Flutter vs Fibrillation: Which Is Tied to Lower Stroke Rate?

TOPLINEPatients with atrial flutter (AFL) alone had a 40% lower rate of ischaemic stroke events than those with atrial fibrillation (AF) alone, whereas those with both AF and AFL had an 11% higher rate of ischaemic stroke events.METHODOLOGYResearchers conducted a nationwide retrospective cohort study in Finland using digitally interpreted ECG data to evaluate the risk for ischaemic stroke in patients with AF and AFL.The study included 40,986 patients with a total of 532,041 digitally interpreted ECGs collected between 2007 and 2018; patients were categorised into three groups on the basis of the ECG findings: the AF-only group (n = 30,261; mean age, 71.8 years; 51.8% men), the AFL-only group (n = 2409; mean age, 70.8 years; 61.2% men), and the combined AF and AFL group (n = 8316; mean age, 72.4 years; 46.1% men).Ischaemic stroke events were identified from hospital records to ensure that only clinically significant events were included.Patients were followed up until the first documented ischaemic stroke event, death, or the end of the observation period in 2018, whichever occurred first, with analyses accounting for oral anticoagulation (OAC) use.A separate analysis focused on follow-up before OAC initiation or catheter ablation because untreated stroke rates guided decisions on stroke prevention.TAKEAWAYOverall, 7.7% of patients had an ischaemic stroke event, with crude ischaemic stroke rates of 1.1 per 100 patient-years (95% CI, 0.9-1.3) in the AFL-only group, 1.9 per 100 patient-years (95% CI, 1.8-1.9) in the AF-only group, and 2.1 per 100 patient-years (95% CI, 1.9-2.2) in the combined AF and AFL group.After adjustment, AFL alone was associated with a significantly lower rate of ischaemic stroke than AF alone (adjusted incidence rate ratio [IRR], 0.60; 95% CI, 0.49-0.74), whereas combined AF and AFL was associated with a slightly higher rate of ischaemic stroke (adjusted IRR, 1.11; 95% CI, 1.02-1.20).In the analysis restricted to follow-up before OAC initiation or catheter ablation, AFL alone remained associated with a lower rate of ischaemic stroke than AF alone (adjusted IRR, 0.55; 95% CI, 0.40-0.76).IN PRACTICE"The risk of IS [ischaemic stroke] was significantly lower in patients with AFL-only compared with those with AF-only, suggesting clinically meaningful differences in thromboembolic risk between these two arrhythmias. These findings highlight a potential need to re-evaluate anticoagulation strategies," the researchers wrote.SOURCEThe study was led by Hermon Eyob Fesseha, University of Eastern Finland, Kuopio, Finland. It was published online on September 03, 2026, in European Heart Journal.LIMITATIONSThe retrospective registry-based design precluded causal inference. Digitally interpreted ECGs may have misclassified some rhythms and did not distinguish between different subtypes of AF or AFL. The rate of stroke may have changed over time as patients aged, comorbidities progressed, or arrhythmias transitioned between AF and AFL, and these changes were not fully captured in the analysis.DISCLOSURESThis study received support from the Aarne Koskelo Foundation, Finnish Foundation for Cardiovascular Research, Sigrid Jusélius Foundation, and other sources. Several authors disclosed receiving research grants from funding sources and serving as speakers, consultants, advisory board members, or stockholders in multiple companies.This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.