Undetected arrhythmia could underlie some wake-up strokes

By Eleanor McDermid, Senior medwireNews Reporter

Unrecognized atrial fibrillation (AF) could be a cause of some wake-up strokes, say researchers who found an increased prevalence of the arrhythmia in patients who had stroke symptoms on waking.

Patients with wake-up stroke were 3.6-fold more likely to have newly detected AF than patients who had stroke when awake, report Luciano Sposato (University Hospital, Favaloro Foundation, Buenos Aires, Argentina) and team. The association was independent of such factors as age, hypertension, stroke severity, left ventricular ejection fraction, and diabetes.

"Newly diagnosed AF could be the expression of unnoticed paroxysmal episodes of AF occurring during the night" before wake-up stroke, write the researchers in Neurology.

They note: "Circadian variations in the frequency of paroxysmal AF have… been demonstrated, with peaks occurring during night and early morning hours."

The rate of previously diagnosed AF was similar in both groups in the current study, occurring in 29.3% of 41 patients with wake-up stroke or transient ischemic attack (TIA) and 22.9% of 315 patients who had stroke or TIA when awake. However, continuous electrocardiographic monitoring of all patients for at least 3 days after admission revealed previously unsuspected AF in 17.1% of patients with wake-up stroke, compared with just 6.3% of the other group.

Patients with wake-up stroke also had poorer outcomes than those who had stroke while awake. Their average National Institutes of Health Stroke Scale scores at discharge were 6 versus 2, and 29.3% versus 10.5%, respectively, had neurologic deterioration or died while in hospital. This was despite the two groups having similar demographics, risk factors, and distribution of stroke subtypes according to the TOAST criteria.

However, the researchers note that there could be some reverse causality, with the severe strokes in the wake-up stroke group giving rise to new AF, "because infarct area is directly correlated with the odds of involving the central autonomic network with the potential of triggering cardiac arrhythmias."

The associations are worthy of investigation in a larger cohort of patients, the team concludes.

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