@susieq1957 All the beta blocker is meant to do is to keep a lid on the heart rate when you ARE fibrillating. Any sustained HR over 100 beats per minute should be tended to at an ER if it goes any longer than 24 hours. The reason is that a rate higher than about 100 indicates RVR (rapid ventricular response). You can have a high atrial rate and live for years, but your ventricle needs a break and can't run a race 24/7. It needs rest, which it can't do AND keep up with the more rapid atrial rate if the atrium is fibrillating. So the beta blocker helps to keep the rate down, and it helps to keep the force lower for each contraction. And yes, some people find their BP gets too low and that their HR goes to low when on beta blockers, almost dangerously low. So, the cardiologist needs to know this if it happens. Some say that a beta blocker will also help with the arrhythmia, but it is more about rate control. It's not designed to be an anti-arrhythmia drug like flecainide, Multaq, propafenone, Sotalol, or amiodarone.