MitraClip or PASCAL? Two-year results of the CLASP IID trial

What is degenerative mitral regurgitation?

The mitral valve sits between the left atrium and left ventricle. When it does not close effectively, blood leaks backward during ventricular contraction. This is called mitral regurgitation (MR).

In primary or degenerative MR, the abnormality lies within the valve apparatus itself, such as leaflet prolapse, a flail segment or chordal degeneration. This differs from secondary MR, in which ventricular or atrial remodeling prevents an otherwise structurally different valve from closing effectively. The distinction is important because treatment pathways differ.

What do MitraClip and PASCAL do?

Both systems are used during mitral transcatheter edge-to-edge repair (M-TEER). A catheter is generally advanced through a vein in the groin, across the interatrial septum and into the left atrium. The anterior and posterior mitral leaflets are approximated at the site of regurgitation to reduce backward blood flow.

MitraClip and PASCAL use the same fundamental therapeutic concept but have differences in device design and leaflet engagement. Whether those differences matter for a particular patient depends largely on valve anatomy and procedural planning.

Is every patient with severe MR a candidate for TEER?

No. Surgical mitral valve repair remains the principal treatment for appropriate operable patients with severe primary MR. The 2025 ESC/EACTS guidelines state that TEER should be considered in symptomatic patients with severe primary MR who are anatomically suitable and considered at high surgical risk by the Heart Team.

The decision therefore starts before the question of MitraClip versus PASCAL. The mechanism and severity of MR, symptoms, surgical risk, overall health and mitral valve anatomy must first be evaluated.

Why does valve anatomy matter?

Successful TEER requires secure leaflet capture while preserving an adequate mitral valve opening. Transesophageal echocardiography is used to assess leaflet length and mobility, prolapse or flail anatomy, coaptation geometry, calcification, jet location, valve area and baseline transmitral gradient.

In an echocardiographic analysis of CLASP IID, a smaller flail gap was associated with a greater likelihood of achieving residual MR ≤1+. Other features such as limited valve area, short posterior leaflet tissue, deeper coaptation and substantial calcification may increase procedural difficulty in some patients. These characteristics are interpreted as part of the complete anatomy rather than as isolated pass-or-fail rules.

Why is CLASP IID important?

CLASP IID was the first randomized controlled trial to directly compare PASCAL and MitraClip in patients with significant symptomatic degenerative MR considered at prohibitive surgical risk.

The full randomized cohort included 300 patients: 204 assigned to PASCAL and 96 to MitraClip. At six months, MR ≤2+ was reported in 97.9% and 95.7%, respectively. Thirty-day major adverse event rates were 4.6% and 5.4%. The prespecified noninferiority criteria were met.

What happened at one year?

Mitral regurgitation reduction remained largely sustained in both groups. MR ≤2+ was present in 95.8% of PASCAL patients and 93.8% of MitraClip patients; MR ≤1+ was reported in 77.1% and 71.3%, respectively. Secondary noninferiority endpoints were met.

Differences in survival, freedom from heart-failure hospitalization and major adverse events were not statistically significant at one year. Functional class and quality-of-life measurements improved from baseline in both groups and remained improved at one year.

What did the two-year results show?

The two-year report published in 2025 provided longer follow-up of the randomized cohort.

• MR ≤2+: 95.0% with PASCAL and 91.5% with MitraClip (P=0.500).
• MR ≤1+: 77.2% and 67.8% (P=0.198).
• Freedom from all-cause mortality: 80.8% and 86.2% (P=0.216).
• Freedom from cardiovascular mortality: 88.6% and 90.4% (P=0.666).
• Freedom from heart-failure hospitalization: 86.4% and 94.3% (P=0.058).
• Freedom from nonelective mitral valve reintervention: 97.9% in both groups.

There were numerical differences between the groups, but the randomized two-year comparisons did not demonstrate statistically significant differences for these endpoints. It would therefore be inappropriate to infer device superiority from the raw percentages alone.

So which should be used: MitraClip or PASCAL?

The main message from CLASP IID is that substantial MR reduction could be achieved and largely maintained through two years with both contemporary TEER systems in carefully selected patients with degenerative MR.

Device selection does not depend on a single percentage from a clinical trial. Leaflet anatomy, the location and number of regurgitant jets, valve area, anticipated transmitral gradient, previous cardiac procedures and technical feasibility are considered together. The most appropriate system can therefore differ from one patient to another.

What is known beyond two years?

Direct randomized PASCAL-versus-MitraClip evidence is currently strongest through two years. Longer-term TEER durability literature is more heterogeneous and combines different devices, patient populations and study designs.

A 2026 expert review of 33 studies found that pooled MR recurrence and reintervention rates were approximately 5% to 10% during the first months and remained relatively stable through the first three years. By five years, pooled MR recurrence was approximately 17% and reintervention approximately 9%. The signal for long-term failure was greater in primary MR. These figures are not a five-year head-to-head comparison of PASCAL and MitraClip and should not be interpreted as such.

Two-year CLASP IID findings therefore provide encouraging intermediate-term durability data, while systematic follow-up beyond five years remains important, particularly in primary degenerative MR.