Papillary-annular continuity and left ventricular systolic function after mitral 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 studied in a randomized manner 1 hr after release of the aortic cross-clamp. A significant (p less than .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.(ABSTRACT TRUNCATED AT 250 WORDS)