These data indicate that dogs with previously diagnosed silent MR experienced significant changes in the mitral valve thickness, area, and degree of prolapse vs. dogs previously diagnosed as being healthy. These data suggest that the previous diagnosis of silent MR was indeed true, and that early MVD can be detected by echo prior to development of a heart murmur. These data have potentially great impact on how screening for mitral valve disease is performed. Currently, the diagnostic criteria involve the presence or absence of a left-sided systolic murmur. Under current guidelines, if no murmur is present, the patient is deemed clear of MVD and no further diagnostic are performed. Our data indicate that subtle changes to valve morphology and silent mitral regurgitation jets can be detected during echocardiography and these changes precede the development of a detectable murmur. Thus, the most sensitive test for presence of MVD could be echocardiography. In order for echo to become the gold standard for detection of early MVD, standard regarding valve morphology (length, thickness, area, prolapse) would need to be developed (most likely for each individual breeds) so that there was general agreement as to what constitutes an abnormal echo finding. In other words, while most cardiologists can agree as to whether a murmur is present or absent, there is much greater heterogeneity and possible disagreement surrounding subtle echo changes.