Limited Benefit of Half-Normal Versus Normal Saline Irrigation for Augmenting Current Delivery with Open-Irrigated Temperature-Controlled Ablation

<h2>ABSTRACT</h2><h3>Background</h3> Half-normal saline (HNS) irrigation increases radiofrequency (RF) lesion size during power-controlled ablation by augmenting current delivery to tissue. Whether this benefit persists with temperature-controlled ablation, which modulates power delivery based on catheter tip temperature, remains unknown. <h3>Objectives</h3> This study sought to compare lesion characteristics using HNS versus normal saline (NS) irrigation with power-controlled and temperature-controlled open-irrigated catheters in an ex vivo model. <h3>Methods</h3> RF applications were delivered to left ventricular porcine tissue using a power- and temperature-controlled irrigated catheter with NS and HNS irrigation. Lesions were performed at 10 grams contact force perpendicular to tissue. Temperature-controlled ablation used manufacturer-preset maximum temperature cutoffs of 50°C at 30W and 55°C at 50W. <h3>Results</h3> Among 104 lesions analyzed, HNS irrigation with the power-controlled catheter produced larger lesions at 30Wx30 seconds compared to NS (depth: 7.5±1.0 vs 6.5±0.6 mm, P=0.0005; width: 10.5±1.1 vs 9.4±1.0 mm, P=0.005). However, no difference in lesion dimensions was observed with the temperature-controlled catheter using HNS versus NS at 30W (depth: 6.1±0.4 vs 6.2±0.7 mm, P=0.44; width: 9.4±0.7 vs 9.6±1.2 mm, P=0.23) or 50W (depth: 7.2±0.7 vs 7.5±0.8 mm, P=0.35; width: 10.9±1.3 vs 11.8±1.6 mm, P=0.19). With HNS, the temperature-controlled catheter showed reduced average power delivery (30W: 23.3±5.4 vs 27.1±4.6 W, P<0.05) and increased irrigation flow rates compared to NS, likely due to temperature cutoff enforcement. Fewer steam pops were observed with the temperature-controlled versus power-controlled catheter using HNS (5% vs 23%, P=0.09). <h3>Conclusions</h3> Unlike power-controlled ablation, HNS irrigation does not increase lesion size with temperature-controlled ablation. Enforcement of maximum temperature cutoffs reduces actual power delivery, blunting the current augmentation benefit of HNS irrigation while potentially improving safety.