Underestimation of left-ventricular ejection fraction by radionuclide ventriculography in patients with aneurysm.

The left-ventricular ejection fraction (LVEF) of 72 patients with aneurysm of the anterior wall was measured by multiple gated blood pool acquisition (MUGA) in the anterior and left anterior oblique (LAO) positions, and by cineangiography (CA) in right anterior oblique (RAO) and LAO projections of 30 degrees and 60 degrees, respectively. The LVEF was overestimated by CA in the LAO projection and by MUGA in the anterior position, but underestimated by CA in the RAO projection (6.1 percentage points) and by MUGA in the LAO position (6.2 percentage points). In 50 patients without aneurysm, no systematical error occurred using MUGA. The underestimation of the LVEF in patients with aneurysm by MUGA in the LAO position is due to differences of photon attenuation in various parts of the cardiac blood pool. This systematical error can be overcome by biplane MUGA.