Precision of preoperative electrophysiological study in predicting the intraoperatively defined location of single left-sided accessory pathways.

In 34 patients with a left-side anomalous pathway (AP) considered for arrhythmia surgery, the atrial insertion of the anomalous pathway in the preoperative investigation was determined by using three different techniques. The atrial activation sequence during orthodromic tachycardia or ventricular stimulation was recorded in the coronary sinus by using either (a) unipolar leads from an eight-polar electrode catheter with an interelectrode distance of 1 cm, (b) bipolar leads from consecutively positioned pairs of electrodes on the same electrode catheter or (c) bipolar leads recorded at one centimeter intervals by withdrawal of the electrode catheter. The corresponding location at surgery was obtained by atrial epicardial mapping during ventricular stimulation. Each way of recording the atrial activation sequence in the coronary sinus during orthodromic tachycardia or ventricular stimulation was compared with regard to their predictive value in assessing the corresponding location by intraoperative mapping. At surgery, a visual grid system was used to define the anatomical landmarks which were located 20 mm apart. When the unipolar technique was used to assess the anomalous pathway location, there was a difference corresponding to a distance of 2-2.5 anatomical landmarks (48 mm) between the preoperative and intra-operative assessments. With the bipolar technique the difference was up to 3 anatomical landmarks (60 mm) while it was up to 4.5 anatomical landmarks (90 mm) when the withdrawal technique was employed. The unipolar technique was superior in differentiating a left lateral from a left posterior or a septal location.