[Transthoracic cardiac ultrasonic shear wave elastography for detecting myocardial stiffness in healthy and hypertrophic cardiomyopathy individuals]

Objective: To explore the feasibility of transthoracic cardiac shear wave elastography (SWE) for non-invasive quantitative measurement of myocardial stiffness in healthy volunteers (HV) and hypertrophic cardiomyopathy (HCM) patients, and analyze the relationship between myocardial shear wave velocity (SWV) and left ventricular diastolic function. Methods: A total of 16 HV who underwent health check-ups and 5 HCM patients who visited the Cardiology Outpatient Clinic at Fujian Medical University Affiliated Union Hospital from September 2022 to October 2023 were prospectively recruited. The SWE technique was used to measure SWV of the basal segment of the interventricular septum, including left ventricular long-axis myocardial shear wave velocity (LA-SWV) and short-axis myocardial shear wave velocity (SA-SWV). The intraclass correlation coefficient (ICC) was employed to evaluate the intra-observer and inter-observer consistency of SWV measurements. Spearman's correlation analysis was performed to evaluate the correlation between baseline characteristics, echocardiography parameters and SWV. Quantitative data were expressed as median (interquartile range) [M (Q₁, Q₃)]. Results: The HV group had the age of 34.5 (24.0, 51.0) years, including 8 males (50%); the HCM group had the age of 34.0 (27.0, 46.0) years, including 3 males (60%). The intra-observer and inter-observer ICC (95%CI) for LA-SWV measurements were 0.806 (0.592-0.907) and 0.785 (0.471-0.949), respectively, indicating high consistency; the intra-observer and inter-observer ICC (95%CI) for SA-SWV measurements were 0.746 (0.359-0.862) and 0.602 (0.245-0.834), indicating moderate consistency. LA-SWV [1.74 (1.65, 1.77) vs 1.25 (1.22, 1.33) m/s, P<0.001] and SA-SWV [1.98 (1.96, 2.15) vs 1.52(1.46, 1.55) m/s, P<0.001] were significantly higher in HCM group than those in HV group. There was no significant correlation between SWV and gender, age or body mass index (all P>0.05). In the left ventricular long-axis view, interventricular septal end-diastolic thickness (IVSDT) (r=0.749, P<0.001), early diastolic mitral valve flow velocity/early diastolic mitral annular peak motion velocity (E/e') (r=0.669, P<0.001), and left ventricular mass index (LVMI) (r=0.679, P<0.001) were positively correlated with LA-SWV, while e' (r=-0.545, P<0.001) and late diastolic mitral annular peak motion velocity (r=-0.489, P=0.021) were negatively correlated with LA-SWV. In the left ventricular short-axis view, IVSDT (r=0.784, P<0.001), E/e' (r=0.657, P<0.001), and LVMI (r=0.660, P<0.001) were positively correlated with SA-SWV, while e' was negatively correlated with SA-SWV (r=-0.658, P<0.001). Conclusions: The use of SWE technique to measure myocardial SWV can be applied to assess the stiffness differences between normal myocardium and HCM myocardium. Additionally, SWV is correlated with left ventricular diastolic function indices and can effectively evaluate the diastolic dysfunction of the left ventricle caused by HCM.