A scintiphotographic method for measuring left ventricular ejection fraction in man without cardiac catheterization

A radioactive tracer method for the measurement of left ventricular ejection fraction in man without cardiac catheterization is described. The tracer (^99mtechnetium-labeled albumin) is injected intravenously. Images of the heart at end-systole and end-diastole are obtained using a scintillation camera and an electronic gate triggered by the patient's electrocardiogram. Each image is composed of 300,000 counts, representing a summation of 200 to 400 heartbeats at end-systole and end-diastole. An outline of the left ventricular free wall is drawn from each gated image. The position of the aortic and mitral valve planes is determined using a radionuclide angiogram obtained at the time of tracer injection. Left ventricular ejection fraction is calculated from the area and length of the long axis of the ventricular outline at end-systole and end-diastole. Determinations of ejection fraction in 20 patients using this tracer method were correlated with measurements obtained by contrast cineangiography with the following results: ejection fraction r = +0.92, P < 0.001; end-diastolic volume r = ?0.76, P < 0.001; and end-systolic volume r = ?0.75, P < 0.001.