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Ann Thorac Surg 1999;68:894-902
© 1999 The Society of Thoracic Surgeons

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Original Articles: Cardiovascular

Effects of mitral valve replacement on regional left ventricular systolic strain

^a Department of Cardiothoracic Surgery, Stanford University School of Medicine, Stanford, California, USA
^b Research Institute of the Palo Alto Medical Foundation, Palo Alto, California, USA

Address reprint requests to Dr Miller, Dept of Cardiovascular and Thoracic Surgery, Falk Cardiovascular Research Center, Stanford University School of Medicine, Stanford, CA 94305-5247
e-mail: dcm{at}leland.stanford.edu

Background. Mitral valve replacement (MVR) with chordal excision impairs left ventricular (LV) systolic function, but the responsible mechanisms remain incompletely characterized. Loss of normal annular-papillary continuity also adversely affects LV torsional deformation, possibly due to changes in myocardial fiber contraction pattern.

Methods. Twenty-seven dogs underwent insertion of LV myocardial markers and a sham procedure (cardiopulmonary bypass, no MVR, n = 6), conventional MVR with chordae tendineae excision (n = 7), or chordal-sparing MVR with reattachment of the anterior leaflet chordae to the anterior annulus (n = 7) or to the posterior annulus (n = 7). In the anterior, lateral, posterior, and septal LV regions, linear chords were constructed from each region’s central marker to its surrounding markers. Percent systolic shortening (regional LV strain) was calculated for each chord, and the chords were assigned to one of four angular groups: I, left-handed oblique (subepicardial fiber direction); II, circumferential (midwall); III, right-handed oblique (subendocardial); or IV, longitudinal. Regional LV strain data were compared before and after MVR.

Results. Sham and anterior chordal-sparing MVR had minimal effects on regional LV strain. With posterior chordal-sparing MVR: anteriorly, left-oblique (I) strain fell (31%, p < 0.05), as did circumferential (II) and right-oblique (III) strains (by 49% and 51%, respectively; p < 0.01). Laterally, left-oblique (I) strain fell by 36% (p < 0.05), as did longitudinal (IV) strain (54% decline, p < 0.01). Conventional MVR with chordal excision disrupted regional fiber shortening diffusely, affecting oblique fibers (I and III) in the anterior and septal regions and impairing longitudinal (IV) strain in all regions (45% to 68% fall, p < 0.05).

Conclusions. Sham and anterior chordal-sparing MVR did not substantially alter regional LV strain; however, loss of normal anatomic valvular-ventricular integrity (conventional MVR) or posterior chordal-sparing MVR resulted in pronounced alterations in LV strain, most notably in the longitudinal and oblique fiber directions. These findings demonstrate that the deleterious effects of chordal excision are associated with perturbed internal myocardial systolic deformation, which suggests that chordal disruption distorts myofiber architecture or regional systolic loading.

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				M. A. Borger, T. M. Yau, V. Rao, H. E. Scully, and T. E. David Reoperative mitral valve replacement: importance of preservation of the subvalvular apparatus Ann. Thorac. Surg., November 1, 2002; 74(5): 1482 - 1487. [Abstract] [Full Text] [PDF]