What is atrial fibrillation? Atrial fibrillation is an atrial arrhythmia where the upper chambers don’t contract normally, causing higher heart rates in the lower ventricles. The Science of Treating Atrial Fibrillation (Home Use) Lone Atrial Fibrillation Towards a Cure A Simple Guide To Ventricular Fibrillation, Diagnosis, Treatment And Related Disorders (A Simple Guide to Medical Conditions)