A NEW ELECTROCARDIOGRAPHIC ALGORITHM USING RETROGRADE P-WAVES FOR DIFFERENTIATING ATRIOVENTRICULAR NODE REENTRANT TACHYCARDIA FROM ATRIOVENTRICULAR RECIPROCATING TACHYCARDIA MEDIATED BY CONCEALED ACCESSORY PATHWAY

Objectives. The purpose of this study was to use an electrocardiograph ic (ECG) algorithm, derived from the results of radiofrequency ablatio n, to discriminate atrioventricular node reentrant tachycardia (AVNRT) from atrioventricular reciprocating tachycardia (AVRT) and to localiz e a concealed accessory pathway, prospectively. Background. Informatio n about ECG criteria for differentiating AVNRT from AVRT is limited an d has not been confirmed by surgical or catheter ablation. Methods. Fo ur hundred six ECGs (obtained from 406 different patients) that demons trated narrow QRS complex (<0.12 s) supraventricular tachycardia with an RP' interval less than the P'R interval or pseudo r' wave in lead V -1 or pseudo S wave in inferior leads, or both, were examined, and the results were confirmed by radiofrequency catheter ablation. The initi al 226 ECGs were analyzed to develop a stepwise algorithm, and the sub sequent 180 ECGs were prospectively evaluated bg the new algorithm. Re sults. The presence of a pseudo r' wave in lead V-1 or a pseudo S wave in leads II, III, aVF indicated anterior-type AVNRT with an accuracy of 100%. With the difference of RP' intervals in leads V-1 and III >20 ms, posterior-type AVNRT could be differentiated from AVRT utilizing a posteroseptal pathway with a sensitivity of 71% (95% confidence inte rval [CI] 55% to 89%), a specificity of 87% (95% CI 67% to 97%) and a positive predictive value of 75% (95% CI 56% to 91%). According to the polarity of retrograde P waves in leads V-1, II, III, aVF and I durin g AVRT, the concealed accessory pathway could be localized to one of t he nine regions on the atrioventricular annuli with an accuracy of 75% (for a right midseptal pathway) to 93.8% (for a left posterior pathwa y). Overall, the new algorithm had an accuracy of 97.8% in discriminat ing AVNRT from AVRT and 88.1% in localizing a concealed accessory path way, prospectively. Prediction was incorrect in only 15 patients (9.1% ). Conclusions. The new ECG algorithm derived from the analysis of ret rograde P waves during tachycardia could provide a criterion for diffe rential diagnosis between AVNRT and AVRT and for predicting the locati on of concealed accessory pathways. (C) 1997 by the American College o f Cardiology.