Some are congenital, but more commonly they can get mitral valve endocardiosis which leads to a murmur that can progress to coughing and exercise intolerance. (vetbabble.com)
Remember this mitral valve since we will be talking about it later in a common heart problem in the geriatric pet called endocardiosis. (lbah.com)
Give the guy a few tubes, an ultrasound probe, a scalpel and a rock star surgical team & watch him do what was considered impossible only a short time ago; surgical repair the ubiquitously failing mitral apparatus from vegetative endocardiosis in a King Charles Spaniel. (sonopath.com)