Limited benefit of half-normal vs normal saline irrigation for augmenting current delivery with open-irrigated temperature-controlled ablation.

BACKGROUND: 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 on the basis of catheter tip temperature, remains unknown. OBJECTIVE: This study sought to compare lesion characteristics using HNS vs normal saline (NS) irrigation with power-controlled and temperature-controlled open-irrigated catheters in an ex vivo model. METHODS: 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 g contact force perpendicular to tissue. Temperature-controlled ablation used manufacturer-preset maximum temperature cutoffs of 50°C at 30W and 55°C at 50W. RESULTS: Among 104 lesions analyzed, HNS irrigation with the power-controlled catheter produced larger lesions at 30W × 30 seconds than did NS (depth: 7.5 ± 1.0 vs 6.5 ± 0.6 mm, P = .0005; width: 10.5 ± 1.1 vs 9.4 ± 1.0 mm, P = .005). However, no difference in lesion dimensions was observed with the temperature-controlled catheter using HNS vs NS at 30W (depth: 6.1 ± 0.4 vs 6.2 ± 0.7 mm, P = .44; width: 9.4 ± 0.7 vs 9.6 ± 1.2 mm, P = .23) or 50W (depth: 7.2 ± 0.7 vs 7.5 ± 0.8 mm, P = .35; width: 10.9 ±1.3 vs 11.8 ± 1.6 mm, P = .19). With HNS, the temperature-controlled catheter showed reduced average power delivery (30W: 23.3 ± 5.4 vs 27.1± 4.6 W, P < .05) and increased irrigation flow rates compared with NS, likely owing to temperature cut-off enforcement. Fewer steam pops were observed with the temperature-controlled than with the power-controlled catheter using HNS (5% vs 23%, P = .09). CONCLUSION: 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.