Extracardiac adjustment of mitral chordae replacement

This study was designed to determine the feasibility of completing mitral chord repair externally when the heart was weaned from bypass. Ten anesthetized dogs (22.9 +/- 4.6 kg) were placed on cardiopulmonary bypass through a left thoracotomy. The left atrium was opened and one or two marginal chords of the anterior mitral leaflet were divided. A double-armed 2-O polypropylene suture was placed in the margin of the mitral leaflet, and both suture ends were brought outside of the ventricle through the anterior papillary muscle, but were not anchored. Production of mitral incompetence was verified when the animals were weaned from bypass. Mean left atrial pressure (LAPm), the v wave of the left atrial pressure (LAPv), systolic billowing of the anterior leaflet into the left atrium above the mitral closure line (two-dimensional echocardiography, long axis), and function curves (left atrial-aortic systolic pressure, LAPv-AoSP) were used to determine valve competence and functionality of the repair. All values are expressed as means +/- SE. Acute mitral incompetence in this model was associated with severe left atrial bulging, left atrial billowing of the anterior leaflet (7-12 mm, 9.6 +/- 1.6 mm), significantly increased left atrial pressure [LAPv, 30.5 +/- 5.8; LAPm, 23.6 +/- 4.3 mm Hg; both P < 0.01 vs control (10.5 +/- 2.5 and 7.5 +/- 2.7 mm Hg, respectively)], and decreased systemic pressure development (AoSP, 84 +/- 8.8 vs 108 +/- 12.3 mm Hg; P < 0.01). The slope of the atrial-systemic pressure curve was decreased significantly, shifted to the right and reduced by more than half (2.1069 vs 0.9190; P < 0.05). External adjustment of the pledgeted suture ends returned all values to within control limits (LAPv, 12.7 +/- 4.1; LAPm, 9.8 +/- 4.3; AoSP, 104 +/- 10.5; LAP-AoSP slope, 2.0909; all P = n.s.), atrial bulging was not evident, and atrial displacement of the valve leaflet could no longer be visualized. These data suggest that mitral chord repair is feasible through a thoracotomy and, more importantly, final adjustments to obtain optimal chord length can be completed externally, guided by changes in dynamic, physiologic parameters.