Right Atrial Hydatid Cyst Prolapsing into the Tricuspid Valve

A 10-year-old girl presented with fatigue and palpitations. On cardiac auscultation, the 1st heart sound was loud, and a presystolic murmur was audible at the 4th intercostal space on the left sternal border. Transthoracic echocardiography revealed a pedunculated cyst measuring 2.6 × 1.5 × 1.5 cm in the right atrium (Fig. 1A). With each atrial systole, the cyst was prolapsing into the tricuspid valve (Fig. 1B). The patient underwent surgery on cardiopulmonary bypass. Upon right atriotomy, a pedunculated cyst with an irregular surface was visible. The cyst was attached to the right atrium between the septal leaflet of the tricuspid valve and the coronary sinus. The cyst was removed, intact. Histologic examination revealed a multilayered, chitinous, fibrotic membrane and several characteristic Echinococcus granulosus scoleces (Fig. 2). A small excised piece of right atrium revealed chronic inflammation and foreign-body giant-cell reaction. Oral albendazole 400 mg/day was begun postoperatively. An abdominal ultrasound and whole-body computed tomographic scan did not reveal any additional cysts. The patient was discharged on the 7th postoperative day without complications.

Fig. 1 Transthoracic echocardiography shows A) the pedunculated cyst in the right atrium and B) the prolapse of the cyst into the tricuspid valve with each atrial systole.

Real-time motion image is available at texasheartinstitute.org/mansuroglu314.html.

Fig. 2 Photomicrograph shows several characteristic Echinococcus granulosus scoleces (H & E, orig. ×400).

Comment

Hydatid cyst is still an important medical problem. In human beings, the organs affected, in order of frequency, are as follows: liver, lungs, spleen, central nervous system, and heart. Cardiac involvement is quite rare and is seen in only 0.5% to 2% of cases.^1,2 In the heart, the left ventricle is the most common location (46%), followed by the right ventricle (21%), interventricular septum (19.3%), right atrium (9.7%), left atrium (1.6%), and sinus of Valsalva (1.6%).³ Pericardial involvement has also been reported.⁴ In our patient, the hydatid cyst originated in the right atrium and prolapsed into the tricuspid valve with each atrial systole, which subjected the cyst to continuous mechanical pressure. We believe that such cysts have an increased risk of rupture. It is important to remove the cyst without perforation to prevent dissemination and anaphylaxis. Surgical excision of the cyst followed by medical therapy for a minimum of 2 years is the treatment of choice.