Objective To report retrospectively on the training and subsequent experience of two operators in transseptal ablation of arrhythmias arising in the left atrium and left atrioventricular annulus, to show whether, with adequate training and careful attention to detail, this is a safe and effective technique.

Setting Electrophysiological studies and transseptal procedures were performed in the electrophysiology laboratories of the Moffatt Hospital, University of California at San Francisco (39) and Manchester Royal Infirmary (65) from January 1993 to June 1997. Close supervision by a fully trained operator was provided for at least the first 20 procedures performed by each operator.

Patients 94 consecutive patients underwent electrophysiological study and ablation for Wolff-Parkinson-White syndrome with left sided accessory connections (81 patients) or ectopic atrial tachycardia (13 patients); 104 transseptal procedures were done; eight patients required multiple procedures.

Results 92 patients (98%) were initially successfully ablated. Five of 81 with accessory pathways (6%) and three of 13 with atrial tachycardia (23%) required further procedures. One patient with Wolff-Parkinson-White syndrome could not be ablated at a second procedure. Long term success rate for accessory pathway ablation was therefore 99%. Procedures were abandoned in three patients because of minor complications. All were subsequently ablated successfully by a transseptal approach on another day.

Conclusions The transseptal approach is safe and effective for ablation of left sided arrhythmias. The technique has similar success rates to the retrograde transaortic approach but without the risk of inadvertent damage to the coronary arteries or aortic valve.