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Atrial Fibrillation (cont.)

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What are the complications of atrial fibrillation (AFib)?

Heart failure

If the heart is unable to pump an adequate amount of blood to the body, as in some people with AFib, the body begins to compensate by retaining fluid. This can lead to a condition called heart failure. Heart failure results in the accumulation of fluid in the lower legs (edema) and the lungs (pulmonary edema). Pulmonary edema makes breathing more difficult and reduces the ability of the lung to add oxygen to and remove carbon dioxide from the blood. The levels of oxygen in the blood can drop, and the levels of carbon dioxide in the blood can increase, a complication called respiratory failure. This is a life-threatening complication. In patients with underlying heart disease, the development of AFib may result in up to a 25% decrease in the pumping function of the heart.

Stroke

Quivering of the atria in atrial fibrillation causes blood inside the atria to stagnate. Stagnant blood tends to form blood clots along the walls of the atria. Sometimes, these blood clots dislodge, pass through the ventricles, and lodge in the brain, lungs, and other parts of the body. This process is called embolization. One common complication of AFib is a blood clot that travels to the brain and causes the sudden onset of one-sided paralysis of the extremities and/or the facial muscles (an embolic stroke). A blood clot that travels to the lungs can cause injury to the lung tissues (pulmonary infarction), and symptoms of chest pain and shortness of breath. When blood clots travel to the body's extremities, cold hands, feet, or legs may occur suddenly because of the lack of blood.

What is new in atrial fibrillation (AFib)?

Pulmonary vein isolation

The four pulmonary veins are blood vessels that carry oxygen-rich blood from the lungs to the left atrium. There is a narrow band of muscle cells that surrounds the openings of the pulmonary veins where they enter the left atrium. This band of muscle cells may begin to actively discharge electrically, and this discharge may initiate atrial fibrillation. During pulmonary vein isolation (PVI), the band of muscle cells is destroyed by energy applied through a catheter. This effectively blocks the electrical discharges from crossing over from the band to the left atrium and hence, prevents atrial fibrillation.

Procedure: Before PVI, the doctor performs a history and physical examination, an EKG, a 24-hour Holter monitor, and a transesophageal echocardiogram to exclude blood clots in the atria, and, sometimes, a CAT scan of the chest. The doctor also may ask the patient to stop certain medications, particularly blood thinners such as aspirin, clopidogrel (Plavix), or warfarin, several days before the procedure. The doctor may check a blood prothrombin time and INR level to make sure that blood clotting is adequate for the procedure.

PVI is usually performed under deep conscious sedation (but occasionally general anesthesia) in a cardiac electrophysiology laboratory and takes 3 to 6 hours. Several catheters are inserted through large veins (in the neck, arm, or groin) and fed into the left atrium under X-ray (fluoroscopy) guidance. One of the catheters is equipped with an ultrasound transducer that allows the doctor to view the structures inside the heart during the procedure. The junction of the pulmonary veins with the left atrium is identified, and energy is then applied through another catheter to this area. This results in the destruction of the band of muscle cells and their replacement by a scar. This process is repeated at the opening of each of the four pulmonary veins into the left atrium.

Course postpulmonary vein isolation: After PVI, patients remain in the hospital telemetry unit so that the heart's rhythm can be monitored.

Many patients will experience AFib and palpitations (irregular heart beat) while in the hospital and during the first 2 or 3 months following PVI. Therefore, they are given medications such as amiodarone to prevent episodes of AFib and anticoagulation with medications such as warfarin to prevent strokes. The palpitations and episodes of AFib gradually decrease. By 3 months after the procedure, the majority of patients will have a normal rhythm, and the doctor may stop warfarin and amiodarone.

Patients usually will have an EKG and a CAT scan of the chest 3 months after PVI. The CAT scan is done to make sure that there is no narrowing of the pulmonary veins (pulmonary vein stenosis) due to the scarring.

Effectiveness of pulmonary vein isolation: PVI in the U.S. is a relatively new procedure. When performed by experienced doctors, PVI can be expected to prevent AFib in 70% to 80% of patients during the first year. Some patients may need additional PVI procedures to prevent further atrial fibrillation episodes. Because this procedure is new, it is difficult to know whether successfully-treated patients will continue in a normal rhythm for a prolonged period of time.

Risks of pulmonary vein isolation: When performed by doctors experienced in PVI, the procedure is safe. The risks of pulmonary vein isolation include cardiac tamponade (bleeding into the pericardium, the sac surrounding the heart), narrowing of the openings of the pulmonary veins, injury to the phrenic nerve that controls the function of the diaphragm, injury to peripheral blood vessels, and, in rare cases, death.

In the early years of PVI, doctors were trying to destroy the tissues inside the pulmonary veins. This led to narrowing (due to scarring) of the pulmonary veins which, in turn, led to pulmonary hypertension, a condition in which the blood pressure in the pulmonary veins and arteries increases. Pulmonary hypertension is a serious condition that can lead to heart failure and even death. Doctors no longer try to destroy tissue inside the pulmonary veins. Instead, they try to destroy the tissues only at the junction of the pulmonary veins and the atria. The current technique is not only safer but is more effective and simpler.

Candidates for pulmonary vein isolation: Generally, good candidates for PVI include:

  • Patients with chronic sustained AFib or paroxysmal (intermittent) AFib
  • Patients who develop recurrent atrial fibrillation while on medications
  • Patients with recurrent atrial fibrillation who cannot tolerate the side effects of long-term medications
  • Patients with recurrent atrial fibrillation who do not wish to continue taking long-term medications or anticoagulation

Medically reviewed by: Robert J. Bryg, MD; Board Certified Internal Medicine with subspecialty in Cardiovascular Disease.

REFERENCES:

UpToDate. Patient information: Atrial fibrillation (Beyond the Basics).

Wann, Samuel L., et al. "2011 ACCF/AHA/HRS focused update on the management of patients with atrial fibrillation (Updating the 2006 Guideline): a report of the American College of Cardiology Foundation/American Heart Association Task Force on Practice Guidelines." Journal of the American College of Cardiology 57.2 (2011): 223-242.


Medically Reviewed by a Doctor on 5/4/2015

Source: MedicineNet.com
http://www.medicinenet.com/atrial_fibrillation/article.htm

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