Background

Esophageal thermal injury (ETI) following pulmonary vein isolation (PVI) ablation is considered a rare but serious complication, with atrio-esophageal fistula as potentially lethal complication after thermal damage. A new non-thermal technology, pulsed-field ablation (PFA), induces pores in cell membranes by applying high voltage ultra-short impulses creating durable ablation lesions. Previous studies have suggested selectivity of PFA in targeting atrial myocardium, while sparing the esophagus. Our study sought to assess esophageal damage by using a novel hybrid imaging approach (⁶⁸Ga-FAPI/positron-emission tomography [PET]/computed tomography [CT]) targeting the protein FAP-alpha specifically expressed by activated fibroblast following tissue injury. The aim of this study was to quantitatively assess esophageal fibroblast activation as surrogate for ETI after PVI, comparing PFA procedures to ablations with established thermal energy sources (cryoballoon (CBA) and radiofrequency ablation (RFA)).

Methods

Data of 29 patients (13 PFA, 11 CBA, 5 RFA) having undergone ⁶⁸Ga-FAPI-PET/CT after PVI for either paroxysmal or persistent AF were analyzed. Figure 1 depicts an example of tracer uptake around the PVs in a patient after PFA without any esophageal uptake. Data were assessed quantitatively, using standardized uptake parameters (SUV_max, SUV_mean, SUV_peak and corresponding target-to-background ratios) of the region of interest placed at the esophageal wall at the CT level of the origin of left superior pulmonary vein.

Results

Imaging was performed after a mean period of 25 days after PVI [range 3-62]. Mean patient age was 63.7±6.5 years, with a mean left ventricular ejection fraction of 55±6.4%. Left atrial volume index was comparable between CBA, RFA and PFA cohort (41.4 vs. 37.2 vs. 38.2ml/m², p=0.32). Quantitatively, there was no statistically significant difference between SUV_max, SUV_peak or SUV_mean values between PVI patients. After adjusting for blood pool uptake, patients after PFA showed significantly lower target-to-background ratios compared to both RFA and to CB-ablated patients (figure 2A-C) whereas no difference could be observed between RFA and CBA procedures.

Discussion and Conclusion

Our study assessing FAPI uptake as a surrogate for fibroblast activation after PVI confirms recent findings from late-gadolinium-augmented MRI studies that PFA enables ablation with high specificity for myocardial tissues while sparing the esophagus. These results suggest that PFA ablation provides an energy source that can potentially be deliberately overpowered without compromising safety with respect to ETI PFA ablation provides an energy source that can potentially be deliberately overpowered without compromising safety with respect to ETI.