Diagnosis and Management of Left Atrial Mass with Syncope

A. Diagnosis and Epidemiology

• The American Heart Association notes that left atrial myxoma is the most common primary cardiac tumor, accounting for approximately 50% of all benign cardiac neoplasms 1, 2, 3
• Myxomas occur most frequently in the left atrium, typically attached to the interatrial septum 1
• Cardiac myxomas have an incidence of 0.02% in autopsy series 1, 3

B. Pathophysiology and Clinical Presentation

• The European Society of Cardiology states that syncope results from mechanical obstruction of blood flow across the mitral valve during diastole, causing transient reduction in cardiac output and cerebral hypoperfusion 4, 5, 3
• The overall embolism rate with cardiac myxomas is 25%, with embolic stroke being the presenting symptom in up to 50% of cases 1, 2, 3

C. Microscopic Findings and Histopathology

• The World Health Organization describes myxoma cells (lepidic cells) as polygonal to stellate-shaped cells with eosinophilic cytoplasm, arranged singly or in small clusters, and stromal cells as spindle-shaped cells embedded in abundant myxoid matrix 3
• Endothelial cells line vascular channels within the tumor 1
• Myxoid matrix is abundant loose, gelatinous extracellular matrix rich in mucopolysaccharides (appears basophilic on H&E staining) 1
• Vascular channels are thin-walled blood vessels of varying caliber scattered throughout 6
• Hemorrhage and hemosiderin are common findings, especially in larger tumors 1
• Surface thrombus is a friable surface with adherent thrombus (source of embolic potential) 2
• Villous or papillary surface architecture in some cases is associated with higher embolic risk 1
• Immunohistochemistry is positive for vimentin, calretinin; negative for cytokeratin, S100 5

D. Management and Treatment

• The American College of Cardiology recommends surgical excision as the definitive treatment and should be performed urgently to prevent life-threatening complications including sudden death, stroke, and recurrent syncope 1, 2, 3
• All symptomatic left atrial myxomas require surgical resection (Class I) 2, 3
• Surgical excision reduces stroke risk compared to conservative management 1
• Complete tumor removal with adequate margin of atrial septum is essential to prevent recurrence 3
• Echocardiography (transthoracic and transesophageal) is the diagnostic modality of choice 3
• Cardiac MRI or CT provides additional characterization for surgical planning 3
• Histopathologic confirmation is mandatory 2
• Long-term follow-up with periodic echocardiography to monitor for recurrence (occurs in 1-5% of sporadic cases) 3
• Anticoagulation or antiplatelet therapy alone is inadequate and does not prevent embolic complications 1

Epidemiology, Anatomy, and Pathophysiology of Left Atrial Myxoma

Epidemiology

Anatomic Characteristics

Pathophysiologic Mechanisms of Clinical Presentation

Embolic Risk Factors

Management of Left Atrial Myxoma in Patients with Cryptogenic Stroke

Diagnostic Evaluation

• Transesophageal echocardiography (TEE) is recommended as the first‑line cardiac imaging modality for younger adults with unexplained cerebrovascular events because it has higher sensitivity than transthoracic imaging for detecting cardiac tumors such as myxoma. 8
• A second BMJ 2018 source corroborates the recommendation to use TEE in the cryptogenic‑stroke work‑up to identify left‑atrial myxoma. 9

Embolic Risk Profile

• Cardiac myxomas carry an overall embolism rate of approximately 25%, and embolic stroke is the presenting symptom in up to half of affected patients. 10
• Myxomas with villous or papillary (friable) surface architecture have a markedly higher propensity for embolization compared with smooth‑surface tumors. 10

Treatment Recommendations

Surgical Excision

• Urgent surgical resection of left‑sided cardiac myxoma is advised to prevent recurrent stroke, sudden death, and cardiac obstruction; the 2021 AHA/ASA Stroke Prevention Guidelines assign this intervention a Class IIa recommendation with Level of Evidence C‑LD. 10

Anticoagulation

• Anticoagulation or antiplatelet therapy alone is insufficient to prevent embolic complications or to relieve mechanical obstruction caused by the tumor; therefore it should not be used as definitive therapy. 10

Special Considerations

• For patients found to have right‑sided cardiac tumors, evaluation for a patent foramen ovale (PFO) is recommended because paradoxical embolism of tumor fragments or venous thrombus can occur. 10

Clinical Algorithm (Key Decision Points)

• In a middle‑aged patient with cryptogenic stroke and no atherosclerotic risk factors, obtain TEE to assess for a cardiac source such as left‑atrial myxoma. [8][9]
• If a left‑atrial myxoma is identified, assess tumor morphology; villous features indicate a higher embolic risk and reinforce the need for prompt surgery. 10
• Proceed urgently to surgical excision with complete tumor removal and an adequate atrial‑septal margin. 10
• Do not rely on anticoagulation or antiplatelet therapy alone as the definitive treatment for myxoma‑related stroke. 10

Physical Examination Findings in Left Atrial Myxoma (American College of Cardiology)

Classic Presentation Triad

• The American College of Cardiology (ACC) notes that left atrial myxoma classically presents with a triad of findings on physical examination: (1) cardiac auscultatory abnormalities (diastolic rumbling murmur or “tumor plop”), (2) signs of systemic embolization, and (3) constitutional symptoms; however, many patients exhibit only one or two components of this triad. 11

Auscultatory Findings

• The ACC reports that a midsystolic or presystolic rumbling murmur at the apex is the most common auscultatory finding, present in approximately 53.5 % of patients, and mimics mitral stenosis due to mechanical obstruction of the mitral valve orifice during diastolic filling. 11
• The ACC indicates that the classic opening snap of mitral stenosis is absent in isolated left atrial myxoma, helping clinicians distinguish it from true valvular mitral stenosis. 11

Diagnostic Technique

• The ACC recommends dynamic auscultation with positional changes (supine, left lateral decubitus, sitting, standing) because murmurs may be soft, intermittent, or position‑dependent; such maneuvers can reveal or accentuate murmurs that are otherwise inaudible. 11