Cardiac lipoma and lipomatous hypertrophy of interatrial septum (LHIS) are very rare disorders with distinct pathological features. While cardiac lipoma is a well-circumscribed encapsulated tumor of mature adipocytes, LHIS is due to entrapment of fat cells in the interatrial septum during embryogenesis. Although a biopsy is the definitive diagnostic test, these disorders can be differentiated by a cardiac magnetic resonance imaging (MRI). Treatment of LHIS is not warranted in asymptomatic patients. In symptomatic patients, surgical resection is the only recommended treatment, which has shown to improve good long-term prognosis.
A 63-year-old Caucasian woman with past medical history significant for hypertension, hypothyroidism, right breast ductal cell carcinoma treated with mastectomy and breast implant, platelet granule disorder, asthma requiring chronic intermittent prednisone use, presented to the outpatient cardiology office with recent onset exertional dyspnea, palpitations, weight gain and weakness. Initial workup with electrocardiogram and holter monitor did not reveal significant findings. During the subsequent hospitalization for community acquired pneumonia, the patient developed symptomatic paroxysmal atrial fibrillation. Transthoracic echocardiogram showed a right ventricular mass. A biopsy was not pursued given the high risk of bleeding due to platelet granule disorder. Cardiac MRI showed characteristic features consistent with cardiac lipoma and LHIS. Prednisone was discontinued. Genetic testing for arrhythmogenic right ventricular dysplasia and 24-h urine cortisol test was negative. As multiple attempts at rhythm control failed with sotalol and flecainide, pulmonary vein isolation and right atrial isthmus radiofrequency ablation were done. She is in follow-up with symptomatic relief and no recurrence of atrial fibrillation for 10 mo.
Benign fatty lesions in heart include solitary lipoma, lipomatous infiltration and lipomatous hypertrophy of interatrial septum. Although transvenous biopsy provides a definitive diagnosis, Cardiac MRI is superior to computed tomography and aids in differentiating benign from malignant lesions. Surgical excision of cardiac lipoma along with capsule and pedicle removal generally prevents recurrence, but with our patient’s unusual tumor features and comorbidities proscribed a surgical approach. Symptom management with antiarrhythmics and ablation techniques were successfully utilized.

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