Coronary artery disease and its impact on the pulsatile brain: A functional NIRS study

Figures

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  FIGURE 1. (a) Posterior–anterior view of the source and detector placements projected on the cortex. The red dots represent the sources, and the blue dots represent the detectors. Sixteen sources and 16 detectors were placed on the helmet. (b) Helmet and optode sockets. Source and detector housings are identical and are fixed on the helmet's sockets. (c) Participant equipped with the system. The prototype is attached on the back of the participant and sends data by Bluetooth to a computer

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  FIGURE 2. Example of single cerebral pulse waveform for a participant. The change in intensity between the systolic and the diastolic peaks represents cerebral pulse amplitude. The shaded area represents the PRF as estimated by dividing the shaded area from systolic peak to the next diastolic peak to the cerebral pulse amplitude (adapted from Tan et al., 2017). x‐axis is time (s) and y‐axis is NIRS signal intensity. PRF, pulse relaxation function

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  FIGURE 3. (a) Example of accelerometer data averaged over three axes including standing rest before short‐duration walking, walkig,and standing rest after short‐duration walking. (b) Example of the NIRS intensity data for wavelength 850 nm. A higher pulse amplitude in the standing rest before short‐duration walking in comparison with after short‐duration walking is clearly identifiable. NIRS, near‐infrared spectroscopy

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  FIGURE 4. Schematic diagram of NIRS data processing to extract pulsatility indices and analysis. ANOVA, analysis of variance; HB, heartbeat epoch; M (SD), mean ±standard deviation; NIRS, near‐infrared spectroscopy; PRF, pulse relaxation function; SCI, scalp coupling index

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  FIGURE 5. Spatial distribution of NIRS channels included in the channel‐wise analysis of pulsatility parameters and the corresponding cortical sensitivity matrix, frontal view. Red numbers indicate near‐infrared light sources and blue numbers indicate near‐infrared light detectors. Yellow lines connecting sources to detectors represent NIRS channels. This figure shows that the 38 channels included in the channels‐wise analysis had reasonable sampling sensitivity in most of the prefrontal areas and in bilateral supplementary motor cortices. NIRS, near‐infrared spectroscopy

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  FIGURE 6. (a) Boxplots of global cerebral pulse amplitude for the three groups, the LCVRF, the HCVRF, and CAD for both before walking (before W) and after walking (after W). (b) Scatter plot for the global cerebral pulse amplitude versus Framingham 10‐year CHD risk prediction after regressing sex with linear regression. (c) Channel‐wise spatial distribution of the cerebral pulse amplitude on the Colin27 template. The mean cerebral pulse amplitude in every channel across all the participants is projected onto the cortex for before walking and after walking, separately. Red regions indicating higher pulsatility and yellow regions indicating lower pulsatility. (a) and (c) are illustrations of the input data for statistical analysis. BW, before walking; CAD, coronary artery disease; CHD, coronary heart disease; HCVRF, high cardiovascular risk factor; LCVRF, low cardiovascular risk factors; NIRS, near‐infrared spectroscopy; SD, standard deviation

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  FIGURE 7. t‐statistics topographic contrast maps (p <.05) for channel‐wise comparison of cerebral pulse amplitude for before walking and after walking, respectively. The channel‐wise comparisons were determined the channel‐wise contrast for CAD versus LCVRF, CAD versus HCVRF, and LCVRF versus HCVRF (maps are FDR‐corrected). CAD, coronary artery disease; FDR, false discovery rate; HCVRF, high cardiovascular risk factor; LCVRF, low cardiovascular risk factors

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  FIGURE 8. (a) Boxplots of global PRF for the three groups before walking (before W) and after walking (after W). (b) Scatter plot for global PRF versus Framingham 10‐year CHD risk prediction of LCVRF, HCVRF, and CAD. (c) Channel‐wise spatial distribution for PRF on the Colin27 template. PRF is projected onto the brain surface before walking and after walking. Blue areas indicate higher wave reflection or lower pulsatility, and green areas indicate higher pulsatility. PRF: pulse relaxation function; NIRS: near‐infrared spectroscopy; BW, before walking; CAD, coronary artery disease; CHD, coronary heart disease; HCVRF, high cardiovascular risk factors; LCVRF, low cardiovascular risk factors; SD, standard deviation

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  FIGURE 9. t‐statistics topographic contrast maps for before walking and after walking. PRF contrast results are presented across the groups. The maps are FDR‐corrected (p <.05) for CAD versus LCVRF, CAD versus HCVRF, and HCVRF versus LCVRF. CAD, coronary artery disease; FDR, false discovery rate; HCVRF, high cardiovascular risk factors; LCVRF, low cardiovascular risk factors