Post-stroke subjects exhibited significantly stronger cross-correlation between the instantaneous phase increments of blood pressure and blood flow velocity compared to healthy controls, indicating impaired cerebral autoregulation.
Observational (n=24)
Yes
Does the cross-correlation of instantaneous phase increments of blood pressure and blood flow velocity differ between healthy subjects and post-stroke subjects during various physiologic conditions?
Post-stroke subjects exhibit significantly stronger and more persistent cross-correlation between instantaneous phase increments of blood pressure and cerebral blood flow velocity compared to healthy subjects, indicating impaired cerebral autoregulation.
Absolute Event Rate: 0.58% vs 0.49%
p-value: p=0.001
We investigate the relationship between the blood flow velocities (BFV) in the middle cerebral arteries and beat-to-beat blood pressure (BP) recorded from a finger in healthy and post-stroke subjects during the quasisteady state after perturbation for four different physiologic conditions: supine rest, head-up tilt, hyperventilation, and CO2 rebreathing in upright position. To evaluate whether instantaneous BP changes in the steady state are coupled with instantaneous changes in the BFV, we compare dynamical patterns in the instantaneous phases of these signals, obtained from the Hilbert transform, as a function of time. We find that in post-stroke subjects the instantaneous phase increments of BP and BFV exhibit well-pronounced patterns that remain stable in time for all four physiologic conditions, while in healthy subjects these patterns are different, less pronounced, and more variable. We propose an approach based on the cross-correlation of the instantaneous phase increments to quantify the coupling between BP and BFV signals. We find that the maximum correlation strength is different for the two groups and for the different conditions. For healthy subjects the amplitude of the cross-correlation between the instantaneous phase increments of BP and BFV is small and attenuates within 3-5 heartbeats. In contrast, for post-stroke subjects, this amplitude is significantly larger and cross-correlations persist up to 20 heartbeats. Further, we show that the instantaneous phase increments of BP and BFV are cross-correlated even within a single heartbeat cycle. We compare the results of our approach with three complementary methods: direct BP-BFV cross-correlation, transfer function analysis, and phase synchronization analysis. Our findings provide insight into the mechanism of cerebral vascular control in healthy subjects, suggesting that this control mechanism may involve rapid adjustments (within a heartbeat) of the cerebral vessels, so that BFV remains steady in response to changes in peripheral BP.
Chen et al. (Wed,) conducted a observational in Minor ischemic stroke (n=24). Minor ischemic stroke vs. Healthy controls was evaluated on Maximum cross-correlation (Cmax) of instantaneous phase increments between blood pressure and blood flow velocity (stroke side vs control left side) (p=0.001). Post-stroke subjects exhibited significantly stronger cross-correlation between the instantaneous phase increments of blood pressure and blood flow velocity compared to healthy controls, indicating impaired cerebral autoregulation.