Download Veterinary Cardiorespiratory Centre

Veterinary Cardiorespiratory Centre
Martin Referral Services, Thera House, 43 Waverley Road, Kenilworth, Warwickshire CV8 1JL
Tel: 01926 863445
INFORMATION SHEET
Therapy of congestive heart failure in dogs
Heart failure is the most common clinical presentation of dogs with heart disease. Congestive heart
failure (CHF) infers that there is a damming back of blood behind the failing heart, into the pulmonary
(eg. pulmonary oedema) or systemic (eg. ascites) circulations. CHF is a sequel to many of the various
causes of heart disease. It’s treatment is very similar in most cases of adult heart disease (except
pericardial effusion), ie. reduction in the congestion (volume overload) and inhibition of the
neuroendocrine responses that are induced.
Rest is important. Caged rest alone will often improve the clinical condition of animals in congestive heart
failure. With outpatients, all animals in CHF should still be rested, at least until the congestive signs have
been treated, after which there can be some return to limited exercise.
ACE inhibitors should be used in all dogs with heart failure (due to valvular endocardiosis or dilated
cardiomyopathy) due to the importance of inhibiting the adverse neuroendocrine response that are induced
by CHF. They can be used as first line approach in dogs with a cough due to left atrial enlargement, which
may avoid the problem of polyuria seen with diuretics. Blood urea and serum creatinine should be checked
before commencing treatment with ACE inhibitors, within 7 to 10 days following commencement and
thereafter at regular intervals. Should the urea levels and/or serum creatinine rise significantly, then the
diuretic dose should be reduced or withdrawn. The standard doses of the ACE inhibitors are: ramipril
(Vasotop) at 0.125mg/kg sid, benazepril (Fortekor) at 0.25mg/kg sid and enalapril (Enacard) at 0.5 mg/kg
sid. In advanced heart failure, the dose of ACE inhibitors can be doubled to twice a day.
Frusemide remains the most effective symptomatic treatment for congestive heart failure (CHF) but
should be used in combination with an ACE inhibitor. The dose used must be appropriate for the stage of
heart failure and severity of presentation. A typical starting dose of frusemide would be 1 to 2 mg/kg bid,
this can often be reduced to the minimum effective dose in a few weeks time (based on clinical response,
resting respiratory rate at home and chest x-rays if necessary). If the congestion remains refractory to
reasonable doses of frusemide (and ACE inhibitors), which is often the case when there is ascites, then
increasing the dose of frusemide to a maximum of 3 to 4 mg/kg bid can be beneficial (thereafter adding
other diuretics).
Co-amilozide (eg. Moduretic) is a combination of two diuretics - hydrochlorothiazide and amiloride (a
potassium sparing diuretic). The thiazide provides the additional diuretic potency, but at the cost of
potassium loss, necessitating the need to add in a potassium sparing diuretic (although these are weak
diuretics). Co-amilozide (in combination with frusemide) is used when there is refractory ascites at the
minimum clinically effective dose; an approximate dose range is 1 - 3 mg/kg bid.
Spironolactone (an aldosterone antagonist) is an alternative to co-amilozide and has beneficial effects
through it’s inhibition of aldosterone, as well as providing additional diuresis.
Pimobendan is a positive inotropic drug and an arterial vasodilator but unfortunately does not inhibit any
of the neuroendocrine responses induced in CHF. The primary indication for a positive inotrope is when
there myocardial failure such as in dilated cardiomyopathy or end-stage mitral valve disease.
Coughing, due to cardiomegaly, can be controlled with injections of carprofen and butorphanol,
followed by oral medication with codeine linctus at 1-2mg/kg tid/qid (or a similar anti-tussive)
given for a week and then reduced to the minimum effective dose or as required.
Martin & Corcoran (2006) Notes on Cardiorespiratory Diseases of the Dog and Cat,
2nd edition. Blackwell Science. ISBN 0-632-03298-7 £29.99