Electrocardiographic differentiation of narrow QRS complex tachycardia: validation of the new aVL and aVR criteria and a unifying approach to ECG analysis

Background Electrocardiographic analysis of narrow QRS complex tachycardias (SVT) is the key to correct diagnosis and choice of immediate and long-term therapeutic interventions. Several novel differentiation criteria for diagnosis of atrioventricular nodal reentrant tachycardia (AVNRT) were proposed in the last decade (e.g. lead aVL and lead aVR criteria). However, differential diagnosis of SVT remains challenging, and classic AVNRT criteria (pseudo r' in V1 and pseudo s in II, III, aVF) remain the most commonly used. Furthermore, the aVR and aVL criteria have never been validated by others. Purpose The primary objective of the study was to validate the new electrocardiographic criteria for AVNRT diagnosis in a large, representative cohort of patients. The secondary objectives were: 1.) to evaluate the new unifying criterion of a retrograde P wave at the end of the QRS complex in any lead. 2.) to evaluate the usefulness of the grading of certainty of retrograde P wave detection, to obtain a criterion with high specificity for the diagnosis of typical AVNRT. Methods This retrospective analysis included all consecutive patients who underwent ablation for SVT over a 14-year period. The definitive diagnosis of SVT was made by electrophysiological study. Two blinded, experienced cardiologists evaluated the SVT recordings including also corresponding ECGs with sinus rhythm. The ECGs were evaluated for the presence of a P wave at the end of the QRS (pseudo r', pseudo s, notch, slur, etc.): in V1, I, II, III, aVF, aVR, aVL. Additionally, the degree of certainty that there is a P wave at the end of the QRS complex in any lead was categorized as "evident", "possible", or "absent". Results A total of 823 patients – 678 adults (mean age 49 years, 64% women) and 145 children (mean age 12 years, 54% girls) were studied. Typical (slow-fast) AVNRT was diagnosed in 73%, atrioventricular reciprocating tachycardia in 17%, atrial tachycardia in 8%, and atypical AVNRT in 3%. For the diagnosis of typical AVNRT, the pseudo r' in V1, pseudo s in II, III, aVF, pseudo r' in lead aVR and retrograde P wave at the end of the QRS complex in lead aVL had SN=66, SP=96, ACC=75, and SN=50, SP=97, ACC=63, and SN=23, SP=98, ACC=44, and SN=30, SP=98, ACC=49, respectively. The unifying criterion - a retrograde P wave at the end of the QRS complex in any lead had SN=80, SP=93, ACC=84. The diagnosis of ''evident'' retrograde P wave (in any lead) had SN=57, SP=97, ACC=68. Conclusions The new criteria (lead aVL and lead aVR) were found to be much inferior to the classic criteria. Our unifying criterion ''a retrogade P wave at the end of the QRS complex in any lead'' had the highest sensitivity and diagnostic accuracy for diagnosing of AVNRT of all the criteria. An ''evident'’ P wave at the end of QRS had a very high specificity for diagnosis of typical AVNRT, potentially making it useful for empirical AVNRT ablation in non-inducible patients.