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CLINICAL STUDY

QRST subtraction combined with a pacemap catalogue for the prediction of ectopy source by surface electrocardiogram in patients with paroxysmal atrial fibrillation

Kee-Joon Choi, MD^*, Dipen C. Shah, MD^,*, Pierre Jais, MD^*, Meleze Hocini, MD^*, Laurent Macle, MD^*, Christophe Scavee, MD^*, Rukshen Weerasooriya, MD^*, Florence Raybaud, MD^*, Jacques Clementy, MD^* and Michel Haissaguerre, MD^*

^* Hôpital Cardiologique du Haut-Lévêque, Bordeaux-Pessac, France
Hôpital Cantonal Universitaire de Geneve, Geneva, Switzerland

Manuscript received March 5, 2002; revised manuscript received July 2, 2002, accepted August 19, 2002.

^* Reprint requests and correspondence: Dr. Dipen C. Shah, Centre de Cardiologie, Hopital Cantonal Universitaire de Geneve, 24, Rue Micheli du Crest, CH 1211 Geneva 14, Switzerland.
Dipen.Shah{at}hcuge.ch

OBJECTIVES: This study evaluated the use of ectopic P-wave morphology to localize pulmonary vein (PV) and non-PV sources of atrial ectopics in patients with paroxysmal atrial fibrillation (PAF).

BACKGROUND: The vectorial information embodied in the morphology of ectopic P waves is concealed by overlying T waves.

METHODS: The P-wave morphology of 56 ectopics was prospectively analyzed in 44 patients with PAF (age, 52 ± 12 years; 36 male) by subtracting the adjacent QRST from the QRST-ectopic P-wave complex using custom-designed software. Subtraction fidelity was validated in 15 other patients (55 ± 19 years, 11 male) by comparing drive beats with simulated ectopics (S2 from the same site) unmasked by subtracting overlying QRST. An algorithm combined with PV pacemaps was used to predict PV sources. Subtracted ectopic P-wave morphologies after PV disconnection were compared with PV and non-PV site pacemaps. Localization was confirmed by mapping and successful ablation.

RESULTS: A 10-lead electrocardiogram (ECG) match was observed in 92% of 644 simulated ectopics (coupling intervals: 190 to 520 ms). In PAF patients, 37 spontaneous ectopics originated from the PV, while 19 were noted after PV disconnection. Using the P-wave algorithm alone, correct prediction of PV origin was achieved in 30/37 ectopics (81%). Combination with PV pacemaps allowed correct prediction in 34/37 (92%). After PV disconnection, ECG localization predicted successful ablation sites in 16/19 (84%).

CONCLUSIONS: Comparison of subtracted ectopic P waves with a pacemap catalogue provides a simple and accurate 12-lead ECG-based method for localization, which can facilitate ablation of arrhythmia triggers irrespective of origin from the PV or elsewhere.

Abbreviations and Acronyms   AF   atrial fibrillation   IVC   inferior vena cava   PAF   paroxysmal atrial fibrillation   PV   pulmonary vein   SVC   superior vena cava