Time Course of Flow-Mediated Dilation and Vascular Endothelial Growth Factor following Acute Stroke

Motor Impairment and Disuse Are Independent Predictors of Vascular Outcomes Poststroke

IMPORTANCE

Cardiorespiratory fitness is reduced after stroke due to inactivity which may cause structural and functional changes to blood vessels in the extremities. Identifying clinical factors contributing to vascular function may be important for tailoring rehabilitation programs that reduce secondary disease risk and adverse events.

OBJECTIVE

The study objective was to compare measures of arterial and intramuscular blood flow between the paretic and nonparetic upper limbs of individuals with stroke and healthy comparators. Associations between these parameters and stroke-related impairment were also examined.

DESIGN

This was a cross-sectional study.

SETTING

The setting was a university laboratory.

PARTICIPANTS

Participants were individuals with stroke (n = 64; mean age = 60.8 [SD = 7.7] years) and matched controls (n = 64; mean age = 59.4 [SD = 7.8] years).

MAIN OUTCOMES/MEASURES

Brachial artery blood flow volume (Vflow) and arterial diameter (AD) were measured using Doppler ultrasound. Intramuscular blood perfusion of the biceps brachii was estimated using the vascularity index (VI). Motor recovery and perceived use of paretic upper limbs were assessed with the Fugl-Meyer Assessment (FMA) and Motor Activity Log (MAL), respectively.

RESULTS

Side × group interactions were observed for AD (F = 22.6) and VI (F = 4.00). Post hoc analyses showed lower AD and VI for paretic sides (stroke group), greater Vflow for dominant sides (comparators), and greater percent side-to-side differences (%SSDs) in AD and VI for the stroke group than for comparators. %SSDs in Vflow, AD, and VI demonstrated weak correlations with impairment (MAL, FMA; ρ = 0.253 to 0.347). MAL was an independent predictor of %SSD in Vflow (β = -0.286), and FMA was an independent predictor of %SSDs in AD (β = -0.307) and VI (β = 0.371).

CONCLUSIONS/RELEVANCE

Relative to the nonparetic and bilateral limbs of comparators, arterial size and intramuscular blood flow in the paretic upper limbs of individuals with stroke were significantly reduced. Motor impairment and disuse emerged as independent predictors of all vascular outcomes and may be potential intervention targets for reducing cardiovascular disease risk after stroke.

Association between impaired brachial flow-mediated dilation and early neurological deterioration in acute ischemic stroke: a retrospective analysis

BACKGROUND

Early neurological deterioration (END) occurs in individuals who had experienced acute ischemic stroke (AIS), impacting long-term functional outcomes. We aimed to investigate the association between endothelial function, measured via flow-mediated dilation (FMD), and END in patients with AIS.

METHODS

We retrospectively reviewed patients who had experienced AIS within 7 days of stroke onset and underwent FMD assessments during their hospitalization (%FMD = Peak diameter - baseline diameter)/baseline diameter x 100). END was defined as ≥ 2-point increase in the National Institutes of Health Stroke Scale total score or ≥ 1-point increase in the motor score within 72 h post-stroke. Through multivariate analysis, we examined factors associated with END and explored the relationship between FMD and END with considering stroke mechanisms.

RESULTS

Among 1,262 patients diagnosed with AIS, 184 (14.6%) experienced END. Those with END were on average older (69 ± 13 vs. 67 ± 13 years; P = 0.033), had a higher prevalence of stroke history (21.2 vs. 12.9%; P = 0.003), and lower FMD (5.0 ± 1.8 vs. 5.4 ± 2.2%; P = 0.029). Multivariate analysis revealed that a history of stroke (adjusted odds ratio [aOR] = 1.728; 95% confidence interval [CI] 1.159-2.578; P = 0.007) and low % were independently associated with END. Subgroup analysis revealed that low %FMD was significantly associated with END within the small vessel disease (SVD) category (aOR = 0.789; 95% CI 0.679-0.920; P = 0.002).

CONCLUSIONS

Impaired FMD may be associated with END, particularly within the context of SVD.

Noninvasive estimation of skeletal muscle oxygen consumption rate and microvascular reactivity in chronic stroke survivors using near-infrared spectroscopy

Understanding post-stroke changes in skeletal muscle oxidative metabolism and microvascular reactivity could help create therapeutic targets that optimize rehabilitative interventions. Due to disuse atrophy, we hypothesized that basal muscle oxygen consumption rate and microvascular endothelial function would be impaired in the tibialis anterior (TA) muscle of the affected leg of chronic stroke survivors compared with the nonaffected leg and versus matched controls. Fifteen chronic stroke survivors (10 females) and 15 matched controls (9 females) completed this study. A near-infrared spectroscopy oximeter measured tissue oxygen saturation (StO2) of the TA in both legs of stroke survivors and the dominant leg of controls. A cuff was placed around the thigh and inflated to 225 mmHg for 5 min while StO2 was continuously measured. The rate of change in StO2 was calculated during cuff occlusion and immediately post-cuff release. The rate of oxygen desaturation was similar between the legs of the stroke survivors (paretic -0.12 ± 0.04%·s-1 vs. nonparetic -0.16 ± 011%·s-1; P = 0.49), but the paretic leg had a reduced desaturation rate versus controls (-0.25 ± 0.18%·s-1; P = 0.007 vs. paretic leg). After cuff release, there was a greater oxygen resaturation rate in the nonparetic leg compared with the paretic leg (3.13 ± 2.08%·s-1 vs. 1.60 ± 1.11%·s-1, respectively; P = 0.01). The control leg had a similar resaturation rate versus the nonparetic leg (control = 3.41 ± 1.79%·s-1; P = 0.69) but was greater than the paretic leg (P = 0.003). The TA in the paretic leg had an impaired muscle oxygen consumption rate and reduced microvascular endothelial function compared with controls.NEW & NOTEWORTHY Secondary consequences of stroke are not well described. In this study, we show that basal muscle oxidative consumption and microvascular endothelial function are reduced in the paretic tibialis anterior muscle of chronic stroke survivors compared with matched controls using near-infrared spectroscopy and the vascular occlusion technique. There was a moderately strong correlation between microvascular endothelial function and paretic leg strength.

Peripheral vascular function in stroke: systematic review and meta-analysis

Peripheral vascular dysfunction, measured as flow-mediated dilation (FMD), is present across all phases of stroke recovery and elevates the risk for recurrent cardiovascular events. The objective of this systematic review and meta-analysis was to characterize baseline FMD in individuals' poststroke, with consideration for each phase of stroke recovery. Three databases (PubMed, CINAHL, and Embase) were searched between January 1, 2000 and October 12, 2023 for studies that examined baseline FMD in stroke. Three reviewers conducted abstract and full-text screening, data extraction, and quality assessment. A random effects model was used to estimate FMD across studies. Meta-regression was used to examine the impact of age and time since stroke (acute, subacute, chronic) on FMD. Twenty-eight studies with ischemic and hemorrhagic stroke were included. Descriptive statistics for the demographics and FMD values of each study are presented. For the meta-analysis, average estimate FMD was 3.9% (95% CI: 2.5-5.3%). We report a large amount of heterogeneity (Cochrane's Q P value <0.001, and I2 = 99.6%). Differences in average age and the time poststroke between studies were not significantly associated with differences in FMD values. Despite the large heterogeneity for FMD values across studies, our primary finding suggests that FMD remains impaired across all phases of stroke.NEW & NOTEWORTHY This systematic review and meta-analysis offers invaluable insight into poststroke vascular function. Despite the inherent heterogeneity among the 28 studies analyzed, we report that peripheral vascular dysfunction, as quantified by flow-mediated dilation, exists across all stages of stroke recovery. This finding underscores the importance for interventions that focus on improving vascular health and secondary stroke prevention.

Amyloid-β: A potential mediator of aging-related vascular pathologies

Aging is one of the most promising risk factors for vascular diseases, however, the precise mechanisms mediating aging-related pathologies are not fully understood. Amyloid beta (Aβ), a peptide produced by the proteolytic processing of amyloid precursor protein (APP), is known as a key mediator of brain damage involved in the pathogenesis of Alzheimer's disease (AD). Recently, it was found that the accumulation of Aβ in the vascular wall is linked to a range of aging-related vascular pathologies, indicating a potential role of Aβ in the pathogenesis of aging-associated vascular diseases. In the present review, we have updated the molecular regulation of Aβ in vascular cells and tissues, summarized the relevance of the Aβ deposition with vascular aging and diseases, and the role of Aβ dysregulation in aging-associated vascular pathologies, including the impaired vascular response, endothelial dysfunction, oxidative stress, and inflammation. This review will provide advanced information in understanding aging-related vascular pathologies and a new avenue to explore therapeutic targets.

Circulating brain-derived neurotrophic factor as a potential biomarker in stroke: a systematic review and meta-analysis

Background

Stroke, an acute cerebrovascular event, is a leading cause of disability, placing a significant psycho-socioeconomic burden worldwide. The adaptation and reorganization process following any neuronal damage is regarded as neuroplasticity. Among many factors believed to attribute to this process, Brain-derived Neurotrophic Factor (BDNF) is a neurotrophin coordinating neuroplasticity after various neurological disorders such as stroke.

Methods

We conducted a systematic search in the main electronic medical databases in January 2021. Primarily we want to compare BDNF levels between patients with stroke and healthy controls (HC). Additional aims included investigation of (1) longitudinal changes in the BDNF levels post-stroke, (2) effects of physical training, (3) repeated transcranial magnetic stimulation (rTMS), and presence of depression on BDNF levels in patients with stroke.

Results

Among 6243 reviewed records from PubMed, Web of Science, and Scopus, 62 studies were eligible for inclusion in our systematic review. Subjects with stroke, n = 1856, showed lower BDNF levels compared to HC, n = 1191 (SMD [95%CI] = − 1.04 [− 1.49 to − 0.58]). No significant difference was detected in the level of BDNF through time points past stroke. BDNF levels were lower in the patients with depression compared to non-depressed subjects (SMD [95%CI] = − 0.60 [− 1.10 to − 0.10]). Physical training had an immediate positive effect on the BDNF levels and not statistically significant effect in the long term; SMD [95%CI] = 0.49 [0.09 to 0.88]) and SMD [95%CI] = 0.02 [− 0.43 to 0.47]). Lastly, rTMS showed no effect on the level of BDNF with 0.00 SMD.

Conclusions

Our study confirms that stroke significantly decreases the level of BDNF in various domains such as cognition, affect, and motor function. As BDNF is the major representative of neuroplasticity within nervous system, it is believed that stroke has a significant impact on the CNS regeneration, which is permanent if left untreated. This effect is intensified with coexisting conditions such as depression which further decrease the BDNF level but the net impact yet needs to be discovered. We also conclude that exercise and some interventions such as different medications could effectively reverse the damage but further studies are crucial to reach the exact modality and dosage for their optimal effect.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-022-03312-y.

Optimizing Recruitment Strategies and Physician Engagement for Stroke Recovery Research

BACKGROUND AND PURPOSE

A major challenge for stroke rehabilitation and recovery research is the recruitment and retention of participants. Our prior challenges and successes have influenced our team to rethink our approach and the potential for large-scale stroke recruitment.

SUMMARY OF KEY POINTS

In this special interest article, we highlight how the adoption and implementation of recruitment strategies such as physician engagement and a streamlined "customer service" approach helped us improve our enrollment and maximize efficiency. Another positive outcome of enrollment was increased representation of those who identify as underrepresented minority or live in rural areas.

RECOMMENDATIONS FOR CLINICAL PRACTICE

Rethinking our recruitment processes and infrastructure allowed for greater interprofessional interactions, minimal burden for our stroke physician team members, and maximized enrollment into our stroke studies.Video Abstract available for more insights from the authors (see the Video, Supplemental Digital Content 1, available at: http://links.lww.com/JNPT/A324).

Underlying mechanisms of oxygen uptake kinetics in chronic post-stroke individuals: A correlational, cross-sectional pilot study

Post-stroke individuals presented deleterious changes in skeletal muscle and in the cardiovascular system, which are related to reduced oxygen uptake ([Formula: see text]) and take longer to produce energy from oxygen-dependent sources at the onset of exercise (mean response time, MTRON) and during post-exercise recovery (MRTOFF). However, to the best of our knowledge, no previous study has investigated the potential mechanisms related to [Formula: see text] kinetics response (MRTON and MRTOFF) in post-stroke populations. The main objective of this study was to determine whether the MTRON and MRTOFF are related to: 1) body composition; 2) arterial compliance; 3) endothelial function; and 4) hematological and inflammatory profiles in chronic post-stroke individuals. Data on oxygen uptake ([Formula: see text]) were collected using a portable metabolic system (Oxycon Mobile®) during the six-minute walk test (6MWT). The time to achieve 63% of [Formula: see text] during a steady state (MTRON) and recovery (MRTOFF) were analyzed by the monoexponential model and corrected by a work rate (wMRTON and wMRTOFF) during 6MWT. Correlation analyses were made using Spearman's rank correlation coefficient (rs) and the bias-corrected and accelerated bootstrap method was used to estimate the 95% confidence intervals. Twenty-four post-stroke participants who were physically inactive took part in the study. The wMRTOFF was correlated with the following: skeletal muscle mass (rs = -0.46), skeletal muscle mass index (rs = -0.45), augmentation index (rs = 0.44), augmentation index normalized to a heart rate of 75 bpm (rs = 0.64), reflection magnitude (rs = 0.43), erythrocyte (rs = -0.61), hemoglobin (rs = -0.54), hematocrit (rs = -0.52) and high-sensitivity C-reactive protein (rs = 0.58), all p < 0.05. A greater amount of oxygen uptake during post-walking recovery is partially related to lower skeletal muscle mass, greater arterial stiffness, reduced number of erythrocytes and higher systemic inflammation in post-stroke individuals.

Vascular Health is Associated with Amyloid-β in Cognitively Normal Older Adults

Background:

Vascular health is closely related to Alzheimer’s disease (AD). Vascular function measured by flow mediated dilation (FMD) or pulsatility index (PI) can be used as marker of peripheral and central vascular health but is poorly characterized in those at risk for AD.

Objective:

To assess the relationship of peripheral and central vascular function with amyloid-β (Aβ) and white matter lesion burden among cognitively normal older adults.

Methods:

We enrolled participants 65 years of age and older. Using Doppler ultrasound, we assessed brachial artery FMD, and middle cerebral artery (PI). Global Aβ burden, quantified using [18F] Florbetapir PET imaging, and white matter lesion volume (WML) were used as measures of AD pathology and vascular brain injury.

Results:

After adjusting for age and cardiovascular risk factors, the data (n = 83) showed a negative association between FMD and Aβ burden (β= –0.03, p < 0.001). FMD at a cut-off of 4.45% had 88% specificity and 75% sensitivity to elevated Aβ (AUC = 0.86, 95% CI: 0.77–0.95). FMD was not related to WML volume (p = 0.8), and PI was unrelated to Aβ burden or WML volume (0 > 0.4).

Conclusions:

Among cognitively normal older adults, blunted peripheral vascular function, as measured by brachial artery FMD, is associated with Aβ burden. These findings provide support for further exploration into the pathophysiological relationship of vascular health and AD risk as measured by Aβ.

Exercise intensity and middle cerebral artery dynamics in humans

Despite its necessity for understanding healthy brain aging, the influence of exercise intensity on cerebrovascular kinetics is currently unknown. We, therefore characterized middle cerebral artery blood flow velocity (MCAv) kinetics associated with two exercise intensities: low and moderate. We hypothesized that increasing exercise intensity would increase the MCAv amplitude response (Amp) and that age and estimated fitness (V̇O2max) would be related to Amp. Baseline (BL) values were collected for 90-seconds followed by a 6-minute exercise bout. Heart rate, end-tidal CO2, mean arterial pressure and MCAv were recorded throughout. MCAv kinetics were described by Amp, time delay (TD) and time constant (τ). Sixty-four adults completed the study. Amp was greater during moderate compared to low exercise intensity (p < 0.001) while no difference was observed in either TD (p = 0.65) or τ (p = 0.47). Amp was negatively associated with age (p < 0.01) and positively correlated with estimated V̇O2max (p < 0.01). Although Amp declines with age, maintaining higher V̇O2max may benefit the cerebrovascular response to exercise.