Year: 2018
Type: dissertation
Abstract: Ischemic stroke is the commonest stroke and a leading cause of disability and death worldwide.Atrial fibrillation (AF) is the most frequent persistent cardiac arrhythmia and a preventable cause of ischemic strokes.The incidence and prevalence of AF have progressively increased over the last few decades and will likely continue to rise, due to the aging population and ongoing growth in other AF risk factors such as obesity, hypertension, diabetes mellitus, heart failure, coronary artery disease and sleep apnea.The social and economic costs associated with the increasing AF burden represent a mounting public health challenge, leading many to consider AF an evolving epidemic in the twenty-first century.Ischemic strokes related to AF usually result from cardioembolism of a large cerebral artery, therefore tend to be larger, more frequently fatal or associated with greater disability than strokes from other causes.However, the pathophysiological mechanisms underlying this association remain unclear.Analysis of serial multimodal magnetic resonance brain imaging in a cohort of acute hemispheric ischemic stroke patients revealed that patients with AF had greater volumes of more severely hypoperfused brain tissue at 3-6 hours following stroke onset, higher infarct growth and larger final infarcts.These findings were best explained by poorer collateral circulation in patients with AF, supporting further investigation of acute stroke therapy that improve cerebral collateral circulation.Analysis of clinical data in a separate large cohort of acute ischemic stroke patients emphasized that serious cardiac adverse events (SCAE) including acute coronary syndrome, symptomatic heart failure, life threatening cardiac arrhythmias, cardiopulmonary arrest and cardiac death were common and occurred early following stroke.SCAEs were significantly more frequent in patients with AF, contributing to the association between AF and higher mortality following stroke, in addition to greater neurological impairment.Given that most SCAEs are potentially remediable, these results highlight the need for more rigorous surveillance of SCAEs following stroke, particularly in patients with AF.CHADS 2 and CHA 2 DS 2 -VASc scores are validated and clinically useful tools for assessing stroke risk in patients with AF.Both scores have also been associated with a number of short and long term outcomes following stroke, suggesting potential utility in stroke prognosis.However, both scores had very modest precision in estimating the probability of mortality, functional outcome and SCAEs within 3 months following ischemic stroke in a large cohort of acute ischemic stroke patients with and without AF.Pre-stroke CHA 2 DS 2 -VASc score did have high negative predictive value for SCAE and high specificity for poor functional outcome, suggesting that it could be used for identifying patients at lower risk of poor outcomes and SCAEs within 3 months following ischemic stroke in patients with and without AF.AF can be persistent or paroxysmal and is frequently asymptomatic, therefore are hard to detect.However, the stroke risk and benefit from validated prevention therapy do not significantly differ between persistent and paroxysmal AF.There is strong evidence that current standard testing paradigm such as 24-hour Holter monitoring following ischemic stroke misses a large proportion of patients with paroxysmal AF.A pilot study in a prospective cohort of 20 cryptogenic stroke patients confirmed previous findings that a significant proportion has paroxysmal AF undetected by 24hour Holter monitoring.However, longer monitoring with 28-day Holter monitoring was poorly tolerated and still insufficiently sensitive.Further studies are urgently needed to elucidate the optimal timing, method and duration of cardiac rhythm monitoring following ischemic stroke.
Author: Hans T.H. Tu
Language: English
Subfield: Clinical Neurology
Field: Medicine
Domain: Health Sciences
Open Access status: green
OpenAlex ID: W2921195292