Coordinate-free analysis of mitral valve dynamics in normal and ischemic hearts

Background-The purpose of this investigation was to study mitral valve 3D g eometry and dynamics by using a coordinate-free system in normal and ischem ic hearts to gain mechanistic insight into normal valve function, valve dys function during ischemic mitral regurgitation (IMR), and the treatment effe cts of ring annuloplasty. Methods and Results-Radiopaque markers were implanted in sheep: 9 in the ve ntricle, 1 on each papillary tip, 8 around the mitral annulus, and 1 on eac h leaflet edge midpoint, One group served as a control (n=7); all others un derwent flexible Tailor partial (n=5) or Duran complete (n=6) ring annulopl asty. After an 8+/-2-day recovery, 3D marker coordinates were measured with biplane videofluoroscopy before and during posterolateral left ventricular ischemia, and MR was assessed by color Doppler echocardiography. Papillary to annular distances remained constant throughout the cardiac cycle in nor mal hearts, during ischemia, and after ring annuloplasty with either type o f ring, Papillary to leaflet edge distances similarly remained constant thr oughout ejection. During ischemia, however, the absolute distances from the papillary tips to the annulus changed in a manner consistent with leaflet tethering, and IMR was observed. In contrast, during ischemia in either rin g group, those distances did not change from preischemia, and no IMR was ob served. Conclusions-This analysis uncovered a simple pattern of relatively constant intracardiac distances that describes the 3D geometry and dynamics of the papillary tips and leaflet edges from the dynamic mitral annulus. Ischemia perturbed the papillary-annular distances, and IMR occurred. Either type of ring annuloplasty prevented such changes, preserved papillary-annular dist ances, and prevented IMR.