Cardiac stereotactic body radiotherapy is an emerging treatment method for recurrent ventricular tachycardia refractory to invasive treatment methods. The single-fraction delivery of 25 Gy was assumed to produce fibrosis, similar to a post-radiofrequency ablation scar. However, the dynamics of clinical response and recent preclinical findings suggest a possible different mechanism. The data on histopathological presentation of post-radiotherapy hearts is scarce, and the authors provide significantly different conclusions. In this article, we present unique data on histopathological examination of a heart explanted from a patient who had a persistent anti-arrhythmic response that lasted almost a year, until a heart failure exacerbation caused a necessity of a heart transplant. Despite a complete treatment response, there was no homogenous transmural fibrosis in the irradiated region, and the overall presentation of the heart was similar to other transplanted hearts of patients with advanced heart failure. In conclusion, our findings support the theorem of functional changes as a source of the anti-arrhythmic mechanism of radiotherapy and show that durable treatment response can be achieved in absence of transmural fibrosis of the irradiated myocardium.

3rd Radiotherapy and Chemotherapy Department Maria Skłodowska Curie National Research Institute of Oncology Gliwice Poland

Anaesthesiology and Intensive Care Unit District Hospital in Oława Oława Poland

Department of Cardiac Surgery and Transplantology Silesian Centre for Heart Diseases Zabrze Poland

Department of Cardiac Surgery Heart and Lung Transplantation Mechanical Circulatory Support Silesian Centre for Heart Diseases Zabrze Poland

Department of Cardiology and Structural Heart Diseases Medical University of Silesia Katowice Poland

Department of Electrocardiology and Heart Failure Medical University of Silesia Katowice Poland

Department of Electrocardiology John Paul 2 Hospital Kraków Poland

Department of Electrocardiology Upper Silesian Heart Center Medical University of Silesia Katowice Poland

Department of Histopathology Silesian Centre for Heart Diseases Zabrze Poland

Department of Medical Physics Maria Skłodowska Curie National Research Institute of Oncology Gliwice Poland

Department of Radiotherapy Maria Skłodowska Curie National Research Institute of Oncology Gliwice Poland

Interventional Cardiac Electrophysiology Group International Clinical Research Center St Anne's University Hospital Brno Czechia

Radiotherapy Planning Department Maria Skłodowska Curie National Research Institute of Oncology Gliwice Poland

Tumor Pathology Department Maria Skłodowska Curie National Research Institute of Oncology Gliwice Poland

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