May 23, 2017

Atrial Fibrillation (AF, AFib)

What is 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.

The 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 person 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 after pulmonary 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, return to good health, 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.

Who are candidates for PVI, and what are the risks?

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

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 congestive 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.

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Reviewed on 1/30/2017
Atrial Fibrillation Quiz