Q: My doctor did an electrocardiogram last week and told me I have atrial fibrillation. What is this? Is it dangerous?
A: Blood is pumped from the heart by contraction of its two lower (ventricular) chambers. These ventricular contractions are normally preceded by contractions of the two atrial (upper) chambers and triggered by regular electrical signals from the upper chambers. Atrial fibrillation is weak, uncoordinated twitching of the atrial muscle that replaces the
usual atrial contractions.
Loss of atrial contractions leads to incomplete filling of the ventricles and reduced output of blood. Also, it causes variability in the intensity of the electrical impulses to the ventricles. As TC result, the ventricular contractions (what we feel as the heartbeat or pulse) become totally irregular and may be very rapid.
Atrial fibrillation is one of the most common disturbances of the heart rhythm and is usually caused by heart disease linked to high blood pressure, coronary artery disease or the valve abnormalities resulting
from rheumatic fever. Other types of heart diseasealso can cause atrial fibrillation.
Atrial fibrillation can kill. Heart failure may occur from the poor filling of the ventricles. In the absence of vigorous atrial contractions, blood stagnates in the atria, and clots may form to break off and cause strokes.
Atrial fibrillation can usually be stopped by drug treatment or electroshock, but it tends to recur. The incidence of stroke from emboli to the brain can be greatly reduced by the long term use of blood thinner to prevent the formation of clots.
Dr. Margolis is professor of medicine and biological chemistry at the Johns Hopkins School of Medicine and associate dean for faculty affairs at the school.