Tx of CHF Flashcards
What is the process of CHF?
- defined as abnormal fluid accumulation as a result of heart disease
- Increased atrial pressures lead to increased capillary hydrostatic pressure
- Fluid accumulates in the interstitial spaces (pulmonary oedema) or body cavities (pleural effusion or ascites)
What are the stages of heart failure?
- Stage A: Animals at risk of heart disease but showing no evidence of disease at present time (e.g. breeds with a predisposition to heart disease such as CKCS, Doberman, Maine Coon, Ragdoll)
- Stage B1: Asymptomatic animals with structural heart disease but no radiographic or echocardiographic evidence of cardiac remodelling
- Stage B2: Asymptomatic animals with structural heart disease and radiographic or echocardiographic evidence of cardiac remodelling
- Stage C: Patients with structural heart disease and current or previous signs of CHF
- C1: Animals on treatment with previous signs of CHF
- C2: Animals with mild to moderate signs of CHF
- C3: Animals with severe life-threatening CHF signs
- Stage D: Patients with chronic CHF who are refractory to standard treatment
How should Stage A pets be treated?
No meds indicated/ nutrition
Screening of breeding stock is usually indicated via auscultation, echocardiography, Holter monitoring or genetic testing
How should Stage B1 pets be treated?
- No drug therapy or dietary changes are indicated in the early stage of the disease
- Haemodynamic function may be relatively unaffected and there may be little or no neurohormonal activation
- Re-evaluation with radiography or echocardiography within 12 months is indicated to assess for progression
What did the EPIC study demonstrate?
• Demonstrated that dogs with preclinical myxomatous
mitral valve disease (MMVD) and cardiomegaly are more likely to go into heart failure within 1-2 years
• Asymptomatic dogs with MMVD and cardiomegaly who received pimobendan (0.4-0/6 mg/kg/day in divided doses) experienced a 15 month delay in onset of clinical signs of CHF, cardiac-related death or euthanasia compared to dogs receiving placebo
What are the recommendations for occult DCM (stage B2)
- The PROTECT study showed that the administration of pimobendan to Dobermans with preclinical DCM delays the onset of CHF or sudden death and improves survival
- A small study in Dobermans with occult DCM in 2009 suggested that ACE inhibitor treatment may be beneficial
- Some clinicians use both pimobendan and ACE inhibitors in dogs of high-risk breeds with occult DCM
What are the recommendations for cats with stage B2 HCM?
- Asymptomatic HCM cats may live many years and most (80%) die from non-cardiac causes
- Some cardiologists initiate treatment in high risk categories of cats with Stage B HCM:
- Cats with ventricular tachyarrhythmias
- Cats with severe left ventricular outflow tract obstruction due to SAM
- Cats with severe left ventricular hypertrophy
- Cats with left atrial enlargement (a risk factor of cardiac death and aortic thromboembolism)
- However, data supporting the clinical or functional benefit of such early therapy are currently lacking
In humans, the clinical signs associated with HCM and SAM primarily occur during exercise/ exertion and beta-blockers are used for symptomatic relief
• Cats are said to sleep 85% of their life
• An indoor cat may never exert itself
• An indoor/outdoor cat may exert itself occasionally
• Sleep is better at keeping the sympathetic nervous system low than any drug
What are the general treatment recommendations for acute life threatening CHF?
• Stabilize patient prior to performing detailed investigations. Gentle handling of cats
• Removal of abnormal fluid accumulation (pulmonary oedema, pleural effusion) is usually a priority
• Improve oxygenation by increasing the inspired oxygen concentration and removing large pleural effusions (by thoracocentesis) or resolving pulmonary oedema (with loop diuretics, with or without venodilation)
• Frusemide dose in acute CHF: 2-4 mg/kg (IV, IM) every 1-2 hours until respiratory rate decreases
• Sedation if anxiety is exacerbating dyspnoea (e.g. butorphanol 0.1-0.2 mg/kg)
Drain pericardial effusions leading to cardiac tamponade
What are the general nutritional recommendations for chronic CHF?
Dietary advice include monitor weight, sustain caloric intake,
ensure adequate protein-intake (avoid low-protein diets), modestly reduce salt intake, omega-3 fatty acid supplementation
In general, what drugs are used to treat CHF in cats?
The most common drugs used for treatment of CHF in cats include:
• Frusemide
• ACE inhibitors
Other drugs used in cats with CHF include:
• Antiplatelet drugs
• Spironolactone
• Pimobendan in DCM and other cardiomyopathies with systolic dysfunction
How can you treat refractory CHF in cats?
- Spironolactone can be beneficial in the treatment of CHF secondary to cardiomyopathy when added to standard treatment with frusemide and ACE inhibitor
- Thiazide diuretics can be used in some refractory cases
- Pimobendan can be prescribed to cats with LV systolic dysfunction
- Periodic thoracocentesis is required in some cases
Outline the use of low salt diets in heart disease?
- Do not use before the onset of CHF as low sodium intake can activate the renin angiotensin-aldosterone system
- Low-salt diets can be unpalatable and difficult to use in advanced CHF when appetite is poor
- Avoid salt loading but modest salt restriction is better than aggressive salt restriction
Outline taurine deficiency in cats
- Taurine is an essential amino-acid for cats
- Taurine deficiency was a common cause of DCM in cats until the late 1980s
- Since then most commercial diets have been supplemented with taurine which has dramatically reduced the incidence of feline DCM
- Cats on vegetarian and vegan diets are most likely to be deficient of taurine
- In suspected cases blood taurine levels should be analysed and treatment with taurine (250-500 mg PO per cat BID) should begin concurrent with medical therapy
Outline taurine deficiency in dogs
• Taurine deficiency and taurine-responsive cardiomyopathy has been found in American
Cocker Spaniels and a number of other breeds
• Dogs with DCM and taurine deficiency that do respond to taurine supplementation generally do not have as dramatic a response as do taurine-deficient cats with DCM
Which drugs should and should not be given with food?
- The bioavailavility of pimobendan is reduced when administered with or shortly after food
- Administration of digoxin with food may result in up to a 50 per cent reduction in serum concentration of the drug
- Spironolactone, conversely, should be given with food
What are general exercise recommendations for heart disease patients?
- Restrict exercise until signs of CHF resolve
- Regular mild to moderate exercise is generally recommended for dogs with stable heart disease (improves skeletal muscle tone and general quality of life)
- Sudden sprinting or strenuous exercise should be avoided in dogs with exertional syncope or at risk of sudden death due to arrhythmias
- As always, cats will do their own thing (especially sleeping)
Which diseases can be treated with sx/ a catheter?
- Surgical ligation of PDA
- Occlusion device for PDA closure
- Balloon catheter dilation of severe pulmonic stenosis
- Pacemaker implantation for symptomatic bradyarrythmias
- Pericardiocentesis/subtotal pericardiectomy of idiopathic pericardial effusions
When are diuretics indicated?
- Indicated in all cases with cardiogenic pulmonary oedema
- Indicated in most cases of CHF with the exception of pericardial effusion (best treated by pericardiocentesis)
- Large pleural effusions are best managed by thoracocentesis although diuresis can also be helpful
What types of diuretics are normally used in CHF?
Loop diuretics • Frusemide • Torasemide Potassium-sparing diuretics • Spironolactone • Amiloride Thiazides • Hydrochlorthiazide
Outline dosing with frusemide
- First-line choice for diuresis in dogs and cats with CHF
- It can induce activation of the RAAS if used before the onset of CHF
- Dose very variable: 0.5-4 mg/kg q 1-24 h (IV, SC, IM, oral). Acts within 20 minutes of parenteral administration
- In acute CHF: 2-4 mg/kg IV, IM every1-2 hours until respiratory rate decreases
- Chronic CHF in dogs: 0.5-4 mg /kg SID to TID. Titrate to the lowest dose adjusting for respiratory rate and prerenal azotaemia
- Chronic CHF in cats: from 1 mg/kg every 2 to 3 days to 2 mg /kg SID to TID
- Some venodilating effects when given slowly IV (transient deafness if given rapidly in some cases)
- Easier to judge response to treatment with bolus dosing than constant rate infusions
Outline the use of spironolactone in CHF
• Weak potassium-sparing diuretic but more importantly an aldosterone antagonist (with
effects on vasculature and myocardial fibrosis and remodelling)
• Many cardiologists will use it addition to frusemide, an ACE inhibitor and pimobendan in dogs with Stage C CHF
• A recent study in cats showed that spironolactone was beneficial in the treatment of CHF secondary to a cardiomyopathy when added to standard therapy with benazepril and frusemide
• Dose: 2 mg/kg SID with food
• Ulcerative facial dermatitis is a rare side effect seen in cats
Outline the use of hydrochlorothiazide
- Thiazide diuretics act at the distal convoluted tubule of the nephron
- They tend to be used in refractory CHF (Stage D) in combination with other diuretics (sequential nephron blockade) and it is often available in combination with amiloride
- Dose: 1-2 mg/kg sid to bid
- Prerenal azotaemia is a common result of diuresis
What are the neurohormonal blockers?
ACE inhibitors • Enalapril • Benazepril • Ramipril • Imidapril Spironolactone Beta-blockers
Outline the use of beta blockers
- Generally not recommended in dogs and cats with CHF as they reduce myocardial contractility and can exacerbate CHF signs
- They can be effective in reducing heart rate and in the treatment of supraventricular and ventricular tachyarrhythmias in dogs and cats
- Atenolol has been used in cats with asymptomatic HOCM and also in cats with asymptomatic HCM and ventricular dysrhythmias (dose 6.25 mg /cat SID-BID)
