MATTERHORN Signals Non-Inferiority of M-TEER Versus Surgery for Functional Mitral Regurgitation in the Short-Term

The MATTERHORN trial, presented at ESC 2024 and published in The New England Journal of Medicine, demonstrates that, for patients with heart failure (HF) and functional mitral regurgitation (FMR), transcatheter edge-to-edge mitral valve repair (M-TEER) is non-inferior to surgical mitral valve repair or replacement, with significantly fewer adverse events at 30 days.

Functional mitral regurgitation (FMR) is a frequent complication of heart failure and is associated with increased mortality and morbidity. Current guidelines from the European Society of Cardiology (ESC) recommend surgical mitral valve repair for patients with secondary MR who are suitable candidates, while transcatheter approaches, particularly M-TEER, are recommended for patients at high surgical risk or with unfavorable anatomy for surgery. U.S. guidelines similarly prioritize surgery, reserving M-TEER for patients with high surgical risk. In practice, surgery is rarely pursued for functional mitral regurgitation as the sole operative indication.

The MATTERHORN trial was a multicenter, randomized, controlled, noninferiority trial that enrolled 210 patients from Germany. These patients had symptomatic heart failure with secondary MR (grade 3+ or 4+), left ventricular ejection fraction (LVEF) between 20% and 50%, and were considered candidates for both surgical repair and M-TEER. Patients were randomized in a 1:1 ratio to either M-TEER or surgical mitral valve repair or replacement. The primary efficacy endpoint was a composite of death, heart failure hospitalization, mitral valve reintervention, left ventricular assist device implantation, or stroke within one year. The primary safety endpoint was a composite of major adverse events at 30 days.

At one year, the composite efficacy endpoint occurred in 16.7% of patients in the M-TEER group compared to 22.5% in the surgery group, meeting the criterion for noninferiority (mean difference, -6 percentage points; 95% CI, -17 to 6; p<0.001). Importantly, M-TEER was associated with significantly fewer adverse events at 30 days, with 14.9% in the M-TEER group experiencing a major adverse event compared to 54.8% in the surgery group (mean difference, -40 percentage points; 95% CI, -51 to -27; p<0.001). These safety outcomes were primarily driven by a lower incidence of major bleeding and new-onset atrial fibrillation in the M-TEER group, both expected to be higher in the surgical arm.

While both treatment groups showed a high level of success in reducing MR severity, with 96.1% of patients in the M-TEER group and 98.6% in the surgery group having MR grade 2+ or lower at one year, the lower rate of procedural complications and faster recovery in the M-TEER group offer significant advantages, particularly for patients at high surgical risk. The short-term, single-year follow-up is a key caveat in contextualizing these results as surgery expectedly has higher rates of short-term bleeding, atrial fibrillation, and re-hospitalization while may offer more durable long-term benefits, although that remains to be seen.

The MATTERHORN trial builds upon previous studies and strengthens the case for M-TEER as a safe and effective alternative to surgery in patients with heart failure and FMR. For patients who are poor surgical candidates, M-TEER provides a less invasive option that is associated with fewer complications and a faster recovery. Longer-term data will be important for guiding decision-making.

Reference:

Baldus S, Doenst T, Pfister R, et al. Transcatheter Repair vs. Mitral-Valve Surgery for Secondary Mitral Regurgitation. N Engl J Med. 2024; DOI:10.1056/NEJMoa2408739.