 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 . 
