Differences in mitral valve-left ventricle dimensions between a beating heart and during saline injection test.

Objective: Saline injection test performed during mitral valvuloplasty is popular; however, discrepancies are sometimes noticed between the 'naked eye' findings of regurgitation during the saline injection test and the echocardiographic findings after surgery. These discrepancies may arise due to the geometric differences in the mitral valve-left ventricular complex between the saline-injected left ventricle (LV) and the beating LV. Therefore, to elucidate these differences, we compared the three-dimensional geometries between these two conditions.

Methods: Sonomicrometry crystal markers were implanted in seven mongrel dogs at the mitral annulus, edge of the mitral leaflets between scallops, tips of papillary muscles, and LV apex under cardiopulmonary bypass. Geometric data of the LV were acquired during the saline injection test and in the beating heart.

Results: The commissural width was greater and the annular height was lesser during the saline injection test than in the beating heart (20.5+/-5.1mm vs 17.2+/-2.2mm, p<0.01 and 5.5+/-1.8mm vs 7.3+/-2.2mm, p<0.05, respectively), indicating that the saddle-shaped mitral annulus was flattened during the test. Additionally, the middle scallop width and the distance between the papillary tips were greater during the test (14.0+/-4.2mm vs 11.3+/-3.6mm, p<0.05 and 22.9+/-5.9mm vs 11.6+/-5.0mm, p<0.01, respectively), implying that the middle scallop was stretched by the traction of the chordae. The distance between the papillary tips and the mitral annular plane remained constant in both the conditions (19.3+/-2.6mm vs 18.6+/-6.2mm, not significant).

Conclusions: The saline injection test could aid in determining the length of the reconstructed chordae. However, the test may provide inaccurate data of the mitral-LV dimensions due to the flattened annulus and overstretched leaflets.