Integration between volumetric change and strain for describing the global mechanical function of the left ventricle

Evaluations of left ventricular systolic function based on ejection fraction (EF) alone are unable to recognize impaired myocardial performance in some dysfunctional states, and strain parameters are often invoked for an improved description of cardiac contraction. A comprehensive framework integrating deformation measures with volumetric changes is therefore necessary.

This study presents a general mathematical background that confirms and generalizes a previously proposed framework relating volumetric changes and strain values. The model is then validated with 5450 data samples made of LV volume, global longitudinal strain (GLS) and global circumferential strain (GCS) from 109 heterogeneous subjects who underwent cardiac magnetic resonance imaging. The GCS was measured by either three short-axis slices or 3D LV geometry reconstructed from 3 long-axis slices.

Results demonstrated the reliability of the relationship EF = 1 - (GLS + 1)(GCS + 1)². Accuracy is higher (correlation coefficient r = 0.997) when GCS is obtained by 3D deformation, although it remains high (r = 0.98) when GCS is measured from short-axis slices. However, the latter may underestimate (about 10% in relative terms) the circumferential deformation due to through-plane motion.

The accuracy of this relationship permits a unitary description of LV systolic function in terms of both EF and global strain values by its position on the strain plane (GLS, GCS). This also allows to monitor pathologic or healing changes, as a consequence of exercise, drugs, surgery or other therapeutic options, as trajectories on that plane.