Background

The optimal freeze duration in cryoballoon pulmonary vein isolation (PVI) is still under debate. Since introduction of the 2^nd generation cryoballoon in combination with the spiral mapping catheter, real time-recordings of the time-to pulmonary vein isolation (TTI) has emerged as an essential procedural parameter. It was shown, that patients treated with a TTI-dependent titration of the cryoenergy experience fewer procedural complications compared to patients with a fixed freeze protocol. Also, short term clinical outcome was not different in patients treated with a TTI vs. a fixed protocol. However, the time of follow-up in those studies is limited.

Aim of the study

We analysed the clinical 2 year outcome in patients undergoing a TTI-guided protocol compared to patients with a fixed ablation protocol to evaluate the efficacy of both ablational strategies.

Methods

In this study, we included 200 patients with symptomatic atrial fibrilation (AF), in which a cryoballoon-PVI was performed. 100 patients were treated  with a time to isolation guided protocol (TTI group), whereas the other 100 patients were treated with a fixed ablation protocol (fixed group). In the fixed group a 240s freeze cycle was followed by a 240s bonus freeze after pulmonary vein isolation. In the TTI group freeze duration was 120s if TTI was < 30s, 180s if TTI was 30s. If TTI was > 60s, a 180s bonus freeze was applied (figure 1).

 Figure 1: Flowchart depicting cryoenergy dosing depending on TTI or fixed group.

Results

After a mean follow-up time of 764±437 days, there is no significant difference regarding the recurrence of atrial arrhythmia including the intake of class I/III antiarrhythmic drugs between the TTI group (57.6%) and the fixed group (66.2%; p=0.1). The number of hospitalisations due to atrial arrhythmia in the first year is not different in both groups (TTI: 2.2±4.8; fixed: 2.1±4.9; p=0.9). In patients with recurrence of atrial arrhythmia, there is no difference regarding the EHRA-score (TTI: 1.9±1.0, fixed: 1.7±0.9; p=0.4) or the left ventricular ejection fraction (LVEF) (TTI: 63.9±10.6, fixed: 63.3±11.5; p= 0.8).

Conclusion

The two year atrial arrhythmia recurrence rate of patients treated with the cryoballoon is not different between the TTI group and the fixed group. Further clinical parameters such as the EHRA-score, rehospitalisation rate or LVEF are also comparable. This indicates, that individualizing, i.e. decreasing cryoenergy is as effective as conventional ablational strategies.