Search

Cerebral pressure-flow dynamics are typically reported between mean arterial pressure and mean cerebral blood velocity. However, by reporting only mean responses, potential differential regulatory properties associated with systole and diastole may have been overlooked.Twenty young adults (16 male, age: 26.7 ± 6.6 years, BMI: 24.9 ± 3.0 kg/mThere were main effects for both cardiac cycle and frequency for phase and gain metrics (p0.001). The systolic phase (mean ± SD) was elevated at 0.05 (1.07 ± 0.51 radians) and 0.10 Hz (0.70 ± 0.46 radians) compared to the diastolic phase (0.05 Hz: 0.59 ± 0.14 radians; 0.10 Hz: 0.33 ± 0.11 radians). Conversely, the systolic normalized gain was reduced (0.05 Hz: 0.49 ± 0.12%/%; 0.10 Hz: 0.66 ± 0.20%/%) compared to the diastolic normalized gain (0.05 Hz: 1.46 ± 0.43%/%; 0.10 Hz: 1.97 ± 0.48%/%).These findings indicate there are differential systolic and diastolic aspects of the cerebral pressure-flow relationship. The oscillations associated with systole are extensively buffered within the cerebrovasculature, whereas diastolic oscillations are relatively unaltered. This indicates that the brain is adapted to protect itself against large increases in systolic blood pressure, likely as a mechanism to prevent cerebral haemorrhages.

To determine whether acute sports-related concussion (SRC) exerts differential effects on cerebral autoregulatory properties during systole versus diastole.One hundred and thirty-six contact-sport athletes tested preseason; 14 sustained a concussion and completed follow-up testing at 72 hours, 2 weeks, and 1 month post-injury. Five minutes of repetitive squat-stand maneuvers induced blood pressure (BP) oscillations at both 0.05 and 0.10 Hz. Beat-by-beat peak-systolic and end-diastolic BP (sysBP/ diasBP) and middle cerebral artery blood velocity (sysMCAv/diasMCAv) were recorded using finger photoplethysmography and transcranial Doppler ultrasound, respectively. Relationships between sysBP-sysMCAv and diasBP-diasMCAv were quantified using transfer function analysis to estimate coherence (correlation), gain (response magnitude), and phase (response latency).Significant main effects of the cardiac cycle were observed across all outcome metrics. A significant main effect of SRC was observed for 0.10 Hz phase: systolic and diastolic phases were reduced at 72 h (21.8 ± 5.2%) and 2 weeks (22.7 ± 7.1%) compared to preseason but recovered by 1 month. Concussion significantly impaired diastolic, but not systolic, gain: 0.10 Hz diastolic gain was increased (27.2 ± 7.7%) at 2 weeks, recovering by 1 month.Impairments in autoregulatory capacity, observed for a transient period following SRC that persist beyond symptom resolution and clinical recovery, appear to be differentially affected across the cardiac cycle. Similar patterns of impairment were observed for systolic and diastolic phases (response latency); however, normalized gain (response magnitude) impairments were identified only in diastole. These findings may explain the increased cerebral vulnerability as well as exercise-induced symptom exacerbation observed post-SRC.