Although hydatid disease is a parasitic infection that is endemic in many parts of the world and pericardial hydatid cysts are very unusual and rare disease as we experienced and as is evident in literature. The anatomical site of location in the heart depends on the amount of regional vascularization. Salati et al. found that in 18 year period, isolated cysts in pericardium is only 11 (1.4%) of 783 cases of cardiothoracic hydatid cysts (
4) Polat P et al. reported that 50%-60% of the cardiac hydatid cysts are located in the left ventricle, 10%-20% are located in the interventricular septum, 5%-15% are located in the right ventricle, 10%-15% are located in the pericardium, and 5%-8% are located in the right or left atrium (
5). Akar et al. found that in 60 patients of case series, left ventricle is the most common site of location by 47%, followed by the right ventricle (19%), interventricular septum (19%) and right atrium (11%) (
6). Isolated hydatid cyst in pericardium reported as a rare entity (
7). Alae F et al. (
8) has shown that thoracic computerized tomography and magnetic resonance imaging showed a large cyst measuring 5 × 3 cm in the interventricular septum, a smaller cyst in the left ventricular lateral wall and a cyst at the upper lobe of the left lung . Geramizadeh B et al. (
9,
10) has reported that three case of alveolar echinococcus of liver and Isolated Adrenal gland hydatid cyst in different geographic region of Iran. In the present case, the hydatid cyst was located in the pericardium adjacent to the left ventricle. Symptoms of a pericardial hydatid cyst are generally due to the pressure exerted on the myocardium by an enlarging cyst or due to rupture of the cyst. Because the pericardium is non-compliant, increases intrapericardial pressure resultant adverse cardiac compressive effect on cardiac filling and output and clinical manifestations of cardiac tamponade, constrictive pericarditis may arose. Patients with cardiac hydatid cysts symptoms can be quite variable, most commonly present to the emergency department with dyspnea, palpitation, and chest pain mimicking coronary syndromes (
7) as in our case. However, echocardiography and MRI/ CT remain the best techniques for diagnosing and locating cardiac hydatid cysts. According to our clinical experiences, the frequency of hydatid cysts by organs in order of decreasing in frequency is following: liver, pulmonary, and cardiac. This area is an endemic zone of hydatid cyst and we were operated multiple number of case of liver and lung hydatid cyst but isolated pericardial hydatid cyst operated first time in my ten years of clinical experience. In a patient with a history of hydatid disease in endemic region, the rupture of a hydatid cyst should be considered as a possible diagnosis when circulatory collapse is the initial symptom. This case is reported because of the diagnostic problems encountered mimicked acute coronary syndrome and it is rare disease even in endemic zone like our state Eastern UP of India. Cardiac hydatid cysts should always be considered in presence of eosinophilia in the differential diagnosis of pericarditis or pericardial effusion, especially in regions where hydatid disease is endemic.