American Heart Association Atrial Fibrillation American Heart Association American Heart Association atrial fibrillation 2.7 million people American Heart Association atrial fibrillation irregular heart rhythms atrial fibrillation quivering or irregular heartbeat Atrial Fibrillation 2.7 million people American Heart Association American Heart Association atrial fibrillation American Heart Association American Heart Association atrial fibrillation American Heart Association atrial fibrillation 2.7 million people irregular heart rhythms atrial fibrillation The American Heart Association American Heart Association 2.7 million people atrial fibrillation Atrial Fibrillation What is Atrial Fibrillation (AFib or AF)? atrial fibrillation