Experimental application of microwave tissue coagulation to ventricular myocardium

Background. It is difficult to create transmural lesions in a beating, normothermic perfused heart. The aim of this study was to evaluate the effect of microwave tissue coagulation on a beating heart. Methods. We used a microwave tissue coagulator that emits microwaves of 2,450 MHz. Studies were conducted on 30 mongrel dogs weighing between 9 and 13 kg, and microwave tissue coagulation was performed at the free wall of the left ventricle in a beating heart without cardiopulmonary bypass. Results. Microwave tissue coagulation created transmural degenerated lesions in the left ventricle without risk of ventricular rupture. The lesion width of microwave ablation increased from 10 to 60 seconds. Histologic examinations revealed well-demarcated areas of heat degeneration consisting of coagulation necrosis and contraction band necrosis of the myocardium. The lesion healed to hard scar tissue, which was sharply demarcated from the normal myocardium. No animals had inducible ventricular tachycardia through programmed ventricular stimulation. Conclusions. Microwave ablation with a monopolar antenna created transmural lesions with only a few proarrhythmic events occurring during ablation.