Page 101 - Small Animal Internal Medicine, 6th Edition

CHAPTER 3 Management of Heart Failure 73

dose of 1 capsule per 10 lb of body weight per day. Several pathogenesis of myocardial dysfunction. Increased circulat-
veterinary fish oil supplements also are available. Cod liver ing cytokines in heart failure can promote oxidative stress.
VetBooks.ir oil and flax seed oil are not recommended for omega-3 FA Although vitamin C supplementation has a beneficial effect
on endothelial function, the role of supplemental antioxidant
supplementation.
Grossly obese pets with heart disease may benefit from a
an antioxidant and co-factor involved in cellular energy pro-
weight-reducing diet. Obesity increases metabolic demands vitamins in animals with CHF is unclear. Coenzyme Q-10 is
on the heart and expands blood volume. Mechanical inter- duction. Whether it provides any measurable benefit is con-
ference with respiration promotes hypoventilation, which troversial; doses of 30(-90) mg PO q12h have been used in
could contribute to cor pulmonale and complicate preexist- dogs with uncertain effect.
ing heart disease. However, animals in heart failure that are
mildly overweight, or that gain or maintain their weight, β-Blockers in Patients With Heart Failure
could have a survival advantage. β-blockers must be used cautiously, especially in animals
with myocardial failure, because of their negative inotropic
Taurine effect. Their main role is in the management of certain
Taurine is an essential nutrient for cats. Prolonged deficiency arrhythmias, such as AF and sometimes ventricular tachyar-
causes myocardial failure and other abnormalities (see rhythmias (see Chapter 4). Although in people with heart
Chapter 8, p. 169). Most commercial and prescription cat failure, chronic use of some β-blockers can improve cardiac
foods are well supplemented with taurine, which has mark- function and reduce pathologic ventricular remodeling and
edly reduced the prevalence of taurine-responsive DCM in mortality, a similar clinical benefit of chronic low-dose
cats. But taurine concentrations should be measured in cats β-blocker therapy has not been proven in dogs or cats. Cur-
diagnosed with DCM, because the diet of some cats may still rently, β-blockers are not recommended as part of routine
be deficient. Taurine-deficient cats are given oral supple- combination therapy for chronic heart failure, unless indi-
ments of taurine (250-500 mg) twice daily. cated for cardiac rhythm or rate control. Careful monitoring
Some dogs with DCM appear deficient in taurine and/or is important because CHF decompensation, bradycardia,
L-carnitine, most notably American Cocker Spaniels but also and hypotension can occur, necessitating β-blocker dosage
others (see Chapter 7, p. 151). Dogs fed protein-restricted or reduction or discontinuation.
vegetarian diets can become taurine-deficient, and some
develop evidence of DCM. Taurine supplementation for CHRONIC DIASTOLIC DYSFUNCTION
dogs less than 25 kg is 500 to 1000 mg every 8 hours; for Furosemide is continued orally in patients with CHF from
dogs 25 to 40 kg the dose is 1 to 2 g every 8 to 12 hours. HCM and other causes of diastolic dysfunction. Gradual
Although not all taurine-deficient American Cocker Span- reduction to the lowest dosage and frequency effective for
iels need both taurine and L-carnitine, most appear to. controlling edema is the aim. An ACEI is thought to be
beneficial in most cases and is instituted during the transi-
L-Carnitine tion to chronic therapy, if not before. Antiplatelet therapy is
Although L-carnitine deficiency has been identified in Boxers recommended for cats (see Chapter 12). Some cats appear to
and Doberman Pinschers with DCM, its prevalence is benefit from pimobendan, especially those with advanced
thought to be low, and the number of affected dogs respon- disease or reduced systolic function (see previous discus-
sive to L-carnitine supplementation even lower. Nevertheless, sion). Spironolactone also can be useful as adjunct therapy,
a trial period of supplementation (at a higher dosage) may especially for cases with recurrent pleural effusion. Diltiazem
be worthwhile. After at least 4 months, reevaluation by echo- or a β-blocker is not recommended routinely for most cats
cardiogram is done to assess LV functional improvement. with CHF from HCM, because efficacy has not been estab-
Dogs treated with carnitine supplementation may give off a lished and their long-term effect is questionable. However,
peculiar odor. one or the other of these agents may be indicated for antiar-
The minimum effective dose of L-carnitine is not known; rhythmic therapy (see Chapter 4). The use of ivabradine (a
it may vary with the type of deficiency, if present at all. “funny” current [I f ] inhibitor) for heart rate control could
Several dose ranges have been suggested, including 50 to prove helpful in the future by improving diastolic filling
100 mg/kg PO every 8 to 12 hours for systemic deficiency or time; clinical experience is needed to guide specific
200 mg/kg every 8 hours for myopathic deficiency. Others recommendations.
use 1 g of oral L-carnitine every 8 hours for dogs less than
25 kg and a dose of 2 g every 12 hours for dogs between 25 REEVALUATION AND MONITORING
and 40 kg. One half teaspoonful of pure L-carnitine powder Client education is important for the long-term management
is the equivalent of 1 g. Both taurine and L-carnitine can be of chronic heart failure. A good understanding of the patient’s
mixed with food for easier administration. underlying disease, the signs of heart failure, and the purpose
and potential adverse effects of each medication make com-
Other Supplements pliance and early identification of complications more likely.
The role of other dietary supplements is unclear. Oxidative Home monitoring of the patient’s resting (ideally, sleeping)
stress and free-radical damage probably play a role in the respiratory rate is hugely helpful for monitoring control of