Non-invasive Techniques May Improve Outcomes for More Heart Patients
Monday, Nov. 28, 2016
Transcatheter aortic valve replacement (TAVR) continues to see dramatic growth in Europe and North America, and multidetector computed tomography (MDCT) is playing an increasingly important role in improving the clinical outcomes of patients undergoing the procedure, according to presenters at a Sunday session.
While open aortic valve replacement continues to be the gold standard for treating patients with severe aortic stenosis, "the rapid evolution of balloon-expandable TAVR — both procedural developments and technical enhancements — indicates it is at least as good, if not better, than the best surgical outcomes in comparable patient groups," said Dominik Fleischmann, MD, a professor of radiology at the Stanford University Medical Center, and session moderator.
And while TAVR has traditionally been a treatment for severe symptomatic aortic stenosis for patients who are at high risk of mortality or complications from traditional open-heart surgery, Dr. Fleischmann pointed out that studies have been carried out demonstrating the value of TAVR for intermediate risk patients.
"And we can predict that even lower-risk patients will be doing TAVR very soon," he said. "The salient point is that if you ask patients, they really want TAVR."
With that in mind, said Jonathon Leipsic, MD, vice chairman of radiology and associate professor of radiology and cardiology at the University of British Columbia, it is apparent that "TAVR is really pushing the boundaries."
Dr. Leipsic described how the use of MDCT has helped improve the clinical outcomes of patients undergoing TAVR.
"While cardiac CT initially played a secondary role in screening patients prior to TAVR, for the last seven or eight years it has really advanced the field through the integration and validation of cardiac CT," Dr. Leipsic said. "Now, it plays an essential role in the pre-procedural planning and guidance of TAVR."
According to Dr. Leipsic, cardiac CT is now the first-line test for device sizing, and the non-invasive gold standard for the discrimination of risk of for annular rupture or coronary occlusion.
"All of this has happened through active research by the CT community, looking first at which measures of CT are reproducible, how to obtain them, and then looking at how to integrate into pre-procedural planning," said Dr. Leipsic.
Dr. Leipsic outlined a number of reasons why pre-procedural MDCT is essential for TAVR, such as preventing vascular injury, obtaining more precise pre-procedural measurements, and preventing annular injury.
"The original reason why we used CT is vascular injury," Dr. Leipsic said, pointing out that patients who experience vascular injury are at an increased risk not only of morbidity, but of mortality." Research has shown that the use of CT helps prevent this, he said.
When it comes to the use of MDCT for annular sizing and valve selection, "we in the CT community can take a lot of pride in improving sizing," said Dr. Leipsic. "In the early days of TAVR people were using 2-D [echocardiography] and you can imagine that the annulus is almost a uniformly non-circular structure. So how are you going to give a two-dimensional measurement of a 20 by 28 millimeter structure?"
"This is where CT has really asserted itself as the primary tool for sizing," he said.
Dr. Leipsic referred to the results of a multi-center trial he participated in that showed that CT integration allowed for a significant reduction in paravalvular regurgitation.
These kinds of results, "show the improvements in paravalvular regurgitation, very much related to — no doubt — iteration of the devices, and improvements in technique, but also to more appropriate sizing." he said. "Putting in the device that actually matches the patient's anatomy."
"Unlike surgical aortic valve replacement where they actually look at and physically assess the size of the annulus, here we rely on imaging," Dr. Leipsic said. "So the very granular information provided by CT allows us to be more accurate in our device sizing, which allows us to reduce the risk of leakage around the valve and improve clinical outcomes in both the short term and long term."