Real-Time Phase-Contrast MRI to Monitor Cervical Blood and Cerebrospinal Fluid Flow Beat-by-Beat Variability

Q: What are the key findings of this study?

Real-Time Phase-Contrast MRI demonstrated higher beat-by-beat variability total power in diastolic venous flow than systolic venous flow.

Q: What is the clinical evidence from this study?

Study design: Cross-Sectional. Population: Healthy volunteers (n=30). Intervention: Real-Time Phase-Contrast MRI (RT-PC-MRI) at 1st cervical level vs. Systolic vs. diastolic flow and arterial vs. venous vs. cerebrospinal fluid compartments. Primary outcome: Total power (PTOT) of beat-by-beat variability in diastolic vs. systolic venous flow (Cohen's dz 0.556, p=<0.001).

Q: What does this research mean for the field?

Diastolic cervical venous flow displays significantly higher beat-by-beat variability total power than systolic venous flow, reflecting strong respiration-driven and low-frequency hemodynamic modulations. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

Q: What question did this study set out to answer?

To evaluate beat-by-beat variability and dynamic coupling between cardiovascular and intracranial fluid flows using real-time phase-contrast MRI.

Giuseppe Baselli; Federica Fasani; Laura Pelizzari; Marta Cazzoli; Francesca Baglio; Maria Marcella Laganà

doi:10.3390/bios12060417

June 15, 2022BiosensorsOpen Access

Real-Time Phase-Contrast MRI to Monitor Cervical Blood and Cerebrospinal Fluid Flow Beat-by-Beat Variability

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Key result

Real-time phase-contrast MRI reveals ~2-fold higher beat-by-beat flow variability in diastolic vs systolic venous flow.

Cohen's dz +0.556
P<0.001
n=30

Figures

Why the study?

Beat-by-beat variability rhythms are observed in both cardiovascular and intracranial compartments, but interactions between the two are not fully understood.

Does Real-Time Phase-Contrast MRI quantify beat-by-beat variability and respiratory modulation across cervical arterial, venous, and cerebrospinal fluid flows in healthy volunteers?

Key Points

To evaluate beat-by-beat variability and dynamic coupling between cardiovascular and intracranial fluid flows using real-time phase-contrast MRI.
Acquired real-time phase-contrast MRI scans at the first cervical level on a 3T scanner in 30 healthy volunteers during unstressed resting conditions.
Calculated arterial flow, venous flow, and cerebrospinal fluid flow via velocity integrals over the internal carotid artery, internal jugular vein, and spinal subarachnoid space.
Applied autoregressive power spectral density analysis to systolic, diastolic, and heart period series to quantify low-frequency (Mayer waves) and high-frequency (respiratory waves) components.
Diastolic venous flow exhibited the highest total power (0.662 ± 0.697 (mL/s) 2), which was significantly greater than systolic venous flow (0.322 ± 0.446 (mL/s) 2, p < 0.001) and diastolic arterial flow (0.230 ± 0.191 (mL/s) 2, p = 0.004).
Low-frequency power was significantly higher in diastole than systole for both arterial flow (45.2 ± 31.0 n.u. vs. 29.5 ± 27.9 n.u., p = 0.039) and venous flow (31.8 ± 26.6 n.u. vs. 18.9 ± 25.3 n.u., p = 0.05).
High-frequency respiratory power was predominant in diastolic cerebrospinal fluid flow (72.0 ± 21.1 n.u.), significantly exceeding diastolic arterial flow (45.3 ± 33.7n.u., p < 0.001) and diastolic venous flow (56.6 ± 27.7 n.u., p = 0.037).

Study Design

Type

Cross-Sectional (n=30)

Multicenter

No

Structured PICO

Does Real-Time Phase-Contrast MRI quantify beat-by-beat variability and respiratory modulation across cervical arterial, venous, and cerebrospinal fluid flows in healthy volunteers?

P

Population

30 healthy adults (age 19-58 years, 30% female) without claustrophobia or prior caffeine/drug intake scanned at rest for 60 seconds.

E

Exposure

Real-Time Phase-Contrast MRI (RT-PC-MRI) on a 3T scanner at the 1st cervical level (C1) during 60 seconds of free breathing to measure arterial flow (AF), venous flow (VF), and cerebrospinal fluid flow (CSFF).

C

Comparator

Within-subject comparisons across vascular/fluid compartments (arterial vs. venous vs. cerebrospinal fluid), cardiac cycle phases (diastole vs. systole), and respiratory phases (inspiration vs. expiration).

O

Outcome

Beat-by-beat variability (BBV) spectral parameters, including total power (PTOT), low-frequency normalized power (PLF, Mayer waves, 0.05-0.15 Hz), and high-frequency normalized power (PHF, respiratory waves) derived via autoregressive power spectral density analysis over 60-second recordings.surrogate

Main Result

Standardized Mean Difference: 0.556

Absolute Event Rate: 0.662% vs 0.322%

p-value: p=<0.001

Limitations

Evaluation of arterial and venous flow was restricted to the internal carotid arteries and internal jugular veins, excluding small collateral vessels.
Motion artifacts required discarding signal intervals (<6 seconds of the 60-second recording) in less than 15% of subjects.
Two separate sequences with different velocity encodings were required to acquire blood and cerebrospinal fluid flows, precluding direct phase and time delay analyses.
No a priori power analysis could be performed to dimension the sample size due to lack of prior similar studies.
Assessments were restricted to supine position and free-breathing conditions without autonomic stimuli such as head-up tilt.
Evaluation of arterial and venous flow was restricted to internal carotid arteries and internal jugular veins, omitting small collateral spinal veins.
Signal windows with movement artifacts had to be removed in <15% of subjects (lasting <6 s over the 60 s sequence).
Separate MRI acquisitions with different velocity encodings (VENC 70 cm/s for blood and 6 cm/s for CSF) were needed, preventing direct assessment of time delays and phase relationships.
Lack of a priori power analysis for sample size determination.
Study was limited to supine position and resting free-breathing without sympathetic stimuli such as head-up tilt.

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Implication

Real-Time Phase-Contrast MRI non-invasively quantifies beat-by-beat variability in cervical arterial, venous, and cerebrospinal fluid flows, revealing prominent low-frequency modulation in diastolic arterial/venous flows and high-frequency respiratory predominance in CSF.

Abstract

Beat-by-beat variability (BBV) rhythms are observed in both cardiovascular (CV) and intracranial (IC) compartments, yet interactions between the two are not fully understood. Real-Time Phase-Contrast (RT-PC) MRI sequence was acquired for 30 healthy volunteers at 1st cervical level on a 3T scanner. The arterial (AF), venous (VF), and cerebrospinal fluid (CSF) flow (CSFF) were computed as velocity integrals over the internal carotid artery, internal jugular vein, and CSF. AF, VF, and CSFF signals were segmented in inspiration and expiration beats, to assess the respiration influence. Systolic and diastolic BBV, and heart period series underwent autoregressive power spectral density analysis, to evaluate the low-frequency (LF, Mayer waves) and high frequency (HF, respiratory waves) components. The diastolic VF had the largest BBV. LF power was high in the diastolic AF series, poor in all CSFF series. The pulse wave analyses revealed higher mean amplitude during inspiration. Findings suggests a possible role of LF modulation of IC resistances and propagation of HF waves from VF to AF and CCSF. PC-RT-MRI could provide new insight into the interaction between CV and IC regulation and pave the way for a detailed analysis of the cerebrovascular effects of varied respiration patterns due to exercise and rehabilitation.

Discussion

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Cite This Study

Baselli et al. (2022) conducted a cross-sectional in Healthy volunteers (n=30). Real-Time Phase-Contrast MRI (RT-PC-MRI) at 1st cervical level vs. Systolic vs. diastolic flow and arterial vs. venous vs. cerebrospinal fluid compartments was evaluated on Total power (PTOT) of beat-by-beat variability in diastolic vs. systolic venous flow (Cohen's dz 0.556, p=<0.001). Real-Time Phase-Contrast MRI demonstrated higher beat-by-beat variability total power in diastolic venous flow than systolic venous flow.

synapsesocial.com/papers/6a8c267029efb9ec64c468bf https://doi.org/10.3390/bios12060417

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Real-Time Phase-Contrast MRI to Monitor Cervical Blood and Cerebrospinal Fluid Flow Beat-by-Beat Variability

Figures

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

Real-Time Phase-Contrast MRI to Monitor Cervical Blood and Cerebrospinal Fluid Flow Beat-by-Beat Variability

Figures

Key Points

Study Design

Structured PICO

Main Result

Limitations

Ask about this paper

Implication

Abstract

Discussion

Cite This Study

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