Interventricular septal hydatid cyst of the heart presenting with syncope: a rare case report.

Background: Cardiac echinococcosis is scarce, constituting <2% of all hydatid cyst infections. Isolated cardiac involvement is infrequent, often affecting the left ventricle. The interventricular septum is an even rarer location, with limited cases reported in the literature. Case summary: A 50-year-old woman presented with a history of chest discomfort, fatigue, exertional dyspnoea, and recurrent syncope. Transthoracic and transoesophageal echocardiography revealed a well-defined, large, intramyocardial cystic mass within the interventricular septum, protruding into the right ventricular cavity and outflow tract (RVOT). Doppler imaging demonstrated turbulent flow with RVOT stenosis (peak/mean gradients: 95/46 mmHg at rest and 107/67 mmHg at exercise, respectively). The serologic Cassoni test confirmed echinococcal infection, albendazole therapy was initiated, and surgical resection was performed successfully. A 2-year follow-up showed no recurrence. Discussion: This case highlights the unusual presentation of an isolated interventricular septal hydatid cyst, which manifested with exertional syncope. It demonstrates the crucial role of early diagnosis via echocardiography, especially in resource-limited settings, and serologic testing to prevent potentially fatal complications. It underscores the need for a multidisciplinary approach combining surgical excision and anti-parasitic therapy to achieve optimal outcomes in endemic settings.