Original Investigation
Geometry as a Confounder When Assessing Ventricular Systolic Function: Comparison Between Ejection Fraction and Strain

https://doi.org/10.1016/j.jacc.2017.06.046Get rights and content
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Abstract

Background

Preserved left ventricular (LV) ejection fraction (EF) and reduced myocardial strain are reported in patients with hypertrophic cardiomyopathy, ischemic heart disease, diabetes mellitus, and more.

Objectives

The authors performed a combined mathematical and echocardiographic study to understand the inconsistencies between EF and strains.

Methods

An analytical equation showing the relationship between EF and the 4 parameters, global longitudinal strain (GLS), global circumferential strain (GCS), wall thickness, and short-axis diameter, was derived from an elliptical LV model. The equation was validated by measuring the 4 parameters by echocardiography in 100 subjects with EF ranging from 16% to 72% and comparing model-predicted EF with measured EF. The effect of the different parameters on EF was explored in the model and compared with findings in the patients.

Results

Calculated EF had very good agreement with measured EF (r = 0.95). The model showed that GCS contributes more than twice as much to EF than GLS. A significant reduction of GLS could be compensated by a small increase of GCS or wall thickness or reduced diameter. The model further demonstrated how EF can be maintained in ventricles with increased wall thickness or reduced diameter, despite reductions in both longitudinal and circumferential shortening. This was consistent with similar EF in 20 control subjects and 20 hypertrophic cardiomyopathy patients with increased wall thickness and reductions in both circumferential and longitudinal shortening (all p < 0.01).

Conclusions

Reduced deformation despite preserved EF can be explained through geometric factors. Due to geometric confounders, strain better reflects systolic function in patients with preserved EF.

Key Words

left ventricular geometry
mathematical modeling
myocardial strain

Abbreviations and Acronyms

CAD
coronary artery disease
DCM
dilated cardiomyopathy
ED
end-diastole/diastolic
EDV
end-diastolic volume
EF
ejection fraction
GCS
global circumferential strain
GLS
global longitudinal strain
HCM
hypertrophic cardiomyopathy
LV
left ventricle/ventricular
ROI
region of interest

Cited by (0)

This work was supported by the Center for Cardiological Innovation, funded by the Research Council of Norway (RCN grant number 203489/o30). Dr. Stokke was funded by a grant from the Medical Student Research Program at the University of Oslo and the Research Council of Norway. Dr. Remme was funded by the K.G. Jebsen Foundation. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.

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