According to the Framingham Heart Study, people with AF have a 3 to 5 times greater risk of stroke, especially individuals who are older than 65, have already had a stroke, or have high blood pressure, diabetes or congestive heart failure. During an episode of AF, the heart muscle does not contract as it normally does to force open the heart valve through which blood passes from the atrium to the ventricle. The valve opens passively, but some blood may not pass into the ventricle as it should. Even small blood clots can cause problems if they leave the heart and are released into the general circulation. They may clog arteries in the body and disrupt the blood supply to vital organs.
Stroke happens when a clot interrupts the blood supply to the brain.
Sometimes, AF also can damage heart muscle, alter the normal electrical signals to the heart and change the patterns of contraction and relaxation of heart muscle. This is known as electrical remodeling . If your pulse is faster than 100 beats per minute and irregular, AF is suspected. The diagnosis can be confirmed with an ECG a simple, painless test that records the electrical activity of the heart through electrodes that are pasted temporarily to the skin of the chest. An ECG often is performed in your doctor s office, using a machine that prints out a graph showing how different parts of the heart are functioning.