Undersized Mitral
Annuloplasty Inhibits Left Ventricular Basal Wall Thickening but Does
Not Affect Equatorial Wall Cardiac Strains
Allen Cheng, Tom C. Nguyen, Marcin Malinowski, David
Liang, George T. Daughters, 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: Undersized mitral annuloplasty
has been widely employed for patients with ischemic mitral regurgitation.
Beyond correction of mitral regurgitation, ring annuloplasty is postulated
to normalize global left ventricular (LV) shape, thereby decreasing LV
wall stress and promoting reverse LV remodeling. The effect of undersized
annuloplasty on regional transmural LV wall thickening and strain patterns,
however, has not been examined.
Methods: In nine sheep, transmural radiopaque beadsets were inserted into
the anterobasal and equatorial lateral LV walls, with additional markers
silhouetting the left ventricle and mitral annulus. Four-dimensional marker
dynamics were studied with biplane videofluoroscopy (open-chest) before
and after tightening a Paneth-type mitral annuloplasty suture. LV volumes,
mitral dimensions, transmural circumferential, longitudinal, and radial
systolic strains, and end-diastolic (ED) and end-systolic (ES) remodeling
strains in the two LV regions were computed.
Results: In the anterobasal LV wall close to the mitral annulus, annuloplasty
increased ED wall thickness |
and surprisingly reduced systolic radial strain (wall
thickening) at all transmural depths. Radial subepicardial, midwall,
and subendocardial wall-thickening strains at ES in the anterobasal LV
site were 0.25 ± 0.15, 0.33 ± 0.16, and 0.47 ± 0.29,
respectively, before tightening the suture annuloplasty, compared to
0.13 ± 0.12, 0.15 ± 0.18, and 0.20 ± 0.26 after
tightening. In the equatorial lateral LV wall further away from the annulus,
most LV transmural systolic and remodeling strains did not change.
Conclusion: Simulated undersized annuloplasty acutely decreased transmural
systolic LV wall thickening in the anterobasal region, without substantially
affecting transmural deformations in the lateral LV wall. These acute effects
of undersized annuloplasty require a better understanding as they may potentially
be deleterious, and a direct ventricular approach may be needed as an adjunct
to promote reverse LV remodeling.
The Journal of Heart Valve Disease 2007;16:349-358 |