Histopathological effects and evolution of transvenous ß-radiation applications in right and left atria: an animal study.

ABSTRACT

AIMS: ß-radiation is a novel potential energy source for the creation of myocardial lesions. While the feasibility of delivering ß-radiation via a deflectable transvenous catheter has been described, dose effects and the time course of histopathological changes have not been previously assessed. The purpose of this study was to characterize pathological aspects of cardiac lesions induced by ß-radiation in an animal model at various stages of evolution and in response to different dose exposures. METHODS AND RESULTS: Nine dogs and one pig were studied. The cavotricuspid isthmus, antrum of pulmonary veins (PVs), and mitral isthmus were irradiated (25, 50, 75, or 100 Gy) with strontium-yttrium-90, delivered via a deflectable catheter (cavotricuspid isthmus and mitral isthmus) or a double-loop catheter (antrum of PVs). Eighteen lesions were created. Animals were sacrificed at 2 weeks, 1 month, 3 months, or 6 months. Lesions were processed for morphometric histopathological analyses. Over the first month, lesions were characterized by inflammation, haemorrhage, and myocyte necrosis. Thereafter, fibrotic replacement was predominant. Transmurality of lesions was observed in 50% of cases, with no dose-response effect (P = 0.976). Surface fibrin thrombus was present in 50% of cases and was essentially limited to lesions assessed within the first month. No neighbouring injury or pulmonary venous stenosis was observed. CONCLUSIONS: Atrial lesions created by ß-radiation are characterized by an inflammatory phase with surface fibrin thrombosis during the first month and replacement fibrosis thereafter. No appreciable dose-response effect was noted within the 25-100 Gy range tested.