Abstract: Abstract Objectives:This study sought to construct an algorithm to differentiate left atrial from right atrial tachycardia foci on the basis of surface electrocardiograms (ECGs). The present study therefore sought to analyze P wave configuration in patients with atrial tachycardia who underwent successful catheter ablation, Our goal was to differentiate ectopic foci originating in left or right atrium on the basis of surface ECG findings. Methods: A total of 37 patients with atrial tachycardia due to either abnormal automaticity or triggered rhythm underwent detailed atrial endocardial mapping and successful radiofrequency ablation of a single atrial focus. To calculate the PRI index ( PR interval/PP interval) evaluated the variation of conduction upon the atrioventricular and to calculate the PCI index ( P width/PR interval) evaluated the variation of conduction in atrial.Results:In 29 patients, the tachycardia was located in the right atrium,and 8 was in the left atrium.Analysis of P wave configuration showed that leads aVL and V1 were most helpful in distinguishing right atrial from left atrial foci. The amplitude of lead II III and aVF are prominently larger in left atrial tachycardia. The PCI values which was located in coronary sinus, Nor-coronary sinus and lateral wall are 0.23, 0.26 and 0.24. There is significant less than other sites of tachycardia, P <0.05. The PRI and PCI values of right atrial appendage, and right superior pulmonary veins are mostly in all sites (p<0.05), 0.49 and 0.55 in right atrial appendage, 0.51 and 0.43 in posteroinferior right atrium, and right superior pulmonary veins are 0.47 and 0.53. Conclusions: 1) P waves in lead I and aVL were most helpful in distinguishing right atrial from left atrial foci. 2) Leads II, III and aVF were helpful in providing clues for differentiating superior from inferior foci. 3) PCI and PRI index was helpful to predict site of tachycardia origin.

Key words: Atrial tachycardia, ECG, P wave, Site origin, Radiofrequency ablation