title: Polymer injection therapy to reverse remodel the papillary muscles: efficacy in reducing mitral regurgitation in a chronic ischemic model.
abstract: BACKGROUND
  Ischemic mitral regurgitation (MR) results from displacement of the papillary muscles caused by ischemic ventricular distortion. Progressive left ventricular (LV) remodeling has challenged therapy. Our hypothesis is that repositioning of the papillary muscles can be achieved by injection of polyvinyl-alcohol (PVA) hydrogel polymer into the myocardium in chronic MR despite advanced LV remodeling.
  
  
  RESULTS
  Ten sheep underwent ligation of the circumflex branches to produce chronic ischemic MR over 8 weeks. PVA was injected into the myocardium underlying the infarcted papillary muscle. Two-dimensional and 3D echocardiograms and hemodynamic data were obtained before infarct (baseline), before PVA (chronic MR), and after PVA. PVA injection significantly decreased MR from moderate to severe to trace (MR vena contracta, 5.8±1.2 to1.8±1.3 mm; chronic MR to post-PVA stage; P=0.0003). This was associated with a decrease in infarcted papillary muscle-to-mitral annulus tethering distance (30.3±5.7 to 25.9±4.6 mm, P=0.02), tenting volume (1.8±0.7 to 1.4±0.5 mL, P=0.01), and leaflet closure area (8.8±1.3 cm(2)to 7.6±1.3 cm(2), P=0.004) from chronic MR to post-PVA stages. PVA was not associated with significant decreases in LV ejection fraction (41±3% versus 40±3%, P=NS), end-systolic elastance, τ (82±36 ms to 72±26, P=NS), or LV stiffness coefficient (0.05±0.04 to 0.03±0.01).
  
  
  CONCLUSIONS
  PVA hydrogel injections improve coaptation and reduce remodeling in chronic MR without impairing LV systolic and diastolic function. This new approach offers a potential alternative for relieving tethering and ischemic MR by correcting papillary muscle position.
authors.affiliation: Cardiac Ultrasound Laboratory, Massachusetts General Hospital, Boston, Mass., USA.
authors.forename: Jorge
authors.initials: J
authors.lastname: Solis
authors.forename: Robert A
authors.initials: RA
authors.lastname: Levine
authors.forename: Benjamin
authors.initials: B
authors.lastname: Johnson
authors.forename: J Luis
authors.initials: JL
authors.lastname: Guerrero
authors.forename: Mark D
authors.initials: MD
authors.lastname: Handschumacher
authors.forename: Suzanne
authors.initials: S
authors.lastname: Sullivan
authors.forename: Kaitlyn
authors.initials: K
authors.lastname: Lam
authors.forename: Jason
authors.initials: J
authors.lastname: Berlin
authors.forename: Gavin J C
authors.initials: GJ
authors.lastname: Braithwaite
authors.forename: Orhun K
authors.initials: OK
authors.lastname: Muratoglu
authors.forename: Gus J
authors.initials: GJ
authors.lastname: Vlahakes
authors.forename: Judy
authors.initials: J
authors.lastname: Hung
mesh_terms: D000818:Animals; D019560:Echocardiography, Three-Dimensional; D020100:Hydrogels / Q000008:administration & dosage* / Q000009:adverse effects; D007267:Injections; D008944:Mitral Valve Insufficiency / Q000517:prevention & control; D023421:Models, Animal; D017202:Myocardial Ischemia / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy*; D010210:Papillary Muscles / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000473:pathology / Q000601:surgery; D011108:Polymers / Q000008:administration & dosage* / Q000009:adverse effects; D011142:Polyvinyl Alcohol / Q000008:administration & dosage* / Q000009:adverse effects; D012756:Sheep; D020257:Ventricular Remodeling / Q000187:drug effects
chemical_list: D020100:Hydrogels; D011108:Polymers; D011142:Polyvinyl Alcohol