title: Effects of annular size, transmitral pressure, and mitral flow rate on the edge-to-edge repair: an in vitro study.
abstract: BACKGROUND
  Although edge-to-edge repair is an established adjunctive procedure, there is still debate on its long-term durability and efficacy.
  
  
  METHODS
  Fifteen porcine mitral valves were studied in a physiologic left heart simulator with a variable size annulus (dilated = 8.22 cm2, normal = 6.86 cm2, contracted = 5.5 cm2). Mitral valves were tested under steady and physiologic pulsatile flow conditions (cardiac outputs: 4 to 6 L/min), at peak transmitral pressures between 100 mm Hg and 140 mm Hg. A miniature force transducer was used to measure the Alfieri stitch force (F(A)). Mitral flow rate (MFR), transmitral pressure, effective orifice area, mitral regurgitation, and F(A) were monitored.
  
  
  RESULTS
  The edge-to-edge repair led to a decrease in effective orifice area of 16.55% +/- 8.22%; further reduction in effective orifice area was attained with annular contraction. Mitral regurgitation after the edge-to-edge repair was significantly higher (p <0.05) with annular dilation. In the pulsatile experiments, two peaks in F(A) were observed: one during systole (F(A) = 0.059 +/- 0.024 N) and a second during diastole (F(A) = 0.072 +/- 0.021 N). Multivariate analysis of variance analysis showed that during systole, transmitral pressure and mitral annular area (MAA) had significant effects on F(A) [F(A) = (4.40 x 10(-4)) transmitral pressure (mm Hg) + (5.0 x 10(-3)) MAA (cm2) - 0.05 (R2 = 0.80)], whereas during diastole MFR and MAA had significant effects on F(A) [F(A) = (1.03 x 10(-4)) MFR2 (L/min) - (1.60 x 10(-3)) MAA (cm2) + 0.02 (R2 = 0.90)].
  
  
  CONCLUSIONS
  With annular dilation, mitral regurgitation persisted even after the edge-to-edge repair. The edge-to-edge repair does not cause clinically relevant mitral valve stenosis in a normal size mitral valve. Mitral flow rate and transmitral pressure are the main determinants of F(A) during the cardiac cycle. Increasing annular area increases F(A) during systole but decreases F(A) during diastole. Systolic F(A) may become dominant with increases in MAA or peak transmitral pressure, or both.
authors.affiliation: Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0535, USA.
authors.forename: Jorge H
authors.initials: JH
authors.lastname: Jimenez
authors.forename: Joseph
authors.initials: J
authors.lastname: Forbess
authors.forename: Laura R
authors.initials: LR
authors.lastname: Croft
authors.forename: Lisa
authors.initials: L
authors.lastname: Small
authors.forename: Zhaoming
authors.initials: Z
authors.lastname: He
authors.forename: Ajit P
authors.initials: AP
authors.lastname: Yoganathan
mesh_terms: D000818:Animals; D001794:Blood Pressure; D001837:Body Weights and Measures; D006348:Cardiac Surgical Procedures / Q000379:methods*; D002311:Cardiomyopathy, Dilated / Q000150:complications / Q000503:physiopathology; D004195:Disease Models, Animal; D006321:Heart / Q000502:physiology / Q000503:physiopathology; D006439:Hemodynamics; D008943:Mitral Valve / Q000503:physiopathology*; D008944:Mitral Valve Insufficiency / Q000209:etiology / Q000503:physiopathology / Q000601:surgery*; D023421:Models, Animal; D008955:Models, Cardiovascular; D011673:Pulsatile Flow; D012039:Regional Blood Flow; D013552:Swine; D020257:Ventricular Remodeling / Q000502:physiology