Fatal End of a Safety Algorithm for Pulmonary Vein Isolation With Use of High-Intensity Focused Ultrasound

BACKGROUND: High-intensity focused ultrasound (HIFU) can achieve pulmonary vein isolation (PVI), but there are safety concerns after severe complications. Therefore, we evaluated an esophageal temperature (ET)-guided safety algorithm to apply HIFU safely. METHODS AND RESULTS: After standard left atrial access, HIFU was repeatedly applied until PVI was complete. A safety algorithm was used: or=40.0 degrees C, use of power modulation (PM) at ET 39.0 degrees C: to reduce ablation temperature in surrounding tissue, acoustic power is switched on/off at 1 Hz; in all first ablations, use of PM after 50% of programmed time. Touch-up radiofrequency ablation was used when PVI failed. Periprocedural ET monitoring and endoscopy 2 days after ablation were performed. Twenty-eight patients (18 males; mean age at enrollment, 63 years), with paroxysmal atrial fibrillation (AF; n=19) and persistent AF (n=9) were included. In 84 of 109 PV (9 of 25 patients), PVI was achieved using HIFU only. In 9 of 109 PV, HIFU was aborted because of high ET. Mean ET at the end of the ablations with and without use of PM were 38.1+/-2.0 degrees C and 37.4+/-1.0 degrees C (P=0.0002). During endoscopy in 2 of 26 patients, a small thermal lesion was found. Other complications included 2 persistent phrenic nerve palsies, 1 ischemic stroke, 1 pericardial effusion 48 days after ablation, 1 unexplained death 49 days after ablation, and 1 lethal atrial-to-esophageal fistula 31 days after ablation. CONCLUSIONS: The safety algorithm failed to prevent lethal complications. Currently HIFU does not meet the safety standards required for treatment of atrial fibrillation.