Reversible, complete atrioventricular block caused by primary cardiac lymphoma in a nonimmunocompromised patient

Primary cardiac lymphoma (PCL) is a rare entity that commonly presents as a heart rhythm disorder. We describe a previously healthy, immunocompetent patient presenting with complete atrioventricular block (AVB). The patient was found to have a cardiac mass on magnetic resonance imaging and underwent percutaneous biopsy eventually diagnosing PCL. After pacemaker implantation, the patient's tumor responded rapidly to chemotherapy and the AVB completely resolved. In otherwise healthy patients presenting with AV block, cardiac tumor should be considered. Additionally, if PCL is diagnosed and the patient is clinically stable with AVB, it may be reasonable to delay pacemaker implantation until the clinical response to chemotherapy is evaluated.