A 74-year-old female patient was referred to our department in 2015 with dyspnea, cough and dysphagia. She had been diagnosed with adenocarcinoma of the right breast in 1986 and underwent mastectomy. When she presented with a local recurrence in 1988, she was receiving high-voltage radiation therapy. Transthoracic echocardiography and magnetic resonance imaging revealed tricuspid regurgitation grade III and unclear right heart failure with a massively dilated right atrium. Coronary heart disease could be ruled out. In summary, the patient’s findings represented right ventricular myocardial restriction which we attributed to irradiation of the right anterior chest 17 years previously.