A new ECG algorithm for the localization of accessory pathways using only the polarity of the QRS complex

A new algorithm is proposed for localization of accessory atrioventricular pathways by use of a 12-lead electrocardiogram (ECG). The polarity of the QRS complex in leads III, V 1, and V 2 from 102 patients with Wolff-Parkinson-White syndrome with manifested preexcitation who underwent successful radiofrequency catheter ablation was analyzed. Accessory pathways on the right side of the heart were localized to three regions around the tricuspid annulus, and left-sided pathways were localized to two regions around the mitral valve annulus. In 42 of 46 patients (91%) with left posterolateral accessory pathways, a common characteristic of the ECG was a positive QRS complex in leads III and V 1 (sensitivity 91%, specificity 95%). Of 19 patients with left inferior paraseptal or inferior accessory pathways, 16 (84%) had a negative QRS complex in lead III and a positive QRS complex in lead V 1 (sensitivity 84%, specificity 98%). All six patients with right anterosuperior paraseptal accessory pathways had a positive QRS complex in lead III but a negative QRS complex in lead V 1 (sensitivity 100%, specificity 97%). The 25 patients with right inferior paraseptal or inferior accessory pathways had a negative or isodiphasic QRS complex in leads III and V 1, but the QRS complex was positive in lead V 2 in 21 (84%) of these patients (sensitivity 84%, specificity 100%). Finally, five of the six patients (83%) with right anterior accessory pathways had a negative QRS complex in leads III, V 1, and V 2 (sensitivity 83%, specificity 96%). With the algorithm, the localization of accessory pathways was thus identified in 90 of the 102 patients (88%).