Discussion
Cardiac blood cyst is a rare benign primary tumor of the heart. It was first reported by Professor Elsasse【1】 in 1844. This disease has a high incidence in infancy, especially in the neonatal. It was reported that in 38 random autopsies of fetuses and infants 2 years of age or younger were examined. Blood cysts were found in 18 cases (47%) in which ages ranged from 26 weeks of gestation to 11 months【2】.
The pathogenesis of blood cyst is not clear, and there are several hypotheses, Zimmerman reported that light microscopic examination of serially sectioned paraffin-embedded tissue and plastic-embedded tissue and scanning electron microscopic examination revealed connections between the cyst lumens and ventricles via small endothelium-lined channels. The cyst structure suggested formation from ventricular endothelial infoldings in the valve leaflet base, which bulged into the atrium because of the pressure gradient present during valve closure【2】. Takeda investigated retrospectively the morphologic aspects of blood cysts of the atrioventricular valve in eight Beagle dogs and clarified the morphogenesis of the lesions. Formation of blood cyst is divided into four basic stages: first, the blood vessels only slight expansion, cannot be detected; then, blood vessels of moderate or significant expansion and contains a large number of red blood cells, changes in this stage can be observed; and the blood flows into the cystic lesions, lesions of degeneration and necrosis. In the connective tissue around the cyst or dense fibrous tissue; finally, lesions formed in metaplasia【3】.
Blood cyst can occur in the normal heart, but also can occur in the lesion of the heart or heart invasive surgery, such as ischemic heart disease, atrial fibrillation, atrial septal defect, ventricular septal defect, transcatheter aortic valve replacement 【4】and so on. The clinical symptoms of the patient are atypical. Most of them are diagnosed by echocardiography. The rupture of the blood cyst may cause chest pain, embolism, heart failure, systemic anaphylaxis and the like. Blood cyst was mostly single and multiple rare, can occur in any part of the heart, the most common is in heart valve and chordae, especially occurred in the ventricular surface of the anterior mitral valve or related chorda. In 6 cases of this group, 5 cases occurred in the ventricular surface of the anterior mitral valve or related chorda, the same results as other researchers. On the other hand, blood cysts in the aortic valve, pulmonary valve, atrium, and ventricle have also been reported【4-7】.
The typical characteristics of cardiac blood cyst in echocardiography is a cystic mass, a single balloon‑like small cyst. The cyst has high tension, the wall is thin and smooth, which calcification can be seen on it. According to the location difference, it can cause different hemodynamic effects. (In some case, it could be a) larger cyst attached to the leaflet, can cause valve regurgitation or blood flow obstruction and stenosis. Cyst located in the outflow tract can cause outflow obstruction. Transthoracic echocardiography may miss blood cyst less than 5mm.Transesophageal echocardiography is sensitive to small cyst.
Small blood cyst which causes no hemodynamic effects do not require any treatment and just requires regularly followed up. Some may rupture and disappear spontaneously. When hemodynamic changes were caused, surgical resection may need. Complete resection can do when the cyst is small or less adhesion with the surrounding tissue and postoperative effect is good with no recurrence; A excision operation with valve replacement is needed when the cyst is large or widely adhesion with valve, chordae or surrounding tissue and it is impossible to excise the cyst with a complete valve structure kept.