Left ventricular ejection fraction calculated from volumes and areas: underestimation by area method.

The ejection fraction is one of the most widely used measurements of left ventricular systolic function. Angiographic measurement of ejection fraction is based on determination of roentgenographic magnification and calculation of end-diastolic and end-systolic volumes, assuming a prolated ellipse. Because it is simple and radiographic magnification may not have been determined, some laboratories have obtained an "ejection fraction" by comparison of end-diastolic and end-systolic areas. A comparison of the two methods was made using ventriculograms of 538 patients from three cardiac catheterization laboratories. The area method of ejection fraction calculation consistently underestimates ejection fraction from left ventricular volumes. A regression equation was derived that allows adjustment of the ejection fraction obtained from areas to that from volumes.