 Heart conditions related to the King Charles Spaniel include mitral valve disease, in which the mitral valve degrades, causing blood to flow backwards through the chambers of the heart and eventually leading to congestive heart failure. Patent ductus arteriosus, where blood is channelled back from the heart into the lungs, is also seen and can lead to heart failure. Both of these conditions present with similar symptoms and are inheritable. The OFA conducted a survey on cardiac disease, where of 105 breeds, the King Charles Spaniel was found to be 7th worst, with 2.1 % of 189 dogs affected.
