USE OF P-WAVE CONFIGURATION DURING ATRIAL TACHYCARDIA TO PREDICT SITEOF ORIGIN

Objectives. This study sought to construct an algorithm to differentia te left atrial from right atrial tachycardia foci on the basis of surf ace electrocardiograms (ECGs). Background. Atrial tachycardia is an un common form of supraventricular tachycardia, often resistant to drug t herapy. Methods. A total of 31 consecutive patients with atrial tachyc ardia due to either abnormal automaticity or triggered rhythm underwen t detailed atrial endocardial mapping and successful radiofrequency ca theter ablation of a single atrial focus. P wave configuration was ana lyzed from 12-lead ECGs during tachycardia during either spontaneous o r 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 hat P waves as isoelectric (0). In 17 patients the tachy cardia was located in the right atrium: crista terminalis (n = 4); rig ht atrial appendage (n = 4); lateral wall (n = 4); posteroinferior rig ht atrium (n = 3); tricuspid annulus (n = 1); and near the coronary si nus (n = 1). In 14 patients, atrial tachycardia was located in the lef t atrium: at the entrance of the right (n = 6) or left (n = 4) superio r pulmonary veins; left inferior pulmonary vein (n = 1); inferior left atrium (n = 1); base of left atrial appendage (n = 1); and high later al left atrium (n = 1). Results. There were no differences in P wave v ectors between sites at the right atrial lateral sail versus the right atrial appendage or between sites at the entrance of right versus lef t superior pulmonary veins. However, analysis of P wave configuration showed that leads aVL and V-1 were most helpful in distinguishing righ t atrial from left atrial foci. The sensitivity and specificity of usi ng a positive or biphasic P wave in lead aVL to predict a right atrial focus was 88% and 79%, respectively. The sensitivity and specificity of a positive P wave in lead V, in predicting a left atrial focus was 93% and 88%, respectively. Conclusions. 1) Analyses of surface P wave configuration proved to be reasonably good in differentiating right at rial from left atrial tachycardia foci. 2) Leads II, III and aVF were helpful in providing clues for differentiating superior from inferior foci.