Dynamic assessment of mitral annular force profile in an ovine model.

Abstract

Limited knowledge exists regarding the forces that act on devices implanted in the mitral annulus. Determining the peak magnitudes, directions, rates, variation throughout the cardiac cycle, and change with left ventricular pressure (LVP) will aid in device development and evaluation. Novel transducers with the ability to measure forces in the septal-lateral and transverse directions were implanted in six healthy ovine subjects. Forces were measured for cardiac cycles reaching a peak LVP of 90, 125, 150, 175, and 200 mm Hg. The septal-lateral force was observed to significantly increase from 3.9 ± 0.8 N (90) to 5.2 ± 1.0 N (125) p < 0.001, 5.9 ± 0.9 N (150) p < 0.001, 6.4 ± 1.2 N (175) p < 0.001, and 6.7 ± 1.5 N (200 mm Hg) p < 0.001. Similarly, the transverse force was seen to increase from 2.6 ± 0.6 N (90) to 3.8 ± 1.0 N (125) p < 0.01, 4.6 ± 1.3 N (150) p < 0.001, 4.3 ± 1.2 N (175) p < 0.001, and 3.5 ± 0.7 N (200 mm Hg) p < 0.05. In comparison, the septal-lateral force was significantly greater than the transverse force at 90 (p < 0.05), 125 (p < 0.05), 175 (p < 0.001), and 200 mm Hg (p < 0.0005). Annular forces and their variations with LVP through the cardiac cycle are described. The results demonstrate differences in force magnitude and rate for increasing levels of LVP between the septal-lateral and transverse directions. These directional differences have strong implications in the development of future mitral devices.