Management of heart failure

• Typical presentation of heart disease

  Heart failure - cough/ dyspnoea

  Exercise intolerance

  Collapse

  Heart disease found by chance

  Non-specific malaise/ weight loss.
• Non-specific treatment of dilated cardiomyopathy

  DCM is due to contractility failure.

  Use drugs that improve contractility = positive inotropes

  Digoxin (digitalis glycosides)

  Pimobendan (Vetmedin)

  Dobutamine

  Dobutamine has to be given in an IV infusion, constant rate so used more as a recovery treatment for dogs with DCM.

  Pimobendan is used the most, is a positive isotope and vasodilates as well.
• Pimobendan

  Positive isotope. Gold standard.

  Inodilator - decreased systemic/ pulmonary vascular resistance.

  Calcium-sensitising drug (positive inotrope)

  PDE III inhibitors - vasodilation.

  Antithrombotic activity - can be useful in cats.
• Digoxin

  Positive inotropic agent. Negative chronotropic agent. Increased vagal tone, decreases sympathetic tone. Alters baroreceptor sensitivity. Predominatly renal excretion - avoid drug or decrease dose in renal failure. Narrow therapuetic range - digoxin toxicity.

  Slows down the heart, useful in animals with heart failure die to cardiomyopathy and tachycardia.
• Non-specific treatment of Hypertrophic/Restrictive cardiomyopathy

  Heart fills poorly. Use drugs that help relax = positive lusitropes.

  Calcium channel blockers - diltiazem, verapamil

  Beta blockers - propranolol, atenolol.

  In asymptomatic cats there is no evidence that any drugs alters the natural history of HCM until they are in heart failure.

  These are diseases of diastole, so need the heart to relax more, only treat when they have signs.
• Diltiazem

  Licensed product, have positive lusitropic properties. May reduce left ventricular hypertrophy.

  Doesn’t have much clinical effect on survival time in cats with severe HCM and HF.
• General treatment of Congestive heart failure

  The therapy for CHF is traditionally based on severity.

  The goal;

  Control salt and water retention.

  Reduced workload

  Decreased afterload

  Decrease physical activity and stress

  Improve pump function

  Improve systolic function

  Improve diastolic function

  Reverse/ modify myocardial remodelling.
• Standard congestive heart failure therapy

  Combination of drugs; triple/quad therapy

  Diuretics (remove salt water)

  Pimobendan (vasodilator)

  ACE inhibitors

  Aldosterone antagonists

  +/- Anti-dysrhythmic medication
• Diuretics

  Remove fluid - diuretic traditionally used (act at kidney to increase urine output).

  Control oedema formation.

  Oedema in CHF is usually due to increase in circulating blood volume.

  Blood volume can be increased by as much as 30% in severe CHF.

  Loop diuretics

  Furosemide - cheap

  Torasemide - used more as has a longer half life so only have to give it once a day.

  Potassium and Thiazide are not very strong diuretics, tend to be used if the loop diuretics are not strong enough by themselves.
• Furosemide

  1st line diuretic, very potent. Plasma half time is 15 minutes, peak effect orally is 1-2 hours, duration of action is 4-5 hours. More potent when given parentally. Works on the loop of Henle to limit sodium absorption.

  Frequently tailored to individual - severity of volume and oedema. Can be high doses in some cases, reduce dose as soon as possible. Monitor animal for azotaemia and hypokalaemia.
• Spironolactone

  Aldosterone antagonist has a potassium sparing effect. Beneficial effects in CHF leads to an improvement in cough, dyspnoea, syncope, mobility.