In patients with implantable devices, prolonged AF episodes raise ischemic stroke risk
In patients with cardiac implantable electronic devices, an episode of atrial fibrillation lasting at least 5.5 hours raised short-term risk for ischemic stroke, according to data published in JAMA Cardiology.
“The fact that AF raises the risk of ischemic stroke four- to fivefold and that this increased risk is largely reversible by long-term oral anticoagulants are core tenets of internal medicine. These facts are mainly based on older studies of patients with persistent or ‘heavy burden’ paroxysmal AF,” Daniel E. Singer, MD, professor of medicine at Harvard Medical School and professor in the department of epidemiology at the Harvard T.H. Chan School of Public Health and the division of general internal medicine at Massachusetts General Hospital, told Healio. “More recent studies of patients with continuous heart rhythm monitoring, mainly by cardiac implantable electronic devices, have revealed that many older patients experience infrequent and brief periods of AF. Several of these studies have found that strokes occur during periods of sinus rhythm temporally distant from a preceding episode of AF. This has led to a widespread suspicion that AF is not a direct causal risk factor but a risk marker indicating the presence of other truly causal features like a diseased left atrium (atrial myopathy).”
Patients with stroke, implantable devices
The case-crossover study included data from 891 patients from a large national electronic health record database (median age, 76 years; 65% men) with cardiac implantable electronic devices who sustained an ischemic stroke and had at least 120 days of continuous rhythm monitoring pre-stroke. These data were linked to a single-vendor database of heart rhythm records in patients with cardiac implantable electronic devices from January 2007 to March 2017.
The primary outcome was OR for stroke comparing AF 1 to 30 days before stroke with AF 91 to 120 days before stroke.
According to the researchers, 76.5% of patients had no AF episodes of at least 5.5 hours in either period, and 16% had AF episodes of at least 5.5 hours in both periods.
There were 66 patients with discordant arrhythmic states. Of these, 52 patients had at least one day with AF meeting the threshold duration in the case period compared with 14 patients with AF meeting the threshold duration in the control period (OR = 3.71; 95% CI, 2.06-6.7). The median total hours in AF for those with the threshold duration in the case period was 116.7 hours, with 44% of patients with an AF episode of 5.5 hours or more the day before stroke.
During days 1 to 5 after an AF episode, risk for ischemic stroke increased (OR = 5; 95% CI, 2.62-9.55), driven by patients with AF greater than 23 hours in one day (OR = 5; 95% CI, 2.08-12.01).
‘Definitive trial’ needed
According to Singer, a key problem with previous prospective studies using cardiac implantable electronic devices was that researchers only observed a small number of strokes. This led to inadequate statistical power, which the current study improved upon by using a larger database, he said.
“We’d be reluctant to urge physicians to change their anticoagulation practices based solely on our study, but our work does highlight the need for a definitive trial of time-delimited anticoagulation limited to covering the AF episode and a brief period after the episode ends,” Singer said in an interview. “Physicians should be aware there is uncertainty how best to use anticoagulants in patients with brief and infrequent episodes of AF.”
For more information:
Daniel E. Singer, MD, can be reached at desinger@mgh.harvard.edu.
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