Dilated cardiomyopathy in dogs: ancillary therapy

Beta-blockers
There is now significant evidence that beta blockers have a beneficial role in the treatment of mild to moderate heart failure with left ventricular systolic dysfunction. Recent evidence (in man) has shown that when beta blockers are added to a regime of diuretics and ACEIs they can substantially decrease mortality and morbidity; at 1.3 years, there was a 34% reduction in mortality, 44% reduction in sudden deaths and 20% reduction in hospital admissions. It is believed that the neurohumoral activation in patients with heart failure contributes to progressive myocyte dysfunction, cell loss and chamber remodelling. Studies have shown that beta blockade can reduce these effects. However there is no convincing evidence of the benefit of beta blockers in the management of severe heart failure.

For many people, the use of beta blockers in patients with heart failure seems to conflict with their earlier training. New guidelines should recommend that beta blockers are used to treat stable patients with mild to moderate heart failure, first with low doses, which should be gradually increasing according to need.

L-Carnitine supplementation
L-carnitine deficiency has been documented in 40 - 50% of dogs with dilated cardiomyopathy, although the mechanism is not clearly understood. Measurement of plasma carnitine is insensitive (although specific) and obtaining tissue samples (endomyocardial biopsy) requires considerable skill and, furthermore, the assay is prohibitively expensive and not available in the UK.  Keene’s clinical impression is that L-carnitine supplementation (at 50mg/kg tid) is a useful addition to current therapy, especially Boxers, American cocker spaniels and Dobermanns.  However, only a proportion of dog’s deficient in carnitine will respond.  The first response is usually within 1 - 4 weeks with a generalised clinical improvement (particularly in appetite and activity) followed by improved echocardiographic parameters over 2 to 8 months. [A separate information sheet about carnitine is available upon request]

Taurine supplementation
In one study plasma taurine concentrations were found to be low in 13 out of 76 dogs with dilated cardiomyopathy - seven of these were Cocker spaniels or golden Retrievers. Whether supplementing taurine (at a suggested dose of 500mg bid) will be of benefit is unclear at this point.

Fish oil supplementation
Canine heart failure secondary to DCM is associated with cachexia, alternations in fatty acids  and reduced caloric intake. In a recent study, fish oil supplementation demonstrated a decrease in the cytokine interleukin-1b and improved cachexia. An increase in survival was also suspected in this study. The recommended dosages for dogs with CHF and cachexia are: 40mg/kg eicosapentaenoic (EPA) and 25mg/kg docosahexaenoic (DHA).

B Vitamins
In animals receiving diuretics there is the potential for urinary loss of water soluble vitamins. In people one study showed that 90% of patients with CHF being treated with frusemide had a thiamine deficiency. It seems prudent to therefore recommend B vitamin supplementation in animals in heart failure and receiving frusemide.

Recommended reading Martin & Corcoran (2006) Notes on: Cardiorespiratory disease of the
dog and cat, 2nd ed. Blackwell Science. ISBN 0-632-03298-7