Gurpreet Gulati, Naresh K Goyal, Shyam S Kothari, 
Sanjiv Sharma, AK Bisoi

Departments of Cardiovascular Radiology, 
Cardiology and Cardiothoracic Surgery, Cardiothoracic Centre,
All India Institute of Medical Sciences, New Delhi

A46-year-old female was referred to our institute with a diagnosis of acute coronary syndrome. She had retrosternal chest pain of 2 days’ duration. On admission, her physical examination was normal but an electrocardiogram showed T-wave inversion in II, III, aVF and I, aVL, V _4-6 . The cardiac enzymes (CPK-MB and Troponin-T) were normal. Chest X-ray revealed gross cardiomegaly and a bulge along the left upper cardiac border which was extending posteriorly (Figs 1A and B).  Transthoracic echocardiography demonstrated a single, anechoic lesion adjacent to the left atrium and left ventricle, with an echogenic rounded mass within it. The lesion was located inside the pericardium but outside the myocardium of the lateral wall of the left ventricle. A presumptive diagnosis of pericardial cyst was considered but a suspicious thinning of the myocardium was noticed at one spot (Fig. 2, arrow head). However, there was no blood flow within the anechoic space. A coronary angiogram showed normal coronary vessels, and the distal obtuse marginal branches of the left circumflex artery were splayed over the mass (Fig. 3). There was no communication between the left ventricle and the lesion. On MRI, the lesion was homogeneously hypointense on spin-echo T ₁ -weighted images and markedly hyperintense on both spin-echo and gradient echo T ₂ -weighted images (Figs 4A and B), indicating a cystic mass. A thin hypointense rim to the lesion was noted on all the sequences, which was characteristic of a hydatid cyst. There were no other cysts in the liver, lungs or brain. Laboratory tests showed no eosinophilia, and hydatid serology was negative. 

The patient subsequently underwent surgery. At thoracotomy, a pericardial cystic lesion was found attached to the left aspect of the heart and diaphragm. This was successfully excised. Histopathologic examination revealed a germinative membrane and scolices within a basophilic laminary structure, consistent with a hydatid cyst. Postoperatively, the patient was put on oral albendazole therapy and has been symptom-free at 4 months’ follow-up.  

Cardiac hydatid cysts represent only 0.5%–2% of cases of systemic echinococcal infection.^1,2 The most common location is the left ventricle, followed by the interventricular septum and right ventricle. Cysts in the pericardium, right atrium or left atrium are very rare.^1,2 The clinical picture depends on the location and size of the cyst. Patients with cardiac hydatid cysts are usually asymptomatic, although mild, recurrent, nonspecific chest pain is the most common complaint. This may be due to episodes of partial rupture into the pericardium, with resulting pericarditis or because of external compression of the coronary artery.^3,4 If cardiac hydatid cysts are left untreated, they usually rupture into the heart chamber or pericardium and may cause pulmonary or systemic embolization, tamponade or anaphylactic shock.^1,2 Even constrictive pericarditis secondary to a pericardial hydatid cyst has been reported.^1,2 

Two-dimensional echocardiography is the best diagnostic procedure to demonstrate a cardiac hydatid cyst. On echocardiography, a unilocular cyst with well-defined margins and internal trabeculations corresponding to daughter cysts is diagnostic of a hydatid cyst.⁵ More recently, MRI has been used to provide a diagnosis of hydatid cyst based on the characteristic low-intensity rim on both the T ₁ -weighted and T ₂ -weighted images in a cystic mass.⁶ This rim represents the fibrous tissue-rich pericyst in a hydatid cyst.

The serologic diagnosis is not reliable, although it has high specificity, but sensitivity is low in patients with intact cysts as the concentration of the antibody in serum is very low until the cyst leaks.⁷

Surgical excision remains the treatment of choice for cardiac hydatid cysts. Oral albendazole therapy has also been used to reduce the size of the cyst and to prevent recurrence.²

Correspondence: 
Dr Shyam S Kothari, 
Department of Cardiology,
Cardiothoracic Centre, 
All India Institute of Medical Sciences, 
New Delhi - 110029. 
e-email: kotharis@del2.vsnl.net.in

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