Microwave Ablation of the Lung in a Porcine Model: Vessel Diameter Predicts Pulmonary Artery Occlusion.

Abstract

To determine the size of pulmonary artery (PA) at risk for occlusion during percutaneous microwave ablation and to assess the effect of vessel diameter, number, and patency, on ablation zone volume. Computed tomography (CT) fluoroscopy-guided percutaneous microwave ablations were performed in 8 pigs under general anesthesia. All ablations were performed at 65W for 5min with a single 17-gauge antenna positioned in the central third of the lungs. A CT pulmonary angiogram was performed immediately after the ablations. The maximum diameter, number and patency of PA branches within each ablation zone were recorded. Ablation volumes were measured at gross dissection and with CT. Student's t test was used to compare ablation zone volumes among groups. Twenty-one pulmonary ablations were performed. Six of the ablation zones (29%) contained at least 1 occluded PA branch. The mean diameter of the occluded PA branches in the ablation zones (2.4mm; range, 2.0-2.8mm) was significantly smaller than non-occluded PA branches (3.7mm; range: 2.1-6.9mm; p=0.009). No PA branches ≥3mm in size were occluded. There was no significant difference in volume of gross ablation zones that contained occluded versus non-occluded PAs (p=0.42), one versus multiple PAs (p=0.71), or PAs <3mm versus ≥3mm in diameter (p=0.44). PAs ≥3mm in size have a low risk for iatrogenic occlusion during percutaneous microwave ablation. The presence of multiple adjacent PA branches, an occluded PA branch, and a vessel diameter ≥3mm within the ablation zone had no observed effect on ablation zone volume.