Cardiac hydatid cyst as a rare presentation of Echinococcal disease

An asymptomatic 61-year-old woman with no known notable diseases was addressed to perform a contrast-enhanced CT scan for the evaluation of a pulmonary opacity detected at chest X-Ray (not included in following images). Risk factors: smoking habits, hypercholesterolemia.

1. Computed Tomography (CT) shows, as an incidental finding, a lobulated hypointense lesion within the interventricular septum (IVS), extended into the right ventricle (RV) cavity. The lesion shows a thin wall with spotty calcification (Fig. 1a). After contrast medium (CM) administration (Fig. 1 b and c), mild enhancement of the walls was detected but not of the lesion content, as fluid-containing.

2. Cardiac Magnetic Resonance (CMR) images demonstrate an intramyocardial cystic, slight hyperintense in T1-weighted (Fig. 2a) and clearly hyperintense in T2-weighted images, with a well-defined edge (Fig. 2b). After CM administration, no enhancement of the lesion was found at first-pass (Fig 3a) whereas a peripheral rim enhancement was observed on late gadolinium enhanced imaging (Fig 3b).

Background

Hydatid disease is a parasitic infection caused by Echinococcus granulosus. Hydatid cysts can be seen in a variety of tissues, although they are most frequently found in the liver (50–70%) and the lung (20–30%) [1]. Cardiac involvement during hydatid disease is an uncommon finding (0,5-2% of all cases) [2]. Cardiac localization of hydatid cysts includes the left ventricle (60%), right ventricle (10%), pericardium (7%), pulmonary artery (6%), left atrial appendage (6%) and interventricular septum (4%) [3].

Clinical Perspective

Clinical presentation of cardiac hydatid cysts is extremely variable and mostly depends on cysts localization. Most patients are asymptomatic due to the slow growth of cysts. Nevertheless, the most common symptom is chest pain, which is often vague and clearly distinguishable from angina [3]. The most frightful complication in subendocardial cysts is the rupture, which can lead to anaphylactic shock, systemic or pulmonary embolization and even sudden death [4].

Imaging Perspective

Echocardiography is the first-line imaging modality in evaluating hydatid cysts and shows the typical cystic appearance of the lesion.
CT and MRI, besides the lesion characterization, are particularly useful in determining its relationship with cardiac chambers and coronary arteries.
At MRI images, hydatid cyst appears as an oval lesion, hypo- or hyperintense in T1-weighted and hyperintense in T2-weighted images, which also shows a peripheral hypointense ring corresponding to the fibrous capsule [3]; in LGE images, the cysts usually show peripheral rim enhancement, with no central enhancement [5]
CT scan usually shows a fluid density cyst, with frequent peripheral calcification, which represents a specific finding and can be circumferential in inactive infection. Fluid attenuation pattern can be variable, depending on the proteinaceous material amount [6].

Outcome

Due to the high risk of associated complications, cardiac hydatid cysts should be removed surgically, even in asymptomatic patients. [7]. Surgical treatment depends on the size, location, and number of the cysts. The mainstay of surgical therapy is to excise the pericyst, empty the cyst, remove daughter cysts and the germinal membrane, carefully avoiding the lesion rupture [8]. During the operation, measures should be taken to prevent perioperative embolization of a germinative membrane. Drug therapy (Mebenadazole and Albendazole) can be useful in preventing post-operative recurrence [8].

Take Home Message

Cardiac hydatid cysts are rare entity with a variety of signs and symptoms but is often asymptomatic.
CMR and CCT are particularly useful in lesion characterization and in detecting its relationship with cardiac chambers and coronary arteries.
Surgery is the treatment of choice in cardiac hydatid cysts due to the high risk of complication, with high rate of complete recovery.