When cancer reaches the heart: A rare presentation of cardiac metastasis with atrioventricular block and left ventricular outflow tract obstruction

Abstract

Metastatic involvement of the heart, although less frequent than pri-mary cardiac tumours, poses a significant complication of malignancy. Secondary tumours often lead to pericardial effusion rather than direct myocardial infiltration. Common cancers with cardiac metastasis in-clude melanoma and primary mediastinal tumours, which can cause ob-structive lesions and arrhythmias.1The occurrence of complete heart block due to metastatic disease is particularly rare.This report describes a 64-year-old male with a history of lung adenocarcinoma presented with fatigue and worsening dyspnoea. Initial evaluation revealed a third-degree atrioventricular (AV) block, significant septal hypertrophy (28 mm), and subaortic obstruction with a maximum gradient of 25 mmHg. Advanced imaging with cardiac magnetic resonance imaging (MRI) and positron emission tomography- computed tomography (PET-CT) identified a mass encircling both ventricular outflow tracts and increased metabolic activity in the inter-ventricular septum, consistent with metastasis (Figure 1).We discuss the pathophysiological mechanisms through which car-diac metastasis can cause both AV block and left ventricular outflow tract (LVOT) obstruction. Direct myocardial invasion by metastatic tis-sue disrupts the normal conduction pathways, leading to AV block, while mass effect within the septum can lead to LVOT obstruction by physic-ally impinging on the outflow tract and altering hemodynamics.2This case is notable for the rare occurrence of cardiac metastasis re-sulting in both complete AV block and LVOT obstruction-previously reported only once in the literature, and that diagnosis was established post-mortem.2The ability to diagnose such conditions pre-mortem through multimodality imaging underscores the essential role of ad-vanced imaging in identifying atypical manifestations of metastatic cancer