Background and aim of the study: One objective of mitral valve repair is to restore the distorted mitral apparatus geometry to its normal dimensions specific for each patient. Because all dimensions of the normal aortic and mitral valves should be related, it was hypothesized that, in the presence of a normal aortic annulus, it would be possible to determine the dimensions of the structures needed for mitral valve repair.
Methods: In seven sheep, sonometric ultrasound crystals were implanted at the left and right trigones (T1, T2), lateral annulus (P1, P2), and the tips of the anterior and posterior papillary muscles (Ml, M2). The distances T1-T2, M1-M2, T1-M1, T2-M2, P1-P2, P1-M1, and P2-M2 were measured at end-systole (ES), end-diastole (ED), and maximum and minimum lengths. Using these measured distances, fractional relationships were computed, and the average fractional relationship was used to determine a 'calculated' distance. The 'measured' and 'calculated' distances were then compared using a paired t-test.
Results: All fractional relationships were close to 1, with ED 1.00 +/- 0.21, ES 0.99 +/- 0.19, maximum length 0.99 +/- 0.19, and minimum length 0.94 +/- 0.21. The intertrigonal distance (T1-T2) expanded by 4.19 +/- 3.81%, and the transverse diameter (P1-P2) contracted by -6.15 +/- 3.69% from ED to ES. The interpapillary muscle distance (M1-M2) contracted -22.3 +/- 6.5%. The two distances with the least amount of contraction were those of T1-M1 and T2-M2, with contractions of -3.06 +/- 2.39% and -3.27 +/- 1.37%, respectively. P1-M1 and P2-M2 expanded 5.60 +/- 2.89% and 6.84 +/- 3.60% from ED to ES.
Conclusion: The mitral valve dimensions and calculated fractional relationships were similar in all sheep. As shown previously, the ratio of aortic annulus diameter (easily measured echocardiographically) to the intertrigonal distance (T1-T2) is 0.79 and 0.80 in humans and sheep, respectively. This distance can be used to determine normal mitral valve geometry and, therefore, preoperatively to calculate the degree of geometric distortion present in individual patients.