Relationship Between Aortic Compliance And Pulsatile Cerebral Blood Flow: Insights From Endurance Training Intervention

The aortic compliance buffers arterial pulsation generated from the left ventricle (LV) and proves the less pulsatile blood flow to end organs. Aerobic exercise training (AET) is associated with larger stroke volume (SV) and higher LV contractility which could be a mechanical stress to the brain. A dynamic orthostatic challenge may evoke substantial pulsatile cerebral blood flow (CBF) via transient increased SV. In this regard, AET-induced superior aortic compliance would buffer the arterial pulsation to the brain. PURPOSE: To investigate the contribution of AET-induced alternation of aortic compliance to the response of pulsatile CBF to the dynamic orthostatic challenge. METHODS: Ten men’s collegiate tennis players underwent an 8-month AET program to improve cardiovascular function. AET-induced LV remodeling was assessed with an echocardiogram. The release of -30 mmHg lower body negative pressure (LBNP) technique was used to initiate a rapid regain of limited venous return and consequently increase in SV. The aortic compliance was calculated by the ratio between changes in estimated SV from finger arterial pressure waveforms and aortic pulse pressure from radial arterial pressure waveforms. CBF pulsatility index (PI) at the middle cerebral artery using transcranial Doppler was measured. The responses to dynamic orthostatic challenge were calculated as the slope of SV and PI responses to changes in time up to 15 seconds after the LBNP release. RESULTS: After the intervention, SV with echocardiogram significantly increased whereas HR decreased. The aortic compliance (2.3 ± 0.7 vs. 2.7 ± 0.7 mL/mmHg, p = 0.032) and the response to LBNP release in SV increased (3.3 ± 1.2 vs. 3.7 ± 1.5 mL/s, p = 0.016) after the intervention whereas the response in PI remained at similar levels (3.8 ± 1.6 vs. 3.8 ± 1.2 a.u./s, p = 0.762). Furthermore, a negative correlation was observed between changes in aortic compliance and the response of PI (r = -0.684, p = 0.029). CONCLUSION: These results suggest that AET-induced improvement of aortic compliance might accommodate the additional SV and buffer the potential increases in arterial pulsation at the brain. Advanced Research Initiative for Human High Performance (ARIHHP), University of Tsukuba