Discussion

Cardiac rhabdomyomas are closely associated with tuberous sclerosis complex and affect approximately half of the patients, and most of them are asymptomatic. However, rarely they may cause arrhythmia, non-immune hydrops, or even death prenatally. Large lesions may rarely cause obstruction of cardiac outflow or embolic events. ^{Reference Curatolo, Bombardieri and Jozwiak1} In clinical practice, an echocardiogram and electrocardiography should be performed on patients with tuberous sclerosis for evaluation of possible rhabdomyomas and arrhythmia, in infantile period. Our patient was consulted to paediatric cardiology when he was 18 months old, but because of the parent’s inconsistency to regular follow-up and consultation, echocardiography could not be performed in infancy. So that first echocardiographic evaluation and diagnosis of intracardiac lesion was delayed.

Cardiac lipomas are rare benign primary cardiac neoplasms of mature adipose tissue and composed of mature collections of adipocytes. ^{Reference Vaughan, Veugelers and Basson3} They are more common in adults. Most lipomas are epicardial; however, they can involve all three layers of the heart, including myocardium and endocardium. ^{Reference Mahani, Lu, Rigsby, Krishnamurthy, Dorfman and Agarwal2} The incidence of cardiac lipoma is reported as 8 to 12% of primary cardiac tumours, whereas true lipoma, particularly in the interventricular septum, is extremely rare. ^{Reference Gulati, Sharma, Kothari, Juneja, Saxena and Talwar5,Reference O’Donnell, Abbara and Chaithiraphan6} These tumours vary in size, ranging from extremely small tumours to massive epicardial masses and size impacts clinical condition. They are usually asymptomatic but may cause symptoms due to pericardial effusion, arrhythmia, or intracardiac obstruction. ^{Reference Vaughan, Veugelers and Basson3} Lipomas are usually solitary, but multiple lipomas have been reported associated with some CHDs, tuberous sclerosis or sometimes sporadically in normal hearts. ^{Reference Mahani, Lu, Rigsby, Krishnamurthy, Dorfman and Agarwal2} There have been reports of cardiac lesions considered as angiomyolipomas or fat-containing lesions in patients with tuberous sclerosis. In a recent study, more than one-third (35%) of adolescents and adults with tuberous sclerosis were found to have cardiac lesions with signal characteristics consistent with fat-containing lesions. ^{Reference Shaaya, Hirshberg and Rabe7} There are also some reports of lipomatous lesions, diagnosed by CT and MRI in tuberous sclerosis. ^{Reference Jabir and Al-Hyassat8} But true cardiac lipomas are very rare. As a very rare association with tuberous sclerosis, the lipomas diagnosed in our patient were not solitary, non-obstructive, and well limited in interventricular septum and asymptomatic, so there was no indication for a surgical extraction of the lesion. Therefore, histological diagnosis could not be performed for our case.

Echocardiographic assessment of our patient revealed a well-bounded fusiform lesion with echogenic borders and less echogenic centre. Transthoracic echocardiography may have some limitations including operator dependency, poor quality of acoustic window in some patients, and limited capability to differentiate cardiac lesion characteristics. ^{Reference Gulati, Sharma, Kothari, Juneja, Saxena and Talwar5} In echocardiographic examination, true cardiac lipomas are encapsulated, containing neoplastic fat cells, and homogeneously echogenic. ^{Reference Ward, Kadoch, Jacobi, Lopez, Salvo and Cham9} Because of the limitations of echocardiography, cardiac MRI is usually needed to describe the characteristics of the lesion and is a useful diagnostic technic that can differentiate fat-containing tumours from other non-fatty lesions. ^{Reference Vaughan, Veugelers and Basson3} Main characteristics of lipomas are homogeneous high-signal intensity on T1-weighted sequences, mildly hyperintense on T2-weighted sequences, loss of signal on fat suppression sequences, and no enhancement on first-pass perfusion sequences. ^{Reference Mahani, Lu, Rigsby, Krishnamurthy, Dorfman and Agarwal2} We also performed cardiac MRI for our patient, and it revealed two lesions on interventricular septum, which were hyperintense in T1 sections. On fat suppression sequence, the masses appeared hypointense, non-enhancing, and these MRI findings were compatible with a benign cardiac lipoma. As these findings were sufficient for diagnosis, no further tests were performed, and clinical follow-up was planned for our patient as he was asymptomatic.

In conclusion, most of the cardiac lesions associated with tuberous sclerosis are rhabdomyomas, but rarely other cardiac lesions of different nature can be seen. True cardiac lipomas are very rarely in association with tuberous sclerosis although other fat-containing lesions like angiomyolipomas are some more frequent. Echocardiography should be used as screening test for cardiac lesions in tuberous sclerosis but cardiac MRI is needed to determine nature of the lesion, rhabdomyoma, lipoma, etc.