Imaging Ultrasound Assessment of Exercise-Induced Endothelial Shear Stress of the Brachial and Carotid Arteries

Abstract

Endothelial shear stress (ESS) has a possible effect on regulation of gene expression in the protection against atherosclerosis. During exercise, ESS should increase as systolic blood pressure and heart rate (HR) increase too; however, it is hard to determine ESS changes during exercise. Imaging ultrasound assessment of the brachial and the carotid arterial blood flow during exercise might help to estimate exercise-induced ESS. We present here the methodology at the Clinical Applied Physiology Laboratory to estimate exercise-induced ESS. We normally perform 2 exercise tests in 2 different visits. First, a cardiopulmonary exercise test with serial microblood sampling to determine blood lactate (La) levels on a stationary cycle ergometer to determine maximal oxygen consumption, maximal exercising HR, and lactate threshold curve. The second exercise test includes three 5-min steady state stages determined by La levels from test 1 (La <2 mmol/L, La 2–4 mmol/L, and La >4 mmol/L). During the second test, we position an ultrasound probe holder on either the arm or neck to image the brachial or carotid arteries, respectively. We obtain images and blood flow velocities through Doppler at each exercise stage and then we analyze the images using edge detection software to determine artery diameters. With these data, we are able to estimate ESS, flow direction, and the presence of turbulent flow.

Differences in Blood Flow Patterns and Endothelial Shear Stress at the Carotid Artery Using Different Exercise Modalities and Intensities

“…Unfortunately, the authors were not able to determine ESS as they found some technical difficulties with ultrasound imaging during their protocol. These technical difficulties were avoided in the current study by using a customized, patent-pending cervical probe holder placed on the participant’s neck ( Gurovich et al, 2021a ; Morales-Acuna et al, 2020 ). Nevertheless, Jiang et al found a significant increase in carotid artery blood flow velocity, up to 52% from baseline values, during exercise.…”

“…Then, resting blood pressure was obtained using an automated brachial blood pressure cuff (BP760, Omnron Healthcare, Inc., Lake Forest, IL, United States). In addition, and at the beginning of every visit, hematocrit (HemataStat II Hematocrit Analyzer, Separation Technology Inc., Sanford, FL, United States) and resting blood lactate (BLa) levels (Lactate Plus, Nova Inc., Boston, MA, United States) were obtained from the lower end of the earlobe as previously described ( Rascon et al, 2020 ; Gurovich et al, 2021a ). Then, for session 1, subjects completed 3 maximal strength tests (Squat, Bench Press, and Biceps curls), then subjects rested for at least 30 min ( Tagesson and Kvist, 2007 ; Neto et al, 2015 ; García-Ramos et al, 2019 ) and performed a graded exercise test on the treadmill (Trackmaster TMX58, Newton, KS, United States) to determine maximal oxygen consumption (VO 2 max) and lactate threshold.…”

“…Ultrasound images and Doppler signals were obtained on the common carotid artery 2 cm below the bifurcation of the anterior and posterior carotid arteries and then analyzed with edge detection technology (Vascular Analysis Integrative System, Medical Imaging Applications, Coralville, IA, United States) and a data acquisition system (MP150WSW, BIOPAC Systems Inc., Goleta, CA, United States) ( Figure 2 ). ESS was obtained by Womersley’s approximation and the presence of turbulent flow via Reynold’s number (Re) as previously described ( Gurovich and Braith, 2012 ; Morales-Acuna et al, 2019 ; Rascon et al, 2020 ; Gurovich et al, 2021a ). The presence of laminar or turbulent flow was defined via Re, where undisturbed laminar flow values were < 200, disturbed blood flow values between 200–1800, and turbulent flow values > 2000 ( Davies, 2009 ).…”

“…Statistical significance was set priori at an alpha level of 0.05. Re was analyzed by visual analysis using a 95% confidence interval (CI) as previously described ( Gurovich et al, 2021a ). Data and data analysis scripts are available in a repository for data analysis replication in https://github.com/Samuelmontalvo/Modalities .…”

In Vitro Exercise-Induced Endothelial Shear Stress Protects the Vascular Endothelium

“…However, there is a lack of information about endurance exercise intensity and its relationship with molecular changes. The present study used human in vivo exercise-induced ESS 16 to unveil the relationship between exercise intensity and molecular changes in the endothelial cells and provide evidence of precision medicine to clinicians.…”