Abstract 12826: Geometric Factors Explain why Left Ventricular Ejection Fraction may be Preserved in Ventricles With Reduced Global Longitudinal Strain
Aim: A significant reduction in left ventricular (LV) global longitudinal strain (GLS) without a significant reduction in ejection fraction (EF) is reported regularly. Our aim was to investigate if this apparent contradiction could be explained by geometric factors. We therefore derived the relation between EF and wall strains using a geometric model and compared the findings from this model with measurements from patients.
Methods: Based on an ellipsoidal LV model we derived the mathematical relation between EF, GLS, and global circumferential strain (GCS) as EF=(1-(1+GCS/100%)2*(1+GLS/100%))*100%. We measured EF, GLS, and GCS by echocardiography in 37 patients with verified or suspected cardiovascular disease. The geometric model was validated by comparing measured EF with predicted EF from the model using the measured GLS and GCS as inputs to the equation.
Results: EF was dominated by its quadratic dependency on GCS in the model: A change in GCS was amplified to a large change in EF as a result of the steep slope between them (Fig. a). In contrast a change in GLS resulted in a small change in EF due to the flat slope, particularly at high EF, of the weaker, linear relation between EF and GLS (Fig. b). In the patients mean EF was 45±16%, GLS was -14±6%, and GCS was -18±7% .The predicted EF from the model was in very good agreement with real measurements (Fig. c). Interestingly, there was a significant relation between EF and GLS in patients with EF≤50% (R2=0.65, p≤0.05), while this relation was not significant in patients with EF≥50% (R2=0.08, p=ns), consistent with the weaker relation between EF and GLS at higher EFs in the model.
Conclusions: EF reflects predominantly circumferential shortening, while longitudinal shortening has relatively small impact. This could explain the intuitively inconsistent finding that there may be a significant reduction of GLS with no significant change in EF and indicate that GLS may be a more sensitive marker of myocardial function than EF.
- © 2013 by American Heart Association, Inc.