Carotid Artery Viscoelasticity Following Acute Exercise: Insight From Shear Wave Elastography

PURPOSE: To compare measures of carotid artery viscoelasticity from SWE with traditional measures of carotid artery stiffness during recovery from acute aerobic exercise (AE) and resistance exercise (RE). METHODS: Participants (n = 11, age = 27 ± 5 yrs, n = 9 female) completed parallel experimental conditions on 2 separate days. Acute AE (30 minutes of cycling, 65% of heart rate reserve) was completed the first session for all participants followed by acute RE (30 minutes, 5 sets of 5 repetitions for bench press and 5 sets of 10 repetitions for biceps curl). Ultrasound with radiofrequency echo-based wall tracking and SWE was applied to the common carotid artery to measure carotid compliance, pulse wave velocity (PWV) and Young’s modulus. Lower values of compliance and higher values of PWV suggest higher stiffness, while higher SWE values suggest lower viscoelasticity. Measurements were made at baseline and 5 minutes after acute exercise. Analysis of variance with repeated measures examined condition effects (AE vs RE), time effects (pre vs post) and condition-by-time interactions. RESULTS: There was a time effect for compliance (p = 0.004). The reduction in compliance following acute AE (1.14 ± .31mm2/kPa to .98 ± .26mm2/kPa) and RE (1.14 ± 0.35mm2/kPa to .84 ± .20mm2/kPa) were similar (p for interaction = 0.264). There was a time effect for PWV (p = 0.041). The increase in PWV following acute AE (5.6 ± 1.0 m/s to 6.4 ± 1.1 m/s) and RE (5.4 ± .8 m/s to 5.8 ± .7 m/s) were similar (p for interaction = 0.205). There was a condition-by-time interaction for Young’s modulus measured with SWE (p = 0.007). There was a reduction in Young’s modulus following AE (37.7 ± 9.3 kPa to 29.7 ± 9.2 kPa) and an increase in Young’s modulus following RE (33.9 ± 12.4 kPa to 39.4 ± 10.6 kPa). CONCLUSIONS: SWE provides novel insight into vascular recovery from acute AE and RE not reflected in traditional measures. Following acute RE, there are BP-dependent and independent increases in carotid stiffness and reductions in viscoelasticity. Following acute AE, there are BP-dependent increases in carotid stiffness masking concomitant increases in viscoelasticity.