RESUMEN
Hydatidosis commonly affect the liver and lungs but in rare cases, it can involve heart tissue. A 42-year-old man from urban areas of Khorasan Razavi province, northeastern Iran, was referred to the cardiac clinic with palpitation, and atypical chest pain in 2018. Large pericardial effusion, reduced left ventricle systolic function was found. A cystic-like lesion was also seen in inter-ventricular septum in echocardiography and high-resolution computed tomography (HRCT). Urgent cardiac surgery was done because of echocardiographic evidence of tamponade. Although the serologic analysis was negative for hydatidosis, surgical excision of cyst and the subsequent histopathological findings revealed a hydatid cyst. In endemic areas, hydatidosis should be considered in differential diagnosis of any cystic-like lesions, even if the serological analysis is negative.