Medtronic announced on Jan. 17 that the FDA had approved its CoreValve System for patients with severe aortic stenosis who undergo transcatheter aortic valve replacement, based on results from the CoreValve Extreme Risk clinical trial. Co-principal investigator Jeffrey J. Popma, MD, director of interventional cardiology at Beth Israel Deaconess Medical Center in Boston, talked with Cardiovascular Business about the impact of the FDA’s decision.
How does this change care for patients?
The commercial approval of the CoreValve device will make an impact on patients who might not be able to be treated with the prior commercial valve [the Edwards Lifesciences Sapien device].
Currently, there are two different subsets of patients. One of those is patients who have smaller vascular anatomies, smaller vessel sizes in which to pass the valves. The CoreValve device being an 18Fr sheath is smaller than the currently available transcatheter heart valve. More patients will be able to be treated by the transfemoral access than previously.
More importantly, there is a very broad range of aortic valve sizes that the CoreValve will treat. That range of annular diameters ranges between 18 mm and 29 mm. I would guestimate that comprises about 90-95 percent of the aortic valve diameters that we see in clinical practice.
The two pieces that move it forward are: first, there will be more patients who can be treated with the transfemoral access CoreValve device and secondly, there is a broader range of annular diameters for patients to be treated with as well.
Solely a transfemoral approach?
No, there are two categories of access routes that we use for patients with the CoreValve device. The first in the conventional transfemoral approach, that is, where there is adequate size vessel through which we can advance the sheath and the CoreValve device.
Then there is a second classification of approaches that comprises two different access sites. One is through the axillary or subclavian artery, which is the artery through the shoulder. The second is through a direct aortic approach, where the heart surgeon makes a mini-sternotomy or a right thoracotomy, places a purse-string suture in the aorta and then advances the delivery catheter sheath through that purse string.
It is much less complicated than a traditional aortic valve replacement surgery because the patient does not go on the bypass pump machine [and] does not have the old valve excised out or the new valve sewn in. It is less cumbersome approach. For patients who do not have adequate iliofemoral vessel size, we do have alternative approaches through the shoulder artery or through the direct aortic approach, which probably comprises about 20 percent of the patients we treat.
Are there other traits to consider?
Within the [aortic-valvular] anatomy there are myriad differences where over time we will learn one device might be more suitable over another device for specific patient anatomy. What I have given is the most concrete example, and that is the size of the valve. When they also learn other information about the location of calcium within the valve, for example, we may find there are subtle differences between the devices over time.
To what do you attribute the rates for paravalvular leaks?
The CoreValve Extreme Risk clinical study reported very low rates of moderate or severe paravalvular regurgitation at one year—4.2 percent [at one year] was what we reported at TCT [the Transcatheter Cardiovascular Therapeutics scientific session in October 2013, where CoreValve Extreme Risk Iliofemoral trial results were presented]. That is among the lowest rates recorded for the CoreValve or the other commercial transcatheter heart valve as well.
We attribute those low rates from the information we have today to two factors: One is we used CT imaging, three-dimensional imaging, to select the size of the valve for each individual patient. In general, we picked larger-size devices which allowed the valves to expand better. Secondly, we used the frame which has a broader and wider diameter at its inflow, at the very lowest part of the valve, and we tried to put that maximum diameter of the valve as high as we could in the aorta and that allowed us to have more expansion.
Could you comment on the pacemaker rate?
We reported about a 22 percent rate of requirement of new pacemakers. That number is on the lower end of the spectrum for what has been reported in Europe. We believe that is a very acceptable number, given the very low aortic regurgitation rate we have seen with this valve in our study. We did what we could do to mitigate against placing unnecessary pacemakers by strictly following the American College of Cardiology guidelines for pacemaker implantation.
We think that number [22 percent] was achieved through careful sizing and careful operator technique. We think that is an acceptable number given the benefits of very profound reductions on paravalvular regurgitation. As we reported in the deep dive [a session at TCT], we saw no differences in mortality in patients who had a pacemaker and who did not have a pacemaker.
Is there anything you would like to add?
I think this is a good day for patients because now there are two products available in the United States. It is good for physicians because now we can select the appropriate valve for the appropriate patient; it gives us more options. And more patients will benefit from this therapy in general because of the commercial approval.