April 25, 2017

Atrial Fibrillation (AF, AFib)

What are the symptoms of atrial fibrillation?

Many patients with this condition have no symptoms (asymptomatic), and are unaware of the abnormal rhythm. When symptoms do occur, the most common one is heart palpitations, an uncomfortable awareness of the rapid and irregular heartbeat. Other symptoms of the condition are caused by the diminished delivery of blood to the body. These symptoms include:

  • Dizziness
  • Fainting
  • Weakness
  • Fatigue
  • Shortness of breath
  • Angina (chest pain due to reduced blood flow to the heart muscles)

What happens to the heart rate during atrial fibrillation?

  • In a heart that is beating normally, the rate of ventricular contraction is the same as the rate of atrial contraction. In atrial fibrillation, however, the rate of ventricular contraction is less than the rate of atrial contraction. The rate of ventricular contraction in the condition is determined by the speed of transmission of the discharges through the AV node. In people with a normal AV node, the rate of ventricular contraction in untreated disease usually ranges from 80 to 180 beats/minute; the higher the transmission, the higher the heart rate.
  • Some older people have slow transmission through the AV node due to disease within the AV node. When these people develop the problem, their heart rates remain normal or slower than normal. As disease in the AV node advances, these people can even develop an excessively slow heart rate and require a permanent pacemaker to increase the rate of ventricular contractions.

How can I know if I am at risk for developing atrial fibrillation?

There are many risk factors for developing atrial fibrillation. They include:

About 1 in 10,000 in otherwise good health, young adults have the disease without any apparent cause or underlying cardiac problems. Atrial fibrillation of the heart in these individuals usually is intermittent, but can become chronic in 25%. This condition is referred to as lone AFib. Stress, alcohol, tobacco, or use of stimulants may play a role in causing this arrhythmia.

How is the diagnosis of atrial fibrillation made?

Atrial fibrillation can be chronic and sustained, or brief and intermittent (paroxysmal). Paroxysmal atrial fibrillation refers to intermittent episodes of AF lasting, for example, minutes to hours. The rate reverts to normal between episodes. In chronic, sustained atrial fibrillation, the atria fibrillate all of the time. Chronic, sustained atrial fibrillation is not difficult to diagnose. Doctors can hear the rapid and irregular heartbeats using a stethoscope. Abnormal heartbeats also can be felt by taking a patient's pulse and by a doctor's diagnosis.

Tests to diagnose atrial fibrillation

  • EKG (electrocardiogram): An electrocardiogram (EKG) is a brief recording of the heart's electrical discharges. The irregular EKG tracings of AF are easy to recognize provided AF occurs during the EKG.
  • Echocardiography: Echocardiography uses ultrasound waves to produce images of the chambers and valves and the lining around the heart (pericardium). Conditions that may accompany AF such as mitral valve prolapse, rheumatic valve diseases, and pericarditis (inflammation of the "sack" surrounding the heart) can be detected with echocardiography. Echocardiography also is useful in measuring the size of the atrial chambers. Atrial size is an important factor in determining how a patient responds to treatment for the disease. For instance, it is more difficult to achieve and maintain a normal rhythm in patients with enlarged atria.
  • Transesophageal echocardiography (TEE): Transesophageal echocardiography (TEE) is a special echocardiographic technique that involves taking pictures of the atria using sound waves. A special probe that generates sound waves is placed in the esophagus (the food pipe connecting the mouth to the stomach). The probe is located at the end of a long flexible tube that is inserted through the mouth into the esophagus. This technique brings the probe very close to the heart (which lies just in front of the esophagus). Sound waves generated by the probe are bounced off of the structures within the heart, and the reflected sound waves are used to form a picture of the heart. TEE is very accurate for detecting blood clots in the atria as well as for measuring the size of the atria.
  • Holter monitor: If episodes of the disease occurs intermittently, a standard EKG performed at the time of a visit to the doctor's office may not show AF. Therefore, a Holter monitor, a continuous recording of the heart's rhythm for 24 hours, often is used to diagnose intermittent episodes of AF.
  • Patient-activated event recorder: If the episodes of atrial fibrillation are infrequent, a 24-hour Holter recording may not capture these sporadic episodes. In this situation, the patient can wear a patient-activated event recorder for 1 to 4 weeks. The patient presses a button to start the recording when he or she senses the onset of irregular heartbeats or symptoms possibly caused by AF. The doctor then analyzes the recordings at a later date.
  • Other tests: High blood pressure and signs of heart failure can be ascertained (determined) during a physical examination of the patient. Blood tests are performed to detect abnormalities in blood oxygen and carbon dioxide levels, electrolytes, and thyroid hormone levels. Chest X-rays reveal enlargement of the heart, heart failure, and other diseases of the lung. Exercise treadmill testing (a continuous recording of the EKG during exercise) is a useful screening study for detecting severe coronary disease in a doctor's office or hospital.
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Reviewed on 1/30/2017
Atrial Fibrillation Quiz