A Rare Case of an Isolated Interventricular Septal Hydatid Cyst Presenting With Atrioventricular Block in a Non-endemic Region

Cardiac involvement in human echinococcosis is rare, with isolated interventricular septal (IVS) cysts representing an uncommon presentation. This report details the case of a 41-year-old male who presented to urgent care with fever, cough, and exertional dyspnea. Initial evaluation revealed high-grade atrioventricular (AV) block and markedly elevated inflammatory markers. Advanced cardiac imaging (echocardiography, CT, and MRI) identified a large, complex cystic mass within the basal IVS. Serology was positive for <i>Echinococcus</i> antibody, and a history of residence in an endemic region with contact with stray dogs provided epidemiological support. The patient underwent successful surgical excision of the cyst followed by adjuvant albendazole therapy, with an uncomplicated recovery. This case highlights the diagnostic challenge of cardiac hydatid disease, which can mimic sepsis or myocarditis, and emphasizes the critical role of multimodal imaging and exposure history in guiding diagnosis. Given the risk of life-threatening complications, timely surgical intervention combined with medical therapy is essential for management.