Medical Device Daily Washington Editor
WASHINGTON – Percutaneous implantation of coronary artery stents generated volumes of controversy, but cardiologists and device makers who enjoy a good fight needn't worry about the ebbing of those drug-eluting stent controversies. The transcatheter aortic valve implantation (TAVI) procedure has taken center stage and promises to keep those who are controversy junkies stocked with plenty of fodder for mastication.
The problem for device makers is figuring out not only how FDA sees some of these issues, but also how physicians see the question of whether TAVI is appropriate in low-risk patients, even as some express doubts about what the current data say about the procedure in high-risk patients.
One of the sessions held during yesterday's goings-on at CRT (Cardiovascular Research Technologies) 2010, sponsored by the Cardiovascular Research Institute (Washington), was a series of debates over various issues related to replacement valves for the heart. The first debate was over whether aortic valves delivered percutaneously ought to be as durable as those delivered via sternotomy.
Arguing that they should was Eberhard Grube, MD, of the Helios Heart Centre (Siegberg, Germany), whose position seemed grounded in the seemingly unhappy prospect of off-label use, namely to patients who are healthy enough to withstand a sternotomy. "Without any doubt, surgical replacement is still the gold standard," Grube said, although it has "seen evolution."
"There is an in vivo deformation and change of geometry" to valves when they are compressed for percutaneous delivery, Grube noted, and the environment inside the aorta is not exactly kind to anything flexible enough to be handled that way. He also acknowledged that some porcine pericardial valves have been subjected to accelerated wear to simulate five years of wear and tear, but he acknowledged that durability "is a relative concept. The life expectancy with therapy has to be taken into consideration," he said, a question of whether the device will outlive the patient.
The current high-risk group has no good FDA-approved options, Grube observed, but subsequent device iterations and course corrections will follow high-risk experience into lower risk patients, thus extending what he said he sees as a lack of solid data into an inappropriate patient population. Bench testing can provide insight into durability, he acknowledged, but held his ground nonetheless.
"Yes, TAVI should strive to match surgical" aortic valve implantation "if we want it to displace surgical" implantation for lower risk patients, Grube closed.
Taking the opposite tack was Peter Block, MD, of the Emory Clinic (Atlanta), who opened his remarks by stating, "I want to do a little philosophy."
Surgical implant "is pretty good," he said, but "the surgeons have this great advantage" in that they "don't have to worry about valve deformation due to handling." Comformation of the replacement valve to the valve bed is an especially big problem for the percutaneously implanted valve, which is "going to deteriorate more quickly" than the surgically placed valve.
"To try to make it the same at the front end is a little foolish," Block argued, adding that "this business of age and time of implantation is really the issue." Many of the high-risk patients who are candidates for a replacement valve have a short life expectancy and don't fare in the long term in any event. He asserted that at least one study shows that 35% of these patients "don't make it out to a year," but that "they don't die because the valve failed. They die because they have so many co-morbidities," he said.
Block added that a parsing of the data in another study returned numbers that showed that 30% of high-risk patients whose valves are delivered transfemorally "do not need an aortic valve more than 18 months." Of those who get a valve delivered transapically, a cross between a surgical and a catheter-based procedure, 57% do not need the valve for more than 18 months. He also said, "We must anticipate that patients will not do well."
However, "just in case patients do survive their TAVI and get out of the hospital," the gauntlet is not yet traversed, Block said. Assuming that one or both of aortic stenosis and congestive heart failure improve and the patient hangs on for another five years, the valves do not demonstrate meaningful deterioration. The valve-in-valve concept "gives us another leap forward," Block said, even if these devices are not ready for middle-aged patients. "We do not need to have a valve that will last 200 years," he asserted.
In a group discussion that followed the presentations, Block said of the off-label use problem, "I guess it boils down to the fact that we as physicians sort of get it right" when expanding the use of devices. If the Partners EU trial, which examines this procedure on European patients is successful, "why do we need anything more than that?"
Jeffrey Popma, MD, of St. Elizabeth's Hospital (Boston), said in response that FDA "wants hard endpoints," adding that media scrutiny of FDA is "not going to change," so data are and will remain crucial.
Block rebutted: "Let's talk about truth" where outcomes are concerned. "FDA is not truth, registries are not truth," he said, but in the long run "we're more frequently right" about the legitimate use of a device. "If you throw out what FDA wants, what's the right thing to do?"
Popma responded that he does not know what the durability of the device is and cited an "obligation on our part to prove" the devices are appropriate. Block's riposte was that for patients over the age of 70, this should not be an issue. "We already have nine, or [at least] seven years with the valves that are out there."
Bill Maisel, MD, of Beth Israel Deaconess Medical Center (Boston), told Block: "I think you're half right." He said surgeons in the trials are good at assessing a patient, but "I disagree that once we have some RCT data, that physicians are good at applying it to the general population." He said off-label use isn't always bad, but that "the DES is a good example where concern over off-label use" was warranted. He cited the boomerang experienced by DES, stating that the rush to use these devices and the concomitant backlash "really impeded that market and resulted in huge decreases in sales." Maisel posed the question of whether industry really wants to incur that risk again.
Mark McCarty, 703-268-5690