Background: The 2005 P wave morphology algorithm by Kistler et al was highly accurate in predicting the site of focal atrial tachycardia (AT). An updated algorithm was developed in light of advances in multipolar 3D mapping, recognition of additional AT sites and a renewed interest in the P wave in mapping non PV triggers in AF ablation
Objective: To update and prospectively evaluate a P wave morphology algorithm against a contemporary patient cohort who underwent successful radiofrequency ablation (RFA) for AT
Methods: The P wave algorithm (see figure) was modified to improve clinical utility and recognise the spatial limitations of foci within close anatomic proximity at the paraseptal location. This includes CS ostium, perinodal, non-coronary cusp, left (LS) and right septum (RS), and superior mitral annulus. 30 consecutive patients with focal AT and unencumbered P waves who underwent successful ablation were included, and the revised algorithm was prospectively evaluated by 3 blinded assessors
Results: Focal AT originated from the RA in 10 (33%), LA in 9 (30%) and paraseptum in 11 (37%). RA sites included crista terminalis (CT) 6, tricuspid annulus (TA) 3, right atrial appendage (RAA) 1; LA cases include left pulmonary vein / left atrial appendage (LPV/ LAA) 2, and right pulmonary vein (RPV) 7. Using the algorithm the correct anatomic location was determined in 93%. Blinded assessors did not identify 4 paraseptal cases due to incorrect interpretation of the terminal positive P wave component (3) and initial negative P wave deflection (1) in lead V1
Conclusion: The revised 2020 P wave morphology algorithm offers a simplified and accurate method of localising the responsible focus for AT