Suspected Radiation-Induced Complete Atrioventricular Block Presenting 39 Years After Childhood Thoracic Cancer Treatment: A Case Report.

Complete atrioventricular block is a serious cardiac conduction abnormality with multiple etiologies. We present the case of a 50-year-old man who presented to the emergency room with bradycardia found at home, associated with fatigue and exertional dyspnea, which eventually progressed from sinus rhythm to complete atrioventricular block with mild elevation in high-sensitivity troponin. Further inquiry revealed a remote history of childhood lung malignancy treated with surgical resection, chemotherapy, and thoracic radiotherapy approximately 39 years prior, representing one of the longest reported latency periods between thoracic radiation exposure and suspected radiation-induced complete atrioventricular block. The patient underwent permanent pacemaker placement with a favorable clinical outcome. This case report highlights the importance of detailed past medical history in identifying delayed cardiovascular complications of childhood cancer treatment. Clinicians should maintain a high index of suspicion when assessing conduction abnormalities as possible radiation-induced cardiac disease in cancer survivors, even decades after initial exposure.