MitraClip Effective for Post-MI Acute Mitral Regurgitation With Cardiogenic Shock

Bruce Jancin

October 19, 2020

Percutaneous mitral valve repair with the MitraClip appears to be a safe, effective, and life-saving new treatment for severe acute mitral regurgitation (MR) secondary to MI in surgical noncandidates, even when accompanied by cardiogenic shock, according to data from the international IREMMI registry.

"Cardiogenic shock, when adequately supported, does not seem to influence short- and mid-term outcomes, so the development of cardiogenic shock should not preclude percutaneous mitral valve repair in this scenario," Rodrigo Estevez-Loureiro, MD, PhD, said in presenting the IREMMI (International Registry of MitraClip in Acute Myocardial Infarction) findings at the Transcatheter Cardiovascular Research Therapeutics virtual annual meeting.

Commentators hailed the prospective IREMMI data as potentially practice changing in light of the dire prognosis of such patients when surgery is deemed unacceptably high risk because medical management, the traditionally the only alternative, has a 30-day mortality of up to 50%.

Severe acute MR occurs in an estimated 3% of acute MIs, and in roughly 10% of patients who present with acute MI complicated by cardiogenic shock (CS). The impact of intervening with the MitraClip in an effort to correct the acute MR arising from MI with CS has previously been addressed only in sparse case reports. The new IREMMI study is easily the largest dataset to date detailing clinical and echocardiographic outcomes, Estevez-Loureiro of Alvaro Cunqueiro Hospital in Vigo, Spain, said at the meeting, sponsored by the Cardiovascular Research Foundation.

He reported on 93 consecutive patients who underwent MitraClip implantation for acute MR arising in the setting of MI, including 50 patients in CS at the time of the procedure. All 93 patients had been turned down by their surgical team because of extreme surgical risk. Three-quarters of the MIs showed ST-segment elevation. Only six patients had a papillary muscle rupture; in the rest, the mechanism of acute MR involved left ventricular global remodeling associated with mitral valve leaflet tethering. Percutaneous valve repair was performed at 18 expert valvular heart centers in the United States, Canada, Israel, and five European countries.

Procedural Success

Time from MI to MitraClip implantation averaged 24 days in the CS patients and 33 days in the comparator arm without CS.

"These patients had been turned down for surgery, so the attending physicians generally followed a strategy of trying to cool them down with mechanical circulatory support and vasopressors. MitraClip wasn't an option at the beginning, but after two or three failed weanings from all the possible therapies, then MitraClip becomes an option. This is one of the reasons why the time lapse between MI and the clip is so large," the cardiologist explained.

Procedural success rates were similar in the two groups: 90% in those with CS and 93% in those without. However, average procedure time was significantly longer in the CS patients: 143 minutes versus 83 minutes in the patients without CS.

At baseline, 86% of the CS group had grade 4+ MR, similar to the 79% rate in the non-CS patients. Postprocedurally, 60% of the CS group were MR grade 0/1 and 34% were grade 2, comparable to the rates of 65% and 23% in the non-CS group.

At 3 months' follow-up, 83.4% of the CS group had MR grade 2 or less, again not significantly different from the 90.5% rate in non-CS patients. Systolic pulmonary artery pressure was also similar: 39.6 mm Hg in the CS patients, 44 mm Hg in those without. While everyone was New York Heart Association functional class IV preprocedurally, 79.5% of the CS group were NYHA class I or II at 3 months, not significantly different from the 86.5% prevalence in the comparator arm.

Longer-Term Clinical Outcomes

At a median follow-up of 7 months, the composite primary clinical outcome composed of all-cause mortality or heart failure rehospitalization did not differ between the two groups: a 28% rate in the CS group and 25.6% in non-CS patients. All-cause mortality occurred in 16% with CS and 9.3% without, again not a significant difference.

In a Cox regression analysis, neither surgical risk score, patient age, left ventricular geometry, nor CS was independently associated with the primary composite endpoint. Indeed, the only independent predictor of freedom from mortality or heart failure readmission at follow-up was procedural success, which is very much a function of the experience of the heart team, Estevez-Loureiro continued.

Michael A. Borger, MD, PhD, who comoderated the late-breaking clinical science session, was wowed by the IREMMI results.

"The mortality rates, I can tell you, compared to traditional surgical series of acute MR in the face of ACS [acute cardiogenic shock] are very, very respectable," commented Borger, director of the cardiac surgery clinic at the Leipzig University Heart Center in Germany.

"Extremely impressive," agreed discussant Vinayak N. Bapat, MD, a cardiothoracic surgeon and valve scientist at the Minneapolis Heart Institute Foundation in Minnesota. He posed a practical question: "Should we take from this presentation that patients should be stabilized with something like ECMO [extracorporeal membrane oxygenation] or Impella [left ventricular assist device], then transferred to an expert center for the procedure?"

"I think that the stabilization is essential in the patients with cardiogenic shock," Estevez-Loureiro replied. "Unlike with surgery, it's very difficult to establish a MitraClip procedure in a couple of hours in the middle of the night. You have to stabilize them and then treat for shock with ECMO, Impella, or both. I think they should be transferred to a center than can deliver the best treatment. In centers with less experience, patients can be put on mechanical support and transferred to an expert valve center, not only for MitraClip implantation, but for discussion of all the treatment possibilities, including surgery."

At a press conference in which Estevez-Loureiro presented highlights of the IREMMI study, discussant Dee Dee Wang, MD, said the international coinvestigators "need to be applauded" for this study.

"Having these outcomes is incredible," declared Wang, a structural heart disease specialist at the Henry Ford Health System, Detroit, Michigan.

While this is an observational study, it's a high-quality dataset with excellent methodology. And conducting a randomized trial in patients with such high surgical risk scores — the CS group had an average EuroSCORE II of 21 — would be extremely difficult, according to the cardiologist.

Estevez-Loureiro reported receiving research grants from Abbott and serving as a consultant to that company, as well as Boston Scientific.

Transcatheter Cardiovascular Therapeutics (TCT) 2020: Late-Breaking Clinical Science Session IV. Presented October 17, 2020.

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