Diaphragmatic Evaluation by Fluoroscopy to Identify Phrenic Nerve Dysfunction Related to Electroporation

Overview

Pulsed Field Ablation (PFA) represents a recent advance in the treatment of atrial fibrillation (AF), with a safety profile potentially superior to traditional thermal techniques, such as radiofrequency or cryoablation. Its mechanism of action allows tissue selectivity which in theory limits damage to extracardiac structures. However, several cases of right diaphragmatic paralysis have been reported in the literature after PFA, particularly during applications on the right pulmonary veins, near the right phrenic nerve. The available data are from studies without specific diaphragmatic monitoring. The diagnosis of diaphragmatic paralysis is most often based on chest X-ray, a static examination of limited sensitivity, especially for the detection of incomplete paralysis. To date, no prospective multicentre study has evaluated the incidence of diaphragmatic paralysis after PFA with systematic dynamic imaging, such as fluoroscopy, considered the gold standard for the diagnosis of unilateral paralysis.

The current study, DEFINE-PFA, aims to include 250 patients spread over 9 centres (France, New-Zealand and Canada). Each patient will benefit from dynamic fluoroscopy before and after the procedure. A new fluoroscopy will be performed at 3 months in patients with a significant reduction (\>15%) in postoperative diaphragmatic amplitude. The primary endpoint is based on the appearance of post-procedure inter-hemi diaphragmatic asymmetry, rather than a simple decrease in craniocaudal amplitude compared to the reference fluoroscopy. Indeed, the absolute diaphragmatic amplitude is highly dependent on the examination conditions, in particular the degree of cooperation of the patient and the intensity of forced inspiration, making inter-examination comparisons unreliable. Conversely, the simultaneous comparison of the two hemidiaphragms during the same inspiratory cycle makes it possible to attenuate these biases by using the contralateral hemidiaphragm as a stable internal reference. Pre-procedure fluoroscopy is nevertheless systematically performed in order to check the absence of basic asymmetry. The threshold of 15% inter-hemi diaphragmatic asymmetry was empirically retained, in the absence of a cut-off validated in the literature for dynamic fluoroscopy. In diaphragmatic ultrasound, asymmetry is generally considered significant for differences in amplitude \> 20% between the two hemi domes, but these measurements are performed successively, which makes them sensitive to variations between respiratory cycles. Conversely, fluoroscopy allows simultaneous observation of the two hemidiaphragms during the same respiratory cycle, offering a more reliable comparison. This threshold aims to detect significant asymmetry while minimizing false positives related to physiological variability.