Abstract 3171: Chordal Cutting to Relieve Mitral Leaflet Tethering Diminishes LV Remodeling Following Chronic Inferior Myocardial Infarction

Background. We have previously demonstrated that severing two second-order chordae to the anterior mitral leaflet (AL) in sheep does not adversely affect LV size and function acutely. Objectives. This study tested whether chordal cutting exacerbates long-term LV remodeling when applied to treat ischemic mitral regurgitation (MR) in a chronic myocardial infarction (MI). Methods. A posterolateral MI was created in 18 sheep by ligation of obtuse marginal branches. After chronic remodeling and MR development at 2 months, sheep were randomized to sham surgery versus anterior leaflet (AntL) or bileaflet (BiL) second-order chordal cutting (n=6 each), techniques in clinical application. 2D and 3D echo at baseline, chronic infarction (2 months), and follow-up at a mean of 6.5 months post-MI (sacrifice) measured LV end-diastolic and end-systolic volume (EDV and ESV), ejection fraction (EF), wall motion score index (WMSi), and posterior leaflet (PL) restriction angle relative to the annulus. Results. All measurements were comparable among groups at baseline and chronic MI. At sacrifice, AntL and BiL chordal cutting limited the progressive remodeling seen in controls. LVESV increased by 33.0±7.2% and 28.0±5.0% relative to chronic MI with AntL and BiL chordal cutting, versus 109.0±8.7% in controls (p<0.01) (LVESV=60.6±5.1ml vs 61.8±4.1ml vs 82.5±2.6ml in controls). LVEDV increased by 26.0±5.5% and 22.0±3.4% with AntL and BiL chordal cutting, versus 63.0±2.0% in controls (p<0.01). LVEF and WMSi were not significantly different at follow-up among chordal cutting and control groups. MR progressively increased to moderate in controls but decreased to trace-mild (vena contracta ≤2mm) in 83% of chordal cutting sheep. BiL chordal cutting provided greater PL mobility (decreased PL restriction angle to 54±5° versus 93±3° with AntL chordal cutting, p<0.01). Conclusions: Cutting secondary chordae in the chronic post-MI setting does not adversely affect long-term LV remodeling, and limits progressive increases in LV volumes.