Analysis Of Uncommon Phenomena And Exploration Of Methodology Respecting Radiofrequency Catheter Ablation Of Paroxysmal Superventricular Tachycardia

PART I Investigation of the Methodology of Ablating Left Atrioventricular Accessory Pathway at the Atrial Side of Mitral Annuli through the Transaortic ApproachObjective: To investigate the feasibility of improving the methodology of ablating left atrioventricular accessory pathway (AP) at the atrial side of mitral annuli through the transaortic approach basing on the summarization of our practical experience in order to raise the utility value of this method.Methods: 159 pts who all had undergone the operation of radiofrequency catheter ablation accomplished by the author and cooperators in the last years were included in this study. Electrophysiologic study were performed by a routine procedure. After a left AP was identified, the ablating catheter was introduced transaorticly in every pt. Ablation was given at the atrial and/or ventricular side of mitral annuli. All pts were grouped according to the ablating site. These parameters including the operating duration(min), fluoroscopy time(min), the highest power of RF current pulse(W) and the number of pulses were recorded and a comparative study was made retrospectively.Results: Successful ablation were obtained in all cases, and 2 of them had recurrence of symptom and underwent the second procedure successfully. Thus there were 161 procedures having been accomplished and 165 APs ( including a double-AP existing in 4 pts) ablated in all, 109 of which were ablated at atrial side eventually. Comparing every parameter between the group of ablating at atrial side and that of at ventricular side, it could be found that only the highest power of RF current pulse was significatively higher with the former(P<0.01), but concerning the operating duration, fluoroscopy time and the number of pulse there were no apparent differences(P>0.05). In the two recurrent cases both of the first ablation was done at the ventricular side and the atrial side was selected as ablation target in the second procedure with no more recurrence.Conclusion: With the methodology improving and the experience accumulating, these problems such as difficulty in manipulating the catheter and unstable contact between the catheter tip and the endocardium encountered during ablating left AP at the atrial side of mitral annuli through the transaortic approach could be resolved, and therefore the practical value of this method could be raised, which would be helpful for enhancing the success rate and decreasing postoperative recurrence of ablating left AP. Moreover, transseptal procedure could be avoided in most cases.Radiofrequency Catheter Ablation of Atrioventricular Accessory Pathway with Rapid Rate Dependent Ventriculoatrial ConductionObjective: To report 4 cases of atrioventricular accessory pathway with rapid rate dependent ventriculoatrial conduction and summarize the experience of electrophysiological study and radiofrequency catheter ablation in these cases.Methods: 4 patients, who all had the symptom of paroxysmal palpitation and whose electrocardiograms recorded in the onset of tachycardia all manifested as narrow QRS complex, underwent electrophysiological study and radiofrequency catheter ablation by the routine method.Result: In all pts that special kind of atrioventricular accessory pathway with rapid rate dependent ventriculoatrial conduction were demonstrated to exist by electrocardiophysiological study and the atrioventricular reentrant tachycardia with the earliest atrial activated site locating in left atria were induced. Targets for ablation were identified during rapid rate ventricular pacing and a successful ablation was attained in every patient.Conclusion: Rapid rate dependent conduction of atrioventricular accessory pathway was existent as a rare phenomenon and this special kind of accessory pathway could also induce atrioventricular reentrant tachycardia, which should be paid attention to in case it should be misdiagnosed.PART III Reinvestigation of the significance of Junctional Rhythm with ventriculoatrial block appearing during Radiofrequency Ablationof the Slow PathwayObjective: To reinvestigate the significance of junctional rhythm with ventriculoatrial block appearing during radiaofrequency ablation of the slow pathway.Methods: 91 pts who had been performed the operation of radiofrequency catheter ablation for atrioventricular reentrant tachycardia (AVNRT) by the author and cooperators in the last years were included in this study. After the diagnosis of AVNRT has been confirmed according to the result of electrophysiological study, ablation was initially performed at the site that was approximately 2 cm lower than the distal His bundle electrode (HBE) , and then the ablation catheter was moved high stepwise until the endpoint has been attained. Special attention was paid to the phenomenon of junctional rhythm with ventriculoatrial block appearing during discharging radiofrequency energy. For each procedure, these data including procedure duration, fluoroscopy time, number of applications, X ray image of each effective target site and the result of electrophysiological retest performed after each applicatuion were recorded in detail.Results: All cases had undergone successful procedures. Tachycardia recurred after the first procedure in 3 pts and all of them had received repeat ablation. Therefore there were 94 cases of ablation beening accomplished in all. Junctional rhythm with ventriculoatrial block were observed during procedures in 48 cases. Comparing with those cases without ventriculoatrial block, procedure duration and fluoroscopy time were not significantly different, but more applications were needed. Of the total 325 effective applications, there were 98 with ventriculoatrial block (A group) and 227 without (B group) , respectively. The perpendicular distance between the target site and the His bundle catheter was significantly shorter and the percentage of temporal atrioventricular block (AVB) was significantly larger in A group than in B group. However, logistic regression analysis revealed that the perpendicular distance between the target site and HBE being not larger than 1.5 cm was the only significant predictor of AVB (0R=13.42,P=0.015) and the correlation between junctional rhythm with ventriculoatrial block and AVB was uncertain (P>0.05). In addition, if atrioventricular conduction could be found just at the time of ventriculoatrial block appearing, the negative predictive value for consequent AVB was 97.6%.Conclusion: During the procedure of ablating slow pathway, the appearance of junctional rhythm with ventriculoatrial block was certainly correlative with AVB. On the contrary, performing ablation at a too high target site was just the independent predictor. When the distance between the target site and HBE was larger than 1.5 cm, there was just little possibility of AVB occurring even if ventriculoatrial block appeared.