A feasibility study of noninvasive ablation of ventricular tachycardia using high-intensity focused ultrasound.

BACKGROUND: Current transcatheter ablation of ventricular tachycardia (VT) techniques is limited in part by its invasive nature and superficial depth of ablation lesions.

OBJECTIVES: This study was aimed at evaluating the feasibility of targeted ablation of cardiac tissues using high-intensity focused ultrasound (HIFU) as a potential means for noninvasive ablation of VT.

METHODS: Ablation of ventricular myocardium was performed in anesthetized closed-chest dogs using a HIFU therapeutic system that is currently used clinically for ablation of human solid tumors. Ventricular pacing using a bipolar catheter was performed at a rate slightly higher than intrinsic sinus rate to mimic VT. The myocardium at the tip of the pacing catheter was targeted for ablation. Ablation endpoint was loss of ventricular capture first and confirmed by electrical nonexcitation with 10-mA, 2-ms pulse-width unipolar stimulation.

RESULTS: Optimal ablation energy was identified at 400 W for 2-4 seconds. In five separate experimental preparations, pacing could be terminated successfully during HIFU energy delivery, which was further confirmed by electrical nonexcitation. However, capture could be obtained at other nonablated locations using the same pacing catheter. Both transmural and localized lesions could be created in a controlled fashion without apparent injury to skin, lung, or pericardium on postmortem examination.

CONCLUSION: This pilot study suggests that HIFU is potentially useful for noninvasive ablation of targeted, localized myocardial tissues, and it may be potentially applicable for VT ablation, particularly for those with intramyocardial/epicardial origins.