Safety and efficacy of high-intensity focused ultrasound atop coronary arteries during epicardial catheter ablation.

ABSTRACT

BACKGROUND: Coronary arterial injury continues to be a limitation of epicardial catheter ablation using currently available energy sources. Application of high intensity focused ultrasound (HIFU) energy may avoid such injury due to its theoretical ability to focus energy beyond the ablation element and create lesions at depth. OBJECTIVE: This study evaluated the safety of HIFU applications delivered directly over the left anterior descending (LAD) artery in an open-chest swine model. METHODS: Ten swine underwent median sternotomy. A prototype HIFU probe was placed atop the LAD. Forty-three therapies along the LAD (60-seconds/6 watt) were analyzed. Three, 3, and 4 swine were studied at 2, 4, and 8 weeks and subsequently sacrificed. Lesions were scored (0-4) depending on the percent circumferential involvement of arteries. RESULTS: Lesion area increased minimally from 54.5 ± 18.0 mm(2) at 2 weeks to 56.9 ± 20.6 mm(2) at 8 weeks, and depth increased moderately from 13.2 ± 2.5 mm to 15.5 ± 3.4 mm. At 2, 4, and 8 weeks, the mean injury score of the LAD was 0.8 ± 0.3, 1.5 ± 0.9, and 2.0 ± 0.7. No/minimal arterial injury was seen in 64% of all sections. However, a progressive increase in injury resulted in 89% of all sections showing any injury at 8 weeks. One animal developed occlusion of the distal LAD. CONCLUSIONS: HIFU has the potential to create deep ventricular lesions with relative sparing of the LAD. The incremental arterial damage noted over time warrants further evaluation to support the viability of focusing ultrasound energy beyond vulnerable critical structures to ablate deeper targets.