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Temporal Association Between AF Episodes and Risk of Ischemic Stroke
Quick Takes
- It is unknown whether subclinical atrial fibrillation (AF) as detected on implantable cardiac devices represents a causal risk factor for ischemic stroke.
- Using an electronic health record database linked to a heart rhythm database, the investigators evaluated the temporal (time-related) association between multi-hour episodes of AF and subsequent ischemic stroke in patients with continuously monitoring implantable cardiac devices.
- An episode of multi-hour AF was associated with a more than tripling of the 30-day risk of ischemic stroke, and the risk of stroke was highest within 5 days of an episode of AF, suggesting a causal relationship in this population.
Study Questions:
To better understand the mechanism of ischemic stroke in atrial fibrillation (AF), what is the temporal (time-related) association between episodes of AF and subsequent ischemic stroke in a population of patients with implantable cardiac devices?
Methods:
This is an observational study using 10 years of data from a deidentified electronic health record database linked to a database of heart rhythm records from patients with implantable cardiac devices capable of continuous heart rhythm monitoring. The analysis was restricted to patients hospitalized with stroke who had ≥120 days of continuous heart rhythm recording pre-stroke. This is a case-crossover study, so each patient served as his or her own control, with a case period and a control period. The case period was 1-30 days pre-stroke. The control period was 91-120 days pre-stroke. A period was considered to have AF if ≥5.5 hours of AF on any given day were detected. The subjects of interest were those with discordant rhythm patterns: AF during one period but not the other.
Results:
Of 891 patients included in the analysis, 66 patients (7.4%) had discordant rhythm patterns: 52 (5.8%) had ≥1 day with ≥5.5 hours of AF during days 1-30 pre-stroke but not in the control period, and 14 (1.6%) had ≥1 with ≥5.5 hours of AF during the control period but not during days 1-30 pre-stroke (odds ratio [OR], 3.71; 95% confidence interval [CI], 2.06-6.70). When dividing the case period into 5-day epochs and comparing each epoch to a corresponding control epoch, the risk of stroke was highest on days 1-5 pre-stroke (OR for ischemic stroke, 5.00; 95% CI, 2.62-9.55).
Conclusions:
Among patients with implantable cardioverter-defibrillators (ICDs) and discordant presence of AF in the time periods remote (90-120 days) and proximate (1-30 days) to ischemic stroke, multi-hour AF was associated with a more than tripling of the 30-day risk of ischemic stroke, suggesting that AF is a causal risk factor for ischemic stroke in this population.
Perspective:
This is a well-designed observational study in a “convenience” population of patients with an implantable cardiac device capable of continuous heart rhythm monitoring and with a history of being hospitalized for acute ischemic stroke. Given the temporal association observed between AF and ischemic stroke, these results support the hypothesis that AF is causal (rather than an epiphenomenon) in the development of ischemic stroke. Because all the patients in this study had an indication for an ICD, the results of this study are not readily generalizable to a wider population.
Clinical Topics: Anticoagulation Management, Arrhythmias and Clinical EP, Prevention, Anticoagulation Management and Atrial Fibrillation, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias
Keywords: Anticoagulants, Arrhythmias, Cardiac, Atrial Fibrillation, Brain Ischemia, Defibrillators, Defibrillators, Implantable, Electronic Health Records, Ischemic Stroke, Risk Factors, Secondary Prevention, Stroke, Vascular Diseases
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