Use of P wave configuration during atrial tachycardi to predict site of origin

Objectives. This study sought to construct an algorithm to differentiate left atrial from right atrial tachycardi foci on the basis of surface electrocardiograms (ECGs). Background. Atrial tachycardi is an uncommon form of supraventricular tachycardia, often resistant to drug therapy. Methods. total of 31 consecutive patients with atrial tachycardi due to either abnormal automaticity or triggered rhythm underwent detailed atrial endocardial mapping and successful radiofrequency catheter ablation of single atrial focus. P wave configuration was analyzed from 12-lead ECGs during tachycardi during either spontaneous or pharmacologically induced atrioventricular block. P waves inscribed above the isoelectric line (TP interval) were classified as positive, below as negative, above and below (or conversely, below and above) as biphasic and flat P waves as isoelectric (0). In 17 patients the tachycardi was located in the right atrium: crist terminalis (n = 4); right atrial appendage (n = 4); lateral wall (n = 4); posteroinferior right atrium (n = 3); tricuspid annulus (n = 1); and near the coronary sinus (n = 1). In 14 patients, atrial tachycardi was located in the left atrium: at the entrance of the right (n = 6) or left (n = 4) superior pulmonary veins; left inferior pulmonary vein (n = 1); inferior left atrium (n = 1); base of left atrial appendage (n = 1); and high lateral left atrium (n = 1). Results. There were no differences in P wave vectors between sites at the right atrial lateral wall versus the right atrial appendage or between sites at the entrance of right versus left superior pulmonary veins. However, analysis of P wave configuration showed that leads aVL and V1 were most helpful in distinguishing right atrial from left atrial foci. The sensitivity and specificity of using positive or biphasic P wave in lead aVL to predict right atrial focus was 88% and 79%, respectively. The sensitivity and specificity of positive P wave in lead V1 in predicting left atrial focus was 93% and 88%, respectively. Conclusions. 1) Analyses of surface P wave configuration proved to be reasonably good in differentiating right atrial from left atrial tachycardi foci. 2) Leads II, III and aVF were helpful in providing clues for differentiating superior from inferior foci.