Left ventricular active strain energy density: a promising new measure of systolic function
Authors: MacIver David Hunter , Agger Peter , Rodrigues Jonathan , Zhang Henggui 
Published: June 2022

Background:
The left ventricular ejection fraction does not accurately predict exercise capacity or symptom severity and has a limited role in predicting prognosis in heart failure. A better method of assessing ventricular performance is needed to aid understanding of the pathophysiological mechanisms and guide management in conditions such as heart failure. In this study, we propose two novel measures to quantify myocardial performance, the global longitudinal active strain energy (GLASE) and its density (GLASED) and compare them to existing measures in normal and diseased left ventricles. GLASED calculates the work done per unit volume of muscle (energy density) by combining information from myocardial strain and wall stress (contractile force per unit cross sectional area).
Methods:
Magnetic resonance images were obtained from 183 individuals forming four cohorts (normal, hypertension, dilated cardiomyopathy, and cardiac amyloidosis). GLASE and GLASED were compared with the standard ejection fraction, the corrected ejection fraction, myocardial strains, stroke work and myocardial forces.
Results:
Myocardial shortening was decreased in all disease cohorts. Longitudinal stress was normal in hypertension, increased in dilated cardiomyopathy and severely decreased in amyloid heart disease. GLASE was increased in hypertension. GLASED was mildly reduced in hypertension (1.39 ± 0.65 KJ/m3), moderately reduced in dilated cardiomyopathy (0.86 ± 0.45 KJ/m3) and severely reduced in amyloid heart disease (0.42 ± 0.28 KJ/m3) compared to the control cohort (1.94 ± 0.49 KJ/m3).
Conclusion:
GLASED progressively decreased in the hypertension, dilated cardiomyopathy and cardiac amyloid cohorts indicating that mechanical work done and systolic performance is severely reduced in cardiac amyloid despite the relatively preserved ejection fraction. GLASED provides a new technique for assessing left ventricular myocardial health and contractile function.
Graphical abstract
The figure shows a graphical summary of the study with the derivation, meaning and primary results of the novel measurements GLASED and GLASE. The left-hand panel shows the calculations for peak stress and strain with the middle-panel showing the calculations for active strain energy and strain energy density. The right-hand panel shows the changes in global longitudinal active strain energy density (GLASED) and global longitudinal active strain energy (GLASE) of the left ventricle in the various cohorts.
Clinical perspective
Current measures of left ventricular performance such as ejection fraction and myocardial strain have important shortcomings. These limitations are attributable to the confounding effects of abnormal geometric changes and the loading conditions. This study introduces a novel measure of left ventricular systolic function called the global longitudinal active strain energy density (GLASED). GLASED combines information from left ventricular structural pattern (wall thickness and internal cavity size), systolic pressure and myocardial strain and calculates the work done (mechanical energy produced) per unit volume of myocardium during systole. GLASED should prove to be more accurate than the ejection fraction and myocardial strain in assessing left ventricular myocardial function.