Varying power and duration during radiofrequency ablation (RFA) may confer different ablation lesion characteristics that can be tailored based on the substrate or anatomy that is being ablated, according to a study presented May 10 during the Heart Rhythm Society's 39th Annual Scientific Sessions in Boston, MA, and simultaneously published in JACC: Clinical Electrophysiology.

Ryan T. Borne, MD, FACC, et al., assembled an ex vivo model consisting of viable bovine myocardium, a submersible load cell, circulating bath, and an open irrigated ablation catheter. RFA was delivered at powers of 20, 30, 40, and 50 W and at various time intervals (15, 30, 60, and 90 s) for each power. Ablation lesion characteristics and volumes were analyzed. In addition, for ex vivo tissue temperature analyses, RFA was delivered at 50 W for 5 s and 20 W for 30 s with 10 g of force while tissue temperatures at various depths and lesion volumes were measured. An in vivo porcine thigh preparation model was used to perform RFA at 50 W for 5 s and 20 W for 30 s. Lesion volumes were analyzed.

In the ex vivo model, both greater power delivery and longer radiofrequency time increased ablation lesion size. Compared with a proportional change in radiofrequency duration, the same proportional increases in power produced a significantly larger lesion volume. Higher powers for shorter duration created larger ablation lesions than lower powers for longer duration. If force was held constant, lesion size would increase proportionally to power and only half as much for duration of ablation. Peak tissue temperatures were not statistically different for 50 W/5 s and 20 W/30 s at 2 mm and 4 mm depths. However, for 50 W/5 s, the slope of temperature rise was greater at 2 and 4 mm compared with 20 W/30 s.

In the in vivo model, neither lesion volume nor diameter was statistically different for 50 W/5 s and 20 W/30 s, although there was a trend toward smaller lesion volumes and larger lesion diameters for the high-power/short-duration group.

According to the authors, these findings have important implications during ablation procedures, such as pulmonary vein isolation, or for refractory myocardial tissues, such as those responsible for certain ventricular arrhythmias.

“Although the ex vivo and in vivo models provide insight into ablation lesion characteristics associated with differences in power and duration of ablation, this insight does not necessarily equate to how best to perform ablation in clinical practice,” the authors write. “Randomized trials should be performed with the specific outcomes being patient-centered clinical endpoints, in which the risks and benefits in differences of ablation strategies can be determined.”

Keywords: Pulmonary Veins, Temperature, Thigh, Catheter Ablation, Myocardium, Parturition, Ablation Techniques, Arrhythmias, Cardiac, Electrophysiology, Risk Assessment

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