To develop an anatomically correct mitral valve prosthesis, one needs
to study the dynamics of the mitral valve apparatus in vivo. The autho
rs used three-dimensional (3D) sonomicrometry and custom visualization
software to develop a system to study the mitral valve. Sixteen ultra
sonic transducers each were implanted into the hearts of pigs under ca
rdiopulmonary bypass. Four of these crystals were affixed to the base
and apex of both papillary muscles, four were attached to the free edg
e of the anterior and posterior leaflets where the main chordae attach
, six were placed around the mitral annulus, and two were affixed to t
he epicardial wall. The digital sonomicrometer system sequentially fir
ed each transducer and listened for an ultrasound signal at the other
15. This process was repeated so that all 16 transducers were sequenti
ally fired, and each cycle of 16 was repeated 200 times/sec. The matri
x of distances obtained between all the combinations of pairs of the 1
6 transducers was converted to x,y,z coordinates, the shape of the mit
ral valve apparatus was reconstructed in 3D on a graphics computer, an
d the valve's motion was analyzed over several cardiac cycles. The aut
hors conclude that mapping of the mitral valve apparatus in pigs by 3D
sonomicrometry provides quantitative measurements that can aid in the
design of a mitral valve prosthesis that closely replicates the anato
my and function of the natural valve.