Microwave ablation of myocardial tissue: the effect of element design, tissue coupling, blood flow, power, and duration of exposure on lesion size.

摘要

INTRODUCTION: The biophysical properties of microwave electromagnetic radiation suggest that it may be an alternative to radiofrequency (RF) energy for ablation of arrhythmias resistant to treatment using RF ablation. METHODS AND RESULTS: The aim of this study was to characterize lesions produced using simple element designs in a blood superfused ovine tissue model to simulate endocardial ablation. The effect of tissue bath flow, duration of microwave exposure, and changes in forward power on lesion size were examined using a modified monopole element. Lesion size increased with increasing duration of exposure and increasing forward power (P < 0.05). Lesion depth was 0.7+/-0.7 mm after 30 seconds and 11.5+/-1.9 mm after 360 seconds. Lesion depths at 61, 71, and 80 W were 6.4+/-3.7, 8.9+/-2.0, and 11.9+/-1.2 mm, respectively. Altering flow within the bath from 3 to 5 L/min did not significantly change lesion size. CONCLUSION: Simple element designs can be used to produce a range of lesions from very small sizes to lesions that are transmural in the ventricle. The temperature half-time for microwave ablation is far greater than that of RF ablation. Like RF lesions, the lesions produced by microwave ablation have greater width than depth. Deep penetration of lesions into the ventricular myocardium can only be achieved with these elements by producing lesions of perhaps unnecessarily large volume.