Optimising the management of patients with atrial fibrillation
thesisposted on 2017-02-23, 01:53 authored by Ball, Jocasta Clare
Background: Atrial fibrillation (AF) is the most common form of cardiac arrhythmia found in clinical practice and indeed the adult population. Although AF can present in an acute and non-sustained (paroxysmal AF) form, it typically progresses into a chronic and often silent disorder. Over a prolonged period, chronic AF is associated with detrimental mechanical changes that result in progressive cardiac dysfunction. An enhanced thrombo-embolic state coupled with blood stasis in the atria leads to increased thrombus formation. Consequently, AF is closely linked to thromboembolic stroke and chronic heart failure; two of the most deadly and disabling forms of cardiovascular disease. Chronic AF is, therefore, commonly associated with recurrent hospitalisations and poor patient outcomes overall; including a poor prognosis. Overall, despite the known risks, health outcomes associated with AF continue to be sub-optimal within the context of predominantly older patients who require a careful assessment of risk and individualised management to ensure the benefit-to-risk ratio of often complex therapeutic regimes are optimised. Aims: In addition to understanding the true extent of the global burden of AF, the primary aim of this research was to establish enhanced and potentially effective methods for the assessment of risk in order to direct more individualised AF patient management in an attempt to improve outcomes. More specifically, the influence of gender, mild cognitive impairment and effective rate/rhythm control on patients with AF and as methods for risk delineation was assessed. Methods: The framework for this research was the Standard versus Atrial Fibrillation spEcific managemenT studY (SAFETY), a multi-centre randomised controlled trial of a nurse-led AF-specific intervention involving home-based assessment, extensive risk profiling (over and above conventional profiling) and individualised management compared to usual post-discharge care. Participants included were those > 45 years of age with documented chronic AF for which this has been the cause of hospitalisation. For this research program, quantitative analysis to assess risk delineation strategies was undertaken using data collected at the baseline time point. Results: In a comprehensive review and meta-analyses of the literature, the prevalence of AF was found to be greater than commonly reported. Here, the population prevalence was found to be between 2.5% and 3.5%, substantially higher than the reported 1.0% to 2.0%. Furthermore, the economic consequences were found to be equally as large, with up to 2.5% of health care costs in Europe, North America and Australia spent on AF alone. When a detailed evaluation of gender differences was undertaken, key differences in the clinical presentation, thrombo-embolic risk and therapeutic management of women compared to men were detected. Most importantly, women were, on average, older than their male counterparts and were also more likely to report depressive symptoms and have poorer quality of life. There were also potentially important social, clinical and treatment differences that might adversely influence health outcomes in women. The prevalence of cognitive impairment within this cohort was found to be substantially higher than expected, with 65% of the SAFETY cohort demonstrating mild cognitive impairment (MCI) on initial assessment. Those with MCI were less educated but at a higher thrombo-embolic risk with multiple cognitive domains being affected. When cardiac rate and rhythm were assessed on Holter monitoring in intervention patients post-discharge, a substantial divergence between intended and detected control was found. Of those intended for rhythm control, 43% had reverted back to AF and an uncontrolled heart rate was identified in 26% of all patients. A novel method for classifying heart rate control was determined with three phenotypes being described. Patients who were more clinically complex with diagnosed coronary artery disease (CAD) and/or renal disease/dysfunction were less likely to display heart rate stability. Conclusions: In addition to providing a more contemporary and accurate description of an evolving global epidemic of AF, this research has the potential to enhance and extend current risk delineation strategies to optimise clinical management and outcomes in high risk individuals. Specifically, by focussing on gender differences, the common presence of MCI and a frequent disconnect between intended versus achieved rate/rhythm control target this research identified a number of practical ways to enhance risk delineation in AF. Ongoing research will evaluate the cost-effectiveness of enhanced risk delineation in AF via more proactive management.