Trans-catheter Aortic Valve Implantation
Christopher Feindel
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New technologies are rapidly transforming how cardiac surgeons manage cardiovascular
disease. Minimally invasive technologies hold the promise of reducing the risk and
morbidity associated with cardiac procedures. Patients who would otherwise be deemed
"inoperable" are now benefiting from these new minimally-invasive cardiac procedures.
Amongst the areas in cardiac care that are rapidly changing is the management of
valvular heart disease. Minimally-invasive, trans-catheter techniques for the implantation
of aortic valves have been developed recently. We are privileged to have the leadership
and expertise of Dr. Christopher M. Feindel, the Antonio and Helga DeGasperis Chair
of Cardiovascular Surgical Research and Epidemiology at the Peter Munk Cardiac Centre,
to bring this new technology in cardiac surgery to Toronto. Feindel is currently
performing the innovative trans-apical trans-catheter technique of aortic valve
implantation at Toronto General Hospital. He recently reviewed the current status
of trans-catheter aortic valve implantation for us at the Surgical Services Grand
Rounds at the University Health Network.
Aortic stenosis has a very poor prognosis once symptoms develop. The two year mortality
exceeds 50% in symptomatic patients with aortic stenosis. As our population's life
expectancy increases, more patients will present with aortic stenosis and increasing
comorbidities. Dr. Feindel pointed out that the operative mortality for open aortic
valve replacement in highly selected patients over the age of 80 currently ranges
between 10 and 14%. However, there are and will be many patients who have comorbidities
that increase the operative mortality to prohibitive levels. The driving force behind
the development of alternative aortic valve replacement techniques has been the
quest to treat these patients, who have an operative mortality >20% but who have
a reasonable anticipated life expectancy.
The "proof of concept" studies of trans-catheter aortic valve implantation were
performed in animal models by Andersen and colleagues in 1992. The initial studies
involving porcine aortic valves mounted inside of stents and compressed on balloon
catheters demonstrated the feasibility of the transcatheter implantation technique.
The technique and technology evolved dramatically over the next 10 years and the
first successful percutaneous trans-catheter aortic valve implantation in a human
was performed in 2002 by Dr. Alain Cribier in France.
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Trans-catheter aortic valve implantation has evolved into two approaches: a percutaneous
trans-femoral approach and a trans-apical approach through a mini-thoracotomy incision.
Dr. Feindel highlighted the important contributions that Canadians have made to
the development and adoption of these techniques. Dr. John Webb in Vancouver has
been a world leader in the trans-femoral approach which involves passing a 24-French
catheter up the femoral artery, in a retrograde fashion, to the heart. Unfortunately,
many elderly patients have aortoiliac vascular disease that prohibits this approach,
and the alternative is a trans-apical approach involving a minithoracotomy incision
and passing a catheter up through the apex of the heart. Dr. Samuel Lichtenstein,
formerly at St. Michael's Hospital and now in Vancouver, has been a world leader
in the development of this approach. He visited Toronto and guided Dr. Feindel through
his first trans-apical, trans-catheter aortic valve implantations at Toronto General
Hospital.
Implanting an aortic valve through a trans-catheter approach in the operating room
demands change, not only in the surgeon's traditional operative technique, but also
a change in operating room technology. A combination of echocardiography and angiography
equipment is required to visualize the valve as the heart is rapidly paced and a
balloon inflates to expand the stented valve into place. As this technology becomes
adopted, operating rooms will have to change to become "multipurpose" or "hybrid"
operating rooms that incorporate multiple imaging modalities.
Currently, Dr. Feindel is implanting these valves primarily as part of the REVIVAL
(tRanscatheter EndoVascular Implantation of VALves) multi-center randomized clinical
trial. This trial is evaluating the safety and efficacy of the transcatheter implantation
technique in high-risk, symptomatic patients with aortic valve disease. The hope
is that this technology will prove to be safe and effective and provide a treatment
option for high-risk patients that was previously unavailable. After having implanted
over 7 aortic valves using the trans-catheter technique, Dr. Feindel thinks that
this is the future of cardiac surgery. He sees the future involving the adoption
of this and other innovative catheter-based technologies in the operating room.
Finally, during these rapidly changing times in cardiac surgery, Dr. Feindel reassuringly
observes through his own experience that, "you're never too old to learn new things!"
Mitesh Badiwala
Cardiac Surgery Resident
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