echocardiogram ejection fraction left ventricular lvef echo muga assessed radionuclide gated muga acquisition multi echocardiogram fraction scan ejection cardiac echo gated muga acquisition echocardiogram lvef left fraction ejection ventricular scan fraction echocardiogram shortening ejection radionuclide angiogram gated muga study cardiac ejection fraction cardiac echocardiogram radionuclide echo normal angiogram muga function multigated acquisition muga echocardiogram fraction ejection left scan ventricular echo echocardiography ejection left fraction muga ventricular acquisition lvef gated scan