Atrial fibrillation (AF) is the most common heart rhythm disorder in the US. Heart rhythm disorders are disruptions in the pattern and rhythm of the heartbeat. The heartbeat is controlled by an internal electrical system that sends impulses to the heart muscle signaling it to rhythmically expand and contract, causing blood to be pumped. Sometimes the heart's internal electrical system loses its regular pattern, which can cause many different heart rhythm disorders, including AF. Click here for more detailed information on the heartbeat and the anatomy of the heart.
In AF, the electrical impulses are no longer coming from the heart's natural pacemaker (the sinus node), but from other cells in the heart's top chambers (the atria). The atria fire the electrical impulses in a very rapid and disorganized manner (called fibrillation)—more than 300 impulses per minute, compared to the typical rate of 60 to 70 impulses per minute. These rapid, disorganized impulses arrive in the heart's pumping chambers (the ventricles), causing the ventricles to contract rapidly and irregularly but not at the same rate as the atria. When the ventricles and the atria don't beat in a coordinated manner, it results in an irregular, rapid heartbeat.
AF can be continuous (persistent AF), or episodes may alternate with periods of normal heart rhythm, a condition known as paroxysmal AF. When the rhythm disturbance has lasted for more than a week, it is considered persistent AF.
How is atrial fibrillation related to heart failure?
AF can cause heart failure, and heart failure can cause AF.11, 12 It is not always clear which happens first, as it varies from person to person.
AF can cause heart failure because the rapid, uncoordinated muscle contractions of the atria and the ventricles prevent the heart from pumping blood effectively. The atria are not pumping blood into the ventricles as well as they should, and the ventricles are not filling with blood as well as they should. As a result, not enough blood is pumped to the body, causing the heart muscle to work harder to keep pumping blood efficiently. Over time, this can weaken the heart and lead to heart failure.
Heart failure can cause AF because the added strain on the heart muscle that occurs with heart failure as it tries to keep pumping enough blood can stretch and enlarge the atria, disturbing the electrical impulses and resulting in rapid, uncoordinated contractions that can limit the ventricles' ability to fill with blood.
How does atrial fibrillation affect my risk of developing heart failure?
Women with AF have an increase risk of developing heart failure. A 20-year study of over 15,000 adults (54% were women) found that women with AF had 3 times the risk of developing heart failure compared with women without AF.13 Despite the increased risk, AF accounts for a relatively small portion of heart failure cases because it's not as common as other heart failure risk factors. One study found that among 268 women who developed heart failure, AF was a risk factor in only 14 (5%) cases.14
Heart failure, in turn, increases your risk of developing AF, affecting 10% to 30% of people with long-term AF.15 In the Framingham Heart Study, women with heart failure had a 6-fold increase in AF risk.16 AF tends to occur more often in people with more severe heart failure symptoms: 50% of heart failure patients who are unable to carry out any physical activity without discomfort have AF, compared with 10% of patients whose physical activity is slightly limited at most.12 Click here for more information on how heart failure symptoms are classified.
AF seems to precede heart failure as often as heart failure precedes AF, according to one study of nearly 1500 participants 50 years and older.17 Of the women and men who developed both conditions, 41% had heart failure first, 38% had AF first, and 21% were diagnosed with both at the same time.
What can I do to prevent heart failure if I have atrial fibrillation?
There are many treatments available to improve your symptoms and prevent serious complications. The best way to keep your AF from leading to heart failure is to get your AF under control by slowing your heart rate or by restoring your heart's normal rhythm. Antiarrhythmic medications, beta-blockers, digoxin, and calcium channel blockers are used to slow the heart rate during AF, which decreases the heart's extra workload and prevents it from working too hard and enlarging.
Sometimes medications alone are not enough. Other options include:
- Cardioversion: a brief shock to the chest is used to restore normal rhythm
- Catheter ablation: in this treatment, a catheter uses radiofrequency energy to destroy small areas of tissue either in the pulmonary veins or in the AV node, stopping the abnormal rhythm. Destroying the AV node causes a permanent slow heartbeat, so the patient requires a pacemaker afterwards.
- Implantable atrial defibrillator: when AF occurs, the defibrillator issues an electrical pulse that restores the heart to its normal rhythm.
- Pacemaker: a pacemaker sends small electrical impulses to the heart muscle, substituting for the abnormal pulses of AF.
- Surgical treatment: When medication or procedures have failed to relieve chronic AF, surgery may be used as a last resort. During these procedures, incisions, radiofrequency, very cold temperatures, microwave energy, or lasers are used to selectively destroy small areas of the heart tissue, blocking the transmission of abnormal rhythms.
How do I prevent atrial fibrillation if I have heart failure?
The best way to keep heart failure from causing AF is by decreasing the heart's workload; the harder the heart has to work to pump enough blood, the higher the chances are of developing AF. The most commonly used medications to prevent atrial fibrillation in heart failure patients are angiotensin-converting enzyme (ACE) inhibitors or angiotensin-receptor blockers (ARB), which reduce the strain on your heart by expanding your blood vessels. ACE inhibitors or ARBs may prevent or delay AF in heart failure patients.18-20 In African Americans, who often don't respond as well to ACE inhibitors as whites do, adding hydralazine and isosorbide dinitrate to the standard treatment can improve survival.15