Functional mitral stenosis after surgical annuloplasty for ischemic mitral regurgitation: Importance of subvalvular tethering in the mechanism and dynamic deterioration during exertion

Objective

Diastolic subvalvular mitral leaflet tethering by left ventricular remodeling that restricts leaflet opening in the presence of annular size reduction by surgery for ischemic mitral regurgitation potentially causes functional mitral stenosis in the absence of organic leaflet lesions. Exercise, known to worsen systolic tethering and ischemic mitral regurgitation, might also dynamically exacerbate such mitral stenosis by increasing tethering. This study evaluates the mechanism and response of such mitral stenosis to exercise.

Methods

We measured the diastolic mitral valve area, annular area, and peak and mean transmitral pressure gradient by echocardiography in 20 healthy individuals and 31 patients who underwent surgical annuloplasty for ischemic mitral regurgitation.

Results

Although the mitral valve area and annular area did not significantly differ in healthy individuals (4.7 ± 0.6 cm² vs 5.2 ± 0.6 cm², not significant), mitral valve area was significantly smaller than the annular area in patients after annuloplasty (1.6 ± 0.2 cm² vs 3.3 ± 0.5 cm², P < .01). The mitral valve area was less than 1.5 cm² only after the surgery (P < .01) and was significantly correlated with restricted leaflet opening (r² = 0.74, P < .001), left ventricular dilatation (r² = 0.17, P < .05), and New York Heart Association functional class (P < .05). Exercise stress echocardiography of 12 patients demonstrated dynamic worsening in functional mitral stenosis (mitral valve area: 2.0 ± 0.5 cm² to 1.4 ± 0.2 cm², P < .01; mean pressure gradient: 1.5 ± 0.9 mm Hg to 6.0 ± 2.2 mm Hg, P < .01).

Conclusions

Persistent subvalvular leaflet tethering in the presence of annular size reduction by surgery in ischemic mitral regurgitation frequently causes functional mitral stenosis at the leaflet tip level, which is related to heart failure symptoms and can be dynamic with significant exercise-induced worsening.

CTSNet classification: 35

Abbreviations and Acronyms: EDV, end-diastolic volume, ESV, end-systolic volume, LV, left ventricular, MR, mitral regurgitation, MS, mitral stenosis, MVA, mitral valve area, NYHA, New York Heart Association, PG, pressure gradient, PM, papillary muscle