Thumping in the chest
The most specific symptom of AFib is the change in the pattern of your heartbeats. Many people with this condition experience moments when their heart rate suddenly increases and they become aware of each beat. It often feels like the heart is flip-flopping or pounding [3] against the chest cavity. It may feel like your heart has skipped a beat or added an extra beat.
These symptoms are often described using several medical terms. Heart palpitations describe the feeling of your heart fluttering and beating rapidly. A rapid heart rate that is typically more than a hundred beats per minute is known as tachycardia. For people with atrial fibrillation, episodes often feature heart rates as high as this.
Atrial fibrillation is considered a type of arrhythmia (irregular heart rhythm). Arrhythmia by itself is not life-threatening and you can have arrhythmia without atrial fibrillation.