TAVR Could Have a Blood Flow Problem

Researchers at the University of Pennsylvania followed patients with low-flow aortic stenosis.

Nancy Crotti

A study of 984 patients who had transcatheter aortic valve replacements to treat low blood flow showed that the device didn't help one-third of them, according to researchers at the University of Pennsylvania.

Further, those patients with low-blood-flow aortic stenosis (AS) who did not improve with TAVR had worse clinical outcomes one year later, according to the five-year study, published in the Journal of the American Medical Association - Cardiology. The study's results raise questions about the $5 billion opportunity that TAVR represents for manufacturers, including Edwards Lifesciences, Boston Scientific and Medtronic.

The Penn researchers actually performed a substudy based on data from the Placement of Aortic Transcatheter Valves (PARTNER) clinical trial and continued access registry of Edwards' Sapien TAVR device in the United States and Canada. The procedure uses a catheter to snake an artificial heart valve through the femoral artery in the leg--called the transfemoral approach--or directly through the apex of the heart--called the transapical approach. It is an option for patients who cannot tolerate open-heart surgery.

The Penn research took place from April 2014 through January 2016, assessing baseline and follow-up echocardiograms, evaluation of post-TAVR blood flow, and one-year outcomes. In the first six months following TAVR, blood flow improved in roughly 66 percent of the patients evaluated. However, those with severe low-flow AS had the highest mortality rate--26%--at one year, as compared to approximately 20% for those with moderate low flow and even less for those with normal flow.

"Unfortunately, many centers do not routinely measure flow, but rather focus more on a patient's pressure gradient or valve area when evaluating aortic stenosis pre-and post-TAVR," said Howard Herrmann, MD, director of Penn Medicine's interventional cardiology program, in a statement from Penn. "While low flow is more challenging to monitor, this measurement can better inform the patient's risk of mortality, and in turn lead to better treatment."

TAVR can be a good option for low-flow arterial stenosis patients, who generally have higher surgical mortality than others, according to Herrmann, whom Penn acknowledged had previously received research funding and speaking honoraria from Edwards. Not all low-flow patients will be able to normalize flow following the procedure, however, and these persistently low-flow patients have a 60% higher rate of mortality at one year following surgery, Herrmann said.

Low flow is difficult to measure post-surgery, he added. However, if clinicians can identify treatable causes of persistent low blood flow following TAVR, such as severe mitral regurgitation and atrial fibrillation, they may have a better opportunity to improve the outcomes of these patients.

Edwards, which pioneered TAVR, did not immediately provide comment on the Penn research. The company had strong TAVR sales in 2015 and reported sales of  $367.8 million for the device in the first quarter of 2016, a 37% jump compared with the first quarter last year when it garnered $366.1 million.

Its CEO, Mike Mussallem, told analysts in April that the TAVR market "is more than a $5 billion opportunity once you get out to just a few years from where we are right now."

FDA has approved four TAVR studies this year alone, including one on Edwards' Sapien 3.

Nancy Crotti is a contributor to Qmed.

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