CARDIOLOGY
Canine Idiopathic Dilated
Cardiomyopathy
Dr. Alain Carter BVSc (Hons) MMEDVet(Med)
Fourways Veterinary Hospital and Specialist Referral Centre.
Cardiomyopathies are diseases of the myocardium associated with cardiac dysfunction and dilated
cardiomyopathy is characterised by dilation and impaired contraction of the left ventricle or both
ventricles. Dilated cardiomyopathy (DCM) is the most common form of cardiomyopathy in dogs and
the second most common form of acquired heart disease in dogs. Diagnosis, pathophysiology and
current treatment recommendations will be discussed in this article.
Signalment
DCM tends to be a disease of large breed dogs with a
higher prevalence in male dogs. A genetic predisposition to the disease has been identified in Dobermans,
Irish Wolfhounds, Great Danes, New Foundlands,
Spaniels and Portuguese Water Dogs. The disease
in the American cocker Spaniels has been frequently
characterised as a taurine deficient condition with
supplementation markedly improving the outcome.
Pathophysiology
DCM is characterised by ventricular enlargement, diastolic and systolic dysfunction and resulting congestive heart failure. The symptomatic phase is preceded
by an asymptomatic phase where a number of compensatory mechanisms work in concert to maintain
cardiac output and prevent the development of congestive heart failure. These compensatory mechanisms include the rennin-angiotensin aldosteronesystem (RAAS), catecholamine’s and other vasoactive
substances. These compensatory mechanisms are
beneficial in the short to medium term but have deleterious effects in the long term. Increasing blood
pressure with RAAS increases the cardiac work load
as does increased plasma catecholamine’s by increasing the heart rate.
The end result may increase the rate of myocardial
cell death. These deleterious compensatory mechanisms are balanced by vasodilator, diuretic and natriuretic factors such as the natriuretic peptides.
In symptomatic DCM plasma catecholamines have
been found to be significantly increased in both humans and dogs. Increased cat