Abstract 2550: Fatal End of a Safety Algorithm for High-Intensity Focused Ultrasound (HIFU)
Introduction: As a curative treatment of AF, HIFU can achieve electrical PVI. Safety issues after severe & lethal complications led us to evaluate an esophageal temperature (ET) guided safety algorithm in order to apply HIFU safely.
Methods: After double transseptal puncture, selective pulmonary vein (PV) angiograms & HIFU balloon catheter placement at PV ostium, HIFU was repeatedly applied until complete PVI. Safety algorithm:
≤3 ablations per PV,
early abortion when no effect after 50% of programmed time or when ET ≥40.0°C,
use of Power Modulation (PM) at ET 39.0°C: to reduce ablation temperature in targeted myocardial tissue & adjacent structures, acoustic power is switched on & off with a frequency of 1 Hz,
in all 1st ablations use of PM after 50% of programmed time.
Max. sonication time: 90 sec. Touch-up radiofrequency ablation was performed in case of failed PVI. Continuous ET monitoring with an ET probe. Endoscopy was performed 2 days after ablation.
Results: 28 patients (pt) (18 male, age 63±7 years), with PAF (n=19) & persistent AF (n=9) (duration: 6±4 years). In 85/109 PV (9/25 pt) persistent PVI was achieved using HIFU only. In 9/109 PV HIFU was aborted due to high ET, these PV could not be isolated using HIFU. In 191/311 ablations PVI could be achieved using HIFU only. In 57/191 successful ablations PM was used, 26/57 initially isolated PV reconducted during or after ablation with PM. In the remaining 134/191 successful ablations no PM was used: 49/134 PV reconducted after end of ablation (p=0.26). Mean ET at start of PM was 37.6±1.2°C. Mean ET at the end of the ablations with & without use of PM were 38.1±2.0°C & 37.4±1.0°C (p=0.008). Endoscopy was performed in 26/28 pt. In 2/26 pt a small thermal lesion was found in the anterior part of the esophagus. In 2/28 pt PN palsy persisting >3 months (PNP) occurred during RSPV ablation. Mean maximal ET was equal in pt with & without PNP: 37.5±1.4°C. Other complications were: 1 ischemic stroke, 1 pericardial effusion 48 days after ablation, 1 pt died without clear cause 49 days after ablation, 1 pt developed lethal atrial-to-esophageal fistula 31 days after ablation, max. ET: 39.3°C.
Conclusion: The proposed safety algorithm failed to prevent lethal complications. Therefore the HIFU ablation programme was stopped worldwide.