Atrial Fibrillation (cont.)
What is new in atrial fibrillation?
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 AF.
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 AF.
Procedure. Before PVI, the doctor performs a history and physical examination,
an EKG, a 24-hour Holter monitor, and a trans-esophageal 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 performed under deep conscious sedation (but not general anesthesia) in
a cardiac electro-physiology laboratory and takes three to six 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 post-pulmonary vein isolation. After PVI, patients remain in
the hospital telemetry unit for several days so that the heart's rhythm can be
monitored.
Many patients will experience AF and palpitations (irregular
heart beat) while in the hospital and during the first two or three months
following PVI. Therefore, they are given medications such as amiodarone to prevent episodes
of AF and anticoagulation with medications such as warfarin to prevent strokes.
The palpitations and episodes of AF gradually decrease. By three 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 three 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 new
procedure. Most cardiologists in the U.S. have limited experience with PVI. When
performed by experienced doctors, PVI can be expected to prevent AF in 70% to
80% of patients during the first year. Some patients may need additional PVI
procedures to prevent further AF 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 AF or paroxysmal
(intermittent) AF
- Patients who develop recurrent AF while on medications
- Patients with recurrent AF who cannot tolerate the
side effects of long-term medications
- Patients with recurrent AF who do not wish to continue taking long-term
medications or anti-coagulation
- Atrial fibrillation is an abnormal rhythm of the
heart.
- Atrial fibrillation is caused by abnormal electrical
discharges within the atria
- Atrial fibrillation reduces the ability of the atria
to pump blood into the ventricles and usually causes the heart to beat too
rapidly.
- Symptoms of atrial fibrillation include palpitations,
dizziness, fainting, weakness, fatigue, shortness of breath and chest pain
although some people have no symptoms.
- Complications of atrial fibrillation include heart
failure and stroke.
- Atrial fibrillation can be diagnosed by physical
examination, electrocardiogram, Holter monitor or patient-activated event
recorder.
- Treatment of atrial fibrillation is directed toward
controlling underlying causes, slowing the heart rate and/or converting the
heart to normal rhythm, and stroke prevention using blood-thinning
medications.
- Medications are commonly used in the longer-term to
control or prevent recurrence of atrial fibrillation, but medications may not
be effective and may have intolerable side effects.
- Electrical cardioversion is successful in over 95% of
patients with atrial fibrillation, but 75% of patients have a recurrence of
atrial fibrillation within one to two years.
- Some doctors may leave patients in atrial fibrillation
for the longer-term provided the heart rate is under control, blood flow is
adequate, and blood is adequately thinned with medications.
- Non-medication treatments of atrial fibrillation
include pacemakers, AV node ablation, atrial defibrillators, and the Maze
procedure.
- Pulmonary vein isolation shows promise for the treatment of atrial fibrillation and
has a high rate of success; however, longer-term experience is
necessary.
Last Editorial Review: 8/28/2005
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