Response of the carotid artery longitudinal motion to submaximal physical activity in healthy humans—Marked changes already at low workload

Figures

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  FIGURE 1. Ultrasound image of the common carotid artery. The yellow lines mark the demarcations between lumen and tunica intima and the green lines the demarcation between media and adventitia. The lines are 5 mm wide. In this study we measure the longitudinal movement at the far wall between the yellow and the green lines, and the shear strain between the blue crosses at intima‐media and adventitial layers.

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  FIGURE 2. (a) The longitudinal movement of the intima‐media complex during normal breathing (dashed) and when the subject (64‐year‐old women) has gentle stopped breathing during five cardiac cycles at rest (solid line). Note that breathing causes a low frequency movement that is superimposed on the distinct multi‐phasic movement. (b) The corresponding averaged movement curves. Note that the novel phase averaging algorithm can remove the superimposed movement. End‐diastole is denoted by the origin of coordinates, based on the simultaneously measured diameter change curve. Five different phases of displacement are identified and marked by A, B, C, X and W, respectively (for description see the Result section and Cinthio et al., 2018). In short, A denotes the first antegrade displacement (i.e., in the direction of blood flow) when the diameter starts to increase, followed by a retrograde displacement (B), that is, in the direction opposite to blood flow.

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  FIGURE 3. The longitudinal movement of the intima‐media complex during rest and up to six different loads (30, 50, 70, 90, 110 and 130 W) in eight different subjects. The different colors denote different loads (se explanations in panel a); thus, the red curve show the motion at rest. End‐diastole at the measurement site is denoted by origin of coordinates (based on the simultaneously measured diameter change curve). Note the dramatically increase of longitudinal movement of the arterial wall during exercise.

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  FIGURE 4. The longitudinal movement of the intima‐media complex during rest and up to seven different loads (30, 50, 70, 90, 110, 130 and 150 W) in four different subjects. The different colors denote different loads (see explanations in panel a), thus the red curve show the motion at rest. End‐diastole at the measurement site is denoted by origin of coordinates (based on the simultaneously measured diameter change curve). Note the absent of a phase A at rest in three of the subjects (panel a, c, d). During exercise the phase A show up and increases dramatically.

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  FIGURE 5. Examples of individuals in whom the correlation between the amplitude of A and systolic blood pressure during exercise was remarkably strong. Note the r‐values close to one.

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  FIGURE 6. Intramural shear strain in relation to systolic pressure in the analyzed subgroup (n = 18). It is to be noted that in some individuals (n = 5) we could not adequately measure shear strain at their highest workloads, despite this a significant correlation to blood pressure is seen.