Scientific Data

ISRS 2007
San Francisco, CA
Presented by Douglas Wong, MD

Myocardial Ablation by Stereotactic Radiosurgery: Clinical, Physiologic, and Histologic Correlation.

Wong D, Weidlich G, Sharma A, Jack A, Adler J, Fogarty T, Maguire P

Objective: Strategic myocardial ablation with multiple invasive catheters is an increasingly common treatment for cardiac arrhythmias. The purpose of this study was to explore the feasibility of noninvasive myocardial ablation by stereotactic radiosurgery.

Methods: Three healthy Hanford pigs were treated on a G-4 CyberKnife radiosurgical system with Xsight image guidance. Targets in the atria (left atrial appendage, left superior and inferior pulmonary veins, and cavotricuspid isthmus) were contoured and optimal treatment plans were defined on the MultiPlan System (versions 1.4 and 1.5.1). All treatments were administered in single isocentric fractions (25Gy and 40Gy). Animals were sacrificed at 16, 33, and 89 days after treatment for histologic examination of the heart and contiguous organs (esophagus, trachea, aorta, and lungs). Prior to sacrifice, EKGs, inter-atrial electophysiologic recordings, and 3-D electroanatomic mappings (CARTO) were performed.

Results: All animals survived treatment without adverse effects. No secondary arrhythmias, valve, or ventricular abnormalities were observed. The treated areas showed focal fibrosis and reduced conduction voltage potentials. In the case of the third animal (treated with 40Gy and studied at 89 days), there was significant voltage attenuation observed in both inter-atrial electrophysiologic recordings and CARTO mapping of the targeted cavotricuspid isthmus.

Conclusions: Radiosurgery with CyberKnife can be used to target and ablate discrete areas of the myocardium, without detrimental effects. Further study into the application of radiosurgery for the treatment of cardiac arrhythmias is warranted.

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