Physiologic left ventricular ejection efficiency assessed at the level of the aorta

Methods Vascular ejection efficiency (VEE) is proportional to the dimensionless ratio of aortic diameter to wavelength of the transmitted blood pulse. The wavelength of ejected blood is proportional to blood wave velocity divided by blood wave frequency measured using phase velocity mapping (PVM) applied to the ascending aorta. Left ventricular function and aortic PVM data were retrospectively obtained in 118 patients who underwent CMR scanning as a clinical routine. The LV end-diastolic and end-systolic volumes were measured using manually drawn contours for a contiguous stack of LV slices. The aortic area was measured from the PVM images along with the average velocity, taken as a measure of blood wave velocity (not to be confused with the more common pulse wave velocity), the end-systolic time was taken as the pulse length and aortic area instead of diameter to yield the VEE index: VEE = Aortic Area × End systolic time / Average blood velocity The VEE was calculated and plotted against the ventricular measures of EF and VVC.