Five-chambered heart: palpitations and syncope due to a left atrial appendage aneurysm

A 37 year old previously healthy man presented to outpatient cardiology clinic with intermittent palpitations for the past year and an episode of syncope. Physical exam and laboratory findings were unremarkable. An office electrocardiogram showed sinus bradycardia with left atrial enlargement (Figure 1A). Chest radiography demonstrated a prominent outpouching of the left cardiac border inferior to the left hilum (Figure 1B). A Holter monitor recorded multiple episodes of paroxysmal supraventricular tachycardia (SVT) up to 176 beats per minute (Figure 1C). Trans-thoracic echocardiogram (TTE) demonstrated a large 7.0 × 4.0 cm focal outpouching of the left atrium with a 2 cm neck (Figure 2A–B, Video 1), suggestive of a left atrial appendage aneurysm or pseudoaneurysm. Doppler imaging revealed moderate posteriorly-directed mitral valve regurgitation secondary to mild mitral annular dilation with normal left ventricular ejection fraction (Video 2).

Figure 1. Initial electrocardiogram, chest radiography, and Holter monitor.

(A) Office electrocardiogram showing sinus bradycardia and a biphasic P wave in V1 consistent with left atrial enlargement. (B) Chest radiography demonstrating a prominent atrial auricular arch (demonstrated by arrow). (C) Holter monitor showing an example of the supraventricular tachycardia episodes.

Figure 2. Echocardiography and cardiac magnetic resonance imaging demonstrating a left atrial appendage aneurysm.

(A) Transthoracic echocardiogram image with apical 4-chamber view visualizing a 7.0 × 4.0 cm focal outpouching of the left atrium. (B) Transthoracic echocardiogram image with short-axis view visualizing a 7.0 × 4.0 cm focal outpouching of the left atrium. (C) Cardiac magnetic resonance imaging in the axial plane showing a large 7.6 × 6.9 × 5.9 cm aneurysm arising from the inferior and lateral wall of the left atrium involving the appendage. LA = left atrium, Ao = aorta, AV = aortic valve, RVOT = right ventricular outflow tract, RA = right atrium, * = left atrial appendage aneurysm.

Cardiac magnetic resonance imaging (cMRI) was performed to further anatomically define the left atrial appendage and surrounding structures. The cMRI confirmed a giant 7.6 × 6.9 × 5.9 cm aneurysm arising from the inferior and lateral wall of the left atrium involving the appendage (Figure 2C). No other cardiac structural issues or delayed enhancement was observed. No thrombus was seen within the left atrial appendage aneurysm and apixaban was started for thromboprophylaxis. Coronary artery angiography showed normal coronary arteries without compression from the aneurysm. Given the potential risk of thromboembolic events and the patient’s history of atrial tachyarrhythmias with syncope, the patient was referred to cardiac surgery.¹

Intra-operative trans-esophageal echocardiography (TEE) confirmed the absence of thrombus within the left atrial appendage aneurysm with normal peak left atrial appendage emptying velocity of 49 cm/sec (Figure 3A, Video 3). The patient underwent left atrial appendage aneurysm resection with internal and external primary repair using polypropylene suture via median sternotomy and cardiopulmonary bypass (Figure 3B, Video 4). Mitral valve competency was excellent upon closure of the aneurysm with trivial mitral regurgitation identified on intra-operative TEE. The patient tolerated the procedure well. There were no post-operative arrhythmias observed on inpatient telemetry, and therapeutic anticoagulation was held. The patient was discharged on post-operative day three with metoprolol and a two-week Holter monitor to assess for any recurrence of paroxysmal SVT. The final pathology report confirmed the diagnosis of left atrial appendage aneurysm.

Figure 3. Intra-operative echocardiography and gross pathology.

(A) Trans-esophageal echocardiography showing that peak emptying velocities are preserved in the left atrial appendage. (B) Surgically resected left atrial appendage aneurysm.

At his one-month follow-up visit, the patient felt well without recurrence of palpitations or syncope. Post-operative two-week Holter monitor showed no recurrence of the paroxysmal SVT. At his three-month follow-up visit, he was exercising regularly without symptoms and was back to working full-time.

Left atrial appendage aneurysms are rare.² They can be caused by congenital dysplasia of the atrial pectinate muscles, or secondary to mitral valve disease or conditions that lead to elevated atrial pressure.³ The majority of patients are asymptomatic, while others may present with palpitations, dyspnea, or chest pain. It is commonly detected in the second to fourth decades of life in symptomatic patients when the aneurysms can reach remarkable size. Atrial arrhythmias may occur with origins at the base of the left atrial appendage. Clinicians should use stepwise multi-modality imaging to accurately diagnose and expedite therapeutic strategies for left atrial aneurysms and pseudoaneurysms. Although left atrial appendage aneurysms are rare, this case demonstrates the importance of ruling out a structural etiology for a cardiac arrhythmia. In this case, multimodal imaging was essential because surgery rather than catheter ablation was the most appropriate management strategy. Due to the risk of atrial tachyarrhythmias and thromboembolic events, surgical resection is the treatment of choice even in asymptomatic cases. Cardiac surgery should be undertaken once adequate imaging has been completed to inform an optimal surgical approach. Surgical resection is low risk and curative with excellent prognosis.⁴