A new type of technology that precisely targets the causes of irregular heart rhythms in patients with atrial fibrillation has the potential to nearly double the success rate of treating the condition, according to a landmark study published online in the Journal of the American College of Cardiology this week. The study shows the new targeting method achieved an 86% improvement on the current treatment. Atrial fibrillation is the most common type of arrhythmia, a condition where disorders in the heart's electrical system cause disturbances in the speed or rhythm of the heartbeat. There are about 5 million Americans living with the condition.