RESUMO
Objective To evaluate the frequently used electrocardiographic criteria and propose a modified algorithm for differentiating typical atrioventricular node reentrant tachycardia(AVNRT)from atrioventricular reciprocating tachycardia(AVRT).Methods Twelve-lead electrocardiograms(ECGs)during sinus rhythm and atrioventricular node reentrant tachycardia(AVNRT)or atrioventricular reciprocating tachycardia(AVRT)with a narrow QRS complex were obtained from 154 patients who had received successful radiofrequency catheter ablation from Jan.2003 to Nov.2005.The ECGs of initial 104 patients were analyzed by 3 observers without knowledge of the electrophysiological diagnosis.According to these initial results,we proposed a modified stepwise ECG algorithm which used pseudo r′/S/Q waves,RP interval,and ST-segment elevation in lead aVR during tachycardia.Two observers assessed the algorithm in additional 50 patients.Results The algorithm was able to increase the overall accuracy from 77% and 79% with original algorithm to 84% and 87% with the modified algorithm,respectively.The inter-observer concordance was 85%.The intra-observer concordance was 89% in both investigators.Conclusion The modified algorithm can improve the accuracy of differential diagnosis between typical AVNRT and AVRT via concealed accessory pathway.
RESUMO
Objective The purpose of this study was to clarify the mechanism of 2:1 atrioventricular block (AVB) during AV node reentrant tachycardia (AVNRT) induced during electrophysioloic study.Methods In consecutive patients with AVNRT referred for electrophysiologic study, the data of 2 : 1 AVB during induced AVNRT was retrospectively analysed. Results The data of 4 patients was excluded from analyzing because of the unsatisfactory recording of His bundle potential during AVNRT. A His bundle deflection was present in the blocked beats in three of the remaining 5 patients and absent in the other two. At the beginning of AVNRT induced in those patients whose His bundle deflection was present in the blocked beats, H-V Wenckebach sequence with a QRS pattern of RBBB or LBBB was seen preceding and following the 2 : 1 AVB. A pattern of H-V Wenckebach phenomenon occurred once during AVNRT with 2:1 AVB in one of the two patients whose His bundle deflection was absent in the blocked beats.Conclusion The induced 2:1 AVB during AVNRT is due to functional block in the His-Purkinje system regardless of the presence or absence of a His bundle deflection in blocked beats.