Ventricular Lesion Analysis
In 8 acute animals, 41 lesions were attempted using LI and ICE to guide the catheter to NTC (n=6), LTC (n=14), or HTC (n=17) with 37 of 41 lesions identified and cross-sectioned for analysis during necropsy. Four lesions were excluded because they could not be identified (n=1) or cross-sectioned (n=3). Starting impedance relative to bloodpool was ∆8Ω (IQR, 7-9Ω) for NTC, ∆19Ω (IQR, 15-25Ω) for LTC, and ∆42Ω (IQR, 33-50Ω) for HTC (Figure 3A ). Comparison of pre-ablation impedance deltas confirmed all 3 groups were statistically distinct (HTC-LTC: p<0.005, HTC-NTC: p<0.005, LTC-NTC: p=0.006). No microbubbles, muscle contractions, induced arrhythmias, or ST-elevation were observed during index procedures. No endocardial trauma, thrombus, or char were observed acutely or chronically.
In 2 chronic animals, N=8 lesions were attempted (NTC: n=2, LTC: n=3, HTC: n=3). All LTC and HTC lesions were identified and cross-sectioned and no NTC lesions were identifiable after 30 days. Of the 6 identified lesions, 4 were transmural and therefore not measurable(Supplemental Figure 1). No adverse events were observed during the 30-day waiting period.
Representative acute lesions following TTC staining are provided for each cohort (Figure 3B) . LTC and HTC lesions were similar in appearance and size (consistently >3mm depth), while NTC yielded superficial lesions, moderate endocardial blanching, or no visible effect. H&E and Masson’s Trichrome (Figure 1C ), revealed necrotic myocardium, mild edema, and early-stage fibrosis on ventricular lesions with no visible impact to surrounding vessels.
Figure 3C further represents the relationship between lesion size and CTC. Average RV lesion size was not significantly different between LTC and HTC cohorts (depth: 5.7±2.0mm vs 5.7±2.1mm, p>0.99; width: 15.7±5.2mm vs 17.0±4.5mm, p=0.74). Mean NTC lesion size was significantly smaller than mean LTC and HTC sizes (1.7±1.2mm depth, 6.0±4.5mm width, p<0.001). Above a minimum threshold of ∆10Ω, increasing CTC did not increase lesion depth. Lesion depth and width were not impacted by catheter orientation or spline placement once ≥2 splines reached LI >∆10Ω (Supplemental Figure 2 ).