Blood-pool radionuclide angiography in patients with a Novacor left ventricular assist device. Blood-pool radionuclide angiography was used to investigate the left ventricular function in eight patients who received a Novacor assist device as a bridge-to-cardiac transplantation. Studies were performed during maximal and minimal tolerated assist device flows. The left ventricular ejection fraction, volumes, cardiac output, and the pump ejection fraction were computer-assessed. All patients had severe left ventricular dilation and hypokinesis before insertion of the assist device, with a mean ejection fraction of 18% +/- 4% which improved to 44% +/- 18% (p less than 0.01) during maximal assist device flows, but fell to 25% +/- 15% (p less than 0.01) during minimal flows. The ventricular volumes became normal at maximal assist device flow but increased significantly (p less than 0.05) during minimal flow. The pump was well visualized and had an ejection fraction of 82% +/- 7%. These data indicate that this assist device effectively unloads the left ventricle. The deterioration in ejection fraction following decrease in assist device flow is in keeping with the dependency of these patients on the device to sustain adequate hemodynamics. 