Mitral stenosis
Planimetry and PHT, the rate-dependent gradient, Wilkins anatomy for balloon valvotomy, and LA thrombus.
Numbers to remember
- Clinically significant MS: MVA ≤1.5 cm²; very severe ≤1.0 cm² [6,7]
- MVA from PHT = 220 / PHT [43]
- Mean gradient is rate-dependent: report it with the heart rate [6]
- Wilkins score ≤8 favours percutaneous mitral commissurotomy (PMC) [45]
- Moderate–severe MS with AF → vitamin K antagonist, not a DOAC [6,182]
Questions echo must answer
Rheumatic MS remains common in many countries. Echo grades severity, decides whether percutaneous mitral commissurotomy (PMC) is suitable, and detects contraindications [6,7]. Degenerative (calcific) MS in older patients is a different disease: the annulus calcifies without commissural fusion, and PMC is not suitable [6].
- AetiologyRheumatic (commissural fusion, hockey-stick anterior leaflet, chordal thickening) or degenerative (MAC) [6].
- SeverityPlanimetry MVA (reference), PHT, mean gradient with heart rate, continuity [6,43,44].
- PMC suitabilityWilkins score, commissural calcification, MR, LA thrombus [45].
- ConsequencesLA size, AF, PASP, RV function, TR [6].
- DiscordanceExercise echo if symptoms and severity do not match [28].
Acquisition protocol
- PSAX-MVPlanimetry of the orifice at the leaflet tips in mid-diastole (scan from base to tips to find the smallest orifice). Assess commissural fusion and calcification [6].
- PLAXHockey-stick anterior leaflet; LA size; leaflet thickness and mobility.
- A4C CWMean gradient (trace the envelope) with heart rate; PHT from the early-diastolic slope [43,44].
- WilkinsMobility, thickening, calcification and subvalvular thickening, each scored 1–4 [45].
- MRGrade (moderate or greater MR is a relative contraindication to PMC) [6].
- Right heartTR velocity and PASP, TAPSE, TR severity.
- LA and LAAThrombus. TOE before PMC [6,35].
- ExerciseMean gradient and PASP at peak exercise if symptoms are discordant [28].
- Planimetry MVA
- PHT and MVA-PHT
- Mean gradient and heart rate
- Wilkins score
- Commissural calcification
- MR grade
- PASP, RV, TR
- LA and LAA thrombus (TOE before PMC)
Diagnosis & severity
| Measure | Clinically significant (severe) | Notes |
|---|---|---|
| MVA planimetry | ≤1.5 cm² | Reference method [6,7] |
| MVA by PHT (220/PHT) | ≤1.5 cm² | Unreliable right after PMC, with AR or abnormal LV compliance [43] |
| Mean gradient | Supportive (often >5–10 mmHg) | Varies with heart rate and flow [6,44] |
| PASP | >50 mmHg | Supports significance [6] |
Wilkins score [45]
Four features, each scored 1–4: leaflet mobility, leaflet thickening, calcification and subvalvular thickening (total 4–16). A score ≤8 predicts a good PMC result. Commissural calcification and bilateral commissural fusion also influence the outcome.
Thresholds that change management
- Symptomatic clinically significant rheumatic MS (MVA ≤1.5 cm²) with favourable anatomy → PMC [6,7].
- Unfavourable anatomy, moderate or greater MR, or LA thrombus → surgery (or PMC in selected patients after thrombus resolution) [6].
- Asymptomatic patients → PMC may be considered with favourable anatomy and high thromboembolic risk (previous embolism, dense LA contrast, new AF), PASP >50 mmHg, need for major non-cardiac surgery, or pregnancy desire [6].
- Moderate–severe MS with AF or LA thrombus → vitamin K antagonist. DOACs are not recommended [6,182].
- Degenerative calcific MS → individualised; surgical and transcatheter options are limited [6].
Pitfalls & mimics
PitfallThe mean gradient is rate- and flow-dependent. Tachycardia or anaemia raises it, and bradycardia lowers it. Always report the heart rate [6,44].
- Planimetry in the wrong plane (above the tips) overestimates the area. Sweep to find the smallest orifice.
- Too much gain thickens leaflet edges and underestimates the area.
- PHT fails immediately after PMC, with significant AR, and with abnormal LV compliance [43].
- Degenerative MS: planimetry is difficult and PHT unreliable. Use the continuity equation with care.
- Cor triatriatum and LA myxoma produce a transmitral gradient without valve disease.