Objective: Treatment of ischemic mitral regurgitation accompanied by strong tethering remains a challenge. Undersized ring annuloplasty is frequently associated with residual/recurrent mitral regurgitation caused by mitral-leaflet tethering. Although chordal cutting is a simple procedure for repairing severe tethering of the anterior mitral leaflet, it often affects mitral valvular-ventricular continuity. In this study, using 3-dimensional echocardiography, we investigated the effects of "chordal translocation" on the geometry of the mitral components in a canine model of acute ischemic mitral regurgitation.
Methods: In 6 mongrel dogs, under cardiopulmonary bypass with cardiac arrest, artificial chordae were implanted to each papillary-muscle tip and passed through the midseptal annulus to an external tourniquet to control the tension of the stitch thereafter. Subsequently, secondary chordae were cut near their point of attachment to the anterior leaflet. After weaning from cardiopulmonary bypass, acute ischemic mitral regurgitation was induced by ligating the obtuse marginal branches. We obtained data in 2 states of the artificial chordae: relaxation (simulating chordal cutting) and gentle traction (simulating chordal translocation).
Results: In the chordal translocation state versus the chordal cutting state, the left ventricle ejection fraction (42.6% +/- 2.9% vs 33.2% +/- 2.3%, P < .0001), preload recruitable stroke work (54.8 +/- 2.7 mm Hg vs 34.1 +/- 2.2 mm Hg, P = .0002), and end-systolic elastance (6.7 +/- 0.5 mm Hg/mL vs 4.2 +/- 0.2 mm Hg/mL, P = .0013) improved markedly. The mitral-valve tethering volume, defined as the volume enclosed by the mitral annulus and 2 leaflets, was smaller in the chordal translocation state than in the chordal cutting state (812 +/- 88 mm(3) vs 1213 +/- 41 mm(3), P = .03). In the chordal translocation state (CT-1 and CT-2) versus the chordal cutting state, the posterior mitral-leaflet tethering area (15.7 +/- 0.7 mm(2) vs 25.1 +/- 1.2 mm(2), P < .0001 for CT-1 and 15.0 +/- 0.7 mm(2) vs 25.1 +/- 1.2 mm(2), P < .0001 for CT-2) showed a greater improvement than the anterior mitral-leaflet tethering area (41.0 +/- 0.7 mm(2) vs 46.1 +/- 1.3 mm(2) for CT-1, P = .01 and 812 +/- 88 mm(2) vs 1213 +/- 41 mm(2) for CT-2, P = .03). The mitral annular geometry did not differ between the states.
Conclusion: Compared with chordal cutting alone, chordal translocation improved both the left ventricle function and mitral geometry in a canine model of acute ischemic mitral regurgitation. Chordal translocation may be beneficial because it ameliorates the tethering of both the anterior and posterior leaflets, which is aggravated by mitral annuloplasty alone.