Surgical Relocation of the Papillary Muscles in Functional Ischemic Mitral Regurgitation: What are the Forces of the Relocation Stitches Acting on the Myocardium?
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Henrik Jensen1,2, Morten O. Jensen1,3, Stefan Vind-Kezunovic1, Rikke Vestergaard1, Steffen Ringgaard4, Morten H. Smerup1, Jesper L. Hønge1, J. Michael Hasenkam1, Sten L. Nielsen1 1Department of Cardiothoracic and Vascular Surgery T, Aarhus University Hospital-Skejby, 2Institute of Clinical Medicine, University of Aarhus, 3Department of Biomedical Engineering, Engineering College of Aarhus, 4The Magnetic Resonance Imaging Research Centre at Aarhus University Hospital-Skejby, Denmark |
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Background and aim of the study: In patients with chronic functional ischemic mitral regurgitation (FIMR), papillary muscle relocation has the potential to induce reverse left ventricular remodelling. However, in order to optimize function and durability, the forces imposed on the left ventricular myocardium by papillary muscle relocation should be assessed. Methods: Eight pigs with FIMR were subjected to down-sized ring annuloplasty in combination with relocation of the anterior (5 mm) and posterior (15 mm) papillary muscles towards the respective trigone. Papillary muscle relocation was obtained by a 2-0 expanded polytetrafluoroethylene stitch fixed to the trigone, exteriorized through the myocardium overlying the papillary muscle, and fixed to an epicardial disc. Tension in these stitches was measured at a systolic blood pressure >80 mmHg using a custom-made sliding caliper with a strain gauge mounted in line. This allowed assessment of the cyclic change from minimal diastolic to maximum systolic papillary muscle relocation stitch tension. |
Results: Maximum cyclic change in the posterior papillary muscle (PPM) stitch tension was 1.1 N at 15 mm relocation. In comparison, the anterior papillary muscle (APM) tension was increased to a maximum of 1.4 N with only 5 mm relocation. Surprisingly, during each step of isolated PPM relocation, the APM stitch tension increased concomitantly, but in contrast APM relocation did not influence the magnitude of PPM stitch tension. There was no statistically significant difference between cyclic changes in APM and PPM stitch tension at any step of relocation. Conclusion: Papillary muscle relocation using stitches attached between epicardial discs and respective trigones induced a cyclic change in papillary muscle relocation stitch tension of 1.1-1.4 N. These values were in the range of normal tension in the mitral valve apparatus, and equivalent to only 19-24% of the total papillary muscle forces. Therefore, this technique does not appear to induce a non-physiologically high cyclic load on the mitral valve complex. The Journal of Heart Valve Disease 2013;22:524-531 |
| Surgical Relocation of the Papillary Muscles in Functional Ischemic Mitral Regurgitation: What are the Forces of the Relocation Stitches Acting on the Myocardium? | |
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