Dilated Cardiomyopathy
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ALso know as: DCM — Congestive Cardiomyopathy
Introduction
This disease is common in dogs and is rare in cats (with adequate taurine supplementation).
Dilated cardiomyopathy (DCM) occurs when there is a progressive reduction in systolic myocardial contractility. Decreased myocardial contractility affects the removal of blood from the ventricle at systole. A larger volume of blood increases the end diastolic pressures causing dilation of the ventricle and the development of eccentric hypertrophy.
Signalment
In the dog, giant and large breeds (e.g. Dobermann Pinscher, Boxer, Great Dane) are most at risk. Male > Females and risk increases with age.
In the cat the most commonly effected breeds are the Siamese, Burmese, Abyssinian. Again Male > Female and middle age & old age cats are most at risk.
Clinical Signs
Can be asymptomatic (Occult) DCM: Seen in predisposed breeds (e.g. Doberman Pinschers).
Clinical signs include syncope, weight loss, dyspnoea, lethargy, weakness and hindlimb paresis (cats with saddle thrombi).
Diagnosis
History and clinical signs suggest heart failure.
Physical examination will show presence of a systolic murmur, a gallop rhythm, S3 heart sound, arrhythmias, pulse deficits and pulmonary crackles.
Blood tests will show azotemia, elevated liver enzymes (+ liver congestion), signs of congestive heart failure, signs of thromboembolism (cats) and plasma taurine reduction (cats).
Radiography will show left ventricular hypertrophy (seen in Dobermans & Boxers), left atrial enlargement (seen in Dobermans & Boxers), generalised cardiomegaly (seen in giant breeds), left sided congestive heart failure signs e.g. pulmonary congestion & edema and right sided congestive heart failure signs e.g. pleural effusion and ascites.
Electrocardiography (ECG) will show rhythm disturbances e.g. atrial fibrillation (giant breeds), ventricular arrhythmias (Doberman Pinchers, Boxers), conduction disturbances and characteristic signs of hypertrophy.
Echocardiography will show a hypokinetic left ventricle (i.e. reduced fractional shortening therefore reduced contractility), reduced ejection fraction (i.e. % end diastolic volume ejected at systole), decreased ventricular wall thickness, left atrial enlargement and mitral regurgitation.
Treatment and Control
Treat congestive heart failure (reduce preload & afterload; improve systolic function; control cardiac arrhythmias), therapeutic thoracocentesis (to remove pleural effusion in cats) and taurine supplementation (cats).
Prognosis
Dogs:
Poor: Most breeds survive 6-12 months and in Dobermans and Boxers the prognosis is grave.
Cats:
Good: When cardiomyopathy results from taurine deficiency, but grave in other causes of cardiomyopathy.
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References
Ettinger, S.J. and Feldman, E. C. (2000) Textbook of Veterinary Internal Medicine Diseases of the Dog and Cat Volume 2 (Fifth Edition) W.B. Saunders Company
Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (6th edition, volume 2) W.B. Saunders Company
Fossum, T. W. et. al. (2007) Small Animal Surgery (Third Edition) Mosby Elsevier