We performed a histological and immunohistochemical analysis of myocardia from 3 patients who underwent radiosurgery and died for various reasons 3 months to 9 months after radiotherapy. In Case 1 (death 3 months after radiotherapy) we observed a sharp transition between relatively intact and irradiated regions. In the myolytic foci, only scattered cardiomyocytes were left and the area was infiltrated by immune cells. Using immunohistochemistry we detected numerous inflammatory cells including CD68+/CD11c+ macrophages, CD4+ and CD8+ T-lymphocytes and some scattered CD20+ B-lymphocytes. Mast cells were diminished in contrast to viable myocardium. In Case 2 and Case 3 (death 6 and 9 months after radiotherapy, respectively) we found mostly fibrosis, infiltration by adipose tissue and foci of calcification. Inflammatory infiltrates were less pronounced. Our observations are in accordance with animal experimental studies and confirm a progress from myolysis to fibrosis. In addition, we demonstrate a role of pro-inflammatory macrophages in the earlier stages of myocardial remodeling after stereotactic radioablation for ventricular tachycardia.

Department of Cardiology Institute for Clinical and Experimental Medicine Vídeňská 1958 140 21 Prague Czech Republic

Department of Oncology University Hospital Ostrava 17 listopadu 1790 708 52 Ostrava Czech Republic

Department of Pathology Institute for Clinical and Experimental Medicine Vídeňská 1958 140 21 Prague Czech Republic

Faculty of Medicine Masaryk University Brno Kamenice 753 5 625 00 Brno; Agel Hospital Třinec Podlesí a s Konská 453 739 61 Třinec Czech Republic

Institute of Clinical and Molecular Pathology and Medical Genetics University Hospital Ostrava 17 listopadu 1790 708 52 Ostrava Czech Republic

Institute of Histology and Embryology 1st Faculty of Medicine Charles University Albertov 4 120 00 Prague Czech Republic

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