Patients with silent atrial fibrillation are at a risk of suffering from subsequent stroke, according to the Asymptomatic AF and Stroke Evaluation in Pacemaker Patients and the AF Reduction Atrial Pacing Trial (ASSERT).
We all know that the heart beats continuously at a regular rate and rhythm. The upper chambers of the heart are called the atria (single, atrium) and the lower chambers called the ventricles. The impulse for the heart beat starts in a group of cells called the SA node located in the right atrium. This causes the atria to contract and empty the blood into the ventricles. The impulse also reaches another point called the AV node that is located between the atria and the ventricles. The impulses from AV node are carried through the ventricles allowing them to empty the blood.
AdvertisementIn atrial fibrillation, the impulses start at a point outside the SA node. This causes irregular contractions of the atria. There is loss of coordination between the contraction of the atria and the ventricles, resulting in variable and irregular amount of blood leaving the ventricles.
The pumping activity of the atria is thus disturbed in atrial fibrillation, resulting in pooling of blood in the atria. This stagnation of blood can result in the formation of blood clots. The blood clots may travel to the brain resulting in stroke.
Atrial fibrillation can cause symptoms of chest pain and sometimes heart failure. However, in some patients, it may not cause any symptoms at all. This subclinical atrial fibrillation can be detected with the help of pacemakers or defibrillators.
A recent study was conducted on 2580 patients of 65 years or older, suffering from hypertension but no obvious atrial fibrillation, with an implanted pacemaker or defibrillator. These patients were followed up for a mean duration of 2.5 years.
The study found that patients who suffered from subclinical atrial arrhythmias were at an increased risk of nearly two and a half times of suffering from stroke or embolism (presence of a clot in the blood) during the follow-up period.
Thus, atrial fibrillation that does not cause symptoms should not be ignored. Further studies are required to see if treatment with blood thinners will help to prevent stroke in these patients.
Reference: 1 Subclinical Atrial Fibrillation and the Risk of Stroke; Jeff S. Healey et al. N Engl J Med 2012; 366:120-129.