Article

Effects of annular size, transmitral pressure, and mitral flow rate on the edge-to-edge repair: an in vitro study.

Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0535, USA.
The Annals of thoracic surgery (impact factor: 3.74). 11/2006; 82(4):1362-8. DOI:10.1016/j.athoracsur.2006.05.008 pp.1362-8
Source: PubMed

ABSTRACT Although edge-to-edge repair is an established adjunctive procedure, there is still debate on its long-term durability and efficacy.
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.
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)].
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.

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    Article: Effects of papillary muscle position on anterior leaflet stretches under mitral valve edge-to-edge repair.
    Bo Gao, Wei Sun, Sibi Mathew, Zhaoming He
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    ABSTRACT: The mitral valve edge-to-edge repair (ETER) procedure inevitably alters mitral valve leaflet mechanics. The study aim was to quantify the effects of papillary muscle (PM) position on stretches in the central area of the anterior leaflet after mitral valve ETER. Sixteen markers of a 4x4 array were attached onto the central area of the mitral valve anterior leaflet. The free edges of the mitral valve leaflets were sutured together with a single stitch to mimic the ETER. The mitral valve was then mounted in an in-vitro flow loop that was capable of simulating physiological loading conditions. The PM of the mitral valve was set in slack, normal, and taut positions. Displacements of the markers were obtained from the images of the markers, in order to calculate the stretches and stretch rates. The major principal stretch during systole was significantly greater than that during diastole in the three PM positions. The major principal (radial) stretch was significantly greater in the taut PM position than in the normal and slack PM positions during diastole. However, there was no significant difference in the minor principal (circumferential) stretch during diastole in the three PM positions. The loading and unloading stretch rates were not affected by the PM position, except for the major principal stretch rate during loading. With regards to the central region of the mitral valve anterior leaflet, the radial stretch during diastole was significantly less than that during systole. Therefore, the load on the anterior leaflet during systole, rather than that during diastole, should be considered when evaluating ETER durability, especially in the taut PM position. The circumferential stretch during diastole was not influenced by the PM positions.
    The Journal of heart valve disease 04/2009; 18(2):135-41. · 0.81 Impact Factor
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    Article: Mitral web--a new concept for mitral valve repair: improved engineering design and in-vitro studies.
    Ersin Erek, Muralidhar Padala, Kerem Pekkan, Jorge Jimenez, Yusuf K Yalçinba, Ece Salihoğlu, Tayyar Sarioğlu, Ajit P Yoganathan
    [show abstract] [hide abstract]
    ABSTRACT: A new mitral valve repair concept to treat mitral regurgitation (MR) due to valve prolapse was recently proposed. In this study, an improved design of this concept is presented, and the results of preliminary hemodynamic studies conducted in an in-vitro prolapse model are reported. The new repair approach is based on using a web/net attached to a standard annuloplasty ring spanning the annulus of the mitral valve. Experiments were conducted in a left ventricular simulator, using native porcine mitral valves. Severe MR was created by transecting the marginal chordae to induce P2 prolapse, and also by displacing the papillary muscles basally to induce bileaflet prolapse. Implantation of the mitral web prevented leaflet prolapse and restored leaflet coaptation with trace mitral insufficiency, in both posterior and bileaflet prolapse. In posterior leaflet prolapse, implantation of the mitral web reduced the regurgitation volume from 10.43 +/- 3.76 ml to 2.13 +/- 1.83 ml per beat (p < 0.05). No visual damage was observed on the mitral valve leaflets after 4 h of continuous operation. Based on the study results, the mitral web may represent a feasible option to repair different types of mitral valve prolapse. The mitral web may also significantly simplify mitral valve repair for complex lesions.
    The Journal of heart valve disease 05/2009; 18(3):300-6. · 0.81 Impact Factor
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Keywords

Alfieri stitch force
 
cardiac outputs
 
diastole MFR
 
established adjunctive procedure
 
Increasing annular area increases F(A)
 
long-term durability
 
miniature force transducer
 
mitral annular area
 
Mitral flow rate
 
mitral regurgitation
 
Mitral valves
 
Multivariate analysis
 
normal size mitral valve
 
peak transmitral pressure
 
peak transmitral pressures
 
physiologic pulsatile flow conditions
 
porcine mitral valves
 
transmitral pressure
 
variable size annulus
 
variance analysis
 

Jorge H Jimenez