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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

View larger version (36K): [in a new window]   Figure 1 Electrocardiogram shows one ectopic (*), which initiates atrial fibrillation (B). The QRST complex preceding ectopy was used as a template (A) for QRST subtraction from the subsequent QRST-ectopic P-wave complex (C). The QRS complexes of the template and that of the beat preceding the ectopy were compared by a correlation coefficient calculated for each lead (shown above each trace) and, in the example shown here, indicate a high degree of matching. The subtracted ectopic P-wave morphology is flat in lead I, broadly positive in V1, and broad, notched, high-amplitude (100 µV) in lead II with the amplitude ratio of lead III/II >0.8, suggesting that the left superior pulmonary vein (PV) is the ectopic source. During intracardiac mapping of this patient, reversal in activation sequence of atrial (arrow, closed head) and PV potentials (arrow, open head) was observed in the circumferential recording of left superior PV during ectopics (D). This finding confirms the ectopic source predicted by postsubtraction P-wave analysis. CSd = distal coronary sinus; map = mapping catheter in right superior PV; PV 1-2 until PV 10-1 = bipoles from the circumferential catheter in left superior PV.

View larger version (41K): [in a new window]   Figure 2 Ectopic P-wave morphology before (A) and after (B) QRST subtraction. (a) Shows the amplitude of subtracted P-wave in lead I and avL 50 µV and high-amplitude (100 µV) P-wave in lead II with the amplitude ratio of lead III/II <0.8, suggesting right superior pulmonary vein (PV) origin. (b) Shows an ectopic P-wave, which is positive in lead I and avL (50 µV) and low-amplitude (<100 µV) P-wave in lead II, suggesting right inferior PV origin. (c) Shows flat P-wave in lead I, avL and broad, notched, low-amplitude P-wave in lead II, with the amplitude ratio of lead III/II >0.8, suggesting left inferior PV origin. Intracardiac mapping and ablation were confirmatory.

View larger version (37K): [in a new window]   Figure 3 Ectopic P-wave morphology before (A) and after (B) QRST subtraction. The subtracted ectopic P-wave morphology shows prominent positive P-wave in lead I and high-amplitude (100 µV) P-wave in lead II, with the amplitude ratio of lead III/II <0.8. Though this suggests right superior PV as the source of ectopy, comparison with PV pacemapping from left superior pulmonary vein (PV) (C) and right superior PV (D) indicates a 12/12-lead match with left superior PV pacing. Ectopics were eliminated by the disconnection of left superior PV.

View larger version (34K): [in a new window]   Figure 4 Ectopic P-wave morphology before (A) and after (B) QRST subtraction in a patient with frequent ectopics, sometimes in a bigeminal pattern, after pulmonary vein (PV) disconnection. Postsubtraction ectopic P-wave morphology shows biphasic pattern (negative-positive) in lead II, III, and avF, and broad positivity in V1, which is clearly dissimilar to pacemapping P-wave morphologies from PVs (D: right superior PV, E: right inferior PV, F: left superior PV, G: left inferior PV), suggesting a non-PV focus. Pacemapping from several left atrial sites demonstrated that ectopic morphology closely matched the pacemap from the low posterior left atrium between two inferior PVs (C). Successful ablation was performed at a site very close (within 5 mm) to this pacemapping site.

View larger version (45K): [in a new window]   Figure 5 Ectopic P-wave morphology before (A) and after (B) QRST subtraction in cases with ectopics from superior vena cava (SVC) (a) and inferior vena cava (IVC) (b). Subtraction results showed a P-wave taller than sinus rhythm in inferior leads but with similar morphology in V1 for ectopy originating from SVC (a). For IVC ectopics, a tall P-wave in lead I and negative P waves in the inferior leads with deeper negativity in lead III than in lead II was observed (b). a’ and b’ are P-wave morphologies during pacemapping from the medial aspect of the SVC and of the IVC, respectively.