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(Circulation. 2006;114:I-518 – I-523.)
© 2006 American Heart Association, Inc.

Surgery for Valvular Heart Disease

Mitral Leaflet Remodeling in Dilated Cardiomyopathy

Tomasz A. Timek, MD; David T. Lai, FRACS; Paul Dagum, MD, PhD; David Liang, MD, PhD; George T. Daughters, MS; Neil B. Ingels, Jr, PhD; D. Craig Miller, MD

From the Department of Cardiothoracic Surgery (T.A.T., D.T.L., P.D., G.T.D., N.B.I., D.C.M.) and Division of Cardiovascular Medicine (D.L.), Stanford University School of Medicine, Stanford, Calif; Laboratory of Cardiovascular Physiology and Biophysics (G.T.D., N.B.I.), Research Institute of the Palo Alto Medical Foundation, Palo Alto, Calif.

Correspondence to D. Craig Miller, Department of Cardiothoracic Surgery, Falk Cardiovascular Research Center, Stanford University School of Medicine Stanford, California 94305-5247. E-mail dcm{at}stanford.edu

Background— Normal mammalian mitral leaflets have regional heterogeneity of biochemical composition, collagen fiber orientation, and geometric deformation. How leaflet shape and regional geometry are affected in dilated cardiomyopathy is unknown.

Methods and Results— Nine sheep had 8 radio-opaque markers affixed to the mitral annulus (MA), 4 markers sewn on the central meridian of the anterior mitral leaflet (AML) forming 4 distinct segments S₁ to S₄ and 2 on the posterior leaflet (PML) forming 2 distinct segments S₅ and S₆. Biplane videofluoroscopy and echocardiography were performed before and after rapid pacing (180 to 230 bpm for 15±6 days) sufficient to develop tachycardia-induced cardiomyopathy (TIC) and functional mitral regurgitation (FMR). Leaflet tethering was defined as change of displacement of AML and PML edge markers from the MA plane from baseline values while leaflet length was obtained by summing the segments between respective leaflet markers. With TIC, total AML and PML length increased significantly (2.11±0.16 versus 2.43±0.23 cm and 1.14±0.27 versus 1.33±0.25 cm before and after pacing for AML and PML, respectively; P<0.05 for both), but only segments near the edge of each leaflet (S₄ lengthened by 23±17% and S₅ by 24±18%; P<0.05 for both) had significant regional remodeling. AML shape did not change and no leaflet tethering was observed.

Conclusion— TIC was not associated with leaflet tethering or shape change, but both anterior and posterior leaflets lengthened because of significant remodeling localized near the leaflet edge. Leaflet remodeling accompanies mitral regurgitation in cardiomyopathy and casts doubt on FMR being purely "functional" in etiology.

Key Words: cardiomyopathy • mitral regurgitation • mitral valve

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