A method for measuring mean circumferential fiber shortening rate from gated blood pool scans

Abstract

Ejection fraction and ejection rate are easily obtained from gated cardiac images, but no method is available for calculating mean circumferential fiber shortening rate. We assumed that the cube root of left ventricular end-diastolic volume or counts is proportional to the minor axis of the left ventricle at end-diastole or end-systole. Mean circumferential fiber shortening rate is then equal to the [cube root of the end-diastolic volume (count) minus cube root of end-systolic volume (count)] divided by [cube root of end-diastolic volume (count) multiplied by the ejection time]. In 250 contrast ventriculograms, the standard mean circumferential fiber shortening rate (MCFSR) and that derived by the cube root method correlated well (r=0.94). The mean value of MCFSR (0.85±0.35) was greater than the cube root value (0.75±0.35) (P<0.001). The regression equation was y=0.86x+0.02. Similar correlations were obtained from gated radionuclide images using a semiautomated program (r=0.93) in 24 subjects or completely automated program (r=0.85) in 28 patients. The regression equation between MCFSR and that derived from the cube root of counts for the semiautomated program was y=0.82x+0.04 and for the automated program was y=0.84x+0.004. Similar correlations, slopes, and intercepts were seen using circumferential fractional shortening for angiographic data when correlated with both the semiautomated and automated gated blood pool scan programs. These data indicate that MCFSR and circumferential fractional shortening may be obtained from gated blood pool images using cube root estimates of end-diastolic and end-systolic radii with a high degree of correlation with the standard contrast ventriculographic technique.