Dual cryo-radiofrequency ablation enhances lesion depth in beating human left ventricular preparations

Thermally-mediated ablation has utilized various energy sources, including cryothermal, radiofrequency (RF), microwave, laser, and high-frequency ultrasound with the goal of creating lesions to terminate focal sources or block reentrant wavefronts. RF- and cryo-ablation (CR) cause cell death through different mechanisms, and leave behind tissue with altered thermal-electric properties. We aimed to assess the effect of sequential RF and CR combinations on lesion size. Left ventricular (LV) wedge preparations (n=17) were dissected from ten donated human hearts and four epicardial ablation protocols were compared: 1) RF-RF (n=7); 2) CR-CR (n=7); 3) RF-CR (n=7); and 4) CR-RF (n=7). Preparations were continuously paced and perfused with oxygenated Tyrode solution. Ablated tissue was perfused for 3 hours, sectioned, and stained with 2,3,5-triphenyltetrazolium chloride to delineate necrosis. The effect of initial thermal-electric tissue properties on lesion depth during RF application was determined using a finite element method (FEM). CR-RF generated the deepest lesion (p<0.05) compared to protocols 1-3, while lesion width and area were similar among protocols. No energy combination produced a transmural lesion (n=0 of 28) in LV preparations. FEM showed that electrical conductivity plays a more significant role in lesion creation compared to thermal conductivity. A 33% increase in the initial thermal and electrical tissue conductivity generated a 21% deeper lesion. We conclude that sequential application of CR followed by RF created the deepest lesion in beating human LV preparations. This increase in lesion depth may translate into improved therapeutic outcomes for arrhythmias with intramural origins.