Transcranial Doppler (TCD) ultrasound provides rapid, noninvasive, real-time measures of cerebrovascular function. TCD can be used to measure flow velocity in the basal arteries of the brain to ...assess relative changes in flow, diagnose focal vascular stenosis, or to detect embolic signals within these arteries. TCD can also be used to assess the physiologic health of a particular vascular territory by measuring blood flow responses to changes in blood pressure (cerebral autoregulation), changes in end-tidal CO2 (cerebral vasoreactivity), or cognitive and motor activation (neurovascular coupling or functional hyperemia). TCD has established utility in the clinical diagnosis of a number of cerebrovascular disorders such as acute ischemic stroke, vasospasm, subarachnoid hemorrhage, sickle cell disease, as well as other conditions such as brain death. Clinical indication and research applications for this mode of imaging continue to expand. In this review, the authors summarize the basic principles and clinical utility of TCD and provide an overview of a few TCD research applications.
Despite advances in earlier diagnosis and available aggressive treatments for vascular risk factors, stroke remains a leading cause of death and long-term disability worldwide. Disparities exist in ...stroke risk, rates of stroke, and treatment. Stroke is a heterogeneous disease with multiple additive risk factors and causes. Primary prevention of stroke focusing on risk factor modification plays an important role in reducing the burden of stroke in an aging population. Secondary prevention of recurrent strokes relies on the workup and a tailored treatment targeted at the mechanisms responsible for the incident stroke or transient ischemic attack.
Hypertension affects two-thirds of people aged >60 years and significantly increases the risk of both vascular cognitive impairment and Alzheimer's disease. Hypertension compromises the structural ...and functional integrity of the cerebral microcirculation, promoting microvascular rarefaction, cerebromicrovascular endothelial dysfunction and neurovascular uncoupling, which impair cerebral blood supply. In addition, hypertension disrupts the blood-brain barrier, promoting neuroinflammation and exacerbation of amyloid pathologies. Ageing is characterized by multifaceted homeostatic dysfunction and impaired cellular stress resilience, which exacerbate the deleterious cerebromicrovascular effects of hypertension. Neuroradiological markers of hypertension-induced cerebral small vessel disease include white matter hyperintensities, lacunar infarcts and microhaemorrhages, all of which are associated with cognitive decline. Use of pharmaceutical and lifestyle interventions that reduce blood pressure, in combination with treatments that promote microvascular health, have the potential to prevent or delay the pathogenesis of vascular cognitive impairment and Alzheimer's disease in patients with hypertension.
How might the results of TREAT-SVDs influence clinical practice? Because of the small sample size, one must be cautious in relation to interpretation of the results. ...according to current European ...and US guidance for blood pressure management, β blockers are restricted to patients with comorbidities or compelling indications (eg, heart rate control, heart failure, and angina).10 Unless there is a comorbid condition or compelling indication for a β blocker, a reasonable approach for patients with symptomatic cerebral small vessel disease would be to consider administration of a calcium channel blocker or an angiotensin receptor blocker while we await future study results. PBG has served on a data safety and monitoring board for a blood pressure lowering drug administered to heart failure participants for a Novartis sponsored study.
Hemorrhagic transformation and cerebral edema are feared complications of acute ischemic stroke but mechanisms are poorly understood and reliable early markers are lacking. Early assessment of ...cerebrovascular hemodynamics may advance our knowledge in both areas. We examined the relationship between dynamic cerebral autoregulation (CA) in the early hours post ischemia, and the risk of developing hemorrhagic transformation and cerebral edema at 24h post stroke
We prospectively enrolled 46 patients from our center with acute ischemic stroke in the middle cerebral artery territory. Cerebrovascular resistance index was calculated. Dynamic CA was assessed by transfer function analysis (coherence, phase and gain) of the spontaneous blood flow velocity and blood pressure oscillations. Infarct volume, hemorrhagic transformation, cerebral edema, and white matter changes were collected from computed tomography performed at presentation and 24h.
At admission, phase was lower (worse CA) in patients with hemorrhagic transformation 6.6±30 versus 45±38°; adjusted odds ratio 0.95 (95% confidence internal 0.94–0.98), p=0.023 and with cerebral edema 6.6±30 versus 45±38°, adjusted odds ratio 0.96 (0.92–0.999), p=0.044. Progression to edema was associated with lower cerebrovascular resistance (1.4±0.2 versus 2.3±1.5mmHg/cm/s, p=0.033) and increased cerebral blood flow velocity (51±25 versus 42±17cm/s, p=0.033) at presentation. All hemodynamic differences resolved at 3months
Less effective CA in the early hour post ischemic stroke is associated with increased risk of hemorrhagic transformation and cerebral edema, possibly reflecting breakthrough hyperperfusion and microvascular injury. Early assessment of dynamic CA could be useful in identifying individuals at risk for these complications.
•Dynamic cerebral autoregulation was studied in very early stage of ischemic stroke.•Autoregulatory impairment is linked to hemorrhagic transformation and cerebral edema.•Assessment of dynamic CA may provide a therapeutic target for the future.
Introduction
We assessed the association between visit‐to‐visit blood pressure variability (BPV) up to 12 years and subsequent dementia risk, and tested the modifying effect of antihypertensive ...medications.
Methods
We studied 2234 participants from two community‐based cohorts of older adults with normal cognition or mild cognitive impairment. Participants were followed through annual assessments for up to 27 years. Visit‐to‐visit BPV was quantified over 3, 6, 9, and 12 years, respectively.
Results
Higher systolic BPV (SBPV) during 3, 6, 9, and 12 years was associated with a subsequent increased risk of dementia, with hazard ratios ranging from 1.02 (95% confidence interval CI: 1.01–1.04) to 1.10 (95% CI: 1.05–1.16). The association between SBPV and dementia risk was stronger among participants not taking calcium channel blockers (p‐for interaction < 0.05).
Discussion
Among older adults, long‐term exposure to higher visit‐to‐visit SBPV is associated with an increased risk of dementia later in life, and calcium channel blockers may modify this association.
Highlights
Among adults aged >65, higher systolic blood pressure variability spanning 3–12 years is associated with an increased risk of dementia later in life.
Single blood pressure measurement or mean blood pressure levels does not seem to associate with dementia risk among older adults.
The association between systolic blood pressure variability and dementia risk is stronger among those not taking calcium channel blocker medications.
Preservation of brain health has emerged as a leading public health priority for the aging world population. Advances in neurovascular biology have revealed an intricate relationship among brain ...cells, meninges, and the hematic and lymphatic vasculature (the neurovasculome) that is highly relevant to the maintenance of cognitive function. In this scientific statement, a multidisciplinary team of experts examines these advances, assesses their relevance to brain health and disease, identifies knowledge gaps, and provides future directions.
Authors with relevant expertise were selected in accordance with the American Heart Association conflict-of-interest management policy. They were assigned topics pertaining to their areas of expertise, reviewed the literature, and summarized the available data.
The neurovasculome, composed of extracranial, intracranial, and meningeal vessels, as well as lymphatics and associated cells, subserves critical homeostatic functions vital for brain health. These include delivering O
and nutrients through blood flow and regulating immune trafficking, as well as clearing pathogenic proteins through perivascular spaces and dural lymphatics. Single-cell omics technologies have unveiled an unprecedented molecular heterogeneity in the cellular components of the neurovasculome and have identified novel reciprocal interactions with brain cells. The evidence suggests a previously unappreciated diversity of the pathogenic mechanisms by which disruption of the neurovasculome contributes to cognitive dysfunction in neurovascular and neurodegenerative diseases, providing new opportunities for the prevention, recognition, and treatment of these conditions.
These advances shed new light on the symbiotic relationship between the brain and its vessels and promise to provide new diagnostic and therapeutic approaches for brain disorders associated with cognitive dysfunction.
Hypertension is one of the most prevalent vascular risk factors and a leading cause of disability and mortality worldwide. The negative impact of hypertension on brain health is substantial. Already ...well-established as a risk factor for cerebrovascular disease, hypertension also has been shown to increase the risk for cognitive impairment and dementia. Mounting evidence from epidemiological studies suggests that hypertension, particularly in midlife, is associated with late-life cognitive impairment and the development of dementia. The link between late-life hypertension and cognitive function is, however, less clear. Experimental and neuroimaging studies have revealed complexities of mechanisms underlying the link between hypertension and cognitive function. Furthermore, the effect of blood pressure lowering on cognitive function, the optimal target and timing of the intervention, and the optimal antihypertensive agent in the context of cognitive function remain unclear. In this review, we discuss contemporary science on the link between hypertension and cognitive function by reviewing experimental, neuroimaging, and life-course observational studies. Furthermore, we provide a detailed review of randomized clinical trials addressing the effect of blood pressure lowering on cognitive function. Finally, unanswered questions, challenges, and other considerations for blood pressure lowering are highlighted.
In the absence of effective treatments for dementia, maintaining cognitive health in old age is one of the major challenges facing aging societies. Interventions for cognitive health that are ...tailored to the person are more likely to bring the best benefits with a minimum burden. We review the existing literature on this topic and discuss the role of the primary care physician.
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