Atrial fibrillation in young stroke patients: do we underestimate its prevalence?

BACKGROUND AND PURPOSE: The prevalence of atrial fibrillation (AF) in young stroke patients has rarely been reported and is considered an uncommon ischaemic stroke (IS) aetiology. Our objective was to analyse the prevalence of AF in IS patients up to 50 years of age and its relationship with stroke severity and outcomes. METHODS: This was an observational study of consecutive IS patients up to 50 years of age admitted to a stroke centre during a 5-year period (2007-2011). A complete cardiology study was performed with a daily electrocardiogram and cardiac monitoring for 72 h as well as echocardiography. In cases of stroke of unknown aetiology a 24-h Holter monitoring was performed. Baseline data, previously or newly diagnosed AF, structural heart disease (SHD) (valvulopathy/cardiomyopathy), stroke severity on admission as measured by the National Institutes of Health Stroke Scale (NIHSS) (moderate-severe stroke if NIHSS ≥ 8) and 3-month outcomes according to the modified Rankin Scale (mRS) (good outcome if mRS ≤ 2) were analysed. AF was classified as AF associated with SHD (AF-SHD) and AF not associated with SHD (AF-NSHD). RESULTS: One hundred and fifty-seven patients were included (mean age 43 years, 58.6% male). Fourteen subjects (8.9%) presented with AF, four with AF-NSHD and 10 with AF-SHD. AF was previously known in 10 patients (6.3%), two with AF-NSHD and eight with AF-SHD. A multivariate analysis showed an independent association between AF and moderate-severe IS (odds ratio 3.771, 95% CI 1.182-12.028), but AF was not an independent prognostic factor. CONCLUSION: AF may be more common than expected in young patients with IS and is associated with increased NIHSS scores.

Surface and intramural reentrant patterns during atrial fibrillation in the sheep.

INTRODUCTION: This article is part of the Focus Theme of Methods of Information in Medicine on "Biosignal Interpretation: Advanced Methods for Studying Cardiovascular and Respiratory Systems". BACKGROUND: Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in humans and is predicted to dramatically increase its prevalence in the future. High-resolution mapping data and Fourier power spectral analysis with its dominant frequency support the hypothesis that AF in the structurally normal sheep heart and in some patients often presents organized drivers in the form of periodic surface re-entries or breakthroughs. Nevertheless, the dynamics of those surface patterns of activity, as well as their intramural components are still poorly understood. OBJECTIVE: To present data on AF waves from the surface of isolated sheep hearts and discuss the interpretation of their intramural patterns. METHODS: We used a combination of endocardial-epicardial optical mapping with phase and spectral analysis as well as computer simulation of the re-entrant activity in the myocardial wall. RESULTS: Analysis of the surfaces' optical mapping data in the phase domain reveals that activation of the posterior left atrium (PLA) consisted of alternating patterns of breakthroughs and reentries. The patterns on the endocardial and epicardial PLA surface at any given moment of time of the AF could be either identical or not identical, and the activity in the thickness of the PLA wall is hypothesized to conform to either ectopic discharge or reentrant scroll waves, but a definite evidence for the presence of such mechanisms is currently lacking. A universal minimal-principle theory is shown in a computer model to result in a tendency of the axis of the scroll waves to align with the myocardial fibers inside the wall. CONCLUSION: The tendency of filaments of scroll waves to align with myocardial fibers may contribute to the variety and intermittency of surface rotors seen in AF.