Atrial fibrillation (AF or A fib) is an arrhythmia, a disturbance in the heart’s rate or rhythm. Every heartbeat starts in the atria (the heart’s upper chambers) and moves into the ventricles, the heart’s lower chambers, stimulating them to contract. Normally, the atria and the ventricles contract in this coordinated manner, and a normal heart beats between 60 and 100 times per minute. In AF, the electrical signal that normally causes the atria to contract in an organized fashion circles through the muscles of the atria in an uncoordinated manner. This causes the atria to quiver, sometimes firing more than 400 times per minute without contracting. At the same time, this might drive the rate of the ventricles (the lower chambers of the heart), resulting in an irregular fast heart rate. In addition, the activity of the sinus node, which usually initiates every heartbeat, is overridden, which can cause the ventricles to beat irregularly.
There are 3 types of AF:
- Intermittent (paroxysmal);
- Persistent; and
One significant danger of AF is that blood clots (called thrombi) can form during an episode of AF, enter the bloodstream, and lodge in the brain, causing a stroke. Uncontrolled AF can weaken the heart, which may lead to dilated cardiomyopathy or heart failure.
WHAT ARE THE SYMPTOMS?
Many people with AF have no symptoms. When symptoms occur, they can include:
- Dyspnea; and
CAUSES AND RISK FACTORS
AF that develops without an underlying heart disorder is called lone or primary AF. Causes of secondary AF include:
- Alcohol use;
- Atherosclerosis (hardening of the arteries);
- Caffeine consumption;
- Valvular disease;
- Enlargement of the left ventricle (left ventricular hypertrophy);
- Hypertension (high blood pressure);
- Hyperthyroidism (overactive thyroid gland);
- Pericarditis (inflammation of the membrane surrounding the heart);
- Pulmonary embolism (blood clot that travels to and lodges in a lung); and
- Sick sinus syndrome (another type of atrial arrhythmia that involves an improper firing of electrical impulses caused by disease or scarring in the sinus node of the heart.
Causes of secondary AF include:
- Valvular disease;
- Left ventricular hypertrophy;
- Sick sinus syndrome; and
Factors that increase a person’s risk of developing AF include:
- Age older than 60;
- Male gender; and
- Diabetes mellitus.
Because arrhythmias are unpredictable and may be infrequent and last for brief periods of time, they can be difficult to diagnose. Physicians often diagnose AF with the following tests:
- Resting electrocardiogram (ECG);
- Holter or event monitoring (ambulatory ECG);
- Echocardiography; and
- Transesophageal echocardiography (TEE).
Treatment of AF aims to eliminate the factors that could be causing it. It may involve rate control, which means controlling the number of times the heart beats per minute but not treating the AF, or rhythm control, which uses medications, cardioversion, catheter ablation, or surgery to prevent AF and thus restore normal rhythm. AF treatment can also include stroke prevention measures.
Medications. Physicians use medications to control the heart rate or rhythm and to prevent the development of blood clots, including:
- Calcium channel blockers;
- Antiarrhythmic agents.
Medical procedures. Physicians may use interventional procedures or surgery to control AF, including:
- Catheter ablation;
- Pacemaker implantation;
- Atrial defibrillator implantation; and
- Maze procedure.
Stroke Prevention. Because a stroke is the most dangerous outcome of AF, physicians often prescribe an anticoagulant such as heparin, warfarin (Coumadin) or a direct thrombin inhibitor (Xarelto Pradaxa, or Eliquis) to minimize risk of clotting and stroke. Factors that increase one’s risk of a stroke in AF include:
- Age older than 65;
- Cardiovascular disease;
- Heart failure; and
- Valvular heart disease