Impaired Neurovascular Function Underlies Poor Neurocognitive Outcomes and Is Associated with Nitric Oxide Bioavailability in Congenital Heart Disease

We use a non-invasive MRI proxy of neurovascular function (pnvf) to assess the ability of the vasculature to supply baseline metabolic demand, to compare pediatric and young adult congenital heart disease (CHD) patients to normal referents and relate the proxy to neurocognitive outcomes and nitric oxide bioavailability. In a prospective single-center study, resting-state blood-oxygen-level-dependent (BOLD) and arterial spin labeling (ASL) MRI scans were successfully obtained from 24 CHD patients (age = 15.4 ± 4.06 years) and 63 normal referents (age = 14.1 ± 3.49) years. Pnvf was computed on a voxelwise basis as the negative of the ratio of functional connectivity strength (FCS) estimated from the resting-state BOLD acquisition to regional cerebral blood flow (rCBF) as estimated from the ASL acquisition. Pnvf was used to predict end-tidal CO2 (P_ETCO2) levels and compared to those estimated from the BOLD data. Nitric oxide availability was obtained via nasal measurements (nNO). Pnvf was compared on a voxelwise basis between CHD patients and normal referents and correlated with nitric oxide availability and neurocognitive outcomes as assessed via the NIH Toolbox. Pnvf was shown as highly predictive of P_ETCO2 using theoretical modeling. Pnvf was found to be significantly reduced in CHD patients in default mode network (DMN, comprising the ventromedial prefrontal cortex and posterior cingulate/precuneus), salience network (SN, comprising the insula and dorsal anterior cingulate), and central executive network (CEN, comprising posterior parietal and dorsolateral prefrontal cortex) regions with similar findings noted in single cardiac ventricle patients. Positive correlations of Pnvf in these brain regions, as well as the hippocampus, were found with neurocognitive outcomes. Similarly, positive correlations between Pnvf and nitric oxide availability were found in frontal DMN and CEN regions, with particularly strong correlations in subcortical regions (putamen). Reduced Pnvf in CHD patients was found to be mediated by nNO. Mediation analyses further supported that reduced Pnvf in these regions underlies worse neurocognitive outcome in CHD patients and is associated with nitric oxide bioavailability. Impaired neuro-vascular function, which may be non-invasively estimated via combined arterial-spin label and BOLD MR imaging, is a nitric oxide bioavailability dependent factor implicated in adverse neurocognitive outcomes in pediatric and young adult CHD.

Hypertension and cognitive function: a review of life-course factors and disparities

PURPOSE OF REVIEW

Dementia is a life-course condition with modifiable risk factors many from cardiovascular (CV) origin, and disproportionally affects some race/ethnic groups and underserved communities in the USA. Hypertension (HTN) is the most common preventable and treatable condition that increases the risk for dementia and exacerbates dementia pathology. Epidemiological studies beginning in midlife provide strong evidence for this association. This study provides an overview of the differences in the associations across the lifespan, and the role of social determinants of health (SDoH).

RECENT FINDINGS

Clinical trials support HTN management in midlife as an avenue to lower the risk for late-life cognitive decline. However, the association between HTN and cognition differs over the life course. SDoH including higher education modify the association between HTN and cognition which may differ by race and ethnicity. The role of blood pressure (BP) variability, interactions among CV risk factors, and cognitive assessment modalities may provide information to better understand the relationship between HTN and cognition.

SUMMARY

Adopting a life-course approach that considers SDoH, may help develop tailored interventions to manage HTN and prevent dementia syndromes. Where clinical trials to assess BP management from childhood to late-life are not feasible, observational studies remain the best available evidence.

The pressure's on: understanding neurocognitive and psychological associations with pediatric hypertension to inform comprehensive care

The prevalence of hypertension is increasing in pediatric populations. While clinical data and practice guidelines identify the impact of hypertension on organ dysfunction and emphasize the importance for end-organ damage screening, the bidirectional effects of pediatric hypertension on neurocognitive and psychological outcomes are understudied. The objective of this review is to highlight the association between hypertension and cognition, attention, learning, and mental health in children and adolescents. In doing so, this review provides a framework and toolkit to integrate neuropsychology and psychology into the screening and management stages of pediatric hypertension. By recognizing the effects of hypertension on cognition, behavior, and mental health, screenings and interventions can be implemented to proactively and comprehensively improve the health outcomes for children with blood pressure concerns.

The reliability of a breath-hold protocol to determine cerebrovascular reactivity in adolescents

PURPOSE

Cerebrovascular reactivity (CVR) is impaired in adolescents with cardiovascular disease risk factors. A breath-hold test is a noninvasive method of assessing CVR, yet there are no reliability data of this outcome in youth. This study aimed to assess the reliability of a breath-hold protocol to measure CVR in adolescents.

METHODS

Twenty-one 13 to 15 year old adolescents visited the laboratory on two separate occasions, to assess the within-test, within-day and between-day reliability of a breath-hold protocol, consisting of three breath-hold attempts. CVR was defined as the relative increase from baseline in middle cerebral artery mean blood velocity following a maximal breath-hold of up to 30 seconds, quantified via transcranial Doppler ultrasonography.

RESULTS

Mean breath-hold duration and CVR were never significantly correlated (r < .31, P > .08). The within-test coefficient of variation for CVR was 15.2%, with no significant differences across breath-holds (P = .88), so the three breath-hold attempts were averaged for subsequent analyses. The within- and between-day coefficients of variation for CVR were 10.8% and 15.3%, respectively.

CONCLUSIONS

CVR assessed via a three breath-hold protocol can be reliably measured in adolescents, yielding similar within- and between-day reliability. Analyses revealed that breath-hold length and CVR were unrelated, indicating the commonly reported normalization of CVR to breath-hold duration (breath-hold index) may be unnecessary in youth.

Effect of sevoflurane on systemic and cerebral circulation, cerebral autoregulation and CO2 reactivity

Background

Sevoflurane is one of the most frequently used inhaled anesthetics for general anesthesia. Previously it has been reported that at clinically used doses of sevoflurane, cerebral vasoreactivity is maintained. However, there are no data how sevoflurane influences systemic and cerebral circulation in parallel. The aim of our study was to assess systemic and cerebral hemodynamic changes as well as cerebral CO₂-reactivity during sevoflurane anesthesia.

Methods

Twenty nine patients undergoing general anesthesia were enrolled. Anesthesia was maintained with 1 MAC sevoflurane in 40% oxygen. Ventilatory settings (respiratory rate and tidal volume) were adjusted to reach and maintain 40, 35 and 30 mmHg EtCO₂ for 5 min respectively. At the end of each period, transcranial Doppler and hemodynamic parameters using applanation tonometry were recorded.

Results

Systemic mean arterial pressure significantly decreased during anesthetic induction and remained unchanged during the entire study period. Central aortic and peripherial pulse pressure and augmentation index as markers of arterial stiffness significantly increased during the anesthetic induction and remained stable at the time points when target CO₂ levels were reached. Both cerebral autoregulation and cerebral CO₂-reactivity was maintained at 1 MAC sevoflurane.

Discussion

Cerebral autoregulation and CO₂-reactivity is preserved at 1 MAC sevoflurane. Cerebrovascular effects of anesthetic compounds have to be assessed together with systemic circulatory effects.

Trial registration

The study was registered at http://www.clinicaltrials.gov, identifier: NCT02054143, retrospectively registered. Date of registration: February 4, 2014.

Magnetic resonance imaging of cerebrovascular reactivity in healthy adolescents

BACKGROUND

Cerebrovascular reactivity (CVR), an important measure of cerebrovascular health in adults, has not been examined in healthy adolescents. Beyond the direct importance of understanding CVR in healthy youth, studies on this topic can yield insights regarding brain disease. We set out to evaluate 3 different CVR modelling approaches.

NEW METHOD

Thirty-nine healthy adolescents (ages 13-19 years, 20 females) completed six blocks of 15-second breath-holds separated by 30-second blocks of free-breathing. CVR was measured using blood-oxygenation-level dependent functional magnetic resonance imaging at 3-Tesla; voxel-wise analyses were complemented by regional analyses in five major subdivisions of the brain. Hemodynamic response functions were modelled using: (1) an individualized delay term (double-gamma variate convolved with a boxcar function), (2) with a standard 9-second delay term, and (3) a sine-cosine regressor.

RESULTS

Individual-delay yielded superior model fit or larger cluster volumes. Regional analysis found differences in CVR and time-to-peak CVR. Males had higher brain-wide CVR in comparison to females (p = 0.025, η²_part = 0.345). BMI and blood pressure were not significantly associated with CVR (all p > 0.4).

COMPARISON WITH EXISTING METHODS

This was the first study to compare these methods in youth. Regional differences were similar to adult studies.

CONCLUSIONS

These findings lend support to future breath-hold CVR studies in youth, and highlight the merit of applying individualized-delay estimates. Regional variability and sex-related differences in CVR suggest that these variables should be considered in future studies, particularly those that examine disease states with predilection for specific brain regions or those diseases characterized by sex differences.

Cognitive function in hypertensive children

Young hypertensive adults demonstrate decreased performance on neurocognitive testing compared with that of normotensive controls. There is emerging, preliminary evidence that children with hypertension also manifest cognitive differences when compared to normotensive controls. These preliminary studies consist mostly of database and single-center studies that focus primarily on differences in neurocognitive test performance and differences in cerebrovascular reactivity between hypertensive and normotensive subjects. Lessons from the literature on cognition in adult hypertensives and experience from the preliminary studies in children informed the design of a current, multicenter, ongoing study of cognition in children with primary hypertension.

Primary hypertension and neurocognitive and executive functioning in school-age children

Data on neurocognitive function in hypertensive children are limited. In this review, we summarize recent preliminary, early studies that suggest that children with elevated blood pressure demonstrate evidence of worse performance on direct neurocognitive testing, as well as evidence of executive dysfunction based on parent ratings, compared with matched normotensive comparison groups. Furthermore, hypertensive children may have increased prevalence of learning disabilities as well as a blunted cerebrovascular reactivity compared with normotensive controls. Larger, prospective studies are needed to confirm and further explore these emerging but preliminary findings.

Influence of hypertension and type 2 diabetes mellitus on cerebrovascular reactivity in diabetics with retinopathy

BACKGROUND AND OBJECTIVES

Cerebrovascular reactivity (CVR) provides information on the intracerebral arterioles capacity to react to vasodilatory stimuli. The current study aimed to investigate the influence of hypertension and type 2 diabetes mellitus on CVR in diabetics with retinopathy.

DESIGN AND SETTING

Retrospective analysis of data prospectively collected over a 1-year period.

SUBJECT AND METHODS

Subjects were classified into four groups each comprised of 30 participants: diabetic retinopathy with hypertension (DRH), diabetic retinopathy without hypertension (DR), hypertension without diabetes mellitus (H), and healthy controls without diabetes and hypertension (C). CVR was estimated in relation to the increase in the mean flow velocity compared with the basal velocity in both middle cerebral arteries during hypercapnia.

RESULTS

In the DRH group, the mean (SD) increase in CVR was 8.8 (2.49) cm/s, in the H group 14.4 (2.59) cm/s and in the DR group 9.7 (2.97) cm/s. The analysis of variance showed significant differences among the groups in blood flow velocity after a breath-holding test (F=89.83; df=3.116; P < .001).

CONCLUSIONS

Diabetes mellitus influences CVR more than hypertension.

Neurocognitive alterations in hypertensive children and adolescents

Hypertensive adults demonstrate performance deficits on neuropsychological testing compared with scores of normotensive controls. This article reviews emerging preliminary evidence that children with hypertension also manifest neurocognitive differences when compared with normotensive controls. Database and single-center studies suggest that children with hypertension manifest deficits on measures of neurocognition and have an increased prevalence of learning difficulties and that children with hypertension associated with obesity may be at increased risk for depression and anxiety. Studies suggesting blunted cerebrovascular reactivity in children with hypertension are also reviewed.

Pediatric ambulatory blood pressure monitoring: indications and interpretations

The prevalence of hypertension in children and adolescents is increasing, especially in obese and ethnic children. The adverse long-term effects of hypertension beginning in youth are known; therefore, it is important to identify young patients who need intervention. Unfortunately, measuring blood pressure (BP) is difficult due to the variety of techniques available and innate biologic variation in BP levels. Ambulatory BP monitoring may overcome some of the challenges clinicians face when attempting to categorize a young patient's BP levels. In this article, the authors review the use of ambulatory BP monitoring in pediatrics, discuss interpretation of ambulatory BP monitoring, and discuss gaps in knowledge in usage of this technique in the management of pediatric hypertension.