In the United States, stroke is the leading cause of serious long-term disability and the third leading cause of death. One of the major risk factors for stroke is an irregular heartbeat known as atrial fibrillation (AF).
An estimated 2.2 million Americans have AF and this number is expected to increase considerably in the years ahead. Already, during the past 20 years in the U.S., there has been a 66% increase in hospital admissions for AF due to a combination of factors, including an aging population, a rising prevalence of chronic heart disease, and more frequent diagnosis of AF through use of better technology.
AF in and of itself is generally not life-threatening. However, AF requires medical attention because it can result in complications, ranging from palpitations, fainting, and chest pain, to stroke and even heart failure. During AF, the heart's two upper chambers (the atria) beat irregularly resulting in chaotic quivering (referred to as "fibrillation"). When the upper chambers of the heart no longer work in unison with the lower heart chambers (known as the ventricles), the consequence may be a fast irregular heart rate, even up to 160 beats per minute. This can result in very inefficient heart pumping which can cause a drop in blood pressure (leading to fainting) or precipitate heart failure. Moreover, inefficient beating can lead to pooling and clotting of blood within the atria. If a blood clot forms inside the heart and gets pumped out, it can get lodged in an artery in the brain, resulting in a stroke. Patients with AF have two to seven times the risk of stroke compared to patients without AF, which is why people with AF are often given medications that reduce the ability of blood to clot. These anticoagulants include drugs such as warfarin (Coumadin®). Other medications for atrial fibrillation are used to either slow the heart rate (called "rate control") or convert the heart rhythm back to normal (known as "rhythm control" and "chemical cardioversion"). An electrical shock to the heart may be effective in restoring a normal rhythm in some patients ("electrical cardioversion"). Surgical or less invasive catheter-based therapies may be appropriate in selected individuals to prevent recurrences of AF.
Medical conditions that may lead to atrial fibrillation include:
heart failure
coronary artery disease
heart valve disease
previous heart surgery
obesity
stroke
hypertension (high blood pressure)
sleep apnea
diabetes
chronic lung diseases (e.g., emphysema, chronic obstructive pulmonary disease [COPD])
history of rheumatic fever
congenital heart disease
Up to one-third of people with AF have "lone AF," which means there are no clear precipitating factors for AF and there is no evidence of underlying heart or lung disease. Sometimes lone AF will run in families.
There are temporary reversible causes of AF, too, such as binge drinking of alcohol (called "holiday heart syndrome"); exposure to stimulants, such as drugs, caffeine, or tobacco; and hyperthyroidism (an overactive thyroid gland). Surgery (especially heart surgery); inflammatory disease of the heart muscle (myocarditis); inflammation of the sack that surrounds the heart (pericarditis); and pneumonia can all result in temporary/reversible AF as well.
Some people with AF have no symptoms and are unaware of their condition until their doctor discovers it during a physical examination. Individuals who do have symptoms may experience:
- an awareness of their heart beat (known as "palpitations") that can be due to their heart beating too slowly, too fast, or irregularly (some people describe a "flopping" feeling in their chest, or a sensation of skips, or sensations of pauses in the heartbeat)
- intolerance to exercise
- chest pain (especially if the heart rate is faster, and it puts undue strain on the heart)
- shortness of breath or weakness
- lightheadedness or confusion
- excessive fluid buildup in tissues (called edema)
Sometimes AF will be identified only with the onset of a stroke or a transient ischemic attack (TIA or "mini-stroke").
LIFESTYLE MODIFICATIONS AND RISK FACTOR GOALS
The best way to prevent AF from occurring is to take steps toward keeping your heart healthy. If you already have AF, then you and your family should learn how to manage cholesterol, blood pressure, and diabetes. When heart rhythm abnormalities, such as AF, are related to coronary artery disease, heart attack, or heart failure, lifestyle adjustments will also need to target the underlying disease. Physicians and their staff can provide valuable information on diet, weight control, physical activity, tobacco cessation, and other appropriate lifestyle modifications. Recommendations presented below are derived from the ACC/AHA guidelines for atrial fibrillation. It is important to remember that these recommendations may not be appropriate for all patients. It is always prudent to discuss your particular situation with your personal physician.
1. High blood pressure is a major risk factor for AF and a powerful predictor of stroke. Blood pressure should be controlled so that readings at rest consistently fall below 140/90 mmHg. In the presence of diabetes or kidney disease, resting blood pressure levels should be below 130/80 mmHg. If your blood pressure is greater than or equal to 140/90 mmHg (or 130/80 mmHg or higher if you have diabetes or chronic kidney disease), you should make lifestyle changes targeting weight control; increased physical activity; alcohol moderation; sodium reduction; and increase your consumption of fresh fruits, vegetables, and low-fat dairy products.
2. Weight management has been linked to reversing some of the damage to the heart that increases the risk of developing AF, leading experts to conclude that weight loss may decrease the chance of developing atrial fibrillation. For reducing cardiovascular risk in general, you should achieve and maintain a body mass index (BMI) between 18.5 and 24.9. BMI is a measure of a person’s weight in relationship to their height. There are many tools available online to calculate BMI, including our
own tool here on CardioSmart.org. BMI should be assessed regularly. A waist circumference greater than or equal to 35 inches (89 cm) in women or 40 inches (102 cm) in men is also worrisome, and has been shown to be associated with a higher risk of cardiovascular problems. When waist measurements are in this range, it is important to initiate lifestyle changes and consider treatment strategies for metabolic syndrome, if present. You should measure your waist circumference regularly.
3. Exercise is recommended because of its beneficial impact on hypertension, high cholesterol, and insulin resistance (predisposition to diabetes). If you have recently experienced a heart attack, unstable angina, bypass surgery, angioplasty, or you have heart failure, a medically supervised recovery program, known as
cardiac rehabilitation, may be appropriate. Before beginning an exercise program, your doctor may want to assess your condition or conduct an exercise test to guide your activity "prescription." Physical activity should be done for 30 minutes a day, for at least 5 days a week with 7 days a week being even better. Such activity can include walking, biking, swimming, gardening, and even household work.
In general, patients are encouraged to work up to 30 to 60 minutes of moderate intensity aerobic activity each day. Besides aerobic exercise, strength training 2 days a week is a good idea.
4. Dietary therapy is recommended for everyone with, or at risk of developing, cardiovascular disease. Reduce your intake of saturated fats (found mostly in animal products) to less than 7% of total calories, greatly limit the amount of trans fats (also found in animal products and most snack foods), and limit cholesterol intake to less than 200 mg per day. If you have cardiovascular disease, increased consumption of omega-3 fatty acids in the form of fish or in capsules (1 gram omega-3 per day) is recommended. Although omega-3 fatty acids have not been shown to reduce the risk of heart rhythm abnormalities, increasing the intake of these fats is a "reasonable" approach for individuals with cardiovascular disease. For treatment of elevated triglycerides, higher doses of omega-3 fatty acids are usually necessary for risk reduction.
5. Diabetes is a predictor of stroke risk in people with AF, and there is some evidence that the ability of the blood thinner known as warfarin (Coumadin®) to reduce the risk of stroke is diminished in patients with AF and diabetes. Being meticulous in regards to blood sugar control is important. Hemoglobin A1c (commonly written as HbA1c) is a blood test which reflects the average blood sugar level over a 3-month period. In patients with diabetes, and especially those with AF or coronary artery disease, lifestyle efforts and medications should be used as necessary to achieve a normal or near-normal HbA1c (less than 7%).
DRUG THERAPIES
Sometimes AF will correct or "reset" itself, but if an underlying cause can be determined, then whatever triggered the AF in the first place should be treated to reduce the risk of another episode of AF. Treating the underlying cause is especially beneficial when it’s an acute problem, such as exposure to stimulants or a viral infection, or when the problem is amenable to effective therapy. If AF is caused by an over-active thyroid gland, for example, then treating the hyperthyroidism is certainly necessary. If heart valve disease is determined to be the cause of AF, then valve repair or replacement may be required. Whether the problem causing the AF can be resolved or not, some treatment specifically for the AF is usually necessary.
1. When the goal is to revert the heart to a normal rhythm, recommended drugs include flecainide, dofetilide, propafenone, ibutilide, or amiodarone. Cardioversion with drugs is often done in the hospital. If proper heart rhythm is restored, your doctor often will prescribe a version of the same drug or a similar one as long-term therapy to prevent recurrent arrhythmias.
2. When the heart can’t be reset to a proper rhythm, then the goal may be controlling the heart rate so that it stays within a normal range (60 to 100 beats per minute). Sometimes one drug will effectively provide long-term control of heart rate in people with AF, but usually one or more drugs are necessary. Beta-blockers or calcium channel blockers are often used to maintain a normal heart rate in individuals with AF. Another drug called digoxin is used alone or combined with either beta-blocker or calcium channel blocker therapy. When these drugs don’t successfully control the heart rate or they are not tolerated, amiodarone is sometimes used.
3. If cardioversion is not successful or if the individual is at high risk of stroke (for example, they have had a previous stroke or some previous event caused by blood clots), blood thinning drugs ("anticoagulants") may be prescribed indefinitely. The most common anticoagulant is warfarin (Coumadin®). Regular follow-ups with your doctor are essential for preventing complications due to warfarin.
4. If risk of stroke is low, aspirin may be used instead of anticoagulant therapy. Aspirin at 81–325 mg daily is recommended for low risk individuals as well as those with contraindications to anticoagulation. Aspirin may be particularly effective for AF patients with hypertension or diabetes and for reducing the risk of strokes that are not caused by blood clots. Aspirin appears to prevent nondisabling strokes more than disabling strokes.
5. The cholesterol-lowering drugs known as statins help maintain normal heart rhythm in people with persistent lone AF and they decrease the risk of AF recurrence. While several types of drugs will lower cholesterol levels, the beneficial rhythm effects of statins are not just related to their cholesterol-lowering effects.
6. Beta-blockers, angiotensin-converting enzyme (ACE) inhibitors, and angiotensin receptor blockers (ARBs) may decrease the incidence of AF in people who also have reduced function of their hearts left ventricle (the main pumping chamber of the heart). These agents are beneficial because they help control heart rate, improve the function of the left ventricle, and prolong survival. Beta-blockers may be the first line of treatment to maintain rhythm in patients with a heart attack, heart failure, or high blood pressure. In patients with heart failure or left ventricular dysfunction following a heart attack, ACE-inhibitor therapy reduces the incidence of AF. Presumably, the beneficial effects of these drugs are at least partly related to their ability to lower blood pressure. If your blood pressure is greater than or equal to 140/90 mm Hg (or 130/80 mm Hg or higher if you have diabetes or chronic kidney disease), blood pressure medication will likely be necessary in addition to lifestyle modifications. It is important for everyone with high blood pressure to know that a single drug is usually not enough; at least two-thirds of individuals will require multiple medications to achieve blood pressure control.
GUIDELINE-BASED STANDARDS OF CARE: WHAT YOU SHOULD KNOW
The American College of Cardiology (ACC) and the American Heart Association (AHA) work together on an ongoing basis to publish Guidelines addressing standards of care for the diagnosis, management and prevention of cardiovascular disease. The ACC/AHA Guidelines represent a consensus of expert medical opinion, with the goal of establishing a standard on which to base cardiovascular care decisions, serving the patient’s best interests.
The guidelines are intended to help health care providers and patients make informed, best-possible decisions regarding care for specific clinical circumstances. The ACC strongly believes that adoption of these standards leads to higher quality cardiovascular care, cost-effectiveness, and most importantly, better outcomes for patients.
Please note that the ACC/AHA Guidelines attempt to define practices that meet the needs of most patients in most circumstances. However, everyone is unique, and the extent to which the guidelines apply specifically to you should be a key point of discussion between you and your cardiologist or health care provider. The ultimate judgment regarding your care must be made by you and your healthcare provider together, in light of circumstances specific to you as a patient.
Although all ACC/AHA Guideline documents are freely available, and can be downloaded from the ACC’s
Cardiosource web site, these documents are often extremely long, and written primarily for the healthcare provider. Here at CardioSmart you will find a summary of the key points from the Guidelines, written specifically with the patient in mind. We urge you to review these key points, print them out if you like, and engage your healthcare provider in a discussion of how the guidelines relate to you and your condition.
That is, after all, what being CardioSmart is all about – being empowered to work with your physician in managing your care to assure the best possible outcome!
If you’d like to read the full guidelines from which this summary is derived, please click on either of the links below:
ACC/AHA/ESC 2006 Guidelines for the Management of Patients With Atrial Fibrillation
AHA/ACC Guidelines for Secondary Prevention for Patients With Coronary and Other Atherosclerotic Vascular Disease: 2006 Update
