Papillary-annular continuity and left ventricular systolic function after mital valve replacement

The contribution of the subvalvular apparatus to left ventricular function was evaluated in a canine preparation that allowed variation of subvalvular tethering forces after mitral valve replacement. Ten normal dogs were instrumented with micromanometer-tipped pressure catheters in the left ventricle and left atrium and piezoelectric sonomicrometry crystals to measure left ventricular major-axis, minor-axis, and wall thickness dimension changes. After control data were obtained, each dog underwent cardiopulmonary bypass and the mitral valve was replaced with a St. Jude bileaflet valve (No. 23 or 25). The native valve was completely excised and all chordal attachments were severed at the head of each papillary muscle. A 3-0 prolene suture was passed through the head of each papillary muscle, gently tied over a pair of felt pledgets, and exteriorized in a paravalvular manner that allowed both 'attached' and 'detached' states to be studies in a randomized manner 1 hr after release of the aortic cross-clamp. A significant (p < .05) increase in major-axis length from control was observed in the detached state at both end-diastole and end-systole when compared at matched left ventricular end-diastolic pressures. Systolic function measured by load-dependent variables at matched end-diastolic lengths was higher in the detached state. However, when systolic function was examined by load-independent variables such as the slope of the stroke work end-diastolic length relationship, the slope of the end-systolic pressure-volume relationship, or the stroke work end-diastolic volume relationship, no statistically significant difference could be detected between states of papillary-annular continuity. This study demonstrates that absence of chordal attachments after mitral valve replacement in the normal canine heart does not adversely affect systolic left ventricular function, most likely because of the relatively small short-term changes observed in left ventricular geometry. However, papillary-annular continuity may play a more significant role in the distribution of midventricular wall stresses in the chronically dilated ventricle, where changes in ventricular geometry and therefore wall stress are less subtle, or in the late postoperative period after mitral valve replacement.

Duke Scholars

Author Gary Lee Pellom Anesthesiology