Intracardiac thrombosis formation in patients in sinus rhythm is a rare phenomenon. An 84-year-old woman was admitted because of worsening dyspnea on exertion. An electrocardiogram showed sinus rhythm, left atrial overload, marked left axis deviation, low voltage, and poor r-wave progression in leads V1-4. An echocardiogram showed relatively preserved left ventricular ejection fraction with minimal wall thickening. Her serum level of B-type natriuretic peptide (931 pg/mL) was markedly elevated and a diagnosis of worsening heart failure was made. During the course of treatment for heart failure, she was complicated by acute abdominal aortic thromboembolism together with left atrial thrombus. An emergency abdominal aortic thrombectomy was followed by the removal of a left atrial thrombus 2 days later. Left ventricular biopsy performed during the surgery revealed amyloid deposits in the myocardial interstitium. Immunohistochemical study confirmed the diagnosis of transthyretin cardiac amyloidosis. It is postulated that the risk of intracardiac thrombosis and systemic embolism is increased even in sinus rhythm in patients with cardiac amyloidosis.
Keywords: Anticoagulation; Atrial electromechanical dissociation; Atrial failure; Transthyretin cardiac amyloidosis.