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Trans-catheter Aortic Valve Implantation

Christopher Feindel
Christopher Feindel
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.

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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