Intracardiac Thrombus in Sinus Rhythm: A Case of Missed Cardiac Amyloidosis

Abstract

Intracardiac thrombus in patients with amyloid cardiomyopathy in sinus rhythm is a rare phenomenon, and no guidelines currently exist regarding screening, diagnosis, or management. We describe a case of a 59 year-old female who presented to the hospital with dyspnea on exertion, orthopnea, pedal edema, and weight gain. She had a one year history of heart failure with preserved ejection fraction, treated with metoprolol, bumetanide, and metolazone, and three month history of AL amyloidosis, treated with Bortezomib and Dexamethasone. Upon admission, labs showed leukocytosis, thrombocytosis, and elevated troponin and BNP. Electrocardiogram revealed sinus rhythm with left atrial enlargement. CT chest angiography showed pulmonary edema and a hypodense mass in the right atrium/atrial appendage. Cardiac magnetic resonance imaging demonstrated moderate concentric hypertrophy, elevated native T1 (1126 ms), diffuse late gadolinium enhancement, and elevated ECV (52%) consistent with cardiac amyloidosis. A right atrial mass consistent with a thrombus was visualized. Intracardiac thrombus was treated with intravenous heparin, which was transitioned to warfarin. Volume overload secondary to AL-cardiac amyloidosis was managed with diuresis. She was discharged home with hospice and passed approximately one month later. This case illustrates a missed diagnosis of cardiac involvement of systemic AL amyloidosis, ultimately resulting in death within nearly one year from initial diagnosis of heart failure. It also explores the etiology, diagnosis, and treatment of an intracardiac thrombus in patients with cardiac amyloidosis in sinus rhythm. Therefore, this case demonstrates the need for evidence-based guidelines regarding stratification of thrombotic risk and serial monitoring in patients with cardiac amyloidosis without arrythmia. Furthermore, it exemplifies the importance of high suspicion for cardiac amyloidosis to guide early diagnosis and management of patients with cardiac involvement of systemic amyloidosis, in addition to screening and monitoring of associated comorbidities, to improve prognosis and overall survival.