Giant Endocardial Blood Cyst in the Right Atrium
Echocardiographic and Magnetic Resonance Imaging Features
A 62-year-old patient, from the province of Cáceres (a region of endemic hydatidosis), with a history of elevated ferritin unrelated to the hemachromatosis gene, a hiatal hernia, mild esophagitis, and renal sinus cysts, was referred to the cardiology department for presyncopal episodes associated with headache. Cardiological examination revealed no data of interest. Both the ECG and thoracic x-ray were normal. Transthoracic echocardiography showed mild hypertrophy of the left ventricle with preserved systolic function and a 2.8-cm diameter round image with predominant hypogenicity inside, which was mobile and attached to the interatrial septum (Figure 1). Both serology and immunoglobulin E were negative for Echinococcus. Cardiac magnetic resonance imaging (MRI) was performed, which revealed a well-delimited round image attached to the interatrial septum in the right atrium, which exhibited a very low signal in the cine MRI sequence (steady-state free precession) and an isointense signal in the enhanced T1- and T2-weighted sequences. The lesion was heterogeneous, exhibiting a hypointense area in all sequences coincident with the area of calcification shown in the ultrasound scan (Figure 2). After administration of contrast media, no uptake was observed.
The tumor was excised by means of a cardiopulmonary bypass, and a nodule of some 3-cm diameter, with homogeneous characteristics and a purplish color suggestive of a benign growth with hematic content, was observed macroscopically. Histological examination confirmed the diagnosis of a simple blood cyst with a calcified area inside and no tumoral cells present (Figure 3).
Blood cysts are usually small, are found mainly in newborns or young patients, and mainly affect valvular structures. Surgical resection is not necessary unless they impair the normal operation of the valves. They are rare in adults and in some cases may be mistaken for malignancies, or for hydatid cysts in endemic areas.
Echocardiography indicated the cystic nature of the tumor which, because of the patient’s geographical origins, suggested cardiac hydatidosis. However, cardiac MRI was important for its diagnosis. Hydatid cysts exhibit a different behavior under MRI, being hypointense in T1 sequences and hyperintense in T2 sequences. The low signal in the gradient-echo sequence and the isointense signal in T1 and T2 suggested chronic blood content. 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. A blood cyst may be suspected when 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.