Review
Recent Developments in Understanding Epidemiology and Risk Determinants of Atrial Fibrillation as a Cause of Stroke

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Abstract

The prevalence of atrial fibrillation (AF) is increasing because of the aging population and advances in the treatment of acute cardiac conditions. It is now approaching epidemic proportions and is associated with significant clinical and public health consequences. Risk factors for the development of AF are numerous and varied and highlight potential treatment measures that could help prevent the occurrence of AF. The emergence of novel risk factors might allow us to increase our understanding of the pathophysiology of the condition and develop novel therapeutic targets. Stroke is the most devastating consequence of AF, and can be prevented with effective oral anticoagulation in patients at increased stroke risk. Our understanding of stroke risk has advanced; we know that the risk is not homogenous and also that only the very lowest risk patients do not benefit from anticoagulation. Clinicians should target their efforts on identifying this “truly low-risk” patient cohort and consider offering formal anticoagulation to all other AF patients. The purpose of this review is to consider the traditional and emerging risk factors for the development of AF itself, and the risk factors for stroke in AF patients and how knowledge of these risk factors can affect clinical practice.

Résumé

La prévalence de la fibrillation auriculaire (FA) augmente en raison du vieillissement de la population et des progrès dans le traitement des affections cardiaques aiguës. Elle tend maintenant vers des proportions épidémiques, et est associée à d’importantes conséquences cliniques et de santé publique. Les facteurs de risque de développement de la FA sont nombreux et variés, et font ressortir les mesures potentielles de traitement qui aideraient à prévenir l’occurrence de la FA. L’émergence de nouveaux facteurs de risque pourrait nous permettre d’améliorer notre compréhension de la physiopathologie de l’affection et de définir de nouveaux objectifs thérapeutiques. L’accident vasculaire cérébral est la conséquence la plus dévastatrice de la FA, et peut être prévenu par une anticoagulation orale efficace chez les patients ayant un risque d’accident vasculaire cérébral élevé. Notre compréhension du risque d’accident vasculaire cérébral a progressé. Nous savons que le risque n’est pas homogène et savons également que seuls les patients ayant le plus faible risque ne bénéficient pas de l’anticoagulation. Les cliniciens devraient unir leurs efforts à l’identification de cette cohorte de patients « ayant vraiment un faible risque » et envisager d’offrir une anticoagulation systématique à tous les autres patients ayant une FA. Le but de cette revue est de tenir compte des facteurs de risque traditionnels et émergents du développement de la FA en soi, et des facteurs de risque d’accident vasculaire cérébral chez les patients ayant une FA, et d’examiner comment la connaissance de ces facteurs de risque peut influencer la pratique clinique.

Section snippets

Established risk factors for AF

There are numerous well-established and validated risk factors for the development of AF,17 as summarized in Figure 1.

These risk factors are well known and accepted, and it is likely that there is a cumulative effect in that an individual with multiple risk factors is more likely to develop AF than an individual with a single risk factor.18 For patients with concomitant cardiac diseases that increase their risk of AF, effective prevention and control of these disorders might protect patients

Stroke Risk Factors in AF

The risk of stroke in AF is not homogeneous and is dependent on the presence or absence of specific stroke risk factors.78, 79 There has been a concerted effort to identify novel risk factors for stroke and determine the extent to which they confer an additional risk for stroke in patients with AF. Historical landmark trials identified a collection of now accepted stroke risk factors and have been included in various schemata for determining stroke risk.

A recent systematic review of predictors

Stroke Risk Stratification Schemes

Traditional risk factor schemes for stroke in AF classified patients broadly into high-, intermediate-, and low-risk categories, in which patients deemed to be at high risk were recommended for treatment with OAC, and the intermediate risk group could be offered OAC or antiplatelet therapy at the discretion of the clinician, with low-risk patients treated with aspirin or no antithrombotic therapy. The best example of such a scheme is the CHADS2 score,16 which was adopted into international

Conclusions

AF is associated with a significant clinical and public health burden, and the management of this increasingly common arrhythmia is a key challenge facing modern cardiovascular medicine. Epidemiological data have identified many established risk factors for AF, but evidence suggests that a substantial proportion of incident AF cases might not be explained by these traditional factors. Renewed focus on this area has highlighted several emerging clinical and biochemical risk factors. These risk

Key Messages

  • The prevalence of AF is increasing, primarily because of the aging population.

  • Traditional AF risk factors explain only a portion of the AF risk.

  • Novel risk factors for the development of AF are emerging and might yield potential new therapeutic options.

  • Stroke risk in AF is heterogeneous and dependent on the presence of specific stroke risk factors.

  • Newer stroke risk factors (such as female sex and vascular disease) have been identified and are now incorporated into a risk stratification scheme.

Funding Sources

Publication of this article is supported by Bayer Canada and by Pfizer and Bristol-Myers Squibb.

Disclosures

G.Y.H.L. has served as a consultant for Bayer, Astellas, Merck, AstraZeneca, Sanofi, Bristol-Myers Squibb/Pfizer, Daiichi-Sankyo, Biotronik, Portola, and Boehringer Ingelheim, and has been on the speakers bureau for Bayer, Bristol-Myers Squibb/Pfizer, Boehringer Ingelheim, and Sanofi Aventis. D.A.L. is in receipt of an investigator-initiated educational grants from Bayer Healthcare and Boehringer Ingelheim and has been on the speakers bureau for Boehringer Ingelheim, Bristol-Myers

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