High-power, low-flow, short-ablation duration-the key to avoid collateral injury?

BACKGROUND: A common approach to ablating along the posterior wall of the left atrium in atrial fibrillation ablation is to use low power with longer duration for durable lesions and reducing thermal injury. We hypothesize that similar lesions can be safely obtained at high power with low open-irrigation flow and low duration. METHODS: Twenty-two porcine ventricles were placed in a tissue bath with circulating 0.45% NaCl at a maintained temperature of 37 °C. Bipolar radiofrequency ablation (RFA) with a 4-mm-tip irrigated, force-sensing catheter was performed with various combinations of irrigation, power, and duration at 20g of contact force. Fiber optic temperature probes were placed at depths of 3 mm and 5 mm. Temperature was measured during and 30 s after each ablation. RESULTS: Two hundred sixty-eight lesions were made. At a fixed power and flow rate, lesion surface diameter, maximum lesion width, and lesion depth all increased with longer ablation duration. At fixed duration and irrigation flow rate, increased power led to increased lesion dimensions. At a lower flow rate (2 ml/min), surface lesion diameter and maximum width were significantly larger compared to a higher flow rate (17 ml/min), but lesion depth was not significantly different. The maximum temperature and the rate of temperature rise at a depth of 5 mm with different power settings and ablation durations were lower as compared to a depth of 3 mm at both flow rates (2 ml/min and 17 ml/min). CONCLUSIONS: Effective lesions can be performed with high-power and short-ablation durations, thereby reducing RFA procedure time. Higher power, shorter duration lesions result in adequate temperature for myocardial lesion formation at 3 mm, but do not result in excessive temperature at 5 mm depth, potentially reducing the risk of collateral injury. Compared to higher irrigation flow rate, larger surface lesions and comparable maximum lesion width are achieved with lower irrigation flow rate, thus resulting in better lesion contiguity.