NEJM: International Study Compares Self-Expanding and Balloon-Expandable Transcatheter Aortic-Valve Replacement in Patients with Small Aortic Annulus

Published in the New England Journal of Medicine: 

Pittsburgh’s Allegheny General Hospital Serves as Landmark Clinical Trial’s Top Enrolling Site in the United States

PITTSBURGH – Allegheny Health Network’s (AHN) Allegheny General Hospital (AGH) was the top U.S. enrollment site for a landmark international clinical trial comparing the performance and durability of self-expanding and balloon-expandable transcatheter aortic valve replacements (TAVRs) in patients diagnosed with aortic stenosis and small aortic annulus – a ring at the base of the aorta, the main artery that pumps oxygenated blood from the heart to the rest of the body.

The study, reported in this week’s New England Journal of Medicine (doi: 10.1056/NEJMoa2312573) reported that self-expanding valves had better hemodynamic (blood flow) results than balloon-expandable valves after one year, hypothesizing that self-expanding valve replacements could end up being the preferred therapy going forward for this subset of stenosis patients.

Aortic valve stenosis is a progressive disease caused by calcium buildup narrowing the heart’s aortic valve, which in turn leads to restricted blood flow. According to the American Heart Association (AHA), more than 20 percent of older Americans and 7 percent of those older than 65 years suffer from aortic stenosis, making it one of the most common and serious heart valve diseases in the country. Left untreated, severe aortic stenosis carries a 50% risk of mortality after 2-3 years.

A common intervention for aortic valve stenosis is the TAVR procedure, using one of the two valve models reviewed in the study.

Small aortic annulus – the fibrous ring at the base of the aorta, where the ventricle and aorta meet – can further complicate the TAVR procedure because the narrow openings can lead to impaired hemodynamic performance . The “ring” is like a small door that blood can flow through – if the door is too small, blood can have a hard time passing through to the rest of the body.

Results from the “Small Annuli Randomized To Evolut or SAPIEN (SMART) Trial” demonstrated that among the patients who underwent TAVR with a small annulus, self-expanding and balloon-expandable devices produced similar health outcomes after one year. The self-expanding valve, however, saw a dramatically better performance when it came to hemodynamic valve function.

The SMART trial was formally presented at the 2024 American College of Cardiology annual conference. Stephen Bailey, MD, cardiothoracic surgeon and Chair of the AHN Cardiovascular Institute, served as the co-lead investigator of the study at AGH, alongside Ramzi Khalil, MD, AGH interventional cardiologist.

“Patient populations were tracked over the course of 12 months for disabling stroke, rehospitalization for heart failure, and death – and, as expected, both valves saw equivalent, successful health outcomes, with a low rate of adverse events,” explained Dr. Bailey.

Patients enrolled in the head-to-head trial were all diagnosed with symptomatic aortic stenosis with a small aortic annulus. Small aortic annulus is most often seen in women; of the 716 patients enrolled in SMART – across 83 sites spanning Europe, the Middle East, and the United States - about 87 percent were female, with an average age of 80.

“Women comprised nearly 90 percent of the study population,” said Dr. Bailey. “This is incredibly important and a tremendous accomplishment as women have been historically underrepresented in clinical trials investigating cardiovascular disease. As a field, we recognize significant differences between presentations of heart disease in men and women, and this work begins to further explore and address this issue.”

Patients enrolled in the trial will be followed closely for five years to determine long-term outcomes of both TAVR devices.

TAVR was first approved by the Food and Drug Administration in 2011 for high-risk patient populations and to low-risk patients in 2019. Two years prior to the low-risk patient approval, AGH was the only local medical center in the greater Pittsburgh area to participate in clinical trials to prove the procedure’s safety and efficacy, contributing to its ongoing success and use today.

Self-expanding valves and balloon-expandable valves are both animal valves encased mesh stents. Balloon-expandable valves, as the name suggests, are expanded into place by a balloon that is inserted into the patient’s femoral artery then threaded into the patient’s new aortic valve. In a self-expanding valve, the valve is made of nitinol – a metal alloy that expands when it gets warmer. After the valve is put in place, it warms to the temperature of the patient’s body and expands to the proper size.

“These are two of the most commonly used TAVR devices and few randomized comparisons have been performed to date,” said Dr. Bailey. “We await the longer term outcomes with great expectation as these results will help guide multidisciplinary heart teams around the world design the best individualized care plans, including surgical interventions, for patients diagnosed with aortic stenosis.”

The SMART trial was funded through a grant from Medtronic.

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