Harnessing New Technology and Techniques to Eliminate Atrial Fibrillation

Harnessing New Technology and Techniques to Eliminate Atrial Fibrillation

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Description: Atrial fibrillation is the most common and persistent of arrhythmias affecting up to 2.4 million Americans. The arrhythmia is complicated by increased risk of stroke, palpitations, lightheadedness, shortness of breath, fatigue, and heart failure. Not to mention the discomfort and anxiety that arises in patients who experience frenetic heart beats paroxysmal or persistent.

Author: Emile A. Bacha MD, Allan Schwartz MD, Leonard N. Girardi MD, Bruce B. Lerman MD (Senior) | Visits: 557 | Page Views: 628
Domain:  Medicine Category: Therapy 
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Affiliated with Columbia University College of Physicians and Surgeons and Weill Cornell Medicine

Emile A. Bacha, MD
Chief, Division of Cardiac,
Thoracic and Vascular Surgery
Columbia University Medical Center
Director, Congenital and
Pediatric Cardiac Surgery
NewYork-Presbyterian Hospital
Allan Schwartz, MD
Chief, Division of Cardiology
Columbia University Medical Center
Leonard N. Girardi, MD
Cardiothoracic Surgeon-in-Chief
Weill Cornell Medical Center
Bruce B. Lerman, MD
Chief, Maurice R. and Corinne P.
Greenberg Division of Cardiology
Weill Cornell Medical Center

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Harnessing New Technology and Techniques
to Eliminate Atrial Fibrillation
Atrial fibrillation is
during procedures.
the most common
On top of that, we
and persistent of
need to treat them
arrhythmias affecting
using various energy
up to 2.4 million
Americans. The
“In the late 1990s,
arrhythmia is complithere was a novel
cated by increased
observation that the
risk of stroke, palpisource of initiation of
tations, lightheadedatrial fibrillation was
ness, shortness of
in the pulmonary
breath, fatigue, and
veins, which empty
heart failure. Not to
into the left atrium,”
mention the discom- Electroanatomic mapping of atrial fibrillation
says Bruce B.
fort and anxiety that
Lerman, MD, Chief,
arises in patients who experience frenetic heart
Maurice R. and Corrine P. Greenberg Division of
beats – paroxysmal or persistent.
Cardiology at NewYork-Presbyterian/Weill Cornell.
At NewYork-Presbyterian, a significant array of
“Initial data showed that if you electrically isolated
research is underway with the goal of eradicating
each of the four pulmonary veins through ablation,
atrial fibrillation (AF) in patients by improving
one could achieve cure in about 60 to 70 percent
the treatment options and attacking AF at its
of patients. While this was better than medical
source – a challenge that has been readily pursued
therapy, it was still not ideal.”
by physicians in the Divisions of Cardiology at
“Basically electrophysiology is still a relatively
NewYork-Presbyterian/Columbia University
new clinical science,” notes Hasan Garan, MD,
Medical Center and NewYork-Presbyterian/
Director of Cardiac Electrophysiology at NewYorkWeill Cornell Medical Center. Mapping, tracking,
Presbyterian/Columbia. “When we started doing
cornering, and halting the skittering electrical
ablations in the 1990s, it became very obvious
impulses that set off disquieting, and even lethal,
very early that the more you understood about
cardiac arrhythmias remain the means and now
the circuits that are responsible for the arrhythoften attained targets in treating and curing
mia, the more successful the ablation procedure
patients with persistent atrial fibrillation.
would be.”
“Appropriate and significant use of high One of the challenges with atrial fibrillation is
powered technology in mapping, imaging, and
that it is not a stagnant disorder – it can progress
treating many arrhythmias, and especially atrial
and one phase changes into another. Prior to
fibrillation, have infiltrated all phases of diagnosis
recent technological advances, atrial fibrillation’s
and treatment,” says Christopher F. Liu, MD,
complex and often transient nature made mapping
Assistant Director, Cardiac Electrophysiology
and tracking its spillover of electrical impulses
Laboratory, NewYork-Presbyterian/Weill Cornell.
impossible. “We are now able to collect the
“Determining how to best harness this new
electrical activities, or the activation sequence, on
technology is based, in part, on how well we
a beat-by-beat basis during arrhythmia or at any
can record and process electrocardiograms and
time,” says Dr. Garan. “In other words, every
electrical signals. It is essential to go beyond
place in the heart electrically activates and
displaying patients’ arrhythmia; we also have to
deactivates and waits for the next cycle. With a
(continued on page 2)
be able to effectively map these arrhythmias

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Advances in Cardiology, Interventional Cardiology, and CardiothoracicPediatric Cardiology, Interventional Cardiology, and Cardiovascular Surgery

Harnessing New Technology and Techniques to Eliminate Atrial Fibrillation

Dr. Christopher F. Liu, Dr. Bruce B. Lerman, and Dr. James E. Ip

deflectable catheter that can be navigated from one corner of the
heart to the other, you can find out what area, at a given instant,
is activating. In the past few years, clinical research has focused on
how the atrium activates during atrial fibrillation. Before it just
looked like chaotic activity; now patterns are beginning to
emerge and the technology is trying to make it possible for us to
observe these repeating patterns.”

Building on Ablation Technology
“With an arrhythmia, there is an initiator – something has to
trigger it,” says Dr. Lerman. “But then, in order to sustain the
arrhythmia, there needs to be a substrate or perpetuator that
allows atrial fibrillation to continue. This is particularly relevant
for patients with persistent atrial fibrillation. The electrophysiological substrate is believed to be related to rapidly spinning
rotors. These perpetuators are often located in the left atrium;
however, in as many as 25 percent of patients, the right atrium
may participate.
“The rotors cannot be observed with the naked eye,” continues
Dr. Lerman, who is the principal investigator for the Randomized
Evaluation of Atrial Fibrillation Treatment with Focal Impulse
and Rotor Modulation Guided Procedures (REAFFIRM) study.
“But now a novel diagnostic catheter and mapping approach allows
us, through extensive computerized processing of electrical
information, to highlight in a three-dimensional projection
the coordinates of the rotors so that we can direct our ablation
catheter toward those regions.”
The prospective, multicenter, randomized REAFFIRM control
trial, which continues to enroll patients, will determine the safety
and effectiveness of rotor ablation followed by conventional
ablation versus conventional ablation alone for the treatment of
persistent atrial fibrillation.
Two years ago, Dr. Liu added cryoballoon ablation to his
repertoire of techniques for the treatment of atrial fibrillation.
“Our goal is to simplify the ablation procedure and improve
outcomes. Traditional radiofrequency ablation focuses on pulmonary
vein isolation and makes use of a single-point catheter that


(continued from page 1)

Dr. William Whang and Dr. Hasan Garan

applies 20 to 25 meticulously placed points, forming a circle
around each pulmonary vein. Cryoballoon ablation essentially
allows us to go in and freeze the entire circle in one shot.”
According to Dr. Liu, this technology streamlines the
procedure – shortening the time the patient is under anesthesia
and potentially reducing complications. He is now conducting a
retrospective study comparing 100 cases of cryoballoon ablations
with the same number of cases of radiofrequency ablation, looking
at timing, complications, and outcomes, in particular, rates of
recurrence of atrial fibrillation.
“There are multiple subtypes of atrial fibrillation and as a first
step we still perform pulmonary vein isolation,” says Dr. Garan.
“The next steps have to be individualized depending on the kind
of patient you are treating and/or the subtype of atrial fibrillation.
For atrial fibrillation, even with the subtypes that are most
amenable to the ablation – young, healthy people who otherwise
do not have any structural heart disease – we are at 70 to 80 percent
of efficacy. To go to a higher level of efficacy, as we have done
with the other forms of arrhythmias where a single ablation can
achieve 96 to 98 percent efficacy, there’s still a lot to be learned
about down-the-line mechanisms and the different subtypes of
atrial fibrillation, as well as the different techniques and methodologies that work best for each. That is why we are still doing
clinical investigations in this area.”

What You See Is What You Can Get
While ablation techniques have been rapidly evolving, visualizing
the field has also undergone dramatic growth. “In the past, when
we started performing radiofrequency ablations, fluoroscopy was
used to visualize the location of the catheter,” says James E. Ip, MD,
a cardiac electrophysiologist with NewYork-Presbyterian/Weill
Cornell. “Through the years, CT scans or MRI have been utilized
to create a road map. Today, we now combine these technologies
with intracardiac echocardiography and an electroanatomic mapping
system that enable us to pinpoint where we are within the heart.”
William Whang, MD, a specialist in heart rhythm disorders
with the Division of Cardiology, NewYork-Presbyterian/Columbia,

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Advances in Cardiology, Interventional

sees patients with atrial fibrillation related to a number of cardiac
conditions, including cardiomyopathy and adult congenital heart
disease. Similarly, Dr. Whang and colleagues have employed
various new imaging and treatment technologies that provide a
three-dimensional image of the catheter as it is guided inside the
heart, improving the efficacy of radiofrequency ablation.
“We use several imaging modalities simultaneously, such as
fluoroscopy, intracardiac echocardiography, and electroanatomic
mapping,” says Dr. Whang. “I think about electroanatomic
mapping as a GPS-type of system where there is a magnet in the
tip of the catheter as well as a magnet under the cath lab table.
We know at any time where the catheter is in three-dimensional
space. This is so we can mark different areas where there’s
suspicion for electrical activity that could be helping to maintain
or trigger the A-fib.” Dr. Whang and his colleagues create a
three-dimensional map of the atrium through a combination of
touching the endocardial surface of the atrium with the catheter
and integrating this information with the intracardiac echo, as
well as a pre-procedure CT scan to reconstruct the left atrium in
a three-dimensional form.
In addition to new technology permitting greatly enhanced,
three-dimensional visualization, Dr. Whang and Dr. Ip each
use the most advanced catheter ablation technology, including
contact force-sensing (CF-sensing) catheters, enabling them to
assess whether adequate contact has been established with atrial
tissue at the tip of the catheter.
Prior to the availability of the CF-sensing catheter, there was
a 20 to 30 percent recurrence rate for atrial fibrillation ablations.
“The great challenge,” Dr. Whang says, “is trying to draw a
complete line of block in a great many different areas in the
atrium. If there’s a gap in the line of block it can jeopardize the
entire treatment. The force-sensing technology ensures a complete
lesion at each site where we do an ablation.”
“Success rates for ablations vary from institution to institution
and person to person,” adds Dr. Ip. “But the contact force-sensing
catheter has the potential to increase the effectiveness of the
procedure across the board.”

Dr. Steven O. Marx (center) with colleagues Dr. Elaine Y. Wan and Dr. John P.
Morrow, clinical electrophysiologists

Waves of the Future
Future progress in understanding atrial fibrillation also lies
within the basic laboratories of Columbia and Weill Cornell,
with clinicians and scientists seeking to better understand the
mechanisms at the core of arrhythmias. Steven O. Marx, MD,
Director of the Cardiovascular Fellowship Program at NewYorkPresbyterian/Columbia, and his colleagues have been focusing on
arrhythmogenesis in both ventricle and atrial arrhythmias. “All
the electrical signals in the heart are generated through ion
channels,” says Dr. Marx. “We’ve been studying the mechanisms
of regulation of these channels at both the basic science level, as
well as in a mouse model. One of the mouse models we produced
– somewhat serendipitously and out of the ordinary – is capable
of spontaneous atrial fibrillation.”
(continued on page 4)

Leadless Pacemaker Takes Center Stage
“One of the most exciting areas that
I’ve been involved with at Weill
Cornell is studying the leadless
pacemaker – the newest type of
pacemaker that we can offer to
selected patients who have constant
atrial fibrillation with erratic
rhythms,” says James E. Ip, MD, a
cardiac electrophysiologist who served
as principal investigator for NewYorkPresbyterian/Weill Cornell, one of 50
centers in the United States to implant the world’s first leadless
pacemaker as part of St. Jude Medical’s LEADLESS II Clinical
Trial. “This miniaturized device, which is smaller than the size of
a AAA battery, is placed directly into the right ventricle via the
femoral vein with a steerable catheter. While it functions as a
traditional pacemaker, it is less invasive and doesn’t have the wire.”

Considering the conventional pacemaker’s placement near the shoulder
and any patient’s need to move freely
and repeatedly, wires become, as Dr. Ip
suggests, the device’s Achilles heel.
“Now, without wires and given its
miniature stature, the leadless pacemaker can serve to protect patients in
a less obtrusive manner, with a potentially reduced risk of infection and no
Courtesy of St. Jude Medical
risk of wire compromise or damage,”
says Dr. Ip, a co-author of the study’s paper published in the
September 17, 2015 edition of The New England Journal of Medicine.
On April 6, 2016, the U.S. Food and Drug Administration
approved Medtronic’s leadless pacemaker, with the St. Jude
Medical leadless pacemaker – now available throughout Europe
– expected to receive FDA approval in the second half of 2016.


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Harnessing New Technology and Techniques to Eliminate Atrial Fibrillation
According to Dr. Marx, the standard in the field for studying
atrial fibrillation in the mouse model is to induce an arrhythmia
of one second, which is reason for skepticism about the value of
this model. “One second does not mimic the hours or days a person
with atrial fibrillation experiences,” says Dr. Marx. “Because our
mouse has atrial fibrillation spontaneously, and it can last for
hours, we can monitor and map its electrical patterns. So this
mouse model is very useful in figuring out the mechanisms of
atrial fibrillation. Why does it stop? Why does it start? Using
advanced optical mapping techniques, we have persistent rotors in
both the right and left atria of mice, mimicking what is observed
in humans. These rotors are the targets in the REAFFIRM study.”
Perhaps the only thing Dr. Marx finds more singular than the
lab’s serendipitous mice is the human collaboration that creates
all these forefront possibilities. “The unique part of this,” Dr. Marx
says, “is that it’s a team effort, from both the basic science and
clinical aspects of cardiology.”
“The mapping of the atrial fibrillation is still being perfected,
but for arrhythmias that can be analyzed on a beat-by-beat basis,
our techniques are pretty good in enabling us to do successful
ablation,” says Dr. Garan. “Atrial fibrillation is still a little elusive
and there’s more room for research, debate, and perfection.”


(continued from page 3)

Reference Articles
Wan E, Abrams J, Weinberg RL, Katchman AN, Bayne J, Zakharov SI,
Yang L, Morrow JP, Garan H, Marx SO. Aberrant sodium influx causes
cardiomyopathy and atrial fibrillation in mice. Journal of Clinical Investigation.
2016 Jan;126(1):112-22.
Reddy VY, Exner DV, Cantillon DJ, Doshi R, Bunch TJ, Tomassoni GF,
Friedman PA, Estes NA 3rd, Ip J, Niazi I, Plunkitt K, Banker R, Porterfield
J, Ip JE, Dukkipati SR; LEADLESS II Study Investigators. Percutaneous
implantation of an entirely intracardiac leadless pacemaker. The New England
Journal of Medicine. 2015 Sep 17;373(12):1125-35.
Biviano AB, Ciaccio EJ, Knotts R, Fleitman J, Lawrence J, Iyer V, Whang
W, Garan H. Atrial electrogram discordance during baseline vs reinduced
atrial fibrillation: potential ramifications for ablation procedures. Heart Rhythm.
2015 Jul;12(7):1448-55.
Lin FS, Ip JE, Markowitz SM, Liu CF, Thomas G, Lerman BB, Cheung JW.
Limitations of dormant conduction as a predictor of atrial fibrillation recurrence and pulmonary vein reconnection after catheter ablation. Pacing and
Clinical Electrophysiology. 2015 May;38(5):598-607.
For More Information
Dr. Hasan Garan • hg2017@cumc.columbia.edu
Dr. James E. Ip • jei9008@med.cornell.edu
Dr. Bruce B. Lerman • blerman@med.cornell.edu
Dr. Christopher F. Liu • chl7001@med.cornell.edu
Dr. Steven O. Marx • sm460@cumc.columbia.edu
Dr. William Whang • ww42@cumc.columbia.edu