Complete heart block ensuing from a metastatic small cell carcinoma: a case report

INTRODUCTION: Notwithstanding the diagnostic and therapeutic advancements, the incidence of cardiac metastases has increased in recent decades. Lung cancers are the most common primary malignant neoplasms with cardiac metastasis potential. The clinical presentation of cardiac metastases is either silent or vague, and largely depends on the infiltrated location and tumor burden. Although arrhythmias are not uncommon in metastatic cardiac tumors, complete heart block is relatively a rare manifestation. We present a case of complete heart block due to a metastatic small cell carcinoma in a 67-year-old male of African origin. CASE PRESENTATION: A 67-year-old male of African origin from rural Tanzania was referred to us for expert management. He is a retired agromechanic with over 30 years exposure to asbestos-containing brake linings. His past medical history was unremarkable, but the family-social history was evident for a heavy alcohol intake and chronic cigarette smoking. He presented with a 24-week history of progressive shortness of breath and an 8-week history of recurrent syncopal attacks coupled with a significant weight loss. He had normal echocardiographic findings, however, the electrocardiogram showed features of complete heart block. Chest X-ray showed a homogeneous opacification on the right side and computed tomography scan revealed a solid right lung mass with metastases to the liver, heart, bowels, and bone. He underwent bronchoscopy, which revealed an endobronchial mass obstructing the bronchus intermedius. Histological examination of a section of lung biopsy taken during bronchoscopy confirmed the diagnosis of a small cell carcinoma. The patient underwent dual chamber pacemaker implantation with successful sinus rhythm restoration. He made an informed refusal of chemotherapy and inevitably died 18 months post pacing. CONCLUSIONS: Despite the advancements in medical diagnostics and management, lung cancers are often diagnosed in advanced stages, with an inevitable grave prognosis. Small cell carcinoma has the potential to metastasize to the heart, resulting in complete heart block.