Atrial Myxoma

• Mechanical obstruction at mitral valve orifice: The pedunculated tumor originates from the fossa ovalis and prolapsulates into the mitral valve apparatus during diastole. This creates a dynamic obstruction that mimics mitral stenosis with variable severity depending on tumor size, location, and positional changes. The obstruction impairs left ventricular filling, increasing left atrial pressure and triggering pulmonary congestion. Patients may experience orthopnea and paroxysmal nocturnal dyspnea that worsens with postural changes (sitting upright temporarily relieves symptoms as gravity displaces the tumor). Physical examination reveals a characteristic diastolic murmur and occasionally a tumor plop—a pathognomonic low-pitched diastolic sound created by the tumor's motion.

• Thromboembolic phenomena: The tumor's gelatinous surface and slow flow create a hypercoagulable microenvironment. Fragments of tumor and adherent thrombi embolize systemically, causing stroke (most common embolic manifestation), peripheral arterial occlusion, mesenteric ischemia, and coronary artery embolism (potentially causing acute myocardial infarction). Paradoxical embolism may occur if the tumor erodes the atrial septum, creating a right-to-left shunt. The incidence of systemic embolization ranges from 10-30% of cases.

• Constitutional and systemic inflammatory manifestations: The tumor secretes interleukin-6, TNF-α, and other inflammatory cytokines producing paraneoplastic syndrome with fever, malaise, arthralgias, weight loss, and elevated inflammatory markers (ESR, CRP). Myxomas may present with pericarditis from direct extension or myocarditis from inflammatory infiltration. Rarely, immune complex-mediated glomerulonephritis or vasculitis occurs. This constitutional syndrome often triggers initial misdiagnosis as systemic lupus erythematosus or infective endocarditis.

• Sporadic origin (95% of cases): De novo benign neoplastic transformation of endocardial multipotent mesenchymal progenitor cells in the region of the fossa ovalis. No proven causative environmental or genetic factors identified in sporadic cases.

• Carney complex (5% of cases): Autosomal dominant syndrome caused by PRKAR1A gene mutations characterized by myxomas (cardiac, cutaneous, and mammary), lentigines, blue nevi, spotty pigmentation, endocrine neoplasias (pituitary adenomas, Sertoli cell tumors), and primary nodular adrenocortical disease. Patients with Carney complex present at younger ages (mean age 20 years) and have higher recurrence rates (5% after resection versus <1% in sporadic cases).

• Age: Peak incidence 40-60 years in sporadic cases; earlier onset in hereditary forms.

• No association with: Prior radiation, chemical exposure, smoking, or traditional cardiac risk factors.

• Obstructive symptoms (secondary to mitral valve obstruction):
• Dyspnea on exertion and orthopnea (most common, 65% of patients)
• Paroxysmal nocturnal dyspnea
• Syncope or presyncope (occurs with positional changes; tumor prolapsing into mitral orifice suddenly increases left atrial pressure and decreases cardiac output)
• Palpitations
• Rarely, sudden cardiac death from complete mitral obstruction

• Thromboembolic manifestations (15-30% of patients):
• Acute ischemic stroke (most common embolic complication)
• Transient ischemic attack
• Peripheral arterial thromboembolism
• Acute myocardial infarction (from coronary artery embolism)
• Mesenteric ischemia
• Retinal artery occlusion

• Constitutional/inflammatory symptoms (30-50% of patients):
• Fever (often low-grade, persistent)
• Fatigue and malaise
• Arthralgias (mimicking rheumatologic disease)
• Weight loss
• Night sweats

• Physical examination findings:
• Diastolic murmur at the apex (mimics mitral stenosis; may change with position)
• Tumor plop: Low-pitched, early diastolic sound (pathognomonic but present in <25% of cases)
• Atrial fibrillation with irregular rate (due to atrial irritation)
• Signs of congestive heart failure: Crackles, elevated jugular venous pressure, peripheral edema
• Loud S1 (from sudden mitral closure if tumor obstructs)
• Variation of murmur with positional change (distinguishes from fixed mitral stenosis)

• Clinical mimicry triggers diagnostic delays:
• Presentation identical to mitral stenosis with dyspnea and diastolic murmur
• Mimics infective endocarditis: fever, cardiac murmur, positive blood cultures (rare from tumor fragmentation), elevated inflammatory markers
• Resembles systemic lupus erythematosus or rheumatologic disease: fever, constitutional symptoms, elevated ESR/CRP, positive ANA (occasionally)
• Resembles vasculitis from systemic embolization

• Transthoracic echocardiography (2D and color Doppler):
• Gold standard initial imaging modality—highly sensitive (95%) and specific (85-90%)
• Classic findings: Pedunculated, gelatinous mass in left atrium, typically arising from fossa ovalis
• Heterogeneous echogenicity reflecting myxoid material and areas of hemorrhage
• Diastolic obstruction of mitral valve orifice visualized during M-mode and 2D imaging
• Systolic motion into left ventricle during ventricular diastole
• Color Doppler demonstrates turbulent flow across mitral valve
• Right atrial myxomas (25% of cases) or tumors in other chambers identified
• Pericardial effusion may be present (from inflammation or malignancy concern)

• Transesophageal echocardiography (TEE):
• Superior resolution for characterizing tumor morphology and insertion point
• Essential for surgical planning to determine peduncle location and relationship to adjacent structures
• Evaluates for prolapse through mitral valve and dynamic obstruction
• Assesses atrial septation integrity (fossa ovalis involvement)

• Cardiac magnetic resonance imaging (CMR):
• High sensitivity and specificity for tissue characterization
• T1-weighted imaging: Isointense or slightly hyperintense signal
• T2-weighted imaging: Hyperintense signal reflecting myxoid material
• Late gadolinium enhancement: Peripheral enhancement pattern
• Excellent for determining tumor invasion into surrounding structures
• Superior for right atrial tumors and tumors near coronary ostia
• Identifies associated malignancy (infiltration into atrial wall, pericardium)

• Cardiac computed tomography (CT):
• Alternative modality when echocardiography inconclusive or MRI contraindicated
• Hypoattenuating mass in left atrium
• Identifies calcification within tumor (suggesting myxoma over thrombus)
• Determines relationship to coronary arteries

• Laboratory studies:
• Complete blood count: Normocytic anemia (paraneoplastic), normal or elevated WBC
• Comprehensive metabolic panel: Usually normal
• Elevated inflammatory markers: ESR and CRP elevated in 50-85% (nonspecific, reflects cytokine production)
• Negative blood cultures: Exclude endocarditis (cultures sterile in myxoma)
• Autoimmune serology: ANA, rheumatoid factor, complement levels may be abnormal mimicking autoimmune disease
• Electrocardiogram: May show atrial fibrillation, left atrial enlargement (P-wave abnormalities), nonspecific ST/T-wave changes
• Chest X-ray: Cardiomegaly, pulmonary edema if heart failure present, normal in asymptomatic cases

• Diagnostic criteria (clinical):
• Imaging evidence of pedunculated intracardiac mass arising from fossa ovalis with left atrial location
• Diastolic obstruction of mitral valve on echocardiography
• Constitutional symptoms (fever, weight loss, elevated inflammatory markers)
• Absence of features suggesting thrombus (associated with atrial fibrillation, recent MI, dilated atrium)
• Pathology confirmation (post-excision): Mucoid stroma with scattered stellate fibroblasts, myxoid degeneration, absence of malignant features

• Differential diagnosis exclusion:
• Left atrial thrombus: Associated with atrial fibrillation or recent MI; no constitutional symptoms; does not grow over time on serial imaging
• Mitral stenosis: Fixed murmur (not positional), opening snap heard, no systemic symptoms, rheumatic heart disease history
• Vegetation from endocarditis: Positive blood cultures, septic emboli to spleen/kidneys, absence of systemic malignancy
• Left atrial angiosarcoma (most common malignant cardiac tumor): Imaging shows infiltration, pericardial involvement, rapid progression

• Surgical resection (definitive and only curative therapy):
• Indicated for all symptomatic patients and asymptomatic patients with large tumors (>4 cm) or high embolization risk
• Timing: Urgent/emergent if hemodynamic compromise (severe dyspnea, syncope, cardiogenic shock), otherwise elective surgery within 1-2 weeks
• Surgical approach: Median sternotomy with cardiopulmonary bypass (CPB)
• Technique: En bloc resection of tumor with surrounding normal atrial tissue (3-5 mm margin of fossa ovalis region) to reduce recurrence; primary closure of atrial septum or pericardial patch if large defect
• Intraoperative transesophageal echocardiography guides resection and confirms complete removal
• Success rate: 95-99% of patients experience symptom resolution
• Operative mortality: <2% in experienced centers
• Recurrence rate: <1% in sporadic cases; 5% in Carney complex (warrants long-term surveillance)

• Preoperative management:
• Anticoagulation: Unfractionated heparin or low-molecular-weight heparin to prevent thromboembolic complications while awaiting surgery
• Diuretics and vasodilators (ACE inhibitors) for hemodynamic optimization if heart failure present
• Cardiac catheterization: Assess coronary anatomy preoperatively to exclude embolic coronary involvement and plan surgical approach
• Workup for thromboembolic manifestations: CT angiography of brain/neck for acute stroke, peripheral vascular imaging if limb ischemia
• Echocardiographic surveillance preoperatively if surgical delay to detect progressive obstruction or prolapse

• Postoperative management:
• Anticoagulation: Warfarin (INR 2-3) for 6 weeks post-resection recommended by many institutions despite low thromboembolic recurrence (controversial; some experts recommend only antiplatelet therapy)
• Echocardiographic follow-up: Baseline at 6 weeks post-op, then annually for 5 years, then every 2-3 years indefinitely
• Carney complex patients: More frequent surveillance (every 6-12 months) given 5% recurrence risk
• Symptom monitoring: Return precautions for dyspnea, syncope, stroke symptoms

• Nonsurgical/conservative management:
• Reserved for asymptomatic patients with small tumors (<4 cm) and low embolization risk
• Serial echocardiographic surveillance: Baseline, then every 3-6 months for 2 years, then annually
• Anticoagulation consideration: Some recommend antiplatelet therapy (aspirin 325 mg daily) for asymptomatic cases, though evidence limited
• Patient education: Recognition of thromboembolic symptoms (stroke, limb pain), positional dyspnea, syncope; need for urgent evaluation if symptoms develop

• Management of complications:
• Thromboembolic complications: Urgent/emergent imaging (head CT/MRI for stroke, arterial duplex for peripheral thromboembolism); thrombolytic therapy or mechanical thrombectomy for acute stroke (within window); anticoagulation intensification pending surgical resection
• Acute mitral obstruction with cardiogenic shock: Urgent surgical resection; temporary management with positioning (sitting upright to gravity-displace tumor), inotropic support (dobutamine, milrinone), diuretics as bridge to OR

• Systemic thromboembolism (10-30% of patients):
• Acute ischemic stroke (most common, 10-15%)
• Peripheral arterial thromboembolism (limb ischemia requiring embolectomy)
• Mesenteric ischemia (can progress to bowel infarction and perforation)
• Coronary artery embolism (acute myocardial infarction)
• Retinal artery occlusion (transient or permanent vision loss)
• Management: Anticoagulation or antiplatelet therapy, expedited surgical resection, vascular intervention (thrombolysis/thrombectomy) for acute events

• Acute mitral obstruction with hemodynamic collapse:
• Sudden severe dyspnea, syncope, cardiogenic shock
• Occurs when large tumor completely occludes mitral orifice, preventing left ventricular filling
• Potential for sudden cardiac death
• Management: Urgent/emergent surgical resection; temporary measures including upright positioning, inotropic support, mechanical hemodynamic support (IABP, extracorporeal membrane oxygenation) if hemodynamically unstable pending OR

• Atrial fibrillation (secondary to atrial irritation):
• Occurs in 10-20% of patients
• Increases thromboembolic risk
• Management: Rate control (beta-blockers, calcium channel blockers), anticoagulation; rhythm control not typically pursued given resolution post-resection

• Pericarditis and pericardial effusion:
• Direct tumor infiltration or inflammatory response to tumor

Buzzwords that give it away

• Tumor plop: early diastolic sound after S2 but later/lower-pitched than an opening snap. Its presence plus a murmur that changes with body position separates myxoma from fixed rheumatic mitral stenosis.
• Positional syncope or dyspnea: symptoms triggered by leaning forward or rolling over reflect a pedunculated, mobile mass intermittently plugging the mitral orifice — a fixed valve lesion cannot do this.
• Constitutional syndrome with sterile blood cultures: fever, weight loss, arthralgias, anemia, high ESR/CRP driven by tumor IL-6. The examiner's trap is "culture-negative endocarditis" or new-onset SLE; the discriminator is the atrial mass on imaging with repeatedly negative cultures.

Single best next step

• Transthoracic echocardiography is the first test in any patient with an embolic stroke plus a diastolic murmur, unexplained fever, or heart failure of unclear cause; AHA/ASA stroke guidance supports echocardiography in the evaluation of suspected cardioembolic stroke, with TEE added to define the stalk and its attachment before surgery.
• Do not biopsy an intracardiac mass suspected to be myxoma — catheter manipulation risks fragmentation and embolization. Diagnosis is imaging-based; pathology comes from the resected specimen.
• Anticoagulation is not definitive therapy. Prompt surgical resection is curative; heparin is only a bridge.

The association examiners test

• Carney complex: autosomal dominant PRKAR1A loss of function — cardiac and cutaneous myxomas, lentigines and blue nevi, primary pigmented nodular adrenocortical disease (ACTH-independent Cushing), Sertoli cell tumors. Suspect it in a young patient, a multicentric or recurrent myxoma, or one outside the left atrium.

Distractors to avoid

• Metastatic disease (melanoma, lung, breast, lymphoma) is the most common cardiac tumor overall; myxoma is only the most common primary tumor in adults.
• Rhabdomyoma is the most common primary cardiac tumor in children, tied to tuberous sclerosis (TSC1/TSC2) and often regresses spontaneously.
• Papillary fibroelastoma is the classic valvular surface tumor; angiosarcoma is the most common primary cardiac malignancy and favors the right atrium with infiltration and hemorrhagic pericardial effusion.