Right ventricular dysfunction frequently occurs in patients undergoing correction of congenital cardiac defects, as well as in other clinical settings. The purpose of the present study was to surgically induce right ventricular dysfunction and then provide circulatory support with a right ventricular assist device. Right ventricular hypertrophy was created in 13 neonatal lambs by pulmonary artery banding. Right ventricular dysfunction was produced in all animals by performing a right ventriculotomy with the animal supported by cardiopulmonary bypass. In four unassisted animals the circulation failed after separation from bypass. Seven experimental animals underwent the insertion of a pneumatically activated ventricular assist device between the proximal pulmonary artery and the right ventricular apex. Periods with the right ventricular assist device on and off in each animal were compared. The right ventricular assist device increased cardiac output from 0.72 +/- 0.15 to 2.24 +/- 0.23 L/min (p less than 0.0002), increased left atrial pressure from 7 +/- 1 to 11 +/- 1 mm Hg (p less than 0.0005), and increased aortic systolic pressure from 53 +/- 9 to 85 +/- 9 mm Hg (p less than 0.0001). Right ventricular assistance significantly reduced the right ventricular end-diastolic pressure from 19 +/- 3 to 12 +/- 1 mm Hg (p less than 0.0001). Pulmonary artery peak pressure distal to the band increased from 27 +/- 3 to 52 +/- 5 mm Hg (p less than 0.0001). The results indicate that right ventricular dysfunction can be produced by a vertical cardiotomy in a hypertrophied right ventricle with persistent outflow tract obstruction. Right ventricular dysfunction can be effectively reversed by a right ventricular assist device, which may prove clinically useful in managing patients with refractory right ventricular failure.