Unexplained Stroke? Blame it on silent Atrial Fibrillation

Posted by: admin on: February 15, 2012

Ischemic stroke in elderly patients with hypertension and those with pacemakers seems to be attributed to silent atrial fibrillation say researchers in a study .


Subclinical atrial fibrillation is relatively common among patients with pacemakers or implantable cardioverter-defibrillators (ICDs) and is associated with a higher risk of stroke or systemic embolism, researchers found.

In older patients with hypertension but no history of atrial fibrillation, 10.1% had a subclinical atrial tachyarrhythmia within three months of getting their implanted device, according to Stuart Connolly, MD, of McMaster University in Hamilton, Ontario, and colleagues.

Those who did were more than twice as likely to have an ischemic stroke or systemic embolism over two-and-a-half years of follow-up. “Until clinical trials targeting the population with short, asymptomatic episodes of high atrial rate are carried out, the current evidence simply does not address the question of whether treatment with warfarin or other anticoagulants is justifiable for the asymptomatic patient who has had a six-minute episode of atrial fibrillation,” he wrote.

About one-quarter of  ischemic strokes are unexplained, and subclinical atrial fibrillation is believed to be a major culprit. Pacemakers can detect subclinical episodes of rapid atrial rate.

To examine the association between these subclinical atrial tachyarrhythmias and clinical outcomes, Connolly and colleagues started the ASSERT study, which included 2,580 patients 65 and older enrolled from 23 countries. All of the patients had hypertension, either a pacemaker (95%) or ICD (5%) placed recently, and no history of atrial fibrillation.

The researchers monitored the patients for three months with their implantable devices to detect subclinical atrial tachyarrhythmias, defined as episodes involving an atrial rate greater than 190 beats per minute for more than six minutes. Follow-up for clinical events lasted for an average of two-and-a-half years.

Of the 51 patients who had an ischemic stroke or systemic embolism, 11 had a subclinical atrial tachyarrhythmia and none had clinical atrial fibrillation in the first three months.

A second objective in the study was to determine whether continuous atrial overdrive pacing influenced clinical outcomes.. However, the study was underpowered to make firm conclusions about overdrive pacing outcomes.

Connolly and colleagues noted that only 15.7% of patients with subclinical atrial tachyarrhythmias developed clinical atrial fibrillation, “suggesting that there can be a lag between subclinical events and clinical detection.”

The investigators said that patients with pacemakers may have a higher prevalence of subclinical atrial tachyarrhythmias than other high-risk populations, suggesting the findings are not generalizable. However, previous studies have suggested that other elderly populations have a high prevalence of subclinical atrial fibrillation, they said.

Ref: https://mail.google.com/mail/?shva=1#inbox/134d1eea521fb373

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