Effects of chordal disruption on regional left ventricular torsional deformation.

BACKGROUND

Chordal excision during mitral valve replacement (MVR) impairs left ventricular (LV) systolic function, but the mechanisms responsible for this change remain unclear. This study was performed to determine the influence of annular papillary continuity on regional LV torsional deformation acutely following MVR with and without chordal preservation.

METHODS AND RESULTS

Twenty-seven dogs underwent placement of LV subepicardial myocardial markers to measure regional LV systolic torsional deformation throughout the left ventricle. After 1 week, biplane fluoroscopic marker images were obtained pre-MVR in the baseline state and with inotropic stimulation (calcium, 15 mg/kg). Dogs were then randomized to undergo a sham procedure with cardiopulmonary bypass but no valve replacement (n = 6), conventional MVR with chordal excision (n = 7), or chordal-sparing MVR with preservation of the posterior leaflet and reattachment of the anterior leaflet chordae to either the anterior annulus (n = 7) or posterior annulus (n = 7). After chest closure and recovery from anesthesia, post-MVR data were acquired. At the LV apical level, maximal regional LV systolic torsional deformation (theta max) did not fall from pre-MVR values in the baseline state after the sham procedure or anterior or posterior chordal-sparing MVR procedure (P > or = .10). After conventional MVR, baseline theta max fell by 66% to 81% in the anteroseptal, anterior, anterolateral, and lateral regions (P < .05). With calcium, theta max fell in the anteroseptal through lateral regions and the septal wall (P < .05) but did not change in the posterior regions (P > or = .10). With calcium, theta max did not fall in any region after either the sham procedure or anterior MVR; however, after posterior chordal-sparing MVR, theta max fell in the lateral, posterior, and posteroseptal regions (P < .05).

CONCLUSIONS

Sham operation and anterior chordal-sparing MVR did not affect regional LV torsion; however, loss of normal valvular-ventricular integrity with conventional MVR reduced regional LV systolic torsion in the anterior and lateral LV regions. Posterior chordal-sparing MVR impaired torsion only after calcium administration. The deleterious effects of chordal excision may be due in part to perturbation of regional systolic torsional deformation.