Clinical factors and imaging leading to risk of incident atrial fibrillation

This editorial refers to ‘Change in left atrial function predicts incident atrial fibrillation: the Multi-Ethnic Study of Atherosclerosis’, by D.J. Lim et al., pp. 979--987. Atrial fibrillation (AF) and its complications represent a major clinical and healthcare burden globally, with more than 33 million people affected worldwide.1 The arrhythmia is progressive in its nature and once it has developed it likely to re-occur, typically leading to permanent form. Methods to treat AF are limited by their variable success rates and isolated symptomatic benefit. Thus there is an argument to support the early detection of modifiable risk factors to prevent the occurrence of the arrhythmia and potentially improve prognosis. As patients who develop AF have a high risk of disabling complications, such as stroke, dementia, and heart failure, which are often devastating to the patient and are associated with a high mortality, morbidity, and hospitalizations.2,3 Although ageing is a major and irreversible risk factor for AF, its impact can perhaps be mitigated through the control of clinical risk factors known to influence the risk of incident AF.4 There are many clinical risk factors of incident AF, which are generally common with those for cardiovascular disease (e.g. hypertension and obesity).5 In contrast to cardiovascular disease, the clinical benefit of treating these risk factors for the prevention of AF is less established. This likely reflects the differences in their impact on pathogenesis of the two conditions, which are primarily atherosclerosis in cardiovascular disease and in AF, the impact on atrial load, remodelling and fibrosis. Conversely, some risk factors for AF, such as white ethnicity, being taller, lower total cholesterol, and lower diastolic blood pressure actually lower the risk of coronary artery disease.6–8 These findings highlight the need to develop a pragmatic ‘personalized’ approach to identify those individuals at high risk of AF. This can be especially challenging in those without obvious high-risk factors, such as those with already established cardiovascular disease. One way in improving of prediction of future AF on individual level could be gaining a closer insight into risk factors associated with the pathophysiology of AF. The important electrophysiological mechanism contributing to the development AF is left atrial adverse remodelling.9 This role of left atrial enlargement in AF progression has previously been extensively studied and the degree of the left atrial enlargement alone has been shown to be related to the risk of cardiovascular and all-cause mortality.10,11 Similarly there are reports on the association of left atrial enlargement with incident AF in population cohort studies.12,13 A major question is whether the left atrial characteristics can be considered as a modifiable risk factor for incident AF. Lim et al.14 report data on the predictive value of structural and functional left atrial remodelling in the development of AF based on a prospective multi-ethnic population cohort study of individuals free of clinical cardiovascular disease at the time of enrolment. The study has a number of strong points. For the assessment of the prospective changes in left atrial volume and function, they utilized a highly accurate and well-validated cardiac magnetic resonance imaging technique. Although it would be challenging to implement as a population screening tool, it does provide reliable insights into atrial characteristics. The study also benefits from a clinically relevant follow-up period (mean 3.8 years), a time duration which provides a reasonable time to expect the effects of the parameters on AF occurrence, but makes it less likely that the impact of the baseline left atrial properties to be attenuated or amplified by development of significant comorbidities. The study demonstrates that dynamic changes in the left atrial status over the follow-up period are stronger predictors of AF development compared with a baseline assessment alone. The findings from Lim et al. are of clinical importance as they suggest that the risk of AF is associated with the left atrial abnormalities and hence, the risk could potentially be mitigated if the abnormalities are corrected. This study further adds to the understanding of the mechanisms that predispose to AF occurrence in otherwise healthy individuals from the general population to develop AF when changes in risk profile are being assessed. As has already been previously highlighted, the AF patient clinical risk profile does not stay static and frequently the change in the risk profile is more predictive of the outcomes.15,16 Lim et al. further show that both changes in atrial structure and function increase the risk of incident AF, and the study also offers identification of relatively subtle atrial changes in the perceived ‘low risk’ patients. From this perspective, the subtle atrial changes could be considered as ‘cumulative’ risk factors for incident AF resulting from a cumulative multitude of the individual demographic and clinical characteristics. The multifactorial nature of predictors for incident AF and its complications justifies a more holistic or integrated approach to AF prevention and its subsequent management.17,18 Nevertheless, the clinical practicality and cost-effectiveness of longitudinal left atrial assessment needs to be assessed in future studies. The ability to detect small changes (<1% per annum) in [left atrial emptying fractions (LAEF)] and [left atrial volumes (LAV)] over time, its reproducibility and interpretation in a real-world setting is still questionable. Financial costs of patient screening could be mitigated by measuring similar changes by echocardiography in individuals at higher risk of incident AF. However, this would be at the clinical cost of lower reproducibility. An imaging screening programme could arguably be justified in view of the high costs of treating AF, providing there is a practical way to improve the identified atrial abnormalities in high-risk individuals linked to the development of a primary prevention programme. Such exciting possibilities need extensive future research. Conflict of interest: none declared. The opinions expressed in this article are not necessarily those of the Editors of EHJCI, the European Heart Rhythm Association or the European Society of Cardiology.