Atrial fibrillation, or AFib, is a quivery, fluttery heartbeat. You might also hear the doctor call it arrhythmia. It means your heart’s normal rhythm is out of whack. Because your blood isn't moving well, you're more likely to have heart failure. That's when your heart can't keep up with your body’s needs. Blood can also pool inside your heart and form clots. If one gets stuck in your brain, you can have a stroke.
What happens in AFib? Normally, the top part of your heart (the atria) squeezes first, then the bottom part (the ventricles). The timing of these contractions is what moves the blood. When you have AFib, the electrical signals that control this process are off-kilter. Instead of working together, the atria do their own thing.