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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.
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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.