Hydatid cyst of the interventricular septum causing obstruction of the right ventricular outflow tract: cross-sectional echocardiographic, angiographic and pathological findings.

Cardiac echinococcal cysts rarely involve the interventricular septum; when they do, they cause symptoms mainly related to the compression of the atrio-ventricular conduction pathways. Mild obstruction of the right ventricular outflow tract has also been described in some cases. In the case reported here, an unusual large hydatid cyst located in the interventricular septum produced a marked, symptomatic obstruction of the right ventricular outflow tract (more than 100 mmHg gradient). Surgical resection of the cyst was complicated by a 'stone heart' syndrome, probably because of a severely affected right ventricle. Cross-sectional echocardiography gave the exact site and aetiology of the mass. On the basis of these non-invasive findings, early surgery should be performed on asymptomatic patients to reduce the risk of life-threatening evolutions.