Summary

An asymptomatic 18-year-old black woman was found to have an incidental finding of third-degree atrioventricular (AV) block on a routine ECG. 2-Dimensional transthoracic echocardiography showed a heterogeneous mass in the region of the peri-membranous septum in the AV node area. A cardiac MRI showed a well-defined cystic mass arising from the right side of the interatrial septal wall. An MRI compatible permanent pacemaker was implanted with plans to monitor the tumour with non-invasive imaging. Cystic tumour of the AV node is a rare primary cardiac tumour. It is known as the smallest and most common primary cardiac tumour that can cause sudden death. All previous six cases of living patients with cystic tumour of the AV node reported in the literature were females and symptomatic. We present a rare case of a patient with cystic tumour of the AV node, and we highlight the treatment dilemmas for this condition.