title: Epicardial Catheter Ablation Using High-Intensity Ultrasound: Validation in a Swine Model.
abstract: BACKGROUND
  Epicardial radiofrequency catheter ablation of ventricular tachycardia remains challenging because of the presence of deep myocardial scar and adjacent cardiac structures, such as the coronary arteries, phrenic nerve, and epicardial fat that limit delivery of radiofrequency energy. High-intensity ultrasound (HIU) is an acoustic energy source able to deliver deep lesions through fat, while sparing superficial structures. We developed and tested an epicardial HIU ablation catheter in a closed chest, in vivo swine model.
  
  
  RESULTS
  The HIU catheter is an internally cooled, 14-French, side-facing catheter, integrated with A-mode ultrasound guidance. Swine underwent percutaneous subxyphoid epicardial access and ablation with HIU (n=10 swine) at 15, 20, and 30 W. Compared with irrigated radiofrequency lesions in control swine (n = 5), HIU demonstrated increased lesion depth (HIU 11.6±3.2 mm versus radiofrequency 4.7±1.6 mm; mean±SD) and epicardial sparing (HIU 2.9±2.1 mm versus radiofrequency 0.1±0.2 mm) at all HIU powers, and increased lesion volume at HIU 20 and 30 W (P<0.0001 for all comparisons). HIU ablation over coronary arteries and surrounding epicardial fat resulted in deep lesions with normal angiographic flow. Histological disruption of coronary adventitia, but not media or intima, was noted in 44% of lesions.
  
  
  CONCLUSIONS
  Compared with radiofrequency, HIU ablation in vivo demonstrates significantly deeper and larger lesions with greater epicardial sparing in a dose-dependent manner. Further development of this catheter may lead to a promising alternative to epicardial radiofrequency ablation.
authors.affiliation: From the Electrophysiology Section, Division of Cardiology, Department of Medicine (B.N., S.D., Y.T., R.S., E.P.G.), and Thermal Therapy Research Group, Department of Radiation Oncology (V.S., C.J.D., P.D.J., B.N.), University of California San Francisco.
authors.forename: Babak
authors.initials: B
authors.lastname: Nazer
authors.affiliation: From the Electrophysiology Section, Division of Cardiology, Department of Medicine (B.N., S.D., Y.T., R.S., E.P.G.), and Thermal Therapy Research Group, Department of Radiation Oncology (V.S., C.J.D., P.D.J., B.N.), University of California San Francisco.
authors.forename: Vasant
authors.initials: V
authors.lastname: Salgaonkar
authors.affiliation: From the Electrophysiology Section, Division of Cardiology, Department of Medicine (B.N., S.D., Y.T., R.S., E.P.G.), and Thermal Therapy Research Group, Department of Radiation Oncology (V.S., C.J.D., P.D.J., B.N.), University of California San Francisco.
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Diederich
authors.affiliation: From the Electrophysiology Section, Division of Cardiology, Department of Medicine (B.N., S.D., Y.T., R.S., E.P.G.), and Thermal Therapy Research Group, Department of Radiation Oncology (V.S., C.J.D., P.D.J., B.N.), University of California San Francisco.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Jones
authors.affiliation: From the Electrophysiology Section, Division of Cardiology, Department of Medicine (B.N., S.D., Y.T., R.S., E.P.G.), and Thermal Therapy Research Group, Department of Radiation Oncology (V.S., C.J.D., P.D.J., B.N.), University of California San Francisco.
authors.forename: Srikant
authors.initials: S
authors.lastname: Duggirala
authors.affiliation: From the Electrophysiology Section, Division of Cardiology, Department of Medicine (B.N., S.D., Y.T., R.S., E.P.G.), and Thermal Therapy Research Group, Department of Radiation Oncology (V.S., C.J.D., P.D.J., B.N.), University of California San Francisco.
authors.forename: Yasuaki
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: From the Electrophysiology Section, Division of Cardiology, Department of Medicine (B.N., S.D., Y.T., R.S., E.P.G.), and Thermal Therapy Research Group, Department of Radiation Oncology (V.S., C.J.D., P.D.J., B.N.), University of California San Francisco.
authors.forename: Bennett
authors.initials: B
authors.lastname: Ng
authors.affiliation: From the Electrophysiology Section, Division of Cardiology, Department of Medicine (B.N., S.D., Y.T., R.S., E.P.G.), and Thermal Therapy Research Group, Department of Radiation Oncology (V.S., C.J.D., P.D.J., B.N.), University of California San Francisco.
authors.forename: Richard
authors.initials: R
authors.lastname: Sievers
authors.affiliation: From the Electrophysiology Section, Division of Cardiology, Department of Medicine (B.N., S.D., Y.T., R.S., E.P.G.), and Thermal Therapy Research Group, Department of Radiation Oncology (V.S., C.J.D., P.D.J., B.N.), University of California San Francisco. egerstenfeld@medicine.ucsf.edu.
authors.forename: Edward P
authors.initials: EP
authors.lastname: Gerstenfeld
mesh_terms: D000818:Animals; D062906:Cardiac Catheters; D017115:Catheter Ablation / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D004867:Equipment Design; D005260:Female; D057086:High-Intensity Focused Ultrasound Ablation / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D023421:Models, Animal; D010496:Pericardium / Q000473:pathology / Q000601:surgery*; D015641:Radiography, Interventional; D013552:Swine; D007507:Therapeutic Irrigation
keywords: catheter ablation; epicardium; phrenic nerve; swine; ventricular tachycardia