Increases in
Mitral Leaflet Radii of Curvature with Chronic Ischemic Mitral Regurgitation
Frederick A. Tibayan, Filiberto Rodriguez, Frank Langer, Mary K.
Zasio, Lynn Bailey, David Liang, George T. Daughters, Matts Karlsson,
Neil B. Ingels, Jr., D. Craig Miller
Department of Cardiovascular and Thoracic
Surgery, Division of Cardiovascular Medicine, Stanford University
School of Medicine, Stanford, California, Laboratory of Cardiovascular
Physiology and Biophysics, Research Institute of the Palo Alto
Medical Foundation, Palo Alto, California, USA |
Background and aim of the study: Leaflet curvature
is a primary determinant of leaflet stress, but no quantitative in-vivo
leaflet curvature data exist. Chronic ischemic mitral regurgitation (CIMR)
is associated with remodeling of the valvular-ventricular complex. It
was hypothesized that leaflet radii of curvature (ROC) would change with
such remodeling.
Methods: Twelve sheep had placement of radiopaque markers
on the anterior (APM) and posterior (PPM) papillary muscles, mitral
annulus, and anterior (AL) and posterior leaflet (PL) midlines.
After 8 ±
2 days, videofluoroscopy provided baseline 3-D marker data prior to creating
inferior myocardial infarction (MI) by snare occlusion of the obtuse marginal
coronary arteries. After 7 ± 1 weeks, the animals were re-studied;
3-D marker coordinates were used to determine end-systolic leaflet ROC,
leaflet length, annular septal-lateral diameter, and the distance of each
papillary muscle to the mid-septal annulus and each commissure.
Results: Before and after CIMR, the AL had compound |
curvature, and CIMR increased ROC of both curves (proximal
ROC 1.27 ± 0.59 to 1.38 ± 0.60 cm (p <0.05); distal
ROC 1.41 ± 0.61 to 2.60 ± 1.52 cm (p < 0.05)). The PL
ROC also increased with CIMR (from 2.01 ± 1.40 to 3.46 ±
3.93) (p <0.05). Multiple regression analysis determined that annular
septal-lateral diameter (proximal AL and distal AL), distance from the
APM to anterior commissure (distal AL), and PPM to mid-septal annulus (PL)
were independent predictors of leaflet ROC.
Conclusion: CIMR increased ROC of both the AL and PL.
Leaflet extension may be a compensatory mechanism to minimize the
regurgitant orifice, but the attendant increase in ROC will tend
to augment leaflet stress. Annular and subvalvular geometry both
affect leaflet curvature, and should be considered during mitral
repair. These novel quantitative in-vivo data are now available
for modification of finite element models, and for comparison to
finite element model output.
The Journal of Heart Valve Disease 2004;13:772-778 |