A patient with mitral stenosis undergoes closed mitral commissurotomy via a left thoracotomy. The surgeon introduces a finger through the left atrial appendage. Through which valvular structure does the stenotic leaflet fusion most commonly occur, and which interatrial structure can the surgeon feel from within the left atrium?

• A Fusion at the aortic and mural leaflet junction; muscular crista can be felt
• B Fusion at the posterior leaflet; Eustachian valve felt on the septum
• C Fusion at the anterolateral and posteromedial commissures; valve of the fossa ovalis (limbus of foramen ovale) felt on the interatrial septum ✓
• D Fusion at the papillary muscle tips; pectinate muscles felt

Explanation

Mitral stenosis results from rheumatic fusion of the anterolateral and posteromedial commissures of the mitral valve (the two leaflets — anterior/aortic and posterior/mural — fuse at their commissures). The surgeon's finger within the left atrium can palpate the valve of the foramen ovale (limbus fossa ovalis) on the interatrial septum — the thin membranous remnant that demarcates the patent foramen ovale site. This anatomical landmark is important to avoid inadvertent entry into the right atrium. The Eustachian valve is in the right atrium near the inferior vena cava orifice.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.