As a congenital malformation cardiac blood cysts are common in infancy which regress with time but is very rare in children older than six months and in adults. They are small round reddish-brown nodules usually found on the atrial surface of the atrioventricular valves. They are usually sessile but can be pedunculated. In adults it is often solitary but multiple blood cyst has been reported which were present on both leaflets of the mitral valve[11]. Less than 100 cases of cardiac valve blood cyst have been reported yet. Most of the cardiac blood cysts are found on atrioventricular valves[12], it can be found in other parts of the heart such as aortic valve[13], pulmonary valve[6] left atrium[14], right atrium[15], right ventricle[16], papillary muscle[5], and atrial septum[7]. It is very rare entity and has not yet included in many cardiac tumor articles[1, 17]. Even though it is rare but there may be few hundred cases of cardiac blood cyst in the literature and that is enough to include it in benign cardiac tumors list to increase awareness of the healthcare workers in this field.
The cause of cardiac blood cyst is not very clear but there are multiple theories how they are formed. One very early concept by Luschka was that it occurs as extravasation of blood from the vessels which they believed were present in the valve cusps. Berti thought that they may develop in the valves during vascular regression process. Gross believe that it is due to the obliteration of the valvular blood vessels. Haushalter and Thiry theory is that, the blood is pressed by the heart chambers in the cervices and channels in the cusps and leads to blood cyst formation. They called it “Hematomes” [4]. As a known fact that the heart valves are avascular structure except from very short extension of the vessels in its bases. Dow and Harper believe that the theories which explain the cardiac blood cysts are originated from the dilatation of previously present valvular blood vessels is unlikely. They agree with the concept of Haushalter and Thiry. They believe in embryonic stage the traction of chordae tendineae make a furrow in the meshed fibrous structure which has not yet differentiated into special layer of the cusps and the fusion of the edges of the furrow would lead to the development of cardiac blood cyst and this was seen by serial sectioning of the valve cusps[4]. We believe this mechanism maybe true because some cases of acquired blood cyst have been reported after surgery[18-20]. Inflammation, surgery etc may cause the same furrows in the cusps of the valves which can lead to blood cyst formation. In older children and adults, it is very much possible that the congenital blood cyst which has been formed during embryonic stage get enlarge and result in clinical presentation but a part of these cases may be acquired due to one or another reason.
Most cases are asymptomatic and the cyst is diagnosed incidentally when the investigation is performed for some other pathology. Cardiac tumors are generally diagnose first time after pulmonary or systemic embolization[1]. Patients can present with dyspnea, palpitation, syncope, stroke, hemiparesis, myocardial infarction, valve obstruction or regurgitation. This patient presented with weakness of the leg. Arteriovenous ultrasound did not show any thrombus of the leg however brain CT showed lacunar cerebral embolism which may explain the condition. We believe the hemodynamic changes caused by the blood cyst leads to the formation of small thrombus and subsequently lacunar cerebral infarction.
It is very challenging to distinguish cardiac blood cyst form other cardiac tumors such as myxoma, vegetation, thrombus, or hydatid cyst etc[7]. Suspected cardiac tumors diagnosis should begin with investigation for exclusion of thrombus or vegetation[1]. Valve hemangiomas are occasionally found in the heart, and valve cysts are sometimes difficult to distinguish from valve hemangiomas however, valve cysts generally have no blood flow signals by echocardiography. Transthoracic echocardiography is a first line of investigation like for all other cardiac masses[1, 9]. Chang et al. believe that echocardiography is a convenient preoperative and follow up tool of investigation but it is not a very good choice for differential diagnosis[7]. Though the final and definitive diagnosis can be made by histopathological examination, but due to the technical challenges of cardiac biopsy preoperative diagnostic modalities such as CT and magnetic resonance imaging (MRI) is used for preliminary diagnosis[21-23]. It can also help in better understanding of the pathology and surgical decision making. Poterucha et al believe that MRI is the most useful among the available modalities for cardiac tumors as it can help to demarcate the anatomy with surgery serving both diagnostic as well as therapeutic option[17].
As the cardiac tumors can embolize and cause complications, surgery is recommended especially for large cyst in symptomatic patients[1]. About 70% of cases of mitral valve blood cyst were managed surgically according to one research[12]. Some researchers believe that small asymptomatic blood cyst could be followed up without surgical intervention. We believe because the natural history and hemodynamic effect of the blood cyst is not predictable, it is better to perform surgery to avoid future complication which would need surgery at that time. Most of the cases of mitral valve blood cyst have been operated through median sternotomy approach except for few which has been done with minimal invasive surgery[23, 24]. Our case was performed through total endoscopic approach and is an addition to already available cases.