Atrial fibrillation has two main problems and then lots of variations.
1. Rapid heart rate.
2. Increased stroke risk.
When the atria start fibrillating, which is pretty much twitching, the ventricles usually try to keep up. Normal heart rate is 60-100. Most people tolerate going slow and usually we don't much care if their heart rate is 50, unless the person is not tolerating it or they have a new heart block. In atrial fibrillation, the heart can go at 120 or 180 or over 200. Mostly people do not tolerate that for very long. If they are elderly or have coronary artery disease, it can trigger a heart attack because the fast speed does not pump blood into the coronary arteries or anywhere else very well.
Sometimes the ventricles go off on their own and so atrial fibrillation can have a normal heart rate or even a slow one.
Some people go in and out of atrial fibrillation, and this is called paroxysmal atrial fibrillation.
Medicines to slow rate include calcium channel blockers (cardiazem and others), beta blockers (atenolol, metoprolol and propranolol. The cardiologists also use sotolol, which has to be taken a certain number of hours apart. And there are others.) and digoxin. Digoxin is from foxglove and is an old medicine. The Beers Criteria say that we should "consider carefully" before we use it in a patient over 65, but the advantage of digoxin is it does NOT lower blood pressure. The disadvantage is that too much can cause a heart toxic reaction, but I've have not seen this in 30 years of primary care and hospital. Next we use the antiarrhythmics, amiodarone, dronedarone, flecainide, propafenone, others that I as a primary care physician would not start.
The people with paroxysmal atrial fibrillation can be very tricky. They may need their heart slowed when they are in atrial fibrillation but when they convert to sinus rhythm, the medicine that slows them may work too well. They may have too slow a heart rate or too low blood pressure. Sometimes they need a pacemaker.
When do people go into atrial fibrillation? Often when I was still doing inpatient, it's the emphysema and COPD patients, in the ICU, getting albuterol nebs every two hours for their lungs. Albuterol is related to adrenalin, so my impression is that half of them go off into atrial fibrillation. Lung disease irritates the heart and the heart responds with this weird rhythm. I am wondering if we will see a huge spike in atrial fibrillation from marijuana, legal in my state. I am not part of the experiment. I value my lungs and heart.
The second problem is stroke risk. Atrial fibrillation lets the blood pool in the atria and pooled blood tends to want to clot. Then clots get pumped all over, including to the brain. There have been different formulas for deciding what the stroke risk is and whether to anticoagulate someone to reduce the risk of stroke. In the US, the Chads2 is here: https://www.mdcalc.com/chads2-score-atrial-fibrillation-stroke-risk.
For anticoagulation, we used to pretty much have warfarin (coumadin) and aspirin. Warfarin has also been used to kill rats, by giving them too much. Too much means bleeding. Warfarin works well, but the dose is different in every person and pretty much ANY new medicine, including over the counter, screws it up and sends the level high or low. Sulfa drugs send it very high. The minimum testing to track warfarin is once a month. If people won't test, they need to be taken off. Warfarin cuts the stroke risk by half, while aspirin cuts it by a quarter. Better than nothing.
There are three fairly new anticoagulants: Pradaxa (dabigatran), Xarelto (rivaroxaban), and Eliquis (apixaban). I don't leap on the bandwagon. The problem is that they are NOT reversible if someone starts bleeding. Warfarin can be reversed with a vitamin K shot. The new drugs don't need the regular monitoring. The drug companies tend to test them in a fairly narrow ideal group. Once they are approved, the side effects and problems tend to go up because they get used in a less than ideal group. I am not an ideal patient, are you?
If someone shows up in an ambulance in atrial fibrillation with chest pain and shortness of breath and their blood pressure is dropping: that is unstable atrial fibrillation and they get shocked to get them out. Anesthesia first iv. This runs the risk of them sending clot when they convert and having a stroke, but if they were having a heart attack anyway there isn't much choice.
We also shock people out of atrial fibrillation electively, that is, scheduled. They are to be on an antiarrythmic and an anticoagulant for a month first, then to the hospital for a shock. We used to look at measurements of the atria in the heart and if it was not dilated, the patient might be converted back to sinus rhythm. That turns out to not be a good indicator. With an antiarrythmic, the person may stay in sinus rhythm and be able to get rid of the anticoagulant. But sometimes they go back. Rats.
Another treatment is ablation, where a wire is threaded into the heart and cells are burnt to make the aberrant electrical impulses go away. This is a surgery. It works when it works but it doesn't always.
The Mayo Clinic site* lists many sorts of heart disease as causing atrial fibrillation. That may be so, but it is smokers, smokers, smokers. And one in four adults in the US still smokes or uses tobacco. Age is a big factor with 70% of the people with atrial fibrillation age 65-85, women starting five years later than men. Currently there are around 3 million US people with atrial fibrillation. Also alcohol, caffeine, stress and any heart or lung disease.
Stop smoking (not pot either!), exercise, eat a healthy diet, lower stress, minimal alcohol and other drugs. You too can put your cardiologist out of business.
https://www.fda.gov/drugs/newsevents/ucm405148.htm
http://circ.ahajournals.org/content/125/2/381
http://www.acc.org/latest-in-cardiology/articles/2014/07/18/15/12/ten-pearls-for-the-use-of-antiarrhythmic-drugs-for-atrial-fibrillation
*https://www.mayoclinic.org/diseases-conditions/atrial-fibrillation/symptoms-causes/syc-20350624