Catheter Ablation
Catheter ablation is an alternative treatment to drug therapy for
the treatment of atrial fibrillation. The option for catheter ablation
of atrial fibrillation has been increasing promising with improved
results and greater data and experience.
In addition use of new tools will likely lead to simpler and more
effective procedures. For the patient with symptoms catheter ablation
is a reasonable option, particularly after one or more antiarrhythmic
agents are not successfully in adequately controlling atrial fibrillation.
Once the decision has been to proceed to catheter ablation, the
selection of approach and technology allows one to tailor the approach
to the patient. Most patients with paroxysmal atrial fibrillation may
be treated with the new balloon technology or conventional
radiofrequency ablation tools with our without robotic assistance.
Patients with persistent atrial fibrillation may be treated with new
balloon technology with robotic assistance during radiofrequency with
the goal of improving precision and contact with the tissue. Patients
with prior catheter ablation and recurrence of atrial fibrillation or
with long-standing persistent atrial fibrillation or with enlarged
atria the hybrid endocardial-epicardial approach may be an option.
During catheter ablation, the specific regions of the upper
chambers, the atria, felt to be responsible for atrial fibrillation,
are targeted. In most patients, it is felt that vessel structures
called pulmonary veins are important in triggering atrial
fibrillation. The pulmonary veins are tubes which connect the lungs
to the left upper chamber, the left atrium. The pulmonary veins
themselves are not the site of atrial fibrillation, but are instead
the triggers. One may use the analogy that the pulmonary veins are
like a match which is used to light a fire, with the fire being
located in the fireplace, which are the atria.
Atrial fibrillation continues once it is initiated and the
electrical signals travel throughout the atria. Frequently there are
additional areas outside the pulmonary veins that are also responsible
for the atrial fibrillation and these too may be targeted.
During the ablation procedure for atrial fibrillation, it is common
to assess whether the electrical signals in the pulmonary veins have
been eliminated. To do this, one usually records from a catheter
called a halo or loop catheter, which has ten or more very small
recording sites which are called electrodes. By using this catheter,
one can determine whether the electrical signals have been adequately
eliminated. Though the goal is to eliminate electrical signals in the
pulmonary veins, ablation is performed outside the pulmonary veins in
a region called the antrum, which refers to the atrial tissue outside
the pulmonary veins. Blood flow therefore is not impeded in coming
from the lungs, through the pulmonary veins, to the left atrium.
In some cases, catheter ablation may consist also of delivering the
energy along a line. The ablation delivery lines are called an
ablation line. These lines may extend along the top or roof of the
left atrium and therefore are called the roof lines. Another commonly
used ablation line is from one of the pulmonary veins, often the left
inferior pulmonary vein, to part of the heart called the mitral
annulus, which is a ring-like structure from where the mitral valve
connecting the left atrium and left ventricle resides. The use of
these lines is somewhat variable, based on physician practice, but
more dependent upon the persistence of the atrial fibrillation.
Patients with longer-standing atrial fibrillation are more likely to
receive such ablation lines, because it is felt that a more diffuse
region of the heart is responsible for the atrial fibrillation.
Risks of catheter ablation, success, and recurrence
There are serious potential risks of catheter ablation of atrial
fibrillation including stroke, heart attack, death, damage and
puncture of the heart or lungs, damage to the esophagus which is rare
but life-threatening, paralysis of the diaphragm or narrowing of the
pulmonary veins that may lead to breathing difficulties. The
incidence of these serious potential risks is about 3-4 %. In addition
there is a risk of damage to the artery, nerves, and veins requiring
surgery or transfusions, bleeding and bruising, blood clots, and
infection. There is a cancer risk based on the radiation receiving
during the procedure.
Some patients require a cardioversion (electrical shock to the
chest) and may experience a burn to the chest at the site of the
cardioversion. A proportion of the patients may continue to have
atrial fibrillation after the catheter ablation. Some of the patients
are significantly improved symptomatically despite recurrence of
atrial fibrillation and repeat ablation is not necessary. A proportion
of patients have repeat ablation. This proportion of patients with
recurrences is highest in patients with long-standing persistent
atrial fibrillation (atrial fibrillation constantly for more than a
number of years) or enlarged atria. The success rate and recurrence
rate will depend on these factors as well as the increased success
with advances in the technologies and techniques. Patients with
paroxysmal atrial fibrillation, likely depending on the technology
used, have the highest single procedure success, approaching 70-80%,
with increased success after more than one procedure. In patients with
persistent atrial fibrillation and enlarged atria, the single process
success may be 50%.
Some patients may be more symptomatic than prior to the ablation.
Learn more about catheter ablation