Background: Pulmonary vein isolation using the cryoballoon technique has emerged as a standard treatment of drug refractory atrial fibrillation. In this procedure complete occlusion of the pulmonary vein (PV) with the balloon is essential for achieving PV isolation. Typically, PV occlusion is assessed by contrast injection and the whole procedure is guided by catheter movement under fluoroscopy.

Objective: Using an update for the SMARTFREEZE Cryo-Console (Boston Scientific) it is possible to directly visualize occlusion pressure as an indicator of complete PV occlusion during cryoballoon procedures.  Here we aimed to examine whether direct PV pressure monitoring during cryoballoon procedure is practicable and if it is able to reduce the amount of contrast and radiation compared to a classic approach.

Methods: We compared the first 20 patients after installation of the updated SMARTFREEZE console with the last 20 patients treated immediately before. The study population contained patients with paroxysmal and persistent atrial fibrillation. Cryoballon PV isolation was performed as described below.  After vascular access and transeptal puncture selective PV angiography is performed to identify the PV ostia. Then the polarsheath and the 28mm ballon-catheter are inserted via the guidewire. After inflation the cryoballon is advanced to the PV ostium over a spiral catheter. Complete PV occlusion is determined as an abrupt change in the pressure waveform with a loss of the a-wave which characterizes left atrial pressure. After complete PV occlusion a 180 second cryo ablation is applicated. 

Results: In our first observational trial we observed comparable results regarding procedural time using our conventional (73.1 min) compared to the pressure measurement (77.2 min) approach. Further we observed no differences in left atrial dwell time (58.5 vs. 60.8 min), total freezes per patient (5.4 vs. 5.8), achieved minimum temperatures (-56.6 vs. 56.6 °C), time to -30°C (26.3 vs. 26.4 s) or time to isolation (TTI, 47.6 vs. 54.7 s). Additionally, radiation exposure time was similar using both approaches (19.1 vs. 17.6 in the pressure guided group). As expected, a significant reduction of contrast use was achieved in the pressure measurement group (11.2 vs. 28.7 ml).

Conclusion: Monitoring complete PV occlusion by measuring the occlusion pressure is feasible and safe. Acute procedural outcome was comparable to our standard approach using contrast injection to verify complete PV occlusion regarding time to isolation, procedural time, LA dwell time and observed minimum temperatures. Most importantly, a significant reduction in contrast use could be achieved which has to be confirmed in larger patient cohorts.