Ventricular Ejection Fraction and Global Strains in Connection with the Volume Regulation Graph

Ejection fraction (EF) is traditionally considered useful to infer ventricular function. Newer metrics such as global function index (GFI) and various strains add supplemental diagnostic or prognostic value. All these candidates refer to dimensionless ratios, rather than to the characteristics of the underlying components. Therefore, we introduced the volume regulation graph (VRG), relating end-systolic volume (ESV) to end-diastolic volume (EDV). An individual patient is then uniquely defined by the prevailing working point in the volume domain. Alternatively, the combination of EF=(1-ESV/EDV) and any suitable companion (denoted as C) metric (e.g. the Pythagorean mean) specifies this working point. An expression relates EF to global longitudinal (GLS) and circumferential strain (GCS): ESV/EDV = (GLS+1) (GCS+1)(2), resembling the empirical regression equation for the VRG. However, the latter has a non-zero intercept (mL). The discrepancy can be solved by the introduction of one or more pertinent companion metrics. We studied 96 patients by cardiac magnetic resonance imaging and calculated EF, EFC, GFI, GLS and GCS. The GFI is inversely related to GLS (R-2=0.26). For regression we found: ESV=0.74 EDV-27.0 with R-2=0.81 for N=96. Similar results were obtained for echocardiography data (N=25). Graphs relating EF to GLS and GCS indicate that EFC can distinguish patients with nearly identical values for these 3 metrics. Thus, the VRG offers a unifying framework that visualizes the association between ESV and EDV, while documenting iso-EF and iso-EFC trajectories. Newer metrics including GFI, GLS and GCS require consideration of a companion variable such as EFC to permit a comprehensive analysis.