Right ventricular outflow pouch associated with double-chambered right ventricle.

Of 12 patients who underwent complete hemodynamic and cineangiocardiographic study for double-chambered right ventricle, seven were found to have a previously undescribed abnormality. Each of these patients exhibited an actively contractile, pouchlike structure closely associated with the right ventricular outflow tract, which occupied a right medial position in respect to the right ventricle. It varied considerably in size but not in location. This abnormality could be best defined when the distal, low-pressure, aspect of the doubled-chambered right ventricle was the injection site. It was best seen in those angiographic projections which allowed optimal viewing of the right medial aspect of the right ventricle. This structure is considered to develop postnatally, secondary to altered flow patterns produced by the underlying malformation, and it appears to constitute a unique finding with double-chambered right ventricle.