MitraClip and TEER: How Transcatheter Edge-to-Edge Repair Works, What the Evidence Shows

The Scene

The following scene is drawn from the composite of patients I have cared for in clinic and on the hospital floor. All identifying details are changed.

Thomas is 71 years old, a retired civil engineer from Springfield, Illinois. He has ischemic cardiomyopathy and a left ventricular ejection fraction of 28%. He has been on guideline-directed medical therapy for four years: sacubitril-valsartan, carvedilol, spironolactone, dapagliflozin. His most recent echocardiogram showed moderate-to-severe secondary mitral regurgitation: 3+ MR by color Doppler, effective regurgitant orifice area (EROA) 0.36 cm2.

His cardiologist refers him to a structural heart disease team at a tertiary center in Chicago.

Thomas is not a surgical candidate. His surgical mortality for mitral valve repair would be 8 to 12% given his reduced EF and comorbidities. He has been in and out of the hospital twice in the past year for acute decompensated heart failure episodes, both attributed to the worsening MR.

The structural heart team reviews his case. He meets the COAPT criteria: guideline-directed medical therapy improved, EROA 0.3 cm2 or above, LV not severely dilated, meaningful symptoms. They recommend MitraClip.

Thomas had never heard of MitraClip.

What It Is

Transcatheter edge-to-edge repair (TEER) is a catheter-based technique in which a clip is placed across the mitral valve leaflets to reduce mitral regurgitation. The principle is derived from a surgical technique (the Alfieri stitch, described by Ottavio Alfieri in 1991) in which the central portions of the anterior and posterior mitral leaflets are sewn together to create a double-orifice valve.

The MitraClip (Abbott Structural Heart) is the dominant TEER device in the United States, with FDA approval since 2013 for primary MR (symptomatic primary MR with prohibitive surgical risk) and expanded in 2019 for secondary MR meeting specific criteria. The Edwards PASCAL system received FDA approval in 2022 as an alternative platform with slightly different mechanical design.

Primary MR arises from a structural leaflet abnormality: prolapse, flail segment, chordal rupture, or rheumatic disease. The valve itself is the problem. In primary MR, the preferred treatment is surgical repair when the anatomy is favorable and the patient is operable; TEER is reserved for patients at prohibitive surgical risk.

Secondary (functional) MR arises not from leaflet disease but from ventricular dysfunction: the dilated or ischemic LV pulls the papillary muscles inferiorly and laterally, tethering the leaflets and preventing complete coaptation. The valve leaflets themselves are structurally normal. In secondary MR, TEER has shown mortality and heart failure hospitalization benefit in a specific patient population (COAPT criteria), making it a meaningful option alongside continued improvement of heart failure therapy.

The Mechanism

Mitral Valve Anatomy Relevant to TEER

The mitral valve consists of two leaflets (anterior and posterior) attached to a fibrous annulus and connected to papillary muscles via chordae tendineae. Normal coaptation requires leaflet contact zone height of at least 5 to 10 mm throughout systole. In MR, the leaflets fail to coapt: in primary MR, a structural leaflet defect creates the gap; in secondary MR, ventricular remodeling restricts leaflet mobility or displaces the coaptation zone.

The mitral leaflets are divided anatomically into segments: A1/P1 (anterolateral), A2/P2 (central, the most important coaptation zone), and A3/P3 (posteromedial).

How the MitraClip Works

The MitraClip delivery system is introduced via transfemoral venous access and advanced through a transseptal puncture into the left atrium. Under echocardiographic (TEE) and fluoroscopic guidance, the steerable delivery catheter positions the open clip over the mitral valve. The clip is advanced through the valve during diastole (when the leaflets are open), then withdrawn in systole to grasp both leaflets. When the clip arms close, the anterior and posterior leaflet edges are joined, creating a double-orifice valve with reduced regurgitant orifice.

The deployment is reversible until the clip is fully locked: the team can open, reposition, and recapture the clip multiple times to improve positioning and confirm adequate MR reduction by TEE before final deployment. Multiple clips can be placed if needed.

The hemodynamic result is a reduction in regurgitant volume, which reduces left atrial pressure, reduces pulmonary venous congestion, and improves effective forward cardiac output 5 / Solid .

The Physics of TEER: What It Fixes and What It Cannot

TEER reduces regurgitation but creates a double-orifice valve with a reduced total mitral valve area. For this reason, patients with pre-existing mitral stenosis (mean gradient above 4 mmHg, or valve area below 1.5 cm2) are poor candidates; clip placement will worsen the stenosis 5 / Solid .

TEER also does not address the secondary mechanism in functional MR: the dilated ventricle and annular dilation that generate the regurgitation remain unchanged. For this reason, the benefit of TEER in secondary MR depends entirely on the degree to which reducing MR volume unloads the LV and breaks the cycle of progressive remodeling.

How It Is Used

TEER for Primary MR

For primary MR (degenerative, prolapse, flail leaflet), surgical mitral valve repair remains the gold standard in operable patients at experienced mitral valve centers. For patients at prohibitive surgical risk (STS repair mortality above 8 to 10%), TEER is indicated (Class IIa) for:

• Symptomatic severe primary MR (stage D)
• Anatomy favorable for clip placement (A2/P2 segment pathology, adequate leaflet length, no severe calcification of the coaptation zone, no valve area below 4.0 cm2 before clip)

TEER for Secondary MR

For secondary MR in patients with heart failure, TEER is a Class IIa recommendation for patients with:

• Persistent moderate-to-severe (3+) or severe (4+) secondary MR
• improved guideline-directed medical therapy
• LV end-systolic dimension less than 70 mm (non-severely dilated LV)
• LVEF 20% or above
• Increased filling pressures (pulmonary capillary wedge pressure above 15 mmHg)
• Symptomatic heart failure (NYHA class II to IV)

This profile is derived from the COAPT inclusion criteria. Patients outside these parameters should not be expected to receive the COAPT trial mortality benefit 5 / Solid .

The Echo Anatomy Requirements

TEER requires meticulous pre-procedural echocardiographic planning. The key measurements:

• Coaptation depth (CD): distance from annulus to coaptation point; CD above 11 mm predicts higher clip failure
• Leaflet length of posterior mitral leaflet: below 7 mm increases the risk of insufficient leaflet tissue for clip grasp
• Location of regurgitant jet: A2/P2 central jet = ideal; commissural jet = higher difficulty
• Baseline valve gradient: mean transmitral gradient should be below 4 mmHg
• EROA and regurgitant volume: used for severity quantification

A dedicated structural heart echo team performs a protocol-driven TEE assessment before every TEER case.

Geographic Access

MitraClip centers require FDA-approved structural programs with dedicated operators, structural echocardiographers, and cardiac surgical backup. In Illinois, MitraClip is performed at Northwestern Medicine, Rush University Medical Center, and University of Chicago Medicine in Chicago, and at a small number of regional centers. Patients from Springfield and central Illinois frequently receive these procedures in Chicago, requiring coordination between referring cardiologists and structural heart programs.

The Evidence

EVEREST II: TEER vs. Surgery for Primary MR

EVEREST II (Feldman T, et al. N Engl J Med. 2011; doi:10.1056/NEJMoa1009355) enrolled 279 patients with moderate-to-severe or severe primary MR randomized to MitraClip versus surgical repair or replacement. At 12 months, the primary composite endpoint of freedom from death, surgery, or MR above 2+ favored surgery (73% vs. 55%; p < 0.001) 5 / Solid . Surgical patients had more residual MR reduction, but the MitraClip group had substantially lower rates of major adverse events at 30 days (15% vs. 48%; p < 0.001), primarily driven by lower transfusion requirements and shorter hospital stays. At 5 years, outcomes were similar between groups for those who survived without surgery for residual MR. What EVEREST II showed: MitraClip is less effective than surgery at eliminating MR but has lower procedural morbidity in operable patients. For primary MR in operable patients, surgery remains preferred.

COAPT: TEER for Secondary MR in HFrEF

COAPT (Stone GW, et al. N Engl J Med. 2018; doi:10.1056/NEJMoa1806640) is the landmark trial for TEER in secondary MR. 614 patients with symptomatic HFrEF (LVEF 20 to 50%) and moderate-to-severe or severe secondary MR despite improved GDMT were randomized to MitraClip plus GDMT versus GDMT alone.

Primary endpoint: rate of all hospitalizations for heart failure per patient-year. TEER: 35.8% per patient-year. GDMT alone: 67.9% per patient-year. Rate ratio 0.53, 95% CI 0.40 to 0.70; p < 0.001 5 / Solid .

Secondary endpoint: all-cause mortality at 24 months. TEER: 29.1%. GDMT alone: 46.1%. HR 0.62, 95% CI 0.46 to 0.82; p < 0.001 5 / Solid .

Heart failure hospitalizations were reduced by 47%. This mortality signal was unexpected and has driven rapid expansion of the COAPT-defined indication in clinical practice. What COAPT did not show: the benefit required careful patient selection; the mean EROA in COAPT was 0.41 cm2, higher than the threshold that defined benefit in the parallel French trial MITRA-FR.

MITRA-FR: The Contradictory Trial

MITRA-FR (Obadia JF, et al. N Engl J Med. 2018; doi:10.1056/NEJMoa1805374) enrolled 304 patients with secondary MR and HFrEF, also comparing MitraClip versus GDMT alone. At 12 months, the primary endpoint of death or unplanned hospitalization for heart failure showed no difference (54.6% vs. 51.3%; HR 1.16, 95% CI 0.73 to 1.84; not significant) 5 / Solid .

The COAPT/MITRA-FR discordance: why did two similar trials show opposite results?

The explanation proposed by Grayburn, Sannino, and Zoghbi (JACC 2019) is the concept of “proportionate” versus “disproportionate” MR in HFrEF 4 / Promising . In MITRA-FR, patients had more severely dilated LVs (proportionate MR: severe LV dilation explains the MR). In COAPT, MR was disproportionate to the degree of LV dilation: the MR itself was driving hemodynamic deterioration, not simply reflecting it. Fixing disproportionate MR breaks a cycle of deterioration; fixing proportionate MR does not change the underlying LV disease.

COAPT 5-Year Follow-Up

At 5 years, the COAPT benefit was maintained: all-cause mortality 57.3% (TEER) vs. 67.2% (GDMT alone); p = 0.013. Recurrent MR (grade 3+ or 4+) at 5 years was 19.7% in the TEER group, representing an acceptable durability for a catheter-based mitral intervention 5 / Solid .

MitraClip for HFpEF?

Secondary MR in HFpEF is a distinct phenotype. The MATTERHORN trial is examining TEER in this population 3 / Early . No RCT data exist for TEER in HFpEF secondary MR; current use is based on individual clinical judgment and COAPT extrapolation, which is not supported by the trial design.

The Patient Experience

Thomas’s MitraClip procedure took 90 minutes. He was under general anesthesia with TEE guidance throughout. Two clips were placed at the A2/P2 coaptation zone. His post-procedure TEE showed residual trace-to-mild MR. The mean transmitral gradient was 2 mmHg with two clips, within the acceptable range.

He went home on post-procedure day 1. His echocardiogram at 30 days showed persistent mild MR, stable LV function, and improved filling pressures by clinical assessment (no jugular venous distension, no peripheral edema).

At 6 months, he had not been hospitalized for heart failure. His exercise tolerance was modestly improved. He walked one to two blocks without dyspnea.

What Your Cardiologist Will Not Have Time to Explain

• MitraClip does not cure heart failure. Thomas still has ischemic cardiomyopathy with EF 28%. The clip reduces the MR volume that was worsening his heart failure; it does not improve LV systolic function. His GDMT continues unchanged. The clip is additive to guideline-directed medical therapy, not a replacement for it.

• Residual MR is expected and usually acceptable. TEER rarely eliminates MR completely; the goal is reduction from severe to mild or trace. Persistent mild MR after a technically successful procedure is the intended outcome in many cases, not a failure.

• Anticoagulation is required for a short period. Most centers use systemic heparin during the procedure and either antiplatelet or anticoagulant therapy for 30 days post-procedure while the clip endothelializes. Patients with AF continue their anticoagulation without interruption.

• The clip can fail. Partial or complete clip detachment (single leaflet attachment) occurs in approximately 2 to 5% of cases within the first 30 days 5 / Solid . If this occurs, recurrent severe MR returns. Repeat clipping or salvage surgery may be required.

• The transseptal puncture creates a small atrial septal defect. In most patients, this closes spontaneously within weeks. A small residual ASD is present in approximately 10 to 15% of patients at 6 months 4 / Promising and is hemodynamically inconsequential in the vast majority.

Sex Differences in TEER

Women are more likely than men to have primary MR from mitral valve prolapse (MVP is more prevalent in women, particularly younger women). Women referred for TEER for primary MR are older on average and more likely to have non-A2/P2 pathology, which increases procedural complexity 4 / Promising . Outcomes after TEER for secondary MR appear similar between sexes in registry data.

Decisions and Trade-Offs

When TEER Is Appropriate vs. When Surgery Is Better

For primary MR in a good surgical candidate at a high-volume mitral valve repair center (annual volume above 25 mitral repairs), surgical repair is standard. TEER should be offered when the surgical risk is prohibitive, the anatomy is favorable, and symptoms are significant. TEER outcomes for primary MR are not equivalent to expert surgical repair; a surgeon’s 98% successful repair rate with durable outcomes cannot be replicated by the clip in most hands.

For secondary MR in HFrEF meeting COAPT criteria, TEER provides meaningful mortality and hospitalization benefit and should be offered to eligible patients after GDMT improvement. The decision requires confirmation that the MR is disproportionate to LV dilation, not merely a reflection of it.

What Happens Without TEER in Eligible Patients

In COAPT, patients in the GDMT-alone arm had a 46% 2-year mortality and 68% annualized heart failure hospitalization rate. These are sobering numbers. They mean that for a COAPT-eligible patient with secondary MR who is denied or declines TEER, the 2-year prognosis rivals many malignancies.

The Edwards PASCAL System

The CLASP IID trial (Allen C, et al. J Am Coll Cardiol. 2023; doi:10.1016/j.jacc.2022.12.021) demonstrated non-inferiority of PASCAL to MitraClip for secondary MR at 1 year for heart failure hospitalization and survival 4 / Promising . PASCAL uses a different mechanism (paddle-based grasping with a wider coaptation element) that may be advantageous in certain anatomical configurations. The choice between MitraClip and PASCAL is center- and anatomy-dependent.

The Three Questions Every Patient Should Ask

1. “Have I been on best available guideline-directed medical therapy long enough for you to assess whether my MR is truly disproportionate, or might it improve further with medical improvement?” Most heart failure cardiologists recommend at least 3 months of GDMT improvement before the TEER decision unless the patient is acutely decompensated.

2. “What is my EROA, and does it meet the COAPT criteria?” The EROA threshold that defined COAPT benefit was approximately 0.3 cm2. Below this threshold, the COAPT benefit may not apply.

3. “If the clip fails or provides insufficient MR reduction, what is the surgical backup plan?” Surgical mitral valve replacement after failed TEER is technically more complex than primary valve surgery; the anatomy of the clipped leaflets changes the surgical approach.

Clinical Synthesis

Thomas’s case illustrates the second chance that TEER offers in a very specific patient population. He has ischemic cardiomyopathy from a heart attack that could, hypothetically, have been prevented. His Lp(a) measured at 50 was 178 nmol/L (above the 125 nmol/L risk threshold). His LDL-C at 45 was “borderline” at 148 mg/dL. Neither received treatment.

The LAD occlusion at 58 left him with an EF of 28%. The secondary MR developed over the next decade as his ventricle remodeled. By the time he presented to the structural heart program, his disease had become so complex that even the best interventions were palliative.

That is the core clinical thesis applied to the MitraClip story: the clip is a remarkable rescue device. The goal is to never need it.

If you have secondary MR and heart failure: a structured cardiovascular assessment reviews whether your GDMT is truly improved (many patients who are told their doses cannot go higher have not had uptitration attempts), whether your EROA meets COAPT criteria, and whether a Structural Heart Disease Team consultation is warranted.

If you have primary MR under surveillance: the Signal Check addresses when you should be referred to a mitral valve center of excellence, what the interval echo schedule should be, and what symptoms represent the threshold for urgent consultation.

The Signal Check is fifteen questions mapping the cardiovascular risk pattern across the physiological domains most commonly missed in standard screenings. It produces a specific starting point for your next clinical conversation.