Impact of Intrapericardial Fluid on Lesion Size During Epicardial Radiofrequency Ablation: A Computational Study.

Background and aims: Epicardial RFA is often required when ventricular tachyarrhythmias originate from epicardial or subepicardial substrates that cannot be effectively ablated endocardially. Our objective was to evaluate the impact of intrapericardial fluid accumulation on the lesion size in the myocardium and the extent of thermal damage to adjacent structures, particularly the lung.

Methods: An in silico model of epicardial RFA was developed, featuring an irrigated-tip catheter placed horizontally on the epicardium. A 50 W-30 s RF pulse was simulated. Temperature distributions and resultant thermal lesions in both the myocardium and lung were computed.

Results: An increase in pericardial space from 2.5 mm to 4.5 mm resulted in a reduction of myocardial lesion depth by up to 1 mm, while the volume of lung damage decreased from 200 to 300 mm³ to nearly zero, irrespective of myocardial or epicardial fat thickness. Myocardial lesion size was markedly influenced by the thickness of the epicardial fat layer. In the absence of fat and with a narrow pericardial space, lesions reached up to 262 mm³ in volume and 6.1 mm in depth. With 1 mm of fat, lesion volume decreased to below 100 mm³ and depth to 3 mm; with 2 mm, to under 40 mm³ and 2 mm; and with 3 mm, to less than 16 mm³ and 1.2 mm. Lung damage increased moderately with greater fat thickness. Cooling the irrigation fluid from 37 °C to 5 °C reduced lung damage by up to 51%, while myocardial lesion size decreased by only 15%.

Conclusions: Intrapericardial fluid accumulation can limit myocardial lesion formation while protecting adjacent structures. Cooling the irrigation fluid may reduce collateral damage without compromising myocardial lesion depth.