International
Stroke Conference 2012
NEW ORLEANS — Almost 20% of strokes attributed to unknown causes
were related to short episodes of atrial fibrillation, according to results of
a study presented here.
Researchers examined the medical records of 156 patients (mean age, 68.5
years) who underwent monitoring with Mobile Cardiac Outpatient Telemetry
(CardioNet) no more than 6 months after a stroke or transient ischemic attack,
most of them for 21 days. Ninety-seven percent were not taking prescription
anticoagulation drugs. Of the 156 patients, 17.3% had one or
more paroxysmal AF episodes during the monitoring; this number increased over
time. Nearly 4% experienced an episode of paroxysmal AF in the first 2 days;
9.2% at 7 days; 15.1% at 14 days; and 19.5% at 21 days (P<.05), after
accounting for those who had stopped monitoring early. Two-thirds of the
episodes lasted less than 30 seconds; 26% lasted more than 30 seconds; and 7.5%
were persistent, Daniel J. Miller, MD, senior staff neurologist at Henry
Ford Hospital in Detroit, Mich., said at a press conference.
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Daniel J. Miller
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“We found that detection [of paroxysmal AF] continued … all
the way to 21 days, with statistically significant increases between those time
periods, showing that you need to continue monitoring past those time points in
order to capture the events. A minimum of 21 days would be required to capture
these events,” Miller said.
Premature atrial complex identified on baseline electrocardiogram held
the strongest correlation with paroxysmal AF (P=.001), the researchers found.
Patients identified at study entry with premature atrial contractions were 13.7
times more likely to have paroxysmal AF compared with those without the
condition. Excluding patients who suffered a transient ischemic attack,
premature atrial contractions in stroke survivors increased their risk for
paroxysmal AF to 17 times.
The researchers identified other risk factors for patients with stroke
or TIA. Women had 6.2 times the risk for
paroxysmal AF compared with men; in women with stroke alone,
the risk was 4.6 times higher. Other risk factors include an increased left
atrial diameter, reduced left ventricular ejection fraction and increases in a
patient’s NIH Stroke Scale score.
Approximately one-third of all strokes do not have a known cause.
Paroxysmal AF carries a very high risk for future stroke, Miller said.
“Future study is needed to determine the length of monitoring
beyond 21 days and to investigate the exact association with the short episodes
of AF and their risk for recurrent stroke in these patients,” he said.
– by Katie Kalvaitis
For more information:
Disclosure: Dr. Miller reports no relevant financial disclosures.
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Larry B. Goldstein
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More and more studies, including at least a half dozen here at the
International Stroke Conference, are showing that prolonged cardiac monitoring
detects AF in a not-insignificant proportion of patients with otherwise
cryptogenic stroke. That is particularly important because a patient who has
had a stroke and documented AF is at high risk for recurrence and should
generally be treated with an anticoagulant, be it with warfarin or one of the
newly FDA-approved agents. We have seen a number of reports now with patients
who have had mobile cardiac monitoring that stops at around 21 days, but we do
not know the optimal duration of monitoring. Preliminary data from Denmark
presented at the ISC used an implantable cardiac monitoring device and showed
that the yield was not great within the first 21 days, but researchers found
more and more episodes [of AF] later. For cardiologists, it is important to
appreciate that many cases of so-called cryptogenic stroke may not be
cryptogenic. This may be particularly true in patients with seemingly
cryptogenic stroke who are also found to have a patent foramen ovale.
– Larry B. Goldstein, MD, FAAN,
FAHA
Cardiology Today Editorial Board member
Disclosure: Dr. Goldstein reports no relevant
financial disclosures.