Every 40 seconds, someone in the United States has a stroke -- a sudden disruption in the brain's blood supply that is one of the leading causes of death in this country. While many survivors find out what caused their stroke, many others are released from the hospital without ever learning what was behind theirs.
A new report, presented at the American Heart Associations' International Stroke Conference on Thursday, may help lend some clarity to that issue.
Nearly 20 percent of the strokes with unknown causes are linked to short periods of erratic heart rhythms, the study suggests. Those episodes, the researchers argue, could be detected with proper monitoring and could also be better treated with anticoagulants.
The research has not yet been published in a peer-reviewed journal and should be regarded as preliminary. Researchers relied on the medical records of 156 patients who underwent heart monitoring for approximately three weeks following a stroke or mini stroke, which occurs when there is a temporary stoppage of blood flow to the brain, resulting in symptoms that mirror a full-blown stroke, but leave no permanent disability.
The individuals were hooked up to a pocket-size device that can detect paroxysmal atrial fibrillation or "PAF" -- occasional periods in which a person's heart does not beat efficiently and that may last for seconds or days. The episodes may go unnoticed by the person experiencing them, but past research has suggested they may nonetheless cause small blood clots to form in the heart, leading to stroke.
"Approximately one third of the strokes [in the U.S.] are of unknown cause," said study researcher Dr. Daniel Miller, a senior staff neurologist at Henry Ford Hospital. He explained that the episodes of irregular heart rhythm that may be behind such strokes may not be seen when patients are first evaluated.
"It comes and goes," Miller continued. "We won't know that it's there unless we try prolonged cardiac monitoring."
Monitoring revealed that of the approximately 150 patients in the new study, 17 percent had one or more PAF episodes. Those who were identified at the start as having atrial contractions -- which a press release for the study described as "the most common type of erratic heartbeats" -- were nearly 14 times more likely to have PAF.
The findings, Miller said, suggest at-risk individuals should seriously consider possible evaluation and treatment.
"If you have had a stroke or [mini stroke] of unknown cause and have not had prolonged cardiac monitoring with a device similar to this, you may want to consider getting this procedure done," he told HuffPost. "If you can ID this irregular rhythm, you can be put on specialized treatment and decrease your risk of stroke by 40 percent over aspirin alone."
Indeed, according to the presentation, several new anticoagulants have been approved by the Food and Drug Administration to help combat erratic heart rhythm -- treatments that may be far more effective than daily aspirin therapy. Aspirin is often recommended after a heart attack or stroke and helps lower risk of future cardiovascular events by interfering with the blood's clotting mechanisms.
But the authors of the new study write that "the importance of PAF to patients" is still a subject of debate among stroke specialists, and Miller said that when it comes to very short episodes in particular, researchers are not agreed on what they might mean in terms of stroke risk.
"If I were being perfectly scientifically rigorous, I would say, 'Yes, there are questions left to answer,'" said Dr. Patrick Lyden, chair of the department of neurology at Cedars-Sinai Medical Center. "But as a bedside physician, I have to take a stronger position and say that, right now, we should be taking a much harder look at atrial fibrillation and treating it."
Lyden cautioned that the results of the presentation only apply to patients who have had a stroke and do not know the cause -- not the general public. But for those people and their health care practitioners, he said, the findings are a kind of call to action.
"We know there's a lot of stroke out there and we know a lot of atrial fibrillation patients are not taking blood thinners," Lyden said. "That's a huge problem and it's inexcusable -- a failure of the medical community, not patients."