Syncope in Cavalier King Charles Spaniels
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.
Related Links
Mitral Valve Disease
Epilepsy
Episodic Falling
Syndrome
Veterinary Resources
Clinical usefulness of cardiac event recording in dogs and cats examined because of syncope, episodic collapse, or intermittent weakness: 60 cases (1997-1999). Bright JM, Cali JV. J Am Vet Med Assoc 2000; 216:1110-1114.
Chronic valvular heart disease in dogs. Rush J.E.. In: Proceedings of the 26th Annual Waltham Diets; OSU Symposium for the Treatment of Small Animal Cardiology, pp. 1-7, 2002.
Mitral valve prolapse in Cavalier King Charles Spaniel: A review and case study. Hyun C. J. Vet. Sci. 2005 Mar;6(1):67-73.
Differential diagnosis of collapse in the dog 3. Cardiovascular and miscellaneous causes. Wray,J, In Practice, 31 Mar 2005;27(3): 128-135(8).
Recurrent syncope: only the heart was considered. Peter Stiefelhagen. MMW Fortschr Med. 2006 Sep 28;148 (39):21.
A retrospective study of 153 cases of undiagnosed collapse, syncope or exercise intolerance: the outcomes. L. Barnett, M. W. S. Martin, J. Todd, S. Smith, and M. Cobb. J.Sm.Anim.Prac. (Jan 2011) 52(1):26–31. Quote: "Objectives: To retrospectively assess the long-term outcome for dogs that were presented with collapse, syncope or exercise intolerance for which an underlying cause is not identified. ... Results: One hundred and fifty-three cases were successfully followed up. Clinical signs had resolved in 64 cases (42%), 35 dogs (23%) were continuing to exhibit clinical signs, although 22 of these had improved without medical intervention. In 17 cases (11%), a diagnosis had subsequently been made or treatment was being administered and 37 dogs (24%) had died. Of the deaths, 18 (12%) were considered to be related to the original presentation. The overall prevalence of death and deterioration related to the problems investigated was 16·2% of cases. Death in boxers was significantly more common than in other breeds (36%). ... Age at death ranged from 8 months in a cavalier King Charles spaniel to 17 years 3 months in a border collie. ... A total of 21 of the 37 dogs which had died (56·8%) were over the age of 10 at death. Of the 16 dogs that died before 10 years of age, ... two were cavalier King Charles spaniels ... . Clinical Significance: Death and deterioration are uncommon outcomes for dogs other than boxers presenting with collapse, syncope and exercise intolerance for which a definitive diagnosis cannot be made."
