Atrial fibrillation is a irregular heart disease. Nearly 2.7 million U.S citizens are living with Atrial fibrillation. Atrial fibrillation (Afib) can cause blood clots by creating an abnormal and sometimes very rapid rhythm in the heart. A-fib Increases the risk of heart disease, stroke and other complications. Atrial fibrillation (or irregular heartbeat) can cause a quivering, irregular, or even fatal condition called blood clots, stroke, and other complications.