Hydatid Cyst in the Interventricular Septum: A Rare Cause of Dizziness?

A 35-year-old man was admitted for evaluation of dizziness that occurred while he was playing basketball. The physical examination was normal. An electrocardiogram revealed a 1st degree atrioventricular block. Chest radiography showed a calcified mass on the anterior aspect of the cardiac silhouette (Fig. 1, arrowhead). Transthoracic echocardiography demonstrated a cyst (4 × 3 cm) in the interventricular septum (Fig. 2, arrow), which was partially obstructing the right ventricular outflow tract. A magnetic resonance imaging study confirmed the location of the intramyocardial cyst (Fig. 3, arrowhead) and identified no extracardiac cystic images. Blood samples showed eosinophilia, and a hemagglutination test for hydatid disease was positive.

The patient was operated upon under cardiopulmonary bypass, and the cyst was resected. Microscopic examination of the excised tissue confirmed the diagnosis of hydatid cyst. The patient was treated with albendazole, and after 6 months there is no evidence of recurrence. We hypothesized that the patient's dizziness could be explained by the occurrence of non-registered transient conduction abnormalities and by the partial obstruction of the right ventricular outflow tract, but this theory cannot be proved.