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Atrial Fibrillation Seminar
Johns Hopkins cardiologists presented an atrial fibrillation seminar in the local community. Watch the videos from their presentations.
Atrial fibrillation is a type of cardiac arrhythmia (abnormality of heart rate and/or rhythm). Atrial fibrillation produces a rapid and irregular heartbeat, during which the atria (the upper two chambers of the heart that receive blood) quiver, or fibrillate, instead of beating normally.
During a normal heartbeat, the electrical impulses that cause the atria to contract originate in the sinus node, a small area of the right atrium. During atrial fibrillation, however, these impulses come from all over the atria, triggering 300 to 500 contractions per minute within the heart's upper chambers.
Under normal circumstances, the atrioventricular node would receive these impulses and conduct them to the ventricles (the lower two chambers of the heart that do the pumping). During atrial fibrillation, however, the atrioventricular node becomes overwhelmed by all of the impulses it receives from the atria, and the result is an irregular and rapid heartbeat (80 to 160 beats per minute versus normal 60 to 100 beats per minute).
The rapid and irregular heartbeat produced by atrial fibrillation cannot pump blood out of the heart efficiently. As a result, blood tends to pool in the heart chambers, increasing the risk of blood clot formation inside the heart. Blood clots can travel from the heart into the bloodstream and circulate through the body. Ultimately, they may become lodged in an artery, causing pulmonary embolism, stroke and other disorders. Watch video from our recent health seminar on atrial fibrillation.
Atrial fibrillation often causes no symptoms at all. When symptoms do occur, there may be palpitations (awareness of a rapid heartbeat), fainting, dizziness, weakness, shortness of breath and angina pectoris (chest pain caused by a reduced blood supply to the heart muscle). Some individuals with atrial fibrillation have periods of completely normal heartbeats.
In general, anything that disturbs the normal electrical impulses in the heart can trigger a cardiac arrhythmia, causing the heart to beat too quickly, too slowly or erratically. For atrial fibrillation, the major risk factors are: age, coronary heart disease, rheumatic heart disease (caused by rheumatic fever), hypertension, diabetes and thyrotoxicosis (an excess of thyroid hormones). In many patients, the underlying cause of atrial fibrillation is more serious than the arrhythmia itself.
Atrial fibrillation due to coronary artery disease can be prevented by modifying the appropriate cardiac risk factors: eating a low-fat diet, controlling cholesterol and hypertension, not smoking, controlling weight and getting regular exercise. Unfortunately, some causes of atrial fibrillation are not preventable.
Your doctor will suspect that you have atrial fibrillation based on your medical history and symptoms. During your physical examination, the doctor will check your heart rate and rhythm, together with your pulses. In atrial fibrillation, the pulse (which reflects the activity of the ventricles) is often mismatched with the heart sounds, because all of the atrial beats are not reaching the ventricles.
The diagnosis of atrial fibrillation can usually be confirmed with an electrocardiogram (ECG or EKG). However, because atrial fibrillation tends to come and go, a regular ECG may be normal. If this is the case, ambulatory electrocardiography may be required for which the patient wears a portable ECG machine (Holter monitor), usually for 24 hours.
Initial treatment focuses on finding and treating the underlying cause of atrial fibrillation. If the cause is coronary artery disease, treatment may consist of lifestyle changes, medications that treat high blood cholesterol and hypertension and/or procedures such as angioplasty and coronary artery bypass surgery. Atrial fibrillation due to thyrotoxicosis can be treated with medications or surgery, while fibrillation due to rheumatic heart disease may be treated by replacing damaged heart valves.
The arrhythmia (irregular heart rate) of atrial fibrillation can be treated with medications, such as diltiazem hydrochloride, digoxin or verapamil, which work to slow the heart rate. Another treatment option is electrical cardioversion, a procedure that delivers an electrical "shock" to the heart to restore normal heart rhythm. Although this procedure is effective in most cases, the rate of recurrence is high, and 50 to 75 percent of patients eventually develop atrial fibrillation again.
When medications are ineffective, catheter radiofrequency ablation or minimally invasive surgical ablation can sometimes be performed. In these procedures, an area of tissue in the atrioventricular node is destroyed to prevent the passage of excess electrical impulses from the atria to the ventricles. The result is often complete blockage of all electrical impulses. A pacemaker is then implanted to control the heart rate and rhythm.
In addition to the treatments described above, individuals with atrial fibrillation are often given medications to prevent blood clots that can lead to stroke, pulmonary embolism and other complications. Treatment usually consists of anticoagulant medications (blood thinners), such as aspirin and warfarin.