Double cryoenergy application (freeze-thaw-freeze) at growing myocardium: lesion volume and effects on coronary arteries early after energy application. Implications for efficacy and safety in pediatric patients.

ABSTRACT

INTRODUCTION: Data on radiofrequency current application (RFA) at growing myocardium suggest that coronary artery stenosis may occur with a low incidence. Cryoenergy has emerged as an effective alternative to RFA. Although already used in clinical practice, experience with cryoenergy is low due to lack of data concerning effects of a modified double cryoenergy application, a freeze-thaw-freeze cycle, at growing myocardium. Purpose of the study was to assess lesion volume (efficacy) and risk of coronary artery damage (safety) early, 48 hours, after modified double cryoenergy application in a piglet model. METHODS AND RESULTS: In 5 piglets, following selective coronary angiography, two sequential cycles of cryoenergy were delivered at -75 °C for 4 minutes, interrupted by thawing for one minute, at the atrioventricular groove. Piglets were restudied after 48 hours by coronary angiography and intracoronary ultrasound (ICUS). Ablation lesions were examined morphologically and lesion volume was determined by 3-dimensional morphometric analysis. Lesion volume was 109.21 ± 39.61 mm(3) for atrial and 150.30 ± 53.21 mm(3) (P = 0.02) for ventricular lesions. Lesion depth was not significantly different for atrial, 3.07 ± 1.08 mm, versus ventricular lesions, 3.56 ± 1.3 mm. Cryoenergy induced minor coronary artery damage with medial and adventitial necrosis but a preserved intimal layer was present in 2/31 lesions, which had not been detected by coronary angiography or ICUS. CONCLUSION: Early after double cryoenergy application, subclinical minor changes of the coronary artery wall could be detected occasionally whereas the intimal layer remained intact. These findings may have implications on efficacy and safety when cryoenergy is applied for tachycardia substrates in pediatric patients.