Effects of mitral valve replacement on regional left ventricular systolic strain

Background. Mitral valve replacement (MVR) with chordal excision impairs le ft ventricular (LV) systolic function, but the responsible mechanisms remai n incompletely characterized. Loss of normal annular-papillary continuity a lso 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 reatt achment 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 centra l marker to its surrounding markers. Percent systolic shortening (regional LV strain) was calculated for each chord, and the chords were assigned to o ne of four angular groups: I, left-handed oblique (subepicardial fiber dire ction); II, circumferential (midwall); III, right-handed oblique (subendoca rdial); or IV, longitudinal. Regional LV strain data were compared before a nd after MVR. Results. Sham and anterior chordal-sparing MVR had minimal effects on regio nal LV strain. With posterior chordal-sparing MVR: anteriorly, left-oblique (I) strain fell (31%, p < 0.05), as did circumferential (II) and right-obl ique (III) strains (by 49% and 51%, respectively; p < 0.01). Laterally, lef t-oblique (I) strain fell by 36% (p < 0.05), as did longitudinal (IV) strai n (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 i n all regions (45% to 68% fall, p < 0.05). Conclusions. Sham and anterior chordal-sparing MVR did not substantially al ter regional LV strain; however, loss of normal anatomic valvular-ventricul ar integrity (conventional MVR) or posterior chordal-sparing MVR resulted i n 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 myocardi al systolic deformation, which suggests that chordal disruption distorts my ofiber architecture or regional systolic loading. (Ann Thorac Surg 1999;68: 894-902) (C) 1999 by The Society of Thoracic Surgeons.