Longer Duration vs. Increasing Power During RF Ablation

Study Questions:

How do changes in the duration and power of radiofrequency energy applications affect the size of ablation lesions?

Methods:

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.

Results:

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).

Conclusions:

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.

Perspective:

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.

Clinical Topics: Arrhythmias and Clinical EP, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias

Keywords: Arrhythmias, Cardiac, Atrial Fibrillation, Cardiac Catheters, Catheter Ablation, Electrophysiology, Myocardium, Patient Care


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