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Abstract
We report a rare case of isolated cardiac involvement by hydatid disease in a young female patient, who presented with a recent onset of chest pain and discomfort. The radiological investigations showed an intramyocardial hydatid cyst in the right ventricle-free wall, protruding into the right ventricular cavity. The lesion exhibited characteristic MRI findings of crumpled serpiginous detached membranes within it and delayed peripheral enhancement on dynamic postcontrast late-phase MRIs. The positive hydatid serology consolidated the imaging findings. The patient underwent surgical excision of the hydatid cyst.
- Infectious diseases
- Cardiovascular medicine
- Radiology
- Cardiothoracic surgery
- Ultrasonography
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Background
Hydatid disease is a parasitic infection by the larval stage of the tapeworm Echinococcus granulosus. This infection most commonly affects the liver and lungs (70% and 20% of cases, respectively). Cardiac involvement is observed in less than 2% of cases, with the isolated primary infection of the heart being extremely rare (less than 0.2% incidence). Among cases of cardiac hydatid disease, the most common site of involvement is the left ventricle and affection of the right ventricle is very rare. Here, we present a case of right ventricular intramyocardial hydatid cyst with emphasis on imaging characteristics on various imaging modalities. The typical MRI features along with positive hydatid serology are the key to diagnosis. The multivesicular cystic mass and membrane detachment as in our index case are pathognomonic elements for the diagnosis of cardiac hydatid. The treatment of choice is surgery with excision of the cyst.
Case presentation
A woman in her 20s presented to the outpatient department with intermittent chest pain and left shoulder pain lasting for 1 month. The chest pain was insidious in onset and gradually progressive. She had difficulty sleeping because of chest pain which was not relieved by medications. However, there were no specific cardiovascular or respiratory symptoms. On physical examination, the patient was fully oriented with normal blood pressure (115/72 mm Hg), pulse rate (86 beats/minute) and temperature. Her cardiovascular and respiratory system examinations were normal.
Investigations
The chest radiograph was unremarkable; however, the ECG showed features of an incomplete right bundle branch block. The blood investigations were within normal limit except slightly raised eosinophil count to 8.2%. The patient was further evaluated with the transthoracic echocardiography, which revealed a well-defined oval echogenic solid cystic mass in the right ventricle, compressing the right ventricular cavity (figure 1). The lesion appeared attached to the posterior leaflet of the tricuspid valve. There was no evidence of tricuspid regurgitation or stenosis. The left ventricular (LV) ejection fraction (61%) was within normal limits. The patient underwent contrast-enhanced dynamic cardiac MRI scan with ECG trigger for further characterisation of the mass. It revealed a well-defined oval intramyocardial lesion (size—6.0×4.6×4.0 cm) in the free wall of the right ventricle with a significant reduction in the right ventricle blood volume. The lesion was hyperintense on precontrast T1-weighted image (T1WI), uniformly hyperintense on T2WI with multiple thin T2 hypointense crumpled serpiginous detached membranes within. A T2 hypointense rim was seen around the lesion. On dynamic postcontrast MRIs, the lesion was cystic in nature with no evidence of internal enhancement (online supplemental video 1), however, mild peripheral enhancement is seen on late-phase images (figure 2). On cine images, the lesion demonstrated a to-and-fro motion with the cardiac cycle and it was closely abutting the right ventricular outflow tract anteriorly (online supplemental video 2). The haemodynamic measurement on MRI revealed left ventricle ejection fraction—64%, heart rate—64 beat per minute, end-diastolic volume—12.2 mL, end systolic volume—4.3 mL and stroke volume of 7.9 mL. Based on the characteristic imaging findings, a diagnosis of intramyocardial hydatid of the right ventricle-free wall was made. Hydatid serology test showed elevated IgG antibodies with index value of 2.52 (normal <0.9), consolidating the diagnosis of a hydatid cyst.
Supplementary video
Supplementary video
(A) Chest radiograph posteroanterior projection is unremarkable. (B) Parasternal long axis echocardiography grey scale image shows a complex cystic lesion in the anterior myocardium of the right ventricle with intralesional crumpled serpiginous membranes (arrow). (C) On colour Doppler, the right ventricle lumen shows evident flow and absent intralesional vascularity (arrow).
MRI: axial four-chamber view (A) T2WI and (B) tripple inversion recovery T2WI show a uniformly hyperintense anterior intramyocardial hydatid cyst of the right ventricle with multiple intralesional T2 hypointense serpiginous detached membranes (white arrows) and reduced right ventricular luminal capacity. (C) On precontrast T1WI, the lesion is hyperintense. Postcontrast T1WI in (D) axial and (E) sagittal sections show mild peripheral enhancement and absent internal enhancement within the hydatid cyst (blue arrows). T2WI, T1-weighted image.
Contrast-enhanced CT of the thorax and abdomen was performed to rule out hydatid cysts in other areas of the body. No evidence of any abnormal focal lesion was seen in the abdomen or lungs. The sections through the heart showed peripherally enhancing well-circumscribed oval lesion in the right ventricle-free wall with multiple internal serpiginous membranes. No calcification of the cyst wall was noted (figure 3).
(A) Non-contrast CT image shows the absence of calcification in the hydatid cyst. Contrast-enhanced CT images in (B) axial and (C) coronal planes show the peripherally enhancing hydatid cyst in the right ventricle-free wall with multiple mildly hyperdense internal serpiginous membranes (arrows).
Treatment
The patient underwent surgical excision of the cardiac hydatid cyst. Intraoperatively, the hydatid cyst was in the anterior wall of the right ventricle leading to deformation of the ventricle. The cyst was completely excised along with the daughter cyst. No periprocedural complication occurred. The histopathological evaluation of the resected specimen revealed gross and microscopic features consistent with the diagnosis of a hydatid cyst. The patient received albendazole therapy for 2 months postsurgery.
Outcome and follow-up
Postsurgery, the patient became asymptomatic and she was advised regular follow-up in the outpatient department.
Discussion
Human hydatid cysts are caused by larvae of E. granulosus, which is still endemic in many sheep-raising countries. Cardiac involvement in hydatid disease is infrequent, even in endemic countries, accounting for 0.5%–2% of all cases of hydatidosis.1–4 The fact that the heart’s constant beat stops parasite eggs from adhering to the cardiac wall explains why cardiac involvement is so uncommon.3 5 In cases where cardiac involvement does occur, the E. granulosus enters the heart through the bloodstream, travels through the coronary circulation and lodges in the myocardium. Thereafter, it grows slowly (at the rate of 1 cm per year) and becomes a mature hydatid cyst in 1–5 years.3 6
Most commonly, cardiac hydatid cysts involve the LV cavity (60%), explained by the fact that the LV muscle mass is larger and very rich in vascular supply.3 6 This is followed by the involvement of the right ventricular cavity (10%–15%), pericardium (7%), the atria and the interventricular septum.2 Most patients with cardiac hydatid are asymptomatic, and the disease often remains latent because of the slow growth of the hydatid cyst. When they are symptomatic, chest pain is the most common symptom, as in our case. Dyspnoea, palpitations, angina, heart rhythm disorders and fever are other symptoms seen in cardiac hydatid cysts.7 If the cyst compresses the coronary arteries, it may lead to angina pectoris. A compression of the bundle of His may result in conduction abnormalities, as in our case, where the ECG showed an incomplete right bundle branch block.8
The right ventricular hydatid cysts are usually subendocardial. Therefore, intracavitary rupture is more common in the right ventricle lesions compared with the left ventricle lesions (88% vs 37% incidence, respectively).6 7 The intracavitary rupture can lead to the obstruction of the valvular orifice, anaphylactic shock and pulmonary embolism with post embolic cor pulmonale. Hypereosinophilia is encountered in 20%–30% of cases, especially in ruptured cysts. Serological tests such as immunoglobulin ELISA, indirect hemagglutination, immunoelectrophoresis (arc 5) and immunoblot are useful to confirm the presumptive radiologic diagnosis.3 7 Transthoracic and or transoesophageal echocardiography is the primary imaging modality with excellent diagnostic accuracy. It can well demonstrate the anechoic cyst with a thin wall, membrane detachment or multivesicular structures, which are considered specific signs.8 The location, size and relationship of the hydatid cyst to surrounding structures—particularly the cardiac wall, valves and coronary arteries—can all be described with the aid of echocardiography. Nevertheless, it has several drawbacks, such as operator reliance, a narrowed field of view in individuals with a large body habitus and a restricted view of the right and left heart chambers and the apex of the ventricle.9
The chest radiograph could show localised cardiac silhouette deformities, cardiomegaly or a calcified lobular mass close to the ventricles, however, when the cyst is small or presenting as an intracardiac growth, chest radiographs are usually without abnormalities, as in our index case.10 CT and MRI are essential for evaluation of the precise location, extent and anatomic relationships of the cyst. On CT, it appears as a peripherally enhancing low-density usually univesicular lesion with a well-defined contour and thin wall. Wall calcifications, when present, are considered specific findings. A thoracoabdominal CT identifies other organs’ possible involvement which can occur in up to 40% of cases.11 It further helps in differentiating hydatid cysts from solid tumours such as myxomas or fibromas both by CT density measurements and analysis of enhancement after intravenous contrast injection.12 MRI depicts the exact anatomic location and nature of the internal and external structures and is the preferred technique used for post-treatment follow-up.13 The appearance of a hydatid cyst on MRI is usually a characteristic oval lesion that is hypointense on T1WIs and hyperintense on T1WIs. A typical finding on T1WIs is a hypointense peripheral ring, which represents the pericyst (a dense fibrous capsule from the reactive host tissue).14 15 On dynamic MRI, it is a non-enhancing lesion with peripheral enhancement on delayed phase images. Heart cine MRI offers important insights into the differences between cardiac and cyst motions. It also evaluates the exact lesion location, its fixated character, deformability, impact on myocardial contraction as well as the risk of cyst rupture.14
A variety of tumours in the heart and a congenital pericardial cyst must be considered in the differential diagnosis; however, the multivesicular nature of the cystic lesion and membrane detachment indicate the true diagnosis.9 The cysts may be single or multiple, uninoculated or multiloculated, and thin or thick-walled. More specific signs include calcification of the cyst wall, the presence of daughter cysts and membrane detachment. In addition, peripheral enhancement of a non-enhancing lesion on contrast MRI is extremely valuable for diagnosis of cardiac hydatid.9 Surgery remains the treatment of choice in the management of hydatid disease. Although anthelminthic drugs have been used in the preoperative and postoperative periods since 1977, extirpation of the lesion under cardiopulmonary bypass is recommended.16 17
Learning points
Cardiac involvement in hydatid disease is rare due to the continuous contraction of the heart which prevents the attachment of parasite eggs into the cardiac wall.
Cardiac hydatid may present with angina pectoris, if the cyst compresses the coronary arteries, and conduction abnormalities if it compresses the bundle of His.
Early and accurate diagnosis of the cardiac hydatid is crucial to avoid complications, such as rupture, that can lead to the anaphylactic shock and pulmonary embolism with postembolic cor pulmonale.
Echocardiography is the primary imaging investigation revealing the anechoic cysts, detached membranes or multivesicular structures of the lesions. It can well demonstrate the location and relationship of the lesion with cardiac wall, valves and coronary arteries.
MRI along with hydatid serology is the key diagnostic modality for cardiac hydatid disease. Calcification of the cyst wall, presence of daughter cysts and detached membranes are specific for cardiac hydatid disease. Surgery is the mainstay treatment.
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References
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Footnotes
X @Anam@1986
Contributors The following authors were responsible for drafting of the text, sourcing and editing of clinical images, investigation results, drawing original diagrams and algorithms, and critical revision for important intellectual content: MK, SNP, AM and KPKT. The following authors gave final approval of the manuscript: MK, SNP, AM and KPKT. MK acted as guarantor.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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