Digital filtering of left ventricular heart volume and calculation of aortic valve blood flow

The volume of the left ventricle of the heart can be calculated from measurements taken from cine angiocardiograms. During normal systole, blood leaves the left ventricle via the aortic valve; therefore, the first derivative of left ventricular volume with respect to time (during systole) is equal to aortic valve blood flow. Since a curve of left ventricular volume versus time contains significant scatter, it must be filtered, or smoothed, prior to differentiation. This paper describes three methods of digitally filtering left ventricular volume, and discusses methods of calculating aortic valve blood flow. All three methods of smoothing volume give similar results.