Irregular heartbeat can lead to silent strokes, also known as silent cerebral infarctions (SCIs).
Atrial Fibrillation (Afib) can double the risk of silent strokes, in addition to making other strokes more common. Stroke risk has been linked to greater incidence of dementia and cognitive impairment in earlier studies. These includes studies showing people experiencing Afib suffer clinically evident stroke four to five times more often than those without the condition. Worse average outcomes following strokes were also seen among patients with Afib.
One challenge to researchers was that methods of diagnosis and record-keeping were not consistent among the investigations. This latest meta-study examined records and results from nine previous studies, totaling 5,317 subjects. Of these, four used computed tomography (CT) to examine for lesions consistent with SCI, while the remaining investigations utilized magnetic resonance imaging (MRI).
"MRI is by far the most sensitive imaging we have to look for silent cerebral infarctions, but even within the MRI studies there were variations," Jeremy Ruskin of Massachusetts General Hospital in Boston, said.
Over 2.7 million people in the United States experience Afib. As that condition is the most common arrhythmia condition among seniors, diagnoses are expected to rise to between 5.6 and 12.1 million cases in the next 35 years.
Research published in 2013 suggests a link between Afib and SCI may be even more likely than normal in patients suffering from diabetes.
"[Atrial Fibrillation] occurs if rapid, disorganized electrical signals cause the heart's two upper chambers - called the atria - to fibrillate [quickly contract]... [Blood] isn't pumped completely into the heart's two lower chambers, called the ventricles. As a result, the heart's upper and lower chambers don't work together as they should," the National Heart, Lung and Blood Institute reported on its Web site.
Normal heartbeats are driven by electrical signals that start in the sinoatrial (SA) node, near the top of the organ, and travels downward. In patients with Afib, these signals originate in surrounding areas of the heart, and follow an irregular path.
Study of the role of Afib on SCI may, one day, allow researchers to the predict larger strokes as well as death. Damage done by SCI events could also prove to be the driving cause of cognitive impairment, and Afib tests could help detect patients at risk.
Along with the nine studies incorporated into the final meta-analysis, the researchers also initially examined two additional studies which diagnosed SCI events through autopsies. However, those investigations were disqualified from the final analysis due to questions regarding methodology.
The role of atrial fibrillation on stroke risk was detailed in the journal Annals of Internal Medicine.
