MRC Development Centre for Clinical Brain Ageing, and Institute for Ageing and Health, University of Newcastle upon Tyne, Newcastle upon Tyne, United Kingdom
Address for correspondence: Rose Anne Kenny, Professor of Cardiovascular Research, Falls and Syncope Service, Victoria Wing, Royal Victoria Infirmary, Newcastle upon Tyne NE1 4LP, United Kingdom. Voice: 0191 222 3627; fax: 0191 222 7628.
anne.harrison{at}ncl.ac.uk
Ann. N.Y. Acad. Sci. 977: 183-195 (2002).
Neurocardiovascular instability (NCVI, neurally mediated disorders
causing hypotension with or without bradycardia) represents
abnormal neural control of the cardiovascular system and presents
as dizziness, syncope, or falls. The mechanisms underpinning
NCVI are incompletely understood. The three most common disorders
are carotid sinus syndrome (CSS), orthostatic hypotension (OH),
and vasovagal syndrome (VVS): CSS, cardioinhibition > 3 s
and/or vasodepressor response
50 mmHg drop in systolic pressure
during carotid sinus stimulation; OH: fall in systolic blood
pressure > 20 mmHg during standing; VVS: cardioinhibition
> 3 s and/or vasodepressor response > 50 mmHg during prolonged
head-up tilting. In fallers with cognitive impairment or dementia,
the prevalence of NCVI is 70%. Multifactorial interventions,
including treatment of NCVI, significantly reduce falls and
syncope. The predominant components of NCVI in fallers with
cognitive impairment and dementia are CSS and OH. In Lewy body
and Alzheimer's dementia, the prevalence of NCVI is up to 60%,
again predominantly CSS and OH. The prevalence of cardioinhibitory
carotid sinus hypersensitivity is particularly high in Lewy
body dementia—41% compared with 12% in Alzheimer's disease
and 3% in case controls. In addition, patients with Lewy body
dementia have greater heart rate slowing (>2 s) and falls
in systolic blood pressure (>20 mmHg) than those with Alzheimer's
disease or controls during carotid sinus stimulation. The extent
of deep white matter hyperintensities on MRI correlates with
systolic fall during carotid sinus stimulation (
R = 0.58;
p < 0.005), suggesting a possible causal association between
bradyarrhythmia-induced hypotension and microvascular pathology.
NCVI is common in patients with dementia and may be a reversible
cause of falls and syncope. Repeated hypotensive episodes may
exaggerate cognitive decline in these patients.
