You expected to sail through your yearly check-up. What you didn’t expect was a diagnosis of a heart rhythm problem called atrial fibrillation.
Atrial fibrillation occurs in about 1 percent of adults in their 60s. The incidence rate rises with age after that, with about 10 to 12 percent of people in their 80s having atrial fibrillation.
Atrial fibrillation may or may not cause symptoms. Either way, it can lead to development of blood clots in the heart that can break off and travel to the brain, where they can disrupt blood supply and cause a stroke.
About 15 percent of strokes are attributed to atrial fibrillation — and that number may be higher as undetected atrial fibrillation may be responsible for some of the roughly 25 percent of strokes that have no identifiable cause.
Whether you feel symptoms or not, it’s important to follow through with recommended treatments. These may include medications or surgery designed to help control or reset your heart rhythm, in addition to anti-clotting medications to prevent stroke.
A heartbeat starts with an electric signal from the heart’s natural pacemaker, the sinoatrial (SA) node. This signal passes through the heart’s upper chambers (atria). The signal causes the atria to contract, squeezing blood into the heart’s two lower chambers (ventricles). A split second later, the signal passes through an electrical checkpoint — the atrioventricular (AV) node — that connects the atria and ventricles. This causes the ventricles to contract, pumping blood to the body.
Atrial fibrillation occurs when chaotic electrical signals in the heart’s atria cause the atria to beat irregularly and fast — so fast that they don’t really beat. Instead, they quiver (fibrillate) as they race at 300 to 400 beats a minute. The heart can still pump blood to the rest of the body, but less efficiently.
The chaotic electrical signals from the atria bombard the AV node. The AV node blocks many of the extra signals from reaching the ventricles, but often some get through. This causes the ventricles to beat faster than normal. The average resting heart rate is 60 to 100 beats a minute. People with atrial fibrillation may have an irregular heartbeat in the range of 100 to 175 beats a minute.
Atrial fibrillation can cause lightheadedness, decreased blood pressure, weakness, shortness of breath, heart palpitations, confusion and chest pain. Symptoms may occur in periodic episodes lasting for a few minutes to a week before stopping on their own. They can also occur more persistently or even continually. This is more likely to occur in those with some sort of underlying heart disease.
Diagnosis of atrial fibrillation involves one or more tests to measure the electrical impulses given off by your heart. Imaging tests of your heart may be done to look for structural problems — such as damage from heart disease or heart failure.
Blood tests, a physical exam and other testing may be done to look for any underlying medical conditions — such as excessive thyroid hormone production — that may be triggering the heart rhythm problem.
Treatment for atrial fibrillation often starts with medication to prevent blood clots. Additional treatment decisions involve consideration of factors such as how long you’ve had atrial fibrillation, what the underlying causes may be and how bothersome symptoms are. The worse the symptoms, the more aggressive your treatment may be.
Sometimes, treating an underlying condition can return the rhythm to normal. Otherwise, the main nonsurgical choices are:
- Resetting your heart’s rhythm (cardioversion) — This is the ideal treatment because it resets the heart rhythm to normal, which also means that your heart rate will normalize as well. About 30 to 40 percent of people treated with cardioversion retain heart rhythm control for at least one year. This may not seem like a great success rate, but it’s often worth a try, especially if you have symptoms or if it’s the first time you’ve had the problem. The longer you’ve had atrial fibrillation, the less likely cardioversion will work.Cardioversion to restore normal sinoatrial rhythm can be attempted using anti-arrhythmic drugs. Electrical cardioversion can also be performed. In this brief procedure an electrical shock is delivered to your heart. The shock stops your heart’s electrical activity momentarily. When your heart begins beating again, the hope is that it resumes its normal rhythm.
If your heart rhythm returns to normal with either method, doctors often prescribe oral anti-arrhythmic drugs to help maintain a normal rhythm. Commonly used drugs include amiodarone (Cordarone, Pacerone), dofetilide (Tikosyn), dronedarone (Multaq), flecainide (Tambocor), propafenone (Rythmol) and sotalol (Betapace).
These drugs can cause side effects, such as nausea, dizziness and fatigue. Side effects are sometimes serious enough to prompt taking a different direction with therapy.
- Controlling your heart rate — When your atrial fibrillation can’t be converted to a normal rhythm, the goal may switch to improving symptoms by slowing the rate at which your ventricles are beating. This can be done with medications, such as digoxin (Lanoxin), calcium channel blockers or beta blockers. Heart rate control is done in conjunction with taking anti-clotting medications.
Sometimes, using a drug to maintain a normal heart rhythm or heart rate doesn’t work well — or side effects of a drug aren’t tolerable. An alternative option may be a surgical procedure called radiofrequency ablation.
In this, one or more tubes (catheters) are inserted in a vessel near your groin, threaded up to your heart and used to burn areas of tissue within the atria. This causes scarring of the tissue that disrupts and stops erratic electrical signals. In some cases, other types of catheters that can freeze areas of heart tissue are used.
Radiofrequency ablation stops atrial fibrillation for at least one year in about 75 to 85 percent of people who have occasional episodes. It decreases it in about 10 to 20 percent of people whose atrial fibrillation is continual.
A surgical maze procedure is another way to achieve a similar result, but it requires open-heart surgery. Several precise incisions — or areas of burned or frozen tissue — are made in the atria. This results in scar tissue that disrupts and blocks extra electrical signals. It’s usually reserved for people who don’t respond to other treatments — or it may be done during another open-heart surgery such as a coronary artery bypass procedure or heart valve repair.
When it comes to controlling heart rate — but not atrial rhythm — the main surgical option involves destroying the AV node. This procedure is done using catheters inserted through a leg vein. With the AV node destroyed, electrical signals don’t pass to the ventricles. The atria continue to fibrillate, which makes it necessary to take anti-clotting drugs to prevent stroke. A pacemaker is implanted to establish a normal ventricle rhythm.
Addressing stroke riskWhen the atria can’t pump blood effectively, blood can pool and form clots. If a clot breaks loose, it may be pumped into your bloodstream. The clot can travel to and block an artery leading to the brain, causing a stroke.
The following factors raise your risk of stroke with atrial fibrillation:
- Age. The highest risk level is older than 75.
- High blood pressure.
- Heart failure, cardiovascular disease or heart valve problems.
- Previous stroke.
Your doctor will likely prescribe some form of anti-clotting medication, such as aspirin or warfarin (Coumadin), or possibly one of the newer anti-clotting drugs dabigatran (Pradaxa) or rivaroxaban (Xarelto). Aspirin reduces stroke risk about 20 percent, while warfarin reduces stroke risk by 60 percent. Dabigatran and rivaroxaban are similar to warfarin in their ability to prevent stroke.