Cardiac intervention using high-intensity focused ultrasound: creation of interatrial communication in beating heart of an anesthetized rabbit

High-intensity focused ultrasound for noninvasive fetal therapy

High-intensity focused ultrasound (HIFU) consists of an ultrasonic beam that is focused within the body to induce tissue necrosis through both heat energy and as a result of cavitation, which occurs without damaging any intervening tissues. Therefore, it is possible to cauterize and treat tumors without surgical invasion by administering HIFU irradiation from outside the body. This approach has been clinically applied in various fields in recent years, and fetal therapy is no exception, with several clinical applications reported, mainly in basic experiments. This review summarizes the recent basic and clinical findings focusing on fetal treatment with HIFU.

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.