We’ve covered the Abbott’s MitraClip EVEREST II clinical study before with this article last July. Now UK journalist, Sue Hughes has written for theheart.org (heartwire) on the subject of newly published data from the high risk group within the study population, as reported in the new issue of The American Journal of Cardiology. The study results suggest the device may provide a treatment option in the patient for whom surgery is not an option. The full heartwire article can be found here.
MitraClip and the study
Mitraclip is inserted via the femoral vein and ultimately between the leaflets of the mitral valve, achieving partial closure of the mitral valve in order to reduce its insufficiency. The device was CE marked in 2008 and the EVEREST II pivotal trial is a multi-centre, randomised clinical trial of 279 patients in the United States and Canada with moderate-to-severe (3+) or severe (4+) regurgitation who were candidates for mitral valve surgery.
The trial also included a “high-surgical-risk” arm, made up of 78 symptomatic patients with 3+ to 4+ mitral regurgitation who were judged too high risk to undergo surgery (with an estimated perioperative mortality risk of 12% or more). These patients underwent the MitraClip procedure and were compared with a group of 36 patients with similar degrees of mitral regurgitation, risks, and comorbidities who were screened for the study but were not enrolled for various reasons. Results from the high-surgical-risk arm, published in the January 10, 2012 issue of the journal showed that the procedure-related mortality rate at 30 days was similar in the patients who underwent MitraClip placement and in the comparator group (7.7% vs 8.3%), but the MitraClip patients appeared to have a better one-year survival (76% vs 55%), suggesting reduced mitral regurgitation and improvement in clinical symptoms and left ventricular reverse remodeling at 12 months.
Lead author Dr Patrick Whitlow (Cleveland Clinic, OH) commented to heartwire: “I would say these data are very encouraging. This will be the initial group the MitraClip is used in, as they have no other alternative. In Europe, where the device is already approved, it is this group of patients in whom it is predominantly being used.”
The crux of the debate and the point that Abbott will have to argue with FDA is whether the data is sufficient to support use of the device in the high surgical risk patient in view of the fact that in surgical patients it is seemingly less successful, yet safer than conventional open surgery. Indeed authors of an accompanying editorial in the same journal point out several limitations of the current study that they say make it difficult to interpret. One of the editorialists, Dr Zoltan Turi (Cooper University Hospital, Camden, NJ), told heartwire: “I think the MitraClip may well be a good option for the nonsurgical patient, but I don’t think it’s definitively proven in this study. It will be interesting to see whether these data are strong enough for US approval for this high-surgical-risk group.”
He went on to explain that the problem lay in the comparator group. “This is not a randomized study, and there is little information given about the comparator-group outcomes other than mortality. Many of the comparator patients didn’t meet criteria for the MitraClip, and a fair number who did were not followed. We don’t know if the comparator-group comparison is fair, so the suggested mortality benefit with the MitraClip is uncertain.”
Source: theheart.org, the American Journal of Cardiology, medlatest staff