Translesion stimulus-excitation delay indicates quality of linear lesions produced by radiofrequency ablation in rabbit hearts

Abstract

Failure of cardiac antiarrhythmic ablation to block action potential conduction produces poor outcomes which lead to repeat procedures. To overcome this, an intraoperative index of the quality of an ablation lesion is needed. We hypothesized that a rise in the translesion stimulus-excitation delay (TED) can indicate a continuous, transmural, linear lesion, and that the TED is related to the path length in the viable tissue around the lesion. Rabbit hearts were isolated, perfused with a warm physiological solution and stained with transmembrane potential-sensitive fluorescent dye. Radiofrequency (RF) ablation was performed on ventricular epicardium with a vacuum-assisted coagulation device to produce either a complete or incomplete lesion. Complete lesions were both transmural and continuous. Incomplete lesions were noncontinuous or nontransmural. The TED was determined with bipolar stimulation at one side of the lesion and either a bipolar electrogram at the other side or optical mapping on both sides. Hearts were then stained with tetrazolium chloride and examined histologically to estimate minimum path lengths of viable tissue from the stimulation site to the recording site. Complete lesions increased the TED by factors of 2.6–3.1 (p < 0.05), whereas incomplete lesions did not significantly increase the TED. Larger minimum path lengths were found for cases that had an increased TED. The TED was quantitatively predictable based on a conduction velocity of 0.38–0.49 m s−1, which is typical of rabbit hearts. The TED significantly increases when a linear lesion is complete, suggesting that an intraoperative measurement of the TED may help to improve ablation lesions and outcomes. Predictability of the TED based on the viable tissue path suggests that quantitative TEDs for clinical lesions may be anticipated provided that the conduction velocity is considered.