Catheter ablation of left accessory atrioventricular connections: the transseptal approach

In the past few years, there has been a relative explosion of activity in the realm of interventional cardiology. The high rate of success of radiofrequency energy ablation have transformed catheter ablation from an investigational procedure into the first-line therapy for symptomatic Wolff-Parkinson-White syndrome. Radiofrequency catheter ablation for preexcitation syndrome is commonly based on a ventricular approach. Such an approach might be associated with the risk of prolonged arterial catheter manipulation, retrograde left ventricular catheterization, and production of multiple, potentially arrhythmogenic, ventricular lesions created during ablation. Potential risks can be avoided using atrial insertion ablation procedures. The transseptal procedure that was developed in the 1950s and 1960s as a diagnostic procedure and then shelved in the 1970s and early 1980s has now come back into prominence as a therapeutic technique in the treatment of valvular heart disease, and then in the ablation of the left accessory atrioventricular connections.

Atrial aspect of mitral annulus is a relatively smooth, nonobstructed surface that simplifies catheter movement, thereby permitting rapid and accurate accessory pathway location. Although primary use of earliest endocardial retrograde atrial activation as a marker of accessory pathway atrial insertion is sufficiently accurate to permit successful ablation, direct recording of an accessory pathway potential is an important predictor of successful ablation site. Moreover, the analysis of the unipolar atrial electrogram, recorded during sinus rhythm from the tip of the ablation catheter, provides further information for localizing the atrial insertion of the accessory pathways. Shortest atrial-accessory pathway and negative delta-accessory pathway intervals have been found to be the best predictors of the successful site.

A 90.5% success of the transseptal approach on an overall population of 328 patients, higher for overt than for concealed pathways, is comparable with the results of the retrograde. Complications are 0.5%.

In conclusion, the transseptal approach for ablation at the atrial site is very safe and highly effective, and avoids prolonged arterial cannulation and catheter manipulation in the ascending aorta and left ventricle.