What is intra cardiac blood cyst ?

Blood cyst in the heart is a very  rare finding and was first reported by Elasser in 1844. The cysts are most commonly present on the supporting structures; atrioventricular valves, accounting for 96% of the cysts in infants, and are less often present on pulmonary and aortic valves.

Histologically, it is thin-walled and normally lined by cobblestone-shaped endothelial cells and does not contain any tumorous cells.

Blood cysts are often asymptomatic, small and congenital. The cysts regress spontaneously in most patients and are consequently rare in adults, there are some cases reported in contrast.   Cyst growth potential complications include valve dysfunction, left ventricular outflow tract obstruction, and embolic stroke have been documented.

In differential diagnosis  primary cystic tumor such as hemangioma or myxoma should be taken into account and the right-sided cystic mass includes

aneurysmatic atrioventricular septum, cavitating thrombus, abscess formation as a process  of endocarditis, hydatid cyst, and blood cyst.

However, absence of intracystic calcification, homogenous pattern of cystic

fluid, relation to the tricuspid valve, and clinical history strongly suggested a blood cyst in our patient.

Echocardiography indicated the cystic nature of the tumor which is highly mistaken with cardiac hydatidosis. However, cardiac MRI was important for its diagnosis.

Hydatid cysts exhibit a different behavior under MRI, being a

a round homogeneous image is observed with signs of bleeding (iso- or hyperintense in T1 and iso- or hypointense in T2) with no uptake of IV contrast media, which indicates its hematic and cystic nature

Because of the cyst’s location, a myxoma could be suspected, but myxomas tend to be heterogeneous, and although some may exhibit a more homogeneous behavior, they always exhibit contrast uptake, being solid lesions.
 

A chronic thrombus may have similar intensity in T1 and T2, but its round morphology, its well-defined margins, the presence of a tiny pedicle, and its cystic nature as revealed by MRI and echocardiography do not support this diagnosis.

Although a cardiac blood cyst is a very rare finding, it can

be diagnosed using cardiac MRI and it should be included in

the differential table of masses inside heart cavities.

There are several purposed mechanisms for formation of cystic mass ,however, it is believed that invagination at crevices of the valve surface into stroma by high ventricular pressure may result in blood-filled cyst formation. Subsequently, the mouths of the crevices may fuse to form a closed cyst.

The followings are hypotheses :

The first is that blood cysts are formed during valve development as a result of blood being pressed and trapped in crevices that are later sealed off.

The second hypothesis is that blood cysts are the result of hematoma formation in the subvalvular region secondary to the occlusion of small vascular branches of end arteries due to inflammation, vagal stimulation, anoxia, or hemorrhagic events.

The third hypothesis involves possible heteroplastic changes in the tissue that comes from primitive pericardial mesotheli­um.

The fourth and fifth hypotheses are that these blood cysts simply represent ectatic or dilated blood vessels in the valve or that they represent angiomas.

However, there is still no con­sensus regarding the development of blood cysts.

Dencker et al suggested that a conservative approach in asymptomatic patient with minor cyst, and surgical resection should be considered if symptoms exist or if the cysts lead to any cardiac dysfunction.

References

1)        Michelena HI, Mulvagh SL, Schaff HV, Enriquez-Sarano ML, Klarich KW. A heart-shaped mass inside a heart: echocardiographic diagnosis, pathology, and surgical repair of a flail tricuspid valve caused by a large blood-filled cyst. J Am Soc Echocardiogr 2007;20:771.e3–6.

2)       Jose VJ, Gupta SN, Jose S, Chacko B, Abraham PK, Abraham OC et al. Blood-filled cysts of heart. Indian Heart J 2004;56:174–5.

3)        Shing M, Rubenson DS. Embolic stroke and cardiac papillary fibroelastoma. Clin Cardiol 2001; 24:346-7.

4)       Prasad A, Callahan MJ, Malouf JF. Acquired right atrial blood cyst: a hitherto unrecognized complication of cardiac operation. J Am Soc Echocardiogr 2003; 16: 377–378

5)       López-Pardo F, López-Haldón J, Granado-Sánchez C, Rodríguez- Puras MJ, Martínez-Martínez A. A heart inside the heart: blood cyst of mitral valve. Echocardiography 2008;25:928-30.

6)        

7)       Kuvin J, Saha P, Rastegar H, Salomon RN, Pandian N, Denofrio D. Blood cyst of the mitral valve apparatus in a woman with a history of orthotopic

8)       Dencker M, Jexmark T, Hansen F, Tydén P, Roijer A, Lührs C. Bileaflet blood cysts on the mitral valve in an adult. J Am Soc Echocardiogr 2009;22:1085.e5-8.