Shear wave elastography to unmask differences in myocardial stiffness between athletes and sedentary non-athletes

Abstract

Aims: Myocardial stiffening naturally occurs with aging and contributes to diastolic dysfunction. Assessing myocardial stiffness non-invasively could improve the sensitivity of diastolic function evaluation in clinical practice. Shear wave (SW) elastography is a non-invasive tool for quantifying myocardial stiffness, where higher SW velocities indicate increased stiffness. We investigated whether SW elastography could detect differences in myocardial stiffness between athletes and sedentary non-athletes and, during exercise, reveal differences in operational stiffness that may indicate diastolic dysfunction.

Methods and results: We enrolled 20 master athletes (median age 60 [IQR 59-66] years) and 17 sedentary non-athletes (median age 58 [IQR 52-71] years). Standard exercise echocardiography revealed no significant differences in diastolic function between the groups. Additionally, ultra-high frame rate imaging was used to measure SW velocities after mitral valve closure (MVC) and aortic valve closure (AVC) at rest and during exercise. At rest, athletes had lower SW velocities after MVC compared to sedentary non-athletes (3.2 ± 0.4 m/s vs. 3.9 ± 0.7 m/s, respectively, P = 0.003). During exercise, SW velocities after AVC significantly increased in sedentary non-athletes but not in athletes (+1.6 ± 1.6 cm/s increase per 1% power output increase vs. 0.0 ± 0.8 cm/s, respectively, P = 0.006). An inverse correlation was found between the increase of SW velocity after AVC during exercise and VO₂max (r = -0.51, P = 0.003).

Conclusion: SW elastography reveals reduced myocardial stiffness in athletes compared to sedentary non-athletes at rest and during exercise, which is not detected by conventional echocardiographic measurements. Exercise-induced changes in SW velocities after AVC may potentially serve as an early marker for detecting diastolic dysfunction.

Keywords: diastolic function; high frame rate imaging; myocardial stiffness; shear wave elastography; stress echocardiography.

Graphical Abstract

Shear wave (SW) elastography unmasks stiffness differences at rest and during exercise between athletes and sedentary controls. Ultra-high frame rate imaging was performed at rest and during exercise in athletes and controls. M-mode maps, showing acceleration of tissue, were extracted from the midline of the interventricular septum. The SWs after mitral valve closure (MVC) and aortic valve closure (AVC) appear as tilted bands on the acceleration maps, where steeper bands represent higher velocities. The presented velocities represent the mean velocities in the groups. At rest, SW velocity after MVC revealed reduced passive stiffness in athletes, whereas during exercise, SW velocity after AVC revealed reduced operational stiffness during isovolumic relaxation in athletes. AVC, aortic valve closure; HFR, high frame rate; IVRT, isovolumic relaxation time; MVC, mitral valve closure; SW, shear wave; v, velocity.

Figure 1

Evolution of conventional diastolic parameters during exercise. Conventional echocardiographic parameters were measured at rest and during exercise at 25 and 75% of maximal power output. The plotted values represent means and standard deviations. LA, left atrial; TR, tricuspid regurgitation.

Figure 2

Evolution of SW velocities during exercise. The black and red lines show the mean linear regression lines for the athletes and non-athletes with the dotted lines representing the 95% CIs, for the SW velocity measurements after MVC (left) and after AVC (right). The individual SW velocity measurements for all individuals are plotted as well. SW AVC, shear wave velocity after aortic valve closure; SW MVC, shear wave velocity after mitral valve closure.

Figure 3

Correlation of SW AVC velocity slopes and VO₂max. The slope of SW velocity change during exercise after AVC correlated significantly with VO₂max. The regression line is shown in grey with the dotted lines representing the 95% CI. AVC, aortic valve closure.