Comprehensive Annular and Subvalvular Repair of Chronic Ischemic Mitral Regurgitation Improves Long-Term Results With the Least Ventricular Remodeling
In a sheep model of chronic ischemic mitral regurgitation (MR), does concomitant severing of second-order mitral chordae improve results compared to isolated mitral valve reduction annuloplasty?
A model of posterolateral myocardial infarction previously shown to produce chronic left ventricular (LV) remodeling and ischemic MR was performed in 28 sheep. At 3 months after infarction, sheep were randomized to one of four arms: sham surgery, isolated undersized annuloplasty, isolated bileaflet chordal cutting, or combined therapy (n = 7 each). At each of 3 time intervals (baseline, chronic myocardial infarction/intervention [3 months], and euthanasia [6.6 months]), LV volumes, ejection fraction, and wall motion score index; MR regurgitation fraction and vena contracta; mitral annulus area; and posterior leaflet restriction angle (posterior leaflet to mitral annulus area) were measured using two- and three-dimensional echocardiography.
All groups were comparable at intervals of baseline and chronic myocardial infarction (3 months), with mild to moderate MR (MR vena contracta 4.6 ± 0.1 mm, MR fraction 24.2 ± 2.9%) and mitral annulus dilatation (p < 0.01). At euthanasia, MR progressed to moderate to severe in controls, but decreased to trace with ring plus chordal cutting versus trace to mild with chordal cutting alone versus mild to moderate with annuloplasty ring alone (MR vena contracta 5.9 ± 1.1 mm in controls, 0.5 ± 0.08 with both, 1.0 ± 0.3 with chordal cutting alone, 2.0 ± 0.4 with ring alone; p < 0.01). In addition, LV end-systolic volume increased by 108% in controls versus 28% with ring plus chordal cutting, less than with each intervention alone (p < 0.01). In multivariate analysis, LV end-systolic volume and mitral annulus area most strongly predicted MR (r2 = 0.82, p < 0.01).
Combined annular and subvalvular repair (severing secondary mitral chordae) improved long-term reduction of chronic ischemic MR and LV reverse remodeling in this sheep model, without decreasing global or segmental LV function at follow-up.
In the absence of robust clinical trials, debate persists as to whether chronic ischemic MR is the mechanism or simply a marker of adverse prognosis, and whether intervention for chronic ischemic MR affects clinical outcomes. Current guidelines recommend concomitant mitral intervention at the time of coronary artery bypass surgery among patients with severe ischemic MR, and favor mitral repair (usually performed as an undersized annuloplasty) over replacement. However, MR can recur in up to 30% of patients; debate remains as to the best technique(s) for repair, and whether (and how) less than severe MR should be addressed. Dividing mitral chordae is a potentially simple method that can increase leaflet mobility, limiting apical displacement and leaflet tethering, and allow better leaflet coaptation. Previously published animal data suggest that dividing chordae can result in worsened LV systolic function, whereas the present study suggests superior reduction of MR and preserved systolic function compared to annuloplasty alone. This study adds interesting new data to ongoing debates about the optimal management of patients with chronic ischemic MR.
Clinical Topics: Cardiac Surgery, Heart Failure and Cardiomyopathies, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Cardiac Surgery and Heart Failure, Interventions and Imaging, Echocardiography/Ultrasound
Keywords: Prognosis, Infarction, Ventricular Remodeling, Mitral Valve Annuloplasty, Echocardiography
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