What is atrial fibrillation?
Atrial fibrillation is a rapid and non-regular heart beat of heart muscle tissue. The heart does not pump as effectively as it should when it is in this irregular rhythm. The top chambers called atria twitch instead of pump and it makes the heart much less effective. For a more in detailed description of normal heart physiology visit Anatomy & Physiology. The atria normal pump at a rate between 60-100 at resting state. In atrial fibrillation, the heart twitches at 300-400 times per minute. Signals travel to the “relay center” in the middle of the heart and some eventually reach the ventricles. In atrial fibrillation, the heart rate can reach up to 180’s in normal hearts. At this fast speed, the heart cannot perform its job efficiently, and you may feel significant symptoms.
Causes of atrial fibrillation
Atrial fibrillation is considered a disease of the aging. It is most common in patients over age of 65. However, atrial fibrillation may affect much younger patients. There are many causes of this common arrhythmia. The risk factors are: age; history of heart failure; history of mitral valve disease (both mitral valve stenosis and mitral valve regurgitation); electrolyte imbalances such as hypomagnesemia, hypokalemia, disorders in calcium, and disorders in acid/base levels; pulmonary diseases such as COPD, emphysema, bronchitis, severe uncontrolled asthma, pulmonary embolism, and pulmonary tissue disease; any other valvular disorder such as aortic stenosis or aortic regurgitation, tricuspid stenosis and tricuspid regurgitation, pulmonic stenosis or pulmonic regurgitation. By far the most common cause of atrial fibrillation is age and heart failure. In general, any medical condition that irritates/dilates the atria can cause atrial fibrillation.
Symptoms of atrial fibrillation
Symptoms for atrial fibrillation are typical of any other tachyarrhythmia. Most commonly, patients complain of palpitations, extra beats, dizziness, passing out (syncope), feeling tired, fatigue, racing heart, and malaise. The interesting thing of this most common arrhythmia is that some patients feel like the world is going to end (extreme malaise, palpitations, racing heart) and some do not feel symptoms at all. As doctors, it is easier to find this rhythm when patients have symptoms because we can look for it. When patients do not feel the arrhythmia, it is difficult to detect.
Treatment of atrial fibrillation
Treatment of atrial fibrillation is divided into 2 arms. One is controlling the rate or rhythm, and the other is thinning the blood.
Determining if the rate or rhythm should be target of treatment
For most patients, simple medicines may help symptoms a significant amount. Primarily, patients are usually given medicines to control the rate. Controlling the rate is called “rate control of atrial fibrillation”. These medicines are:
- beta blockers (most common: metoprolol, atenolol, carvedilol)
- calcium channel blockers (diltiazem, verapamil)
- digoxin (usually in patients with heart failure)
In patients that require rhythm control (select population), there are a combinations of treatments including medicine and procedures that can achieve this. In rhythm control we try to restore the heart into regular and normal rhythm. “Rhythm control of atrial fibrillation” include any combination of the following:
- anti-arrhythmic: sotalol, dofetilide, flecainide are most common
- beta blockers: see above
- calcium channel blockers : see above
- procedure based: atrial fibrillation ablation, AV nodal ablation, direct current cardioversion (DCCV)
Determining risk of stroke
Patient with this tachyarrhythmia are at risk for stroke. A simple scoring system is used to determine the risk of stroke. This is called the CHADS2 scoring system:
C : Congestive heart failure (history of heart failure, systolic or diastolic; or left ventricular ejection fraction of 40% or less)
H : Hypertension (history of hypertension, treated or not; on pills for hypertension)
A : Age >75
D : Diabetes (Type I or Type II Diabetes – treated with pills or insulin, or not treated at all
S : Stroke (history of stroke – ischemic or hemorrhagic; or history of TIA – also known as mini stroke)
All conditions above receive 1 point except for the “S” which receives 2 points. For example : a patient with history of hypertension and TIA would have a total of 3 points (CHADS2 = 3).
If your total is 2 or above, you would benefit from full dose anticoagulation. Full dose anticoagulation means you should be on warfarin/Coumadin, Eliquis, Pradaxa, or any other newer agent. If your total is 0 or 1, you would most benefit from just aspirin alone (it must be a full dose aspirin, ie 325mg of aspirin daily). Of course, this decision would be made by your doctor by weight risks and benefits of either treatment.