Fehmi Keçe

Optimizing Ablation Duration using Dormant Conduction 137 6 6.4.5 Outcome in time-to-isolation dependent ablation Two prior studies report on time-to-isolation cryoballoon based ablation. A recent randomized trial by Ferrero-de-Loma-Osorio et al. showed in 140 patients that applying 60s additional ablation after time-to-isolation with a second 120s application was similar to a double 180s fixed duration protocol (70.5 vs. 74.3% success off AAD at one year, p=0.61) (19). In a multicenter trial by Aryana et al. an additional ablation of 120s in 355 patients was applied after time-to-isolation, but a second 120s ablation was added when time-to- isolation was >60s. They compared this strategy to conventional ablation performed in 400 pts, which was defined as 2-3 applications of 2-4 min at the discretion of the operator. Outcomes were similar at 83% and 78% at one year off AAD (p=0.14)(18). Although we performed no additional ablations in our protocol, our results in the 150s group (72%offAAD at one year) are similar to the first study. Interestingly, although we aimed at abolishment of all dormant conducting veins, outcomes were numerically smaller in both the 90s and 120s groups (52 and 56%) compared to the 150s group (72%), suggesting inferiority of this approach. A possible explanation is that during the first incomplete ablation edema occurs(20), making the second ablation less effective. Indeed, in multivariate analysis we observed that reconnection/DC was the only predictor of recurrence while the number of unsuccessful ablations was a predictor of reconnection/DC. Therefore, a complete lesion formation with a single (durable) freeze may be desirable. In addition, success on AAD was 16% higher than success off AAD in the 120s group, compared to only 4 and 3% difference in the 90s and 150s groups respectively. This may indicate that 120s additional ablation creates enough PV activation delay to maintain sinus rhythm with AAD in this group. 6.4.6 Repeat ablation in time-to-isolation dependent ablation The study of Aryana et al. reported 9.9%vs. 15.7% re-ablations in the study and control groups, respectively, with 18.5% vs. 5.0% of the veins reconnected(18). In our study a significant less repeated procedures were requiredwhen the additional ablation durationwas increased from 90s to 150s (36 vs. 4%; p=0.041). As repeated procedures are clinicallymeaningful, these results suggest that 90s or 120s additional ablation after time-to-isolation is insufficient. 6.4.7 Reconnection/dormant conduction in time-to-isolation dependent ablation Acute PV reconnection is also reported in the trial of Ferrero-de-Loma-Osorio et al . In this trial in 140 patients, 3.5% and 2.3% of the veins were acutely reconnected in the study and control groups, respectively (p=0.6)(19). This is comparable to the 4% dormant conduction in our 150s group, while the 90s and 120s groups showed a significant increase in reconnection/DC with decreasing additional ablation.