A comparison of unipolar versus bipolar mapping in the ablation of left-sided accessory atrioventricular conduction pathways

Objective: To compare the utility of unipolar versus bipolar mapping to guide radiofrequency catheter ablation of manifest left-sided accessory pathways.

Methods: University Hospital Methods: We studied twelve patients with a mean age of 42 +/- 13 years, submitted to a successful left-sided accessory pathway ablation. Detailed mapping was performed with the ablation catheter, recording simultaneous unipolar (distal electrode) and bipolar electrograms, in sinus rhythm. Twenty-three recordings were analyzed, including twelve successful, and eleven unsuccessful sites. The following measurements were analyzed: atrial and ventricular amplitude; interval between atrial and ventricular electrogram onset; interval between onset of ventricular electrogram and delta wave; interval between ventricular electrogram activation and delta wave and; unipolar morphology, classified as P-rS, P-QS or PQS.

Results: Accessory pathway ablation required a mean of 6.3 +/- 7.9 (median of 2) energy applications. Analysis of the electrogram revealed that ventricular activation was significantly earlier in successful versus unsuccessful sites. Unipolar morphology was also different according to the ablation result: among unsuccessful applications the P-rS configuration occurred in one, and the P-QS in ten cases, while in successful sites, seven had P-QS, and five had PQS morphology.

Conclusions: Unipolar recordings are useful to guide radiofrequency catheter ablation of manifest left-sided accessory pathways and should be used in association with bipolar electrograms.