Paced P wave morphology templates to guide atrial tachycardia localization

Introduction: Surface ECG is a useful tool to guide mapping of focal atrial tachycardia (AT).We thought to construct an algorithm, based on paced P wave templates from different anatomical sites in both atria in patients with normal hearts. Methods: We prospectively enrolled consecutive patients who underwent electrophysiology study, having no heart disease. Atrial pacing was carried out at different anatomical sites in both atria. Paced P wave morphology (PWM) and duration (PWD) were assessed. P wave morphology was classified into: positive, negative, biphasic (+/- or -/+) and isoelectric. A proposed algorithm was generated from the constructed templates of each pacing site. Results: Sixty-four patients (25 males) were enrolled. Mean age was 37 ± 13 years. Atrial pacing was performed in 61 patients (95%) at the right atrium and in 15 patients (23%) at the left atrium. A neg/iso P wave in V1, a pos/iso P wave in AVL and lead I identified right atrial pacing sites (p=0.01, p=0.02 and p=0.02, respectively). Negative P wave in lead aVL identified left pulmonary veins when compared to right pulmonary veins (P=0.03). PWD was significantly longer when pacing from lateral tricuspid annulus (TA) as compared to medial TA (136 ± 12ms vs. 99 ± 10 ms , P=<0.001) and when pacing from the left superior pulmonary vein as compared to the right superior pulmonary vein (152 ± 12 ms vs. 135± 10 ms, (P=0.001). Conclusions: PWM and PWD derived from templates generated through atrial pacemapping could be used to guide localization of focal AT.