Volume Underload? More TAVRs Done, the Better the Operator Outcomes, Yet Many Patients Go Untreated

CHICAGO, IL—Increasing experience with transcatheter aortic valve replacement leads to improved clinical outcomes, including reductions in in-hospital mortality, vascular complications, and bleeding, according to results presented here at TVT 2017.

Based on data from 42,988 procedures performed at nearly 400 hospitals participating in the Society of Thoracic Surgeons/American College of Cardiology (STS/ACC) TVT Registry, investigators report large decreases in the risk of vascular complications and bleeding within the first 100 procedures, with the event curves flattening but still declining as operators gained further experience. Although there was a significant association between in-hospital mortality and procedure volume, the risk of death with TAVR declined less steeply.

Lead investigator John Carroll, MD (University of Colorado, Aurora), said the results suggest that concentrating experience in higher-volume heart valve centers might be a means of improving clinical outcomes. To TCTMD, Carroll noted that the data are based on operators enrolled in the registry between 2011 and 2015, a time period when many centers were just getting TAVR programs off the ground.

“A lot of them are just starting centers so you really have to cautious because everybody starts the learning the curve as they build programs,” said Carroll. “What we don’t want to happen is 5 or 10 years from now the landscape of TAVR in the US consists of way too many sites, such that the volume is divided so much that it prevents centers and teams from really getting good. That would be a mistake. So it really is a balance between access and quality.”

In the analysis, Carroll and colleagues calculated the risk of adverse in-hospital clinical outcomes for an average patient with the average characteristics of the overall study population. Overall, the mortality rate was 3.57% for the first patient treated versus 2.15% for the 400th TAVR case. Similarly, the risks of vascular and bleeding complications for the first TAVR case were 6.11% and 9.59%, respectively, versus 4.20% and 5.08%, respectively, for the 400th treated patient.

Overall, there was no observed relationship between procedure volume and stroke in the fully adjusted model, although researchers noted this might be due to the low rate of site-reported stroke outcomes.

Time to Develop Dedicated Valve Centers?

The results—a clear volume-outcomes relationship in TAVR, as well as in mitral valve repair and other complex surgical procedures—suggests it might be time to develop “valve centers of excellence,” according to Michael Mack, MD (Heart Hospital Baylor, Plano, TX).

Speaking at TVT, Mack noted that such systems of care are already in place for trauma, stroke, and bariatric surgery and these centers could serve as models for valvular heart disease. “This is not just about performing a procedure,” said Mack. “It’s about a comprehensive approach to treating a disease that maximizes the chance of a patient getting the right procedure, at the right place, at the right time.”

One of the critical issues in the development of such systems, though, is managing to strike the right balance between patient access to TAVR and the appropriate number of centers to maximize clinical outcomes.

In the US, there are currently 2,100 catheterization laboratories, 1,150 cardiac surgery units, 520 TAVR centers, and 212 centers offering MitraClip (Abbott Vascular). Among the sites participating in the STS/ACC TVT Registry, Mack noted these centers are largely located on the coasts. For example, there are 10 sites in Washington, seven in Oregon, and 42 in California. Up the east coast, there 42 centers in Florida, 26 in New York, and 30 in Pennsylvania. In contrast, there is one center in North Dakota, three in Montana, and none in Wyoming. In the south, Texas has 25 sites participating in the TVT Registry.     

Worldwide, the US ranks behind Germany, Switzerland, France, and Austria based on the number of TAVR procedures per one million inhabitants (93 TAVRs/million for the US versus 204 TAVRs/million in Germany). However, the US leads the way when it comes to population-based valve centers: 1.5 per one million individuals. In Germany, Japan, and Canada, there are 1.25, 0.8, and 0.6 centers offering TAVR per one million inhabitants.

The question, said Mack, is whether patients in the US have reasonable access to transcatheter therapy or if there are too many or too few clinical sites. Between 2011 and 2015, data from the TVT Registry showed that the average and median number of TAVR procedures per US practice was 109 and 80 cases, respectively.

“It’s a very complex issue, there’s absolutely no question about it,” said Mack. He noted that 55% of centers performing surgical aortic valve replacement don’t have access to TAVR, but the establishment of dedicated valve centers could improve patient access to every treatment with appropriate decision-making in place by the heart team. This would result in closing down low-volume surgical centers, something Mack said is long overdue.

Mack also noted that the US News & World Report, which annually publishes a list of the best hospitals, is interested in the risks of procedures, such as CABG surgery, performed at low-volume centers. In fact, US News is on record stating they plan to publically report TAVR clinical outcomes based on hospital volumes later this year. 

How Many TAVR Centers Are Needed?

Howard Herrmann, MD (University of Pennsylvania Perelman School of Medicine, Philadelphia), said the appropriate number of TAVR centers in the US is still an open question. He noted the data presented at TVT showed there was not only an early learning curve but that outcomes continued to improve between the 100th and 400th TAVR case.

“Where are we going to draw that line?” asked Herrmann. If outcomes continue to improve beyond 400 cases, and only centers with annual volumes exceeding this number were accredited, “there’d only be about eight regional centers in the US,” he said.

Martin Leon, MD (Columbia University Medical Center, New York, NY), said that certifying valve centers of excellence—where hospitals/institutions are classified in a tiered system based on clinical outcomes and volume, among multiple other variables—has the potential to be a political nightmare, particularly since it’s not known who would certify the centers or what criteria would be used.

Mack said the independent, nonprofit Joint Commission is already working with the American Heart Association to certify comprehensive cardiac centers in the United States, including valve centers. The Centers for Medicare & Medicaid Services is also studying the issue, he said.     

Speaking during the TVT session, Peter Kappetein, MD (Erasmus University Medical Center, Rotterdam, the Netherlands), provided a snapshot of TAVR practices on the other side of the Atlantic Ocean. In Germany, the number of surgical aortic valve replacements remained steady at approximately 10,000 procedures per year between 2010 and 2014, but TAVR grew from approximately 5,000 cases in 2010 to more than 13,000 procedures in 2014.

In Europe, the prevalence of severe aortic stenosis is 0.8% and the incidence rate is 4.4% per year, he said. Kappetein estimated that approximately 3,600 patients are eligible for TAVR each year yet just 1,900 patients are treated. In Germany, slightly more than 20,000 patients are eligible for TAVR, but only a little more than 50% are treated.

The bottom line, said Kappetein, is that severe aortic stenosis is undertreated in Europe.   

In Japan, Kentaro Hayashida, MD (Keio University, Tokyo, Japan), said there are 118 centers now performing TAVR, with approximately 7,000 cases performed to date. For the 433 procedures performed at his institution, 30-day mortality was 1.2% and the rates of cerebral infarction and major vascular complications were 1.2% and 4.4%, respectively. In the last 300 consecutive cases performed from 2015 onward, Hayashida said the 30-day mortality was zero.

Such success, he said, is attributed to learning from the US/European experience and the intensive educational/proctoring system in place in Japan.