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Focal left atrial (LA) tachycardias/ectopy (LATs) that may initiate atrial fibrillation (AF) are often difficult to initiate, non-sustained, and may have multiple origins, often in one or more pulmonary veins (PV). Thus, mapping with conventional techniques is often difficult. The authors tested the hypothesis that a non-contact mapping system capable of global simultaneous mapping of >3000 points in the LA, would facilitate ablation of LAT. The non-contact mapping system was able to rapidly identify the origin of human LATs and focal AF despite the infrequency and short duration of initiating ectopy and guide a conventional mapping catheter to successful ablation sites. The authors also observed that, although isoproterenol is the most successful method of initiating LATs, these originate from multiple sites and therefore appear to be of limited clinical significance.

The conduction characteristics of human ventricular tachycardias (VT) have not been fully defined. The authors used a non-contact system to map 11 reentrant VT in 8 patients. Propagation velocities and 3-dimensional angles of turn were calculated from Cartesian co-ordinates. The complete diastolic pathway (DP) was mapped in 7 VT patients. DP wavefront velocity was 0.82/spl plusmn/0.49 m/s. Significant changes (>5 degrees/mm) in trajectory of propagation (TOP) occurred within 8 DP segments, in which propagation slowed to 0.41/spl plusmn/0.11 m/s compared with 0.91/spl plusmn/0.16 m/s preceding (p

The pattern of left atrial (LA) activation during sinus rhythm (SR) in humans has not been delineated. The authors used a non-contact mapping system to analyze the patterns of left atrial (LA) activation during sinus rhythm and pacing. The system is capable of simultaneously reproducing more than 3,000 electrograms, which are superimposed on a virtual left atrial endocardium. Data were recorded in sinus rhythm and during pacing from the high right atrium, coronary sinus os, and right atrial septum. The authors demonstrate that during sinus rhythm, the LA activates mainly through posterior septal fibers, adjacent to the ostia of the right pulmonary veins. This suggests that, in humans, anterior interatrial connections including Bachmann's bundle may be less important than previously recognized.