Management of heart failure

A. Prevention of heart failure

• In atrial fibrillation, control the ventricular rate thereby increasing the diastolic filling time and normalize the atrial contraction.
  
  In systolic dysfunction polypharmacy involving diuretics, ACE inhibitors, digoxin and
  Beta -blockers are the mainstay of treatment since these drugs complement each other in their mechanisms of action. Diuretics are used for the symptomatic treatment of heart failure. Use of ACE inhibitors and -blockers has been found to be associated with a decrease in mortality.

A. Beta-blockers

Rationale

Congestive heart failure is associated with stimulation of the sympathetic nervous system. The elevated levels of circulating catecholamines produce detrimental effects on the myocardium which can be reversed or prevented by beta-blockers.

Indications and Dosage

• All patients with stable NYHA class II or III heart failure due to left ventricular systolic dysfunction
• Treatment with a -blocker should be initiated in very low doses after a period of clinical stability on standard therapy followed by gradual increments in dose if
  lower doses have been well tolerated, e.g. 3.125 mg carvedilol twice daily,
  followed by a doubling in dose every 2-4 weeks if the patient has tolerated each preceding dose. Target dose is 50 mg/day

Precautions

• Monitor patient for evidence of hypotension, bradycardia, fluid retention or worsening heart failure during the uptitration period
• Contraindicated in patients with bronchospastic disease, advanced heart block and bradycardia
• Treatment should not be initiated in patients who have acutely decompensated heart failure i.e. significant fluid retention or in those who require hospitalization for heart failure

B. ACE Inhibitors

Rationale

Congestive heart failure leads to activation of the renin angiotensin system. ACE inhibitors are used to inhibit the conversion of angiotensin I to angiotensin II

Indications and Dosage

• All patients with heart failure due to left ventricular systolic dysfunction
• Treatment initiated with a low dose followed by gradual increments in dose if
  lower dose has been well tolerated, e.g. 6.25 mg of Captopril 2-3 times daily,
  2.5 to 5 mg of Lisinopril once daily, 2.5 mg of Enalapril twice daily followed
  by doubling in dose every 3-7 days

Precautions

• Optimize diuretic dose before starting ACE inhibitors
• Assess renal function and serum potassium within 1-2 weeks of initiation and periodically thereafter especially in patients with pre-existing hypotension, hyponatremia, diabetes or in those receiving potassium supplements

C. Diuretics

Rationale

Congestive heart failure caused by left ventricular systolic dysfunction is characterized by a steadily progressive state of renal sodium and water retention

Indications and Dosage

• Patients with symptoms of heart failure who have evidence for a predisposition of fluid retention
• Therapy initiated with low doses of a diuretic (e.g. furosemide 20-40 mg daily) followed by increments in dosage until urine output increases and weight decreases by 0.5-1 kg daily

Precautions

• Underdosing can lead to fluid retention, which may diminish the response to ACE inhibitors and increase the risk of treatment with blockers
• Overdosing can lead to volume depletion which may increase the likelihood of hypotension and risk of renal insufficiency with ACE inhibitors
• Diuretic resistance (which accompanies heart failure progression) can be
  overcome by:
  - intravenous administration of diuretics
  - use of 2 or more diuretics in combination
  - short-term use of drugs that increase renal blood flow (e.g. dopamine and dobutamine)

D. Digoxin

Rationale

Digoxin enhances left ventricular function, normalizes the baroreceptor-mediated reflexes and increases cardiac output at rest and during exercise

Indications and Dosage

• Recommended to improve the clinical status of patients with heart failure due to left ventricular dysfunction and should be used in conjunction with diuretics, an ACE inhibitor and a blocker.
• Also recommended in patients with heart failure who have rapid atrial fibrillation
• Digoxin initiated and maintained at a dose of 0.25 mg daily. A lower dose of 0.125 mg appropriate if patient is > 70 years old or has impaired renal function. Drugs like quinidine, verapamil, amiodarone, propafenone, indomethacin, itraconazole, alprazolam and spironolactone raise the serum digoxin, concentration. Hence if these drugs are used concomitantly with digoxin, a lower dose of digoxin should be used.

Precautions

Adverse effects of digoxin include cardiac arrhythmias (ectopic and re-entrant cardiac rhythms and heart block), gastrointestinal symptoms and neurological complaints (e.g. visual disturbances, disorientation and confusion). These side effects are commonly associated with serum digoxin levels >2 ng/ml, but digitalis toxicity may occur with lower digoxin levels, especially if hypokalemia, hypomagnesemia or hypothyroidism co-exist.