The New York Times (6/26, O’Connor) “Well” blog reports that “two major studies suggest that many strokes of unknown origin (i.e. cryptogenic strokes) — up to a third — may stem from atrial fibrillation.”   Atrial fibrillation  (AF) is a cardiac rhythm disturbance which causes the heart to beat erratically.   “These findings are likely to encourage physicians to look more aggressively for signs of atrial fibrillation in patients who suffer strokes of unknown cause.”

Hooman Kamel, MD, Weill Cornell Medical College, New York, says that most patients with cryptogenic stroke or transient ischemic attack should undergo at least several weeks of rhythm monitoring.

Blogfinger Medical  Commentary.  By Paul Goldfinger, MD, FACC

When considering the cause of stroke, the heart is usually not directly involved.   But if that occurs,  it is usually due to a clot  (an embolism,)  originating in the heart,  traveling  to the brain . This condition  is called an “embolic stroke”  and may be due to atrial fibrillation.  Atrial fibrillation  (AF) can be chronic  (i.e. present all the time) or intermittent (paroxysmal—-  PAF)

Stroke patients receive a workup in the hospital to look for a specific cause of the stroke.   After that  initial evaluation, including heart monitoring,  up to 1/3 of stroke cases are found to  have no obvious cause—i.e. they are “cryptogenic strokes.”   But the absence of AF in the hospital does not rule out PAF as the cause of the stroke.

In the past, if we found AF in the hospital, we would soon start anticoagulation (blood thinners) to prevent clot formation. If there was no AF in the hospital,  many doctors would also get an outpatient  24 hour Holter monitor recording done.   But thanks to new extended heart monitoring technology, we now know that AF may  commonly occur intermittently, including very infrequent episodes,  last for short periods of time, produce no warning symptoms, and  can cause embolic  strokes.  So now we have the challenge of finding out if a stroke victim has undetected paroxysmal AF  (PAF,)  and that involves extended ECG monitoring of the heart’s rhythm.  Just a few days of monitoring is not enough.

This fairly new observation about PAF has awakened the cardiology community, and on June 26, 2014, two new clinical trials, one from Canada and the other from Italy, appearing in the New England Journal of Medicine, have confirmed that embolic strokes due to PAF are more common than ever thought before, and that finding those patients  with new monitoring methods may save lives by getting those individuals on anticoagulation treatment and possibly treatment aimed directly at the AF itself.

That is why the American Heart Association now  suggests that doctors order heart monitors for up to 30 days to look for evidence of “silent” PAF  (i.e. the arrhythmia occurs, but there are no symptoms such as palpitations.)  

And now, thanks to long term monitoring (for months or years) using small implantable devices that are on constant alert (Medtronic “Reveal XT”), one of those new studies  reveals that up to one third of those cryptogenic strokes are, in fact, due to parosysmal atrial fibrillation.

Medtronic implantable heart rhythm monitor. It is placed under the skin on the chest . Medtronic graphic.

The NY Times article  linked above speaks in lay terms  about these amazing monitors, and as a cardiologist interested in heart rhythm problems, this is very exciting.  As with all new medical discoveries, new answers generate new questions, and  related issues need to be investigated to identify how to best use the new technologies while keeping costs down.

Some insurance companies may not pay for the expensive implantable monitor.  In my opinion, anybody who is found to have a stroke or TIA due to AF,  should undergo an evaluation by an electrophysiologist—-a cardiologist who specializes in heart rhythm disturbances.