Primary cardiac tumors in newborns are extremely rare and more than 90% of them are benign. They occur approximately in 1 every 100,000 live births . The most frequent tumors of the heart observed in pediatric patients are rhabdomyomas, fibromas and lipomas. Hibernoma is a rare, benign soft tissue tumor of brown fat origin. Less than 300 cases have been reported in the literature . Its genesis is thought to be the result of nonspecific trauma to the brown fat cells, such as inflammation or infection. Intracardiac Hibernoma is very rare location and few cases were reported in the literature. Typical location described is the endocardium of the right atrium.
The first case of cardiac Hibernoma reported in the literature was a case of 64-year-old patient with a very rare cardiac Hibernoma located in the right atrium. Transesophageal echocardiography and computed tomography have been shown to be useful for differentiating between benign and malignant tumors. The tumor was excised with the use of cardiopulmonary bypass surgery. Histology confirmed diagnosis of a benign cardiac Hibernoma .
Luca Di Tommaso et al reported a case of 51-year-old woman, with no clinical history, presented for an acute haemoptysis. A computerized tomography (CT) scan revealed a nodule of the lower left pulmonary lobe and a 4-cm lesion involving almost completely the interatrial septum and extending into the right atrium near the superior cava vein. A Magnetic Nuclear Resonance (MNR) excluded any relationship with the superior cava vein. The patient underwent surgery. The definitive histopathology diagnostic was cardiac Hibernoma .
Rebeca Mata-Caballero et al reported a case of 73 -year-old woman, asymptomatic with previous history of breast cancer in complete remission. The tumour was a casual finding on an fluoro-D-glucose integrated with computed tomography (FDG PET/CT). Transthoracic, transesophageal echocardiography showed a mass in the right atrium and aroud the vena cava. Cardiac magnetic resonance help in the differential diagnosis of benign tumor. The mass was excised, allowing the definitive histological diagnosis of benign cardiac Hibernoma. The subsequent outcome was excellent .
A case of intrapericardial Hibernoma associated with constrictive pericarditis was also reported. The authors present the case of a 20-year-old male who underwent an operation for the treatment of constrictive pericarditis, in which an intrapericardial sessile lesion over the diaphragmatic surface of pericardial sac was incidentally discovered. The tumor was excised and diagnosed as Hibernoma. No recurrence was evident two years after the procedure .
The clinical symptoms vary largely depending on their size, location and mobility of the tumor. It ranges from incidental discovery on imaging tests indicated for other reasons to life-threatening presentations such as cardiac tamponade, arrhythmia, systemic embolization and obstruction. Obstructive symptoms include congestive heart failure, syncope and rarely cardiogenic shock.
In our case the cardiogenic shock was attributed to the obstruction of the right ventricle outflow tract that reduced the cardiac output significantly.
Transthoracic echocardiography (TTE) remains the preferred tool for screening and diagnosing intra cardiac tumors.It allows to specify accurate location, mobility and extent of the tumor. Echocardiography typically reveals a homogeneous, hyperechoic mass, but these findings are not diagnostic of this lipomatous tumor .
Magnetic resonance imaging (MRI) and cardiac computerized tomography scan are useful modalities for diagnosis and characterization of intracardiac masses, studying the limits, basis of implantation, and relation ship to surrounding structures.
Cardiac MRI provides the possibility of diagnosing the nature of the tumor by studying its signal features. The specific sign being the complete signal loss of the mass on fat suppression sequence. It is considered the diagnostic gold standard .
The need for sedation and anesthesia for pediatric population, limits its use in cases of severe symptoms and hemodynamic instability. Such as the case of our patient who was deemed too unstable to undergo sedation and transthoracic echocardiography was sufficient to indicate intervention.
No clear guidelines have been established due to the low incidence of cardiac Hibernoma, but there is consensus that surgical resection of the cardiac tumor is the optimal method of treatment in symptomatic patients. Conservative management may be implemented for asymptomatic patient and prophylactic resection should also be considered .
In our case, surgery is indicated and complete resection of the tumor is recommended, but the overgrowth and myocardial infiltration has led to an unsuccessful complete resection.
Long term recurrence of cardiac Hibernoma after surgical resection is possible. Incomplete removal due to diffuse infiltration in the myocardium seems to be the contributing factor for recurrence.