Newer-Generation MitraClip XTR Shows Promise, but Beware the Learning Curve

PARIS, France—Two studies presented at EuroPCR 2019 provide some reassurances that the newer-generation MitraClip XTR (Abbott), which features longer arms for grasping and increased maneuverability, is safe and effective for the treatment of mitral regurgitation. But a signal of increased single-leaflet device attachment (SLDA), with associated leaflet injury or damage, among patients receiving the new device should serve as a reminder to operators that this clip is different from its predecessor, and that matching the device to the patient is important.

Jörg Hausleiter, MD (Klinikum der Universität München, Munich, Germany), presented 30-day outcomes from the first 500 patients treated in the 60-site Global EXPAND registry, which is tracking outcomes among patients treated in the United States and Europe with the two new MitraClip iterations, the NTR and XTR. The NTR mimics the original MitraClip NT system, but with an enhanced delivery system. The XTR has arms that are 3 mm longer, intended to improve grasping and reach, along with an improved delivery system. Patients enrolled in the registry to date are evenly balanced between primary and secondary MR cases, with approximately one-sixth of the cohort having mixed MR. Most cases (54%) were done with just one clip, 41% needed two clips, and 5% needed three or more.

As Hausleiter showed, the clip implantation success rate was 99.2%, with acute procedural success in 94%. In all, 96% of patients—all of whom had MR grade 3+ (45%) or 4+ (55%) prior to treatment—were discharged with MR grade 2 or better, an outcome that was stable at 30 days. A full 80% of patients were also in NYHA class I or II at 30 days, up from 21% at baseline.

In terms of adverse events, 14 deaths (2.8%), two strokes (0.4%), and seven nonelective CV surgeries for device-related complications (1.4%) have occurred in the registry to date.

Of note, 17 SLDAs occurred, 12 of which occurred in patients with complex, “non-EVEREST II” anatomy. Five SLDAs were associated with leaflet damage and of these, four were with the XTR device.

In the discussion following Hausleiter’s presentation, panelists and audience members zeroed in on the SLDAs, concerned that the improved grasping of the longer clips may also carry the risk of causing more leaflet damage. Hausleiter, in response, emphasized that this is in part a learning-curve issue: SLDAs were more common with the first five cases at any given site.

“One thing we’ve learned is that you probably have to close the clip [more slowly]—not as fast as we used to do with the NTR,” he said, adding that operators should make sure that the clip is “closed but not over-closed” so as not to damage fragile tissue.

SLDAs Highlighted

A second series, this one reported by Fabien Praz, MD (University of Bern, Switzerland), on day two of the meeting, reported outcomes for the MitraClip XTR in 107 patients treated at one of three European centers. Hausleiter is also an investigator for this study, which was simultaneously published in JACC: Cardiovascular Interventions. Hausleiter confirmed to TCTMD that the patients reported in the paper are not also included in the EXPAND registry.

As Praz showed here, clip repair was possible in all patients (a balanced mix of functional and degenerative, or mixed MR patients); the mean number of devices used per patient was 1.5, with 46 patients requiring multiple devices. Overall technical success with the MitraClip XTR was 93%, with 95% of patients experiencing reductions in MR of 2+ or greater.

According to Praz and colleagues, the results hint that the clip’s longer arms and enhanced range of motion has helped mitigate problems with leaflet grasping. In this series, inability to grasp a leaflet occurred in just one patient out of the 107, whereas this rate was 7% in the MITRA-FR trial and 5% in COAPT. “Overall, the use of the new MC XTR resulted in high technical success and effective reduction of MR, comparable to those reported in the COAPT trial,” Praz et al write in the paper. The number of patients who left the hospital with MR grade < 1+ was also greater than that seen in prior registries, they add.

But complications occurred at a rate higher than expected from contemporary trials and registries, as pointed out by an editorial accompanying the paper. Six patients had a device complication, including four SLDAs and two cases of leaflet tearing during grasping. Overall, four patients required conversion to surgery.

“Although reasons for these worrisome complications could not be ascertained in the current study, it is likely that the excess stress applied on the leaflets during grasping with the extended clip arms played a major role,” editorialist Mohamad Alkhouli, MD (West Virginia University, Morgantown, WV), writes. Although the efficacy of the device hints at certain advantages for certain patient anatomy, “the findings of the current study indicate that this powerful device is not a ‘one fits all’ device, and that vigilance is warranted in its selection and use.”

Wait for More

One of the session moderators for Hausleiter’s presentation, Francesco Maisano, MD (University Hospital Zurich, Switzerland), who is also an investigator for EXPAND, appeared to grow impatient with the line of questions following Hausleiter’s presentation, repeating that these 500 patients represent preliminary data that have not yet been adjudicated by a core lab. “Stay tuned!” he barked following a string of questions, saying answers will only come when the full patient cohort is enrolled and followed. This includes any firm advice on which device should be used in which patient.

Indeed, the EXPAND steering committee has made recommendations for which device to use in specific settings. The XTR is recommended for patients with longer leaflets, A2-P2 positioning, large flail, and redundant leaflet, whereas the NTR is better suited for shorter restricted leaflets, calcified annulus/leaflet, and smaller MV area.

Speaking with TCTMD after his presentation, Hausleiter emphasized that “the learning curve makes a huge difference,” noting that SLDA rates were reduced from 6% to around 1% as operators grew more comfortable with the technology. “If we’re going to continue to see this, or if this rate of 1.2% or 1.3% will stay at that same low level—that’s something that we have to analyze with the second half of the patient cohort.”

He continued: “There are for sure anatomical reasons for clip selection, and we tried to already look at this with the steering committee recommendations. Now we’re going to look more deeply into the data to really understand which patients might profit more from a larger clip, without having increased risk, and which patients might benefit more from a smaller clip.”

The bulk of the data so far, however, indicates that the XTR “is a great addition.”

“I think the data demonstrates that although its only site-reported data, the fact that we can achieve, in such a high percentage of patients, really optimal results is phenomenal,” Hausleiter said.