Primary Mitral Regurgitation

Definition

Primary mitral regurgitation (PMR) is MR caused by intrinsic structural abnormality of one or more components of the mitral valve apparatus (leaflets, chordae, papillary muscles, annulus). The most common cause in high-income countries is myxomatous degeneration (prolapse); other causes include rheumatic disease, infective endocarditis, and radiation.

Key Concepts

Evaluation

• Echo: Integrative approach — vena contracta, EROA (PISA), regurgitant volume (RVol); severe PMR: EROA ≥40 mm², RVol ≥60 mL, RFrac ≥50%
• CMR: More accurate LV volumes and LVEF than 2D echo; important in borderline or technically limited studies; direct flow quantification of RVol
• Genetic evaluation: Recommended if connective tissue disease or familial presentation is suspected (e.g., Marfan syndrome)
• Biomarkers: BNP/NT-proBNP — useful for risk stratification and follow-up in asymptomatic patients
• Assess concomitant TR (secondary TR common in severe PMR due to LA/RA dilatation) sources/vhd-esc-2025 very high

Indications for Intervention

• Class I: Symptomatic severe PMR
• Class I: Asymptomatic severe PMR with LVESD ≥40 mm or LVESDi ≥20 mm/m² or LVEF ≤60%
• Class I B (new 2025): Surgical MV repair in low-risk asymptomatic patients with severe PMR, preserved LV function (LVESD <40 mm, LVESDi <20 mm/m², LVEF >60%), when durable repair is likely and ≥3 of the following:
  • AF
  • SPAP at rest >50 mmHg
  • LA dilatation (LAVI ≥60 mL/m² or LA diameter ≥55 mm)
  • Concomitant secondary TR ≥ moderate
• Class IIa: TEER at high surgical risk not suitable for surgery
• Class IIb (new 2025): Minimally invasive MV surgery at experienced centres to reduce length of stay and accelerate recovery sources/vhd-esc-2025 very high

Surgical Repair

• MV repair strongly preferred over replacement when anatomically feasible — especially in degenerative (prolapse) aetiology
• Expert centre outcomes: freedom from moderate/severe MR 87.5% at 20 years; repair durability superior to replacement in PMR due to prolapse
• Minimally invasive approaches reduce hospital stay; reserved for experienced centres
• Repair rates vary widely across institutions; referral to high-volume repair centres is strongly recommended sources/vhd-esc-2025 very high

TEER in PMR

• Transcatheter edge-to-edge repair (MitraClip/PASCAL) is an option for high-risk PMR patients not suitable for surgery
• Anatomical eligibility must be confirmed (MV morphology, coaptation geometry, leaflet length and motion)
• Residual MR and higher gradient rates after TEER vs surgical repair; yearly follow-up recommended
• Failed TEER requiring surgical salvage carries high peri-operative mortality and low repair rates sources/vhd-esc-2025 very high

Follow-up

• Asymptomatic severe PMR not meeting intervention criteria: clinical + echo every 6 months (watchful waiting in Heart Valve Clinic)
• Moderate PMR: yearly follow-up, echo every 1–2 years
• After surgical repair: echo at 3 months, 1 year, then every 2–3 years if no LV dysfunction/arrhythmia
• After TEER: yearly follow-up (higher residual MR rate than surgery)

ACC/AHA 2020 — Intervention Criteria

• Class I B-NR: Symptomatic severe PMR (Stage D) → MV intervention regardless of LVEF
• Class I B-NR: Asymptomatic severe PMR with LVEF ≤60% or LVESD ≥40 mm (Stage C2) → MV surgery
• Class I B-NR: Repair preferred over replacement when degenerative aetiology and durable repair is feasible
• Class IIa B-NR: Asymptomatic Stage C1 (LVEF ≥60%, LVESD ≤40 mm) → repair reasonable when likelihood >95% successful durable repair AND expected mortality <1% at a Primary or Comprehensive Valve Center
• Class IIa B-NR: Severely symptomatic (NYHA III/IV) + high/prohibitive surgical risk → TEER reasonable if anatomy favourable and life expectancy ≥1 year
• Note: ESC 2025 introduced the 3-of-4 additional criteria for asymptomatic PMR surgery (AF, SPAP >50, LA dilatation, concomitant secondary TR); ACC/AHA 2020 used a simpler LVEF/LVESD threshold sources/VHD-AHA-2020 very high
• Vasodilator therapy: NOT indicated in asymptomatic PMR with normal LV and normotension (ACC/AHA 2020 Class III:No Benefit) — may worsen MR by reducing LV size and mitral closing force sources/VHD-AHA-2020 very high

Contradictions / Open Questions

• The new "3-of-4 criteria" (ESC 2025) for asymptomatic PMR surgery is based on observational data and expert consensus — no RCT compares early surgery vs watchful waiting using these criteria specifically; ACC/AHA 2020 does not use this approach sources/vhd-esc-2025 very high vs sources/VHD-AHA-2020 very high
• Minimally invasive MV surgery outcomes are centre-dependent; insufficient evidence for broad adoption outside high-volume centres
• Optimal timing of intervention in asymptomatic patients with progressive LA dilatation but no overt symptoms remains debated

Connections

• Related to concepts/Valvular-Heart-Disease
• Related to concepts/Secondary-Mitral-Regurgitation
• Related to concepts/Tricuspid-Regurgitation
• Related to entities/Atrial-Fibrillation
• Related to entities/Heart-Failure

Sources

• sources/VHD-AHA-2020
• sources/vhd-esc-2025