P wave morphology of an arrhythmogenic focus in patients with atrial fibrillation originating from a pulmonary vein or the superior vena cava.

BACKGROUND It was hypothesized that atrial premature contractions (APCs) originating in the pulmonary veins (PVs) or superior vena cava (SVC) can be localized by evaluating characteristics of the P wave. METHODS AND RESULTS Thirty-eight patients with paroxysmal atrial fibrillation were studied. P wave polarity and morphology of the ECGs during pacing from PVs were analyzed and compared to those of APCs originating from PVs. The P wave angle and notch in lead II during pacing from the right superior (RS) PV and SVC was compared to those of spontaneous APCs originating from those veins. A positive P wave in lead I was helpful in predicting right PV origin. A positive P wave in lead II distinguished superior PV origin. A notched P wave was helpful in predicting left PV origin. P wave polarity in lead II was positive during RSPV and SVC pacing. P waves in lead II during RSPV pacing had notching in 80%, but all P waves were smooth during SVC pacing. A P wave angle of > 40 degrees and notching in lead II showed RSPV origin. CONCLUSIONS These criteria are helpful in selecting which of the 4 PVs should be isolated when APCs cannot be recorded after transseptal puncture.