King Charles Spaniel heart problems
Cavalier King Charles spaniels with mitral valve murmurs from Grade 3 through Grade 6 and enlarged atrial chambers may lose consciousness or display episodic weakness, especially of the hindquarters, ataxia (an inability to coordinate muscular movements), or collapse. This disorder, when loss of consciousness occurs, is called syncope; absent the loss of consciousness, it is called presyncope.
The symptoms of presyncope may appear similar to Epilepsy or Episodic Falling Syndrome.
Technically, syncope is the temporary loss of consciousness, or fainting, due to a sudden decline in blood flow to the brain. It is not unique to dogs with heart disorders and generally may be referred to as canine syncope syndrome.
In cavaliers, syncope and presyncope are associated with Mitral Valve Disease because in mid- to late stages of MVD, when the affected dog experiences excessive excitement, stress, or sudden shock, the heart and blood vessels are prompted to constrict, with the heart rate increasing suddenly, depleting the blood volume from the left ventricle and in the blood vessels to the brain. Syncope associated with the heart's reaction to MVD is called vasodepressor syncope.
Common factors which may precipitate vasodepressor syncope in cavaliers with mid- to late stage MVD are excessive exercise, running, stress, coughing, barking, urination, defecation, or pain. Even grooming or bathing, if stressful to the dog, could prompt syncope. Treatment for syncope involves treating the underlying disorder, which in the case of cavaliers suffering from MVD would be treatment of that disease, including adjustment of the medication. Also, cavaliers in the advanced stages of MVD should avoid stress, excitement, and coughing, and excessive exercise.
January 2014: Holter monitoring shows MVD dogs with syncope had less sinus arrhythmia, and decreased overall heart rate variability. In, of 43 dogs with advanced MVD, which included 21 dogs (6 cavaliers) with syncope and 22 dogs (10 CKCSs) without syncope, cardiologists found that:"Compared with dogs without a history of syncope, dogs with advanced MMVD and a history of syncope did not have a higher occurrence of arrhythmias, but had less sinus arrhythmia, and had changes in HRV variables representing decreased overall HRV, decreased parasympathetic, and increased sympathetic modulation of heart rate."