Towards non-invasive assessment of myocardial work using myocardial stiffness and strain: a human pilot study

Myocardial work assessment has emerged as a promising tool for left ventricular (LV) performance evaluation. Existing non-invasive methods for assessing it rely on assumptions on LV pressure and geometry. Recently, shear wave elastography allowed to quantify changes in myocardial stiffness throughout the cardiac cycle. Based on Hooke's law, it becomes theoretically possible to calculate myocardial stress and work from myocardial stiffness and strain measurements. The main objective of this study is to demonstrate the feasibility of this comprehensive ultrasound approach and to compare myocardial work values between populations where variations are anticipated.

Children with hypertrophic cardiomyopathy (HCM), aortic stenosis (AS) and healthy volunteers (HV) were included in this study. Segment dimensions, strain, thickness, and segmental myocardial stiffness were assessed in the basal antero-septal segment throughout the cardiac cycle. One-beat segmental work, the stress-strain loop area, and contributive and dissipative work were compared between groups. Twenty HV (9.8 ± 5.3 years of age), 20 HCM (10.0 ± 6.1 years of age), and 5 AS (5.3 ± 4.3 years of age) subjects were included. One-beat segmental work was significantly higher in AS (272.0 ± 102.9 µJ/mm) and lower in HCM (38.2 ± 106.9 µJ/mm) compared with HV (131.1 ± 83.3 µJ/mm), P = 0.02 and P = 0.01, respectively. Desynchronized work was prevailing in HCM with dissipative work during systole measured at 17.3 ± 28.9 µJ/mm and contributive work during diastole measured at 15.3 ± 18.0 µJ/mm. The stress-strain loop area was higher in AS (95.2 ± 31.1 kPa%) and HV (66.2 ± 35.9 kPa%) than in HCM (5.8 ± 13.0 kPa%), P < 0.01.

Calculating segmental myocardial work based on myocardial stiffness and strain measurements is technically feasible. This approach overcomes the inherent limitations of current methods by introducing a direct quantitative measure of myocardial stress.