What causes A-fib?
A-fib is caused by a problem with the heart’s electrical system. With A-fib, most electrical signals start from places other than the SA node. This makes the right atrium and left atrium beat very fast and with an irregular rhythm. This irregular beating is called fibrillation. For some people, A-fib is constant. For others, it comes and goes. A-fib occurs most often in people older than 65. Older people are more likely to have medical conditions that increase the risk of A-fib, like heart disease and high blood pressure.