Incremental Gains With Next-Gen MitraClip NTR/XTR: EXPAND

Patrice Wendling

April 03, 2020

Real-world results from the next-generation MitraClip NTR/XTR system (Abbott) highlight gains made in percutaneous repair of primary mitral regurgitation (MR) but also the clinical challenges of measuring MR severity.

Overall, MR was reduced to none or trace in 27.7% of primary MR patients, to grade 1 or lower in 86.9%, and to grade 2 or lower in 97.3% at 30 days in the global EXPAND study.

Among patients with adjudicated baseline grade 3 or higher MR, 82% achieved mild or no MR compared with a little more than half in the prohibitive risk primary MR cohort from the prior EVEREST II trials, said study author D. Scott Lim, MD, University of Virginia in Richmond.

Fluoroscopy and procedure times were reduced to 18 and 82 minutes, respectively, or about half that seen in prior studies.

Nearly one third of patients also had complex mitral valve anatomies, which reflects the difference in patients treated in the real-world than in past clinical trials, Lim said during a virtual presentation at the American College of Cardiology 2020 Scientific Sessions (ACC.20)/World College of Cardiology (WCC).

The study represents the first contemporary report of echocardiographic core lab and independently adjudicated 30-day clinical outcomes in patients with primary MR treated with the NTR and XTR systems, he noted.

The overall EXPAND population includes 1041 patients with primary or secondary MR who were treated with the MitraClip in the United States, Europe, and Middle East between April 2018 through June 2019, of which 835 patients had adequate imaging for echocardiographic core lab assessment.

The analysis focused on 422 of these patients (mean age, 79.5 years) who had at least grade 3 primary or mixed MR, based on site assessment. Their mean Society of Thoracic Surgery (STS) replacement score was 7.3% and mean STS repair score was 5.5%.

A baseline MR of 3+ or 4+ was core lab adjudicated in only 66.4%, with the remainder found to have grade 2 or milder MR, Lim reported.

"Clearly we struggle with quantitating MR echocardiographically," session chair Martin B. Leon, MD, NewYork-Presbyterian/Columbia University Medical Center, New York City, said as part of the online discussion.

"One of the limitations of the study was there was a fair number of patients where the baseline echo was not interpretable or valuable; there were about a third of the cases where the site interpreted the MR as being a little bit less severe than the echo core lab," he said. "So we still struggle, at least I think, with the quantitative and even qualitative assessment of MR severity."

In response, Lim said, "This points out the need for an echo core lab, and therefore, the importance for all of us to take it with a bit of a grain of salt when we're looking at data that does not have an echo core lab.

"The investigators in the EXPAND registry were chosen because they and their sites had significant experience with approaching mitral valve disease," he said. "Yet despite that, as you point out, a third of them had lesser grades of MR that they thought were more severe."

Panelist Alan Zajarias, MD, Washington University School of Medicine in St. Louis, Missouri, asked why the two core labs measured different characteristics, noting it is "somewhat controversial."

"It was more of a logistical determination early on," Lim replied. During the formal presentation, he pointed out that two labs were used to ensure consistent measurements across sites, with one assessing MR etiology and severity and the other focused on detailed mitral valve anatomic characteristics and left ventricular measurements.

Device selection was left to the operators and sites, although recommendations were made early in the study by a core group of investigators. It favored the XTR for patients with longer leaflets and the NTR for those with short, restricted leaflets, more restricted pathologies, and a smaller valve orifice area, Lim noted.

The MitraClip XTR was used in 194 patients, NTR in 146, and both in 80 patients. The type of clip used did not differ in patients with noncomplex vs complex mitral anatomies, but greater MR reduction was achieved using the XTR vs the NTR clip in complex anatomies (P = .03).

Baseline MR severity was significantly different across the three device groups, with more XTR clips used (alone or with the NTR) in patients with severe MR.

Rates of clip implantation and acute procedural success were 99.5% and 94.5%, with a median hospital stay of 1 day. This compares with an acute procedural success rate of 91.8% and 2-day hospital stay in a 2017 transcatheter valve therapy (TVT) registry analysis, Lim noted.

At 30 days, there were 10 deaths (2.4%), five strokes (1.2%), and four (0.9%) nonelective cardiovascular surgeries for device-related complications. No myocardial infarctions occurred.

Single leaflet device attachment was confirmed in eight (1.9%) patients and leaflet tear or perforation in one (0.2%).

At 30 days, pre-procedure mitral gradients increased from 2.51 to 3.51 mm Hg in the XTR-only group, from 2.31 to 3.89 mm Hg in the NTR-only group, and from 2.71 to 3.99 mm Hg in the XTR/NTR group.

"It's remarkable that patients left the procedure with similar gradients, irrespective of the type and number of clips that were placed and, importantly, that around 86% of the patients left the procedure room with less than or equal to 1+ MR in follow-up," Zajarias said.

When drawing comparisons with earlier trials, however, Leon observed that a lot of things have changed including "operator experience, case selection, and certainly imaging has also improved dramatically. So can you really ascribe all of the improvement and the reduction in MR just to the use of different devices — or are we seeing as much procedural evolution as we are technical device evolution?"

Lim replied: "To answer that, I think we have to look back at the more recently published, by Paul Sorajja, TVT registry outcomes, in which case even with them, we found some incremental improvement compared to the early EVEREST trials. But over the TVT registry data, I think there is significant improvement in the data being shown here in terms of MR reduction as well as procedural outcome times."

EXPAND is funded by Abbott. Lim reports consulting for Edwards Lifesciences, Pipeline, and Venus; equity in 510Kardiac and Venus; and institutional research grants on his behalf from Abbott, Boston Scientific, Corvia, Edwards Lifesciences Keystone Heart, LivaNova, Medtronic, and W.L. Gore.

American College of Cardiology 2020 Scientific Sessions (ACC.20)/World College of Cardiology (WCC): Abstract 412-12. Presented March 30, 2020.

Follow Patrice Wendling on Twitter: @pwendl. For more from | Medscape Cardiology, join us on Twitter and Facebook.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.