How long will it take for a blood clot to form during paroxysmal atrial fibrillation?

Paroxysmal Afib: Paroxysmal atrial fibrillation means that it comes on suddenly and then often goes away. Sometimes people can't tell, so it's often recommended to use anticoagulation such as Aspirin or coumadin (warfarin). When and if a clot will form is an inexact science, but is determined by other risk factors, ultimately with your participation in the decision of whether to take medication or not.

It Varies: It depends on lots of things - is the patient on a blood thinner (it would take longer)? Most people think it takes at least 48 hours, but some studies have show an increase in stroke with as little as 5 hours of atrial fibrillation.