the excessive ablation,6 rabbits still remained the sinus rhythm,6 developed atrioventricular block(AVB),4 atrial rhythm,1 junctional rhythm.No perforation of the atrial wall was found in all cas- es.Acute histological findings showed coagulation necrosis of the epicardium,extending to the muscle fibres and affecting the sinus node cells.Conclusion This study demonstrates the feasibility of modification of si- nus pacemaker function for sinus rate control by epicardial radiofrequency ablation.It also lays an experi- mental foundation of modification of sinus pacemaker function by endocardial ablation.It should be consid- ered as an alternative therapy for patients with disabling inappropriate sinus tachycardia(IST)refractory to medical management.