MitraClip: Encouraging results in Nonsurgical Patients

January 06, 2012

January 6, 2012 (London, United Kingdom)Results from the high-surgical-risk arm of the EVEREST II trial with the percutaneous MitraClip (Abbott) device, suggesting reduced mitral regurgitation and improvement in clinical symptoms and left ventricular reverse remodeling at 12 months, have now been published [1].

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."

But authors of an accompanying editorial point out several limitations of the current study that they say make it difficult to interpret [2]. 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."

The main EVEREST II trial, published last April, compared the MitraClip procedure with surgical repair of the mitral valve and suggested that the MitraClip was significantly less effective than surgery at improving mitral regurgitation but seemed safer.

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 this high-surgical-risk arm, published in the January 10, 2012 issue of the Journal of the American College of Cardiology, 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%).

In surviving patients with matched baseline and 12-month data, 78% of the MitraClip patients had a mitral regurgitation grade of 2+ or less, and there were improvements in left ventricular end diastolic and systolic volumes, NYHA functional class, and quality of life, the EVEREST authors report. The annual rate of hospitalization for congestive heart failure in surviving patients with matched data decreased from 0.59 to 0.32.

The authors conclude: "The objective improvements in LV function, in addition to the subjective improvement in symptoms and quality of life reported by the patients, suggest that percutaneous reduction of mitral regurgitation with the MitraClip device results in significant clinical benefit."

But the editorialists raise some caveats.

Turi commented to heartwire : "This very nice study does have some limitations in answering the question as to how beneficial the MitraClip is in this group of patients at high surgical risk. However, the evidence base on treatment of this patient population is quite limited, so these results do fill some of the void."

Problematic Comparator Group

Turi explained that the main problem with the study is 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."

He added: "Our concern is that people will interpret this study as clearly showing that the MitraClip is superior to what are admittedly very limited alternatives for high-comorbidity patients. We would like to see randomized controlled studies for at least a subset of this patient group similar to the PARTNER trials.”

It is a question of whether you think being left with a level of 2+ is acceptable or not.

Turi noted that although mitral regurgitation was reduced in this study, it was still 2+ or greater in 46% of patients after the procedure, which does not compare favorably with the results of surgical repair. "If a surgeon left 46% of his or her routine mitral-repair patients with grade 2+ or more mitral insufficiency I think you would stop sending your patients to him. It is a question of whether you think being left with a level of 2+ is acceptable or not. For truly inoperable patients it may in fact be."

He also pointed out that a procedural mortality rate of 8% was relatively high. "Although it is similar to the comparator group, because we know so little about that group, it doesn't help us very much. These are obviously very sick patients with lots of comorbidities, but I think we have to ask whether this rate of procedural mortality is clearly worth the benefits when half the patients are still left with moderate mitral regurgitation."

And he says the remodeling results are difficult to interpret without similar data from the comparator group, additional data points on the patients who eventually died or were lost to follow-up, and additional information about the management of these patients.

He concluded: "I do believe this device is potentially helpful, and if I had a patient who was inoperable, I would seriously consider having him undergo MitraClip placement. Nevertheless, while I would be thrilled to have the MitraClip available as an option for high-risk patients in general, I would also like to see randomized data if possible."

Whitlow said he accepts Turi's criticism of the comparator group, but he believes the patients were "very representative of those who did receive the MitraClip."

On the effectiveness of the clip, Whitlow said: "We know it is not as effective as surgery. It can reduce regurgitation to 2+ or less but not to 1+ or less. But even if it just reduces it by one grade, this still seems to be associated with left ventricular remodeling. Surgeons may be disappointed with these results, but these patients can't have surgery."

He added: "I agree this is not as good as a randomized controlled trial, but they are the only data we have, and everything does appear to be going in the right direction."