Ejection fraction as related to basic components in the left and right ventricular volume domains.

BACKGROUND

Ejection fraction (EF) is commonly applied as a clinically relevant metric to assess ventricular function. The numerical value of EF depends on the interplay between end-systolic volume (ESV) and end-diastolic volume (EDV). Remarkably, the relative impact of the two constitutive components on EF received little attention.

METHODS

Three patient groups not using beta-blockers were analyzed for a robust investigation into the relative contribution of ESV and EDV when assessing EF: cardiac patients (N=155) with left ventricular (LV) data obtained by biplane ventriculography, near-normals (N=276) by gated SPECT investigation, and an MRI-based post Fallot repair study including right ventricular (RV) data (N=124), besides LV. We compared various routes to evaluate EF via linear and several types of nonlinear regression with ESV as independent variable. Advanced statistics was applied to evaluate sex-specific differences.

RESULTS

In all cases ESV emerges as the dominant component of EF, with less (P<0.0001) impact of EDV. The relationship for EF versus ESV is nonlinear (P<0.0001), and similar for both sexes. A linear approach may be inadequate and generate erroneous statistical outcomes when comparing subgroups of patients.

CONCLUSIONS

Values for EF primarily depend on ESV, both for LV and RV. This relationship is essentially nonlinear, and similar for both sexes. A logarithmic approximation is convenient and often acceptable. However, application of linear regression for EF vs ESV may lead to incorrect conclusions, particularly when comparing males and females.