A case of hydatid disease of the heart: evaluation with CT and MRI

Clinical History

The patient was admitted with acute pulmonary oedema, caused by aortic and mitral pathology.

Imaging Findings

The patient was admitted with acute pulmonary oedema, caused by aortic and mitral pathology.

The chest X-ray examination revealed opacification of the left middle and lower pulmonary fields and elevation of the left diaphragm. CT scans showed multiple cystic masses (5-15Hv) in the left atrium, at the left side of the root of the pulmonary artery, and in the left upper, left lower and right upper pulmonary parenchyma. MRI demonstrated clearly the cystic nature of the masses and their anatomical extension, suggesting cardiac and pulmonary hydatid cystic disease.

Eosinophilia was present and a hydatid haemoglutination test was positive. The diagnosis was confirmed during cardiopulmonary surgery.

The patient is doing well on follow-up.

Discussion

Echinococcus granulosus is a parasite that can infect humans directly, from contact with dogs and sheep, or indirectly via consumption of contaminated food or water. After invasion of the intestinal mucosa, the parasitic embryos enter the portal system and reach the liver, where 60-70% of the embryos are retained. The next filter for the embryos is the lungs (15-25%) and then they will reach the systemic circulation and affect other organs (10-15%). Cardiac involvement in hydatid disease is rare, with a prevalence of 0.02-2%.

The right heart is involved through the passage of parasites in the inferior vena cava. On the other hand the left heart is involved through the passage of parasites in the superior vena cava, via the lymphatics that drain into the thoracic duct.

The growth of hydatid cysts is slow (2-3cm each year). The wall of the cyst is formed of three layers: the inner germinal layer, which gives rise to scoleses and daughter cysts; the intermediate layer, which is an acellular laminated membrane; and the outer granulomatous advential layer, which is produced as a reaction from the host. Initially the cysts growth is slow and asymptomatic, until they become large enough to compress or displace adjacent structures. The left ventricle is affected most often (50-60%), but the interventricular septum (10-20%), right ventricle (5-15%), pericardium (10-15%) and left atrium (5-8%) may be involved.

In the heart the cysts give rise to symptoms such as precordial pain, dyspnoea and palpitations. Cardiac hydatid disease can mimic many diseases, such as left ventricular aneurysm, atrial myxoma, ruptured sinus of Valsava aneurysm, pericardial tamponade and subdiaphragmatic abscess.

The most important complications are life-threatening rupture of the cyst into the cardiac chamber, which can cause an anaphylactic shock, or into the pericardium with the possibility of tamponade. Other major complications are systemic or pulmonary embolisation arising from compression of the coronary arteries and conduction disturbances or complete AV block causing syncope and arrhythmia. A rare complication is intracerebral embolism.

Ultrasound, as the primary imaging technique for detecting cardiac masses, is capable of showing the cystic nature of the lesion, without being able to make the differential diagnosis from congenital pericardial cysts.

MRI can demonsrate the cystic nature of hydatid cysts and can show the position, the extent and the anatomical relationship of the cysts with the cardiac chambers. In this case the masses had the characteristic signal intensity of a cystic lesion with low signal intensity on T1-weighted images and high signal intensity on T2-weighted images, with sharp and regular margins. Also the cystic lesions had a typical low signal intensity rim to the cystic wall, on both T1- and T2-weighted images, an appearance that cannot be found in non-parasitic epithelial cysts. This finding is attributed to the outer granulomatous layer.

Surgery is the best treatment of hydatid cysts. It is imperative that the contents of each parasitic cyst are sterilised with suitable solutions before removal and strict care is taken in avoiding spillages. The presense of hydatid cysts near the pulmonary arteries and veins, as in this case, makes surgical removal more difficult.

In conclusion, knowledge of the imaging findings of hydatid cysts of the heart and the clinical history of the patient are imperative in making the correct diagnosis.

Differential Diagnosis List

Final Diagnosis

Hydatid disease of the heart

URL:	https://www.eurorad.org/case/1656
DOI:	10.1594/EURORAD/CASE.1656
ISSN:	1563-4086