The Heart Series – A-Fib

An Overview of Atrial Fibrillation

Atrial fibrillation is one of the most common of the cardiac arrhythmias, and it can be one of the most frustrating to deal with. While atrial fibrillation is not itself life-threatening, it often causes significant symptoms. Worse, it can lead to more serious problems, especially stroke, and (in people with heart disease), worsening heart failure. Furthermore, while several treatment options are available for atrial fibrillation, it is often not entirely clear—even to heart rhythm experts—which treatment alternative is best under which circumstances.

If you have atrial fibrillation, you should try to learn everything you can about this arrhythmia—its symptoms, its causes, and the available treatments—so you can work with your doctor to decide which therapeutic approach is right for you.

This kind of rapid, chaotic electrical activity in the heart is called “fibrillation.”

When the atria begin fibrillating, three things can happen:

First, the heart rate tends to become rapid and irregular. The AV node is bombarded with frequent, irregular electrical impulses coming from the atria, and as many as 200 impulses per minute are transmitted to the ventricles, leading to a fast and very irregular heart beat. The rapid, irregular heart beat often produces disturbing symptoms.

Second, when the atria are fibrillating, they are no longer contracting effectively. So the normal coordination between the atria and the ventricles is lost.

As a result, the heart works less efficiently and may begin to fail.

And third, because the atria are no longer contracting effectively, after a time (usually after about 24 hours or so) blood clots can begin to form in the atria. These blood clots can eventually break off and travel to various parts of the body, such as the brain.

So, while atrial fibrillation itself often produces significant symptoms, its real significance is that it puts you at risk for medical conditions that can be permanently disabling or fatal.

What Causes Atrial Fibrillation?

Atrial fibrillation can be produced by several cardiac conditions, including coronary artery disease (CAD), mitral regurgitation, chronic hypertension, pericarditis, heart failure, or virtually any other kind of heart problem. This arrhythmia is also fairly common with hyperthyroidism, pneumonia, or pulmonary embolus.

Ingestion of amphetamines or other stimulants (such as cold remedies containing pseudoephedrine) can cause atrial fibrillation in some people, as well as after drinking as few as one or two alcoholic beverages—a condition known as “holiday heart.” While doctors have traditionally said caffeine also causes atrial fibrillation, recent evidence from clinical studies shows that, in most people, it does not.

Different Types of A-Fib?

Not all atrial fibrillation is the same. Some is fast, some is slow; some is intermittent, some is permanent; some causes symptoms, some does not. So in an effort to organize their thinking, doctors over the years have devised several different classification systems to describe the various “types” of atrial fibrillation. As a result, the terminology doctors often use to talk about atrial fibrillation has become potentially quite confusing.

However, in 2014 a classification system was established by the American Heart Association, the American College of Cardiology, and the Heart Rhythm Society that now should supplant all the older ones.

This classification system recognizes that atrial fibrillation is most often a progressive condition. At first, the arrhythmia usually occurs in episodes that are intermittent and brief. As time goes by, the episodes tend to become more frequent and longer-lasting. In many patients, atrial fibrillation eventually supplants the normal heart rhythm and becomes permanent.

The “type” of atrial fibrillation a person has can help the doctor make recommendations about the most appropriate approach to therapy. The further a patient’s arrhythmia has progressed toward permanent atrial fibrillation, for instance, the less likely it is that a normal heart rhythm can be restored and maintained.

The Atrial Fibrillation Classification System

Here is the current standardized system of classifying atrial fibrillation.

1) Paroxysmal Atrial Fibrillation

Atrial fibrillation is said to be paroxysmal (a medical term for “intermittent”) if it occurs in discrete episodes less than seven days in duration. In many cases, paroxysmal atrial fibrillation may last for only minutes to hours. Episodes of paroxysmal atrial fibrillation can be frequent, or quite rare.

Some patients with paroxysmal atrial fibrillation will have brief episodes that produce no symptoms and are entirely “subclinical.” This means that neither the patient nor their their doctor is aware that episodes of atrial fibrillation are occurring. In these cases, the arrhythmia is usually discovered unexpectedly during cardiac monitoring. Subclinical atrial fibrillation is important because it, like more severe cases of atrial fibrillation, can lead to stroke.

2) Persistent Atrial Fibrillation

In this second category, the atrial fibrillation occurs in episodes that fail to terminate within seven days. In order to restore a normal heart rhythm, medical intervention is most often necessary. Patients who have one or more episodes of persistent atrial fibrillation may at other times still have episodes of paroxysmal atrial fibrillation, but they are now classified as having a “persistent” arrhythmia.

3) Long-standing Persistent Atrial Fibrillation

In these patients, an episode of atrial fibrillation is known to have lasted longer than 12 months. For all practical purposes, atrial fibrillation has become the new, “baseline” cardiac arrhythmia in these patients.

4) Permanent Atrial Fibrillation

The only difference between “long-standing persistent” and “permanent” atrial fibrillation is that, with permanent atrial fibrillation, the doctor and patient have agreed to abandon further efforts to restore a normal heart rhythm and have moved on to a different treatment strategy. They have declared the atrial fibrillation to be permanent.

Valvular vs. Non-Valvular Atrial Fibrillation

A different classification for atrial fibrillation that you will commonly hear about is valvular atrial fibrillation versus non-valvular atrial fibrillation; that is, whether or not the atrial fibrillation is associated with valvular heart disease, such as mitral regurgitation.

For practical purposes, this classification is taken into account only when deciding on anticoagulation therapy to prevent stroke. Essentially, patients with valvular atrial fibrillation virtually always need anticoagulation; patients with non-valvular atrial fibrillation may not.

A Word From Verywell

The chief benefit of this classification system is that it standardizes the nomenclature, so that when doctors talk to each other about atrial fibrillation, they all mean the same thing. It helps you, too, to understand your condition.

In addition, it gives doctors some idea about how far a patient’s atrial fibrillation has progressed toward becoming a permanent heart rhythm, and thus, how likely it is that a strategy aimed at restoring a normal rhythm might be effective. Ultimately, it’ll help you and your doctor make a treatment decision that’s best for you.

Control Heart Rate, Treat A-Fib

If you have atrial fibrillation, the right treatment might be a three-prong approach that sounds counter-intuitive —allow the atrial fibrillation to persist, aim therapy at keeping your heart rate from becoming too fast (in order to control your symptoms) and take steps to reduce your risk of stroke. This is called the rate-control method. Intuitively, another method, the rhythm-control approach, which is aimed at restoring and maintaining a normal heart rhythm, sounds much better.

But in most people who have chronic or persistent atrial fibrillation (that is, they have been in atrial fibrillation all or most of the time for many weeks or months), results tend to be much better with the rate-control approach.

To a large extent, this is because rhythm control tends to be rigorous, inconvenient, ineffective and entails a relatively high risk of side effects. Also, most people who are treated with rate control do quite well; clinical studies show that their outcomes are at least as good, if not better, than for those in whom rhythm control is attempted.

The rate-control approach to atrial fibrillation has two goals – to control the heart rate and prevent blood clots and stroke.

Controlling Heart Rate

In most people who have atrial fibrillation, symptoms are directly caused by the rapid heart rate that usually accompanies this arrhythmia.

In fact, as long as the heart rate is controlled, most people with atrial fibrillation can lead essentially normal lives, despite the persistence of their arrhythmia. Generally, control of the heart rate can be achieved by giving beta blocking drugs, often along with calcium channel blockers. In addition, digoxin is often useful in slowing the heart rate in atrial fibrillation.

There Are Different Types of Calcium Channel Blockers

There are three different classes of calcium channel blockers, which include L-type, dihydropyridines, and non-dihydropyridines. Each class has different characteristics that make them suitable for treatment of specific conditions. Dihydropyridines are used to treat high blood pressure, more frequently than the other classes of calcium channel blocker.

This is because they work well to reduce arterial blood pressure and vascular resistance. This class of drug usually ends with the suffix “-pine.” Other calcium channel blockers, including diltiazem and verapamil, are used to treat rapid heart rates and angina. Calcium channel blockers are sometimes prescribed in combination forms with a statin or another blood pressure medication.

Examples of Calcium Channel Blockers

  • Verapamil (Calan, Verelan)
  • Amlodipine (Norvasc)
  • Diltiazem (Tiazac, Cardizem, Dilacor)
  • Nifedipine (Procardia)
  • Nicardipine (Cardene)
  • Amlodipine and benazepril (Lotrel)
  • Amlodipine and atorvastatin (Caduet)
  • Amlodipine and valsartan (Exforge)

Cautions of Calcium Channel Blockers

When taking calcium channel blockers, you should be certain your doctor knows about all of your current medications and supplements, because calcium channel blockers can interact with other compounds. Grapefruit products, including juice, can interfere with metabolism and excretion of these medications, which can result in dangerously high levels of the drugs. If you are taking a calcium channel blocker, you should wait at least four hours after taking the medication before consuming grapefruit or grapefruit juice.

 Magnesium, which is a nutrient found in certain nuts, bananas, spinach, okra, brown rice, and shredded wheat cereal, has natural calcium channel blocker effects, so if your diet includes foods rich in magnesium, check with your doctor to determine if any adjustment is needed. You should not smoke when taking a calcium channel blocker, as this could result in a potentially dangerous rapid heartbeat. Most Americans have low Magnesium levels. You should take a Magnesium Supplement daily. Ask your doctor to have your blood tested to see how your magnesium level is.

Side Effects Associated With Calcium Channel Blockers

There are a number of side effects that can occur with calcium channel blockers, but they do not occur in all patients and the benefits of therapy are greater than the risk of side effects.

These potential side effects include a headache, constipation, dizziness, heartburn, nausea, swelling in the lower extremities, fatigue, and rashes or flushing. Side effects associated with calcium channel blockers are less likely to occur in older patients. Patients may also experience low blood sugar. If you notice any side effects, consult your doctor before stopping the medication. Stopping a medication suddenly is never a good idea. Your doctor will be able to advise you about alternatives, including lowered dosage or different medications.

All three of these drugs work by slowing the conduction of the electrical impulse through the AV node, which reduces the number of impulses that reach the ventricles – thus reducing the heart rate. In the large majority of people with atrial fibrillation, the heart rate can be adequately controlled with some combination of these drugs.

In some cases, however, the heart rate remains rapid enough to cause persistent symptoms despite therapy. In these instances, the heart rate can be readily controlled by a special ablation procedure aimed at damaging the AV node. In this procedure, a special catheter ablates the node by cauterizing or freezing it.

Ablating the AV node prevents the atrial fibrillation impulses from reaching the ventricles, so the heart rate becomes very slow. In fact, AV node ablation usually results in heart block, which often leads to a heart rate that is too slow. So AV node ablation always requires the insertion of a permanent pacemaker. Because modern pacemakers can change the rate at which they pace, depending on the patient’s activity level, the AV node ablation-plus-pacemaker option gives the person with atrial fibrillation heart rates – both at rest and during exercise – that simulate the heart rates of people with normal heart rhythms.

While AV nodal ablation may seem a somewhat drastic approach to controlling the heart rate, it almost always results in a remarkable improvement in symptoms for patients with persistent atrial fibrillation and in whom other measures have failed.

Preventing Blood Clots

Treatment to prevent blood clots from forming in the atria is a critical step in anyone who has atrial fibrillation. Most people with atrial fibrillation should be on therapy with an anti-coagulation drug (drugs that “thin” the blood to prevent blood clots) to prevent strokes. Until very recently Coumadin was the only good option available, but using Coumadin safely and effectively can be a difficult thing to accomplish.

Fortunately, newer and easier-to-use options for effective anti-coagulation in atrial fibrillation have recently become available.

If you take vitamin “E” supplement you should talk to your doctor. Vitamin “E” is a natural blood thinner.

Summary

While it may not be intuitive, the rate-control approach to treating atrial fibrillation is usually quite effective at controlling symptoms and greatly reduces the risk of stroke. Until better methods are developed for getting rid of atrial fibrillation and restoring a normal heart rhythm, the rate-control approach is the better choice for a majority of people who have this arrhythmia.

Source:

January CT, Wann LS, Alpert JS, et al. 2014 AHA/ACC/HRS guideline for the management of patients with atrial fibrillation: a report of the American College of Cardiology/American Heart Association Task Force on practice guidelines and the Heart Rhythm Society. Circulation 2014

Updated July 13, 2016