Global Longitudinal Strain, Ejection Fraction, Ventriculo‐Arterial Coupling and Their Interrelationships in Heart Failure Patients with Different Phenotypes
Authors: Diaz-Navarro Rienzi , Kerkhof Peter L. 
Published: April 2020

Ejection fraction (EF) is a popular metric to evaluate left ventricular (LV) systolic function. The EF is a ratio, based on paired volume measurements, similar as the more recently introduced ventriculo‐arterial coupling (VAC) index, being the ratio of two elastances. Their dimensionless nature requires consideration of the associated companion (i.e., the hypotenuse calculated from the constituent pair and denoted as EFC and VACC, respectively). This insight becomes clear when considering the LV volume domain representation.

Global longitudinal strain (GLS) has been advanced as a preferred alternative for EF. Reportedly, the connection between EF and GLS is weak, thus confirming that these ratio‐based metrics focus on partial and likely dissimilar aspects of LV pump function. To overcome these limitations the present study addresses the relationships between GLS and EF or VAC (assuming vanishing intercept), as well as the newly introduced complementary metrics EFC and VACC.

In 25 heart failure (HF) patients (43 – 83 years, 9 women) end‐systolic volume (ESV), end‐diastolic volume (EDV), diastolic interventricular septal thickness (IVST), and posterior wall thickness (PWT) were determined by echocardiography. Data are analyzed following informed consent. IVST and PWT were used to derive LV mass (LVM). GLS was obtained via speckle tracking echocardiography. When appropriate, these data were indexed (i) to body surface area (BSA).

Significant sex‐specific differences were found for BSA (P<0.0001), LVM (P=0.04) and stroke volume (P=0.02), but the latter not when normalized to BSA. The volume regulation graph (VRG) which relates ESV to EDV yields R=0.92, implying an inverse nonlinear relationship, either logarithmic or of the more robust type EF = 1+c1ESV / (c2+ESV), where c1 and c2 are population‐based constants. These data indicate that a sex‐specific cut‐off at ESVi=30 mL/m2 for men and at ESVi=20 mL/m2 for women separates the two major HF phenotypes, also demonstrating that the current practice of phenotyping via the ratio based metric EF is undesired and not required. LVM correlates (P<0.001) with EDV (R=0.76) and with EFC (R=0.76). GLS moderately correlates with EF (R=−0.63, P<0.001), VAC (R=−0.65, P<0.001), EFC (R=0.49, P=0.025), and with VACC (R=0.43, P=0.03).

The interpretation of EF, VAC and GLS in terms of physiology is debatable, as each refers to a ratio without physical dimension(s). In contrast, EFC and VACC carry a clear physical unit (namely mL), comparable to the primary variables ESV and EDV. The fact that GLS only moderately correlates with major clinically used metrics such as EF and VAC, suggests that there is a future place for the GLS companion, which deserves evaluation of its physiology‐based impact.

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Ejection fraction (EF) versus end‐systolic volume index (ESVi) for two heart failure (HF) phenotypes, distinguished on the basis of a criterion applied to ESVi, which differs for women (red line) and men (blue line).

Figure 1