Heart Failure, Treatment

Goals of Treatment

• Cure
• Slow/Prevent Disease Progression
• Symptomatic Relief

Treatments vary from surgical correction of underlying conditions, such as correction of a PDA, to management changes and pharmacological treatments.

Management Changes

1. Avoid strenuous exercise
2. Reduced Salt Diets (Reduces Preload)
3. Potassium Supplements
4. Taurine Supplements (Cats with dilated cardiomyopathy)
5. L-carnitine Supplements (Dogs with dilated cardiomyopathy)
6. Nutraceuticals (e.g. Omega-3 fatty acids, Anti-oxidants, Co-enzyme Q10)

Heart failure patients can suffer from cardiac cachexia due to the high metabolic demands of this condition. Make sure the patient is eating enough calories per day to maintain their body weight.

Pharmacological Intervention

The following terms are usfule when desribing the effects of various pharmacological agents:

• Preload=amount of maximal myocardial stretch (During Diastole)
• Afterload=amount of maximal myocardial tension (During Systole)

Drug treatments can be used to:

Decrease Preload

This decreases venous tone & fluid volume which can help to relieve congestion & edema Drugs in this class include:

1. Diuretics: These decrease blood volume by increasing sodium loss from the kidneys. They include loop diuretics, that act on the renal Loop of Henle such as Frusemide, and thiazide diuretics that act on the renal Distal Convoluted Tubule, such as Chlorothiazide or Hydrochlorothiazide. Potassium sparing diuretics act on the renal Collecting Duct and include Spironolactone and Amiloride.
2. Venodilation: Dilation of veins causes decreased venous pressures, blood redistribution, and increased capacitance. Venodilators include Glyceryl trinitrate and a group of drugs classified as balanced vasodilators, which includes ACE inhibitors (enalapril (dogs & cats), benazepril (cats), alpha-antagonists and Nitroprusside.

The side effects of Preload Reduction include: hypovolemia, dehydration, hypokalemia, hyponatremia

Decrease Afterload

Decreasing afterload increases flow by decreasing arterial tone. This reduces resistance to outflow which reduces the cardiac workload by decreasing systolic myocardial tension and increase systemic blood flow. Arterial vasodilators include Hydralazine or any member of the balanced vasodilators mentioned above. ACE Inhibitors such as enalapril and benazepril are commonly used - side effects include vomiting, anorexia, diarrhea, hypotension, and azotemia.

Increase Myocardial Systolic Function

This helps with dilated cardiomyopathy & mitral valve disease (Dog & Cat) but is contraindicated in animals with hypertrophic cardiomyopathy (Dog & Cat) Positive Inotropes can be used to stimulates myocardial contractility to improve cardiac output regardless of preload. This class of drug includes:

• Digitalis Compounds (e.g. digoxin, digitoxin)
• Calcium Sensitiser/Phosphodiesterase III. Inhibitor (e.g. pimobendan)
• Pure Phosphodiesterase Inhibitors (e.g. milrinone, amrinone)
• Catecholamines (e.g. dobutamine, dopamine)

The disadvantage of positive inotropes is that increased myocardial work causes increased myocardial oxygen demand

Increase Myocardial Diastolic Function

This helps with hypertrophic cardiomyopathy and myocardial fibrosis where ventricular filling is compromised. Dugs include the beta blockers (e.g. atenolol, propranolol) and Calcium channel blockers (e.g. diltiazem).