Nearly 1.5 million people in the United States are estimated to be living with aortic stenosis, a narrowing of the main heart valve that impedes blood flow from the heart. For years, open heart surgery was the best option to remedy this heart valve disease in patients, but continued research in the field has led to transcatheter aortic valve replacement (TAVR) becoming a new alternative.
As opposed to open heart surgery, TAVR is a surgical alternative that sends a catheter through a small needle puncture, usually in a blood vessel in the leg. TAVR has transformed care for patients with aortic stenosis by offering a minimally invasive treatment option with decreased risk factors and shorter recovery times (one to three versus five to seven days) as demonstrated through multiple research studies and completed clinical procedures.
“Patients with severe, symptomatic, untreated aortic stenosis have a five-year prognosis that’s worse than metastatic breast or lung cancer — with a survival of less than five percent in some cases,” said Robert Stoler, MD, FACC, FSCAI, director of the cardiac catheterization lab at Baylor Heart and Vascular Hospital. “TAVR is revolutionary in its ability to treat patients with this fatal disease.”
TAVR was approved by the U.S. Food and Drug Administration (FDA) as a beneficial option for patients considered inoperable and extremely-high risk in 2011, followed by high-risk patients in 2014 and medium-risk patients in 2017. But these first few approval phases have neglected a large population: low-risk patients.
But thanks to three collaborative research efforts led through the Baylor Scott & White Research Institute, this minimally invasive alternative to open heart surgery could be an option for these patients as soon as 2019.
Low–risk patients are next in line
“Despite the results of the first trials, there was still about 75 percent of the population who were not represented in those studies — the patients who are not inoperable or at high or medium risk for surgery, also known as low-risk patients,” said Timothy Mixon, MD, an interventional cardiologist who is leading Scott & White Medical Center – Temple’s participation in PARTNER 3, a collaborative research effort with The Heart Hospital Baylor Plano.
PARTNER 3 is the third in a series of clinical trials by the Plano/Temple team regarding TAVR, and one of three studies currently underway examining TAVR procedures in low-risk patients.
Baylor Heart and Vascular Hospital in Dallas is conducting a Corevalve Low Risk study to examine the benefits of TAVR for low-risk patients. All three locations in Plano, Temple and Dallas are each participating in an EARLY TAVR study evaluating how the procedure compares to the more prevalent path taken for low risk patients which is general surveillance and monitoring for potential progression of the condition or other changes in health.
Many assume that if TAVR works for the patients at highest risk, a minimally invasive option would certainly work for the lower risk population, which is generally younger and healthier to begin with.
Researchers, however, say it’s not quite that simple.
“Just because TAVR is best for high-risk patients, does not necessarily mean it will be better or even as good as the surgical alternative in low-risk patients,” Dr. Mixon said.
“Part of the reason TAVR fared well in the early trials was that surgical complications were known to be significant, and that allowed the less invasive TAVR procedure to shine, as it is typically associated with fewer severe procedural complications. But the equation is different in low-risk patients, in whom we would expect surgical complications to be very low.”
With this particular group of patients, patient life expectancy and valve durability are other key factors to consider.
“Low-risk patients would be younger with a longer life expectancy, so we need to be sure that the valve is more durable for a longer period of time,” said Michael Mack, MD, medical director of cardiothoracic surgery for Baylor Scott & White Health, who is leading The Heart Hospital Baylor Plano’s involvement in the study. “That’s why, as part of the PARTNER 3 trial, all patients will be followed for 10 years to help answer that question.”
Will TAVR become the new norm?
Researchers believe that while the PARTNER 3 trial will go on for a decade, low-risk patients will not need to wait that long to see if the FDA approves the procedure. As researchers expect to continue enrollment in the PARTNER 3 trial through early summer 2018, it seems very possible that year one results might be submitted by spring 2019 and aid in accelerating FDA approval process for low-risk patients with aortic stenosis.
If the research demonstrates positive outcomes in terms of TAVR’s success in low-risk patients (as they did for inoperable, extremely high-, high- and medium-risk patients), the FDA could grant approval as soon as 2019 or 2020.
Considering the large population of low-risk patients with aortic stenosis, this trial could open the door for many more people to benefit from TAVR.
“In 15 years of research, we’ve seen a major shift from a disease being treated by a totally open surgical approach to being largely treated by a catheter-based approach without a surgical incision, and that’s a pretty momentous shift in a very short period of time,” Dr. Mack said.
“Not everyone will be a candidate for this, but I would guess that somewhere in the range of 75 to 80 percent of patients would be if it eventually gets approved [for low-risk patients].”
Beyond the lifesaving benefit of TAVR, Dr. Mack also pointed to the possible potential cost savings of going from an open heart surgery model to a minimally invasive one.
“Right now, the TAVR valve costs eight to 10 times that of a surgical valve. However, if it ends up saving money on the basis of quicker recovery times, shorter time in the hospital and less use of additional resources once patients are discharged, such as extended care facilities and rehabilitation, it could be more cost effective in the long run,” Dr. Mack said.
Reaching beyond aortic valves
While the research team is eager to see how TAVR may help patients with aortic stenosis at all risk levels, they are also excited about what this may mean for other heart valves.
“These trials are addressing only one valve in the heart, the aortic valve, and now we’re beginning to study the other valves in the heart in a similar manner,” Dr. Mack said. “This will be a rich area for research over the next 15-20 years, not only more research on the aortic valve but also the mitral and tricuspid valves.”
For patients with aortic stenosis and beyond, these clinical research initiatives are shaping the future of cardiovascular care.
“Baylor Scott & White Health has three of the highest volume, highest quality TAVR programs in the country,” Dr. Stoler said. “Now that we’re entering clinical trials as a system, we’re leveraging our research infrastructure and volume to successfully participate in and contribute to the most important trials in heart valve therapy.”