Longer Duration vs. Increasing Power During RF Ablation
How do changes in the duration and power of radiofrequency energy applications affect the size of ablation lesions?
An irrigated-tip ablation catheter oriented perpendicular to the tissue and adjusted to maintain a contact force of 10 g was used to create radiofrequency ablation (RFA) lesions in viable bovine myocardium inside a saline bath. RFA was performed at powers of 20-50 W for durations of 5-90 seconds. In the second part of the study, RFA was performed in an in vivo porcine thigh muscle preparation, and lesion volumes were compared between settings of 50 W for 5 seconds and 20 W for 30 seconds.
In the saline bath preparation, a progressive increase in power and duration both resulted in larger ablation lesions. However, stepwise increases in power had a greater effect on lesion size than did stepwise increases in duration. In the thigh muscle preparation, RFA at 50 W for 5 seconds and at 20 W for 30 seconds resulted in lesion volumes that did not differ significantly (44.2 vs. 35.3 mm3), but the lesions were significantly deeper with the 20 W/30 second applications (2.9 vs. 2.0 mm, respectively).
RFA using 50 W for 5 seconds yields ablation lesions that have a similar volume to the lesions created using 20 W for 30 seconds, but are not as deep. These findings can be used to adjust the RFA power and duration depending on the particular substrate that is being ablated.
The study provides useful insight into the relative biophysical effects of power and duration on the characteristics of RFA lesions. However, in the clinical setting, there is a beating heart, variable catheter orientations to the target sites, a wide range of contact forces, and variable ablation substrates. Therefore, it is unlikely that the findings can be applied directly to patient care.
Keywords: Arrhythmias, Cardiac, Atrial Fibrillation, Cardiac Catheters, Catheter Ablation, Electrophysiology, Myocardium, Patient Care
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