超速阈下刺激终止房室结折返性心动过速的位点与慢径消融成功靶点间关系的研究

Relationship between termination sites of atrioventricular nodal reentrant tachycardia by ultrarapid subthreshold stimulation and sites of successful slow pathway ablation

目的 根据影像法射频消融房室结慢径是一相对盲目的方法 ,其单次放电的成功率低 ,导致房室阻滞的危险性高。本研究比较超速阈下刺激 (U SS)终止房室结折返性心动过速 (AVNRT)的位点与慢径消融靶点之间的关系 ,探讨 USS是否可作为标测慢径的电生理指标。 方法 选择 AVNRT患者 16例 ,所有患者均诱发出持续性 AVNRT,平均心动周期为 (333.31± 43.94) m s。按影像法结合腔内心电图从右后间隔冠状静脉窦口处由下向上标测慢径消融靶点 ,在每个靶点处用 U SS终止 AVNRT,不管终止是否成功均予以试消融 ,观察慢径消融是否成功。U SS从 0 .5 m A开始逐渐递增 ,频率为 6 0 0～80 0 ppm,持续时间 2 s。 结果 38个影像靶点中有 2 3个位点 AVNRT被 U SS终止 ,其中 17个位点改良慢径成功。 17个成功靶点的阈下刺激值平均占阈值的 2 5 .96 % ,6个未成功靶点的阈下刺激值平均占阈值的 43.83% ,两组之间差别有显著性 (P<0 .0 0 5 )。15个位点 AVN RT未被 U SS终止 ,其中一个位点改良慢径成功。利用 U SS判断慢径消融靶点的一次放电成功率为 73.91% ,而影像法的一次放电成功率为 47.36 % ,明显低于前者 (P<0 .0 5 )。 U SS判断慢径消融靶点的阳性预测率为 73.91% ,阴性预测率为93.33% ,成功位点处 A VNRT被 U SS终止?

Objective Radiofrequency catheter ablation of slow pathway based only on fluoroscopy is relatively blind,with low success rate using single RF delivery,and has a high risk of atrioventricular block.In this study,the relation between termination sites of atrioventricular nodal reentrant tachycardia(AVNRT) by ultrarapid subthreshold stimulation(USS) and sites of successful slow pathway ablation was assessed,and the reliability of slow pathway ablation guided by USS technique was investigated. Method 16 patients with AVNRT were studied.Sustained AVNRT with cycle lengths of (333 31±43 94)ms was reproducibly inducible in all patients.Mapping of slow pathway guided by fluoroscopy and endocardiac electrogram was performed near the orifice of coronary sinus at first and then towards midseptum if required.USS was done at each candidate site for slow pathway ablation until the termination of AVNRT or atrial capture was observed.Radiofrequency current was delivered at each site irrespective of the effect of USS.USS intensity started with 0 5mA and increased gradually up to suprathreshold for a duration of 2 seconds and with a frequency of 600～800 ppm.Result Of 38 candidate sites,AVNRT was terminated by USS at 23 sites,17 of which were successful slow pathway ablation sites.The average USS value was 25 96% of the threshold at the successful ablation sites,43 83% at unsuccessful sites( P <0 005).USS did not terminate AVNRT at 15 sites,at one of which slow pathway was successffully ablated.The success rate of single RF delivery guided by USS was 73 91% and only 47 36% guided by fluoroscopy and intracardiac electrogram( P <0 05).Positive predictive value of USS for successful slow pathway ablation was 73 91%,negative predictive value 93 33%.The sensitivity of AVNRT termination by USS at slow pathway sites was 94 44%. Conclusion USS is a good mapping method for slow pathway.The positive predictive value is affected by the intensity and frequency of USS.