19. DRUGS USED FOR THERAPY OF CONGESTIVE HEART FAILURE

Introduction

Congestive heart failure (CHF) is a long-term condition where the heart cannot pump enough blood to meet the body’s needs. To maintain circulation, the body activates several compensatory mechanisms such as increased sympathetic activity, activation of the renin–angiotensin–aldosterone system (RAAS) and cardiac remodeling. These processes initially help but later worsen the condition. CHF leads to fluid retention, breathlessness, swollen legs, fatigue and reduced kidney function. Treatment aims to improve symptoms, prevent fluid overload, slow disease progression and reduce hospital admissions.

Main Drug Classes Used in CHF

  • Diuretics
  • Vasodilators (ACE inhibitors, ARBs, nitrates, hydralazine)
  • Beta blockers
  • Sympathomimetic amines (dopamine, dobutamine)
  • Cardiac glycosides (digoxin)
  • PDE–3 inhibitors
  • Vasopressin receptor antagonists
  • Brain natriuretic peptide (BNP)

1. Diuretics

Diuretics are usually the first-line therapy in CHF because they help remove excess fluid from the body. This reduces breathlessness, ankle swelling and workload on the heart.

Types

  • Loop diuretics: Furosemide, Bumetanide, Torsemide
  • Thiazide diuretics: Hydrochlorothiazide, Metolazone
  • Aldosterone antagonists: Spironolactone, Eplerenone

Key Points

  • Loop diuretics are most effective and used in most patients.
  • Thiazides may be added in resistant cases for better effect.
  • Aldosterone antagonists improve survival and reduce potassium loss.
  • Monitor serum potassium levels carefully.

2. Vasodilators

Vasodilators relax blood vessels, decrease workload on the heart and improve blood flow.

(a) ACE Inhibitors

Examples: Enalapril, Lisinopril, Ramipril, Captopril

They block formation of angiotensin II and reduce vasoconstriction, aldosterone release and fluid retention.

Benefits

  • Lower preload and afterload
  • Reduce cardiac remodeling
  • Improve symptoms and survival

Side Effects

  • Dry cough
  • Hyperkalemia
  • Postural hypotension

(b) ARBs (Angiotensin Receptor Blockers)

Examples: Losartan, Candesartan, Valsartan, Telmisartan

Used when ACE inhibitors cause cough. They block AT1 receptors and prevent the effects of angiotensin II.

Side Effects

  • Hyperkalemia
  • Dizziness
  • Renal impairment

(c) Direct Renin Inhibitor

Example: Aliskiren

Blocks renin and reduces angiotensin I and II levels. Sometimes used as an add-on drug.

(d) Nitrates

Examples: Nitroglycerin, Isosorbide Dinitrate

Primarily venodilators that reduce preload and improve symptoms in acute heart failure.

(e) Arteriolar Dilators

Examples: Hydralazine, Minoxidil, Nicorandil

Reduce afterload and improve cardiac output. Hydralazine is often combined with nitrates for better effect.

3. Beta Blockers

Examples: Metoprolol, Carvedilol, Bisoprolol, Nebivolol

These drugs improve long-term heart function by blocking sympathetic overactivity. They slow heart rate, reduce arrhythmias and reverse harmful cardiac remodeling.

Benefits

  • Improved left ventricular function
  • Reduced hospital admissions
  • Increased survival

Important Note:

Start with low doses and increase slowly under medical supervision.

4. Sympathomimetic Amines

Used mainly in acute or severe CHF to improve pumping action of the heart.

Dopamine

  • Low dose: improves kidney blood flow
  • Medium dose: increases cardiac contractility
  • High dose: causes vasoconstriction (not preferred)

Dobutamine

  • Strong inotropic action
  • Improves cardiac output
  • Used in cardiogenic shock and acute decompensation

5. Cardiac Glycosides

Example: Digoxin

Digoxin increases the force of contraction (positive inotropic effect) and slows AV node conduction.

Benefits

  • Useful in CHF with atrial fibrillation
  • Improves cardiac output
  • Reduces venous pressure and pulmonary congestion

Adverse Effects

  • Nausea, vomiting
  • Arrhythmias
  • Confusion, visual changes

Important Factors Increasing Toxicity

  • Low potassium (hypokalaemia)
  • Kidney failure
  • Elderly age

6. PDE-3 Inhibitors

Examples: Milrinone, Inamrinone

Short-term IV drugs that increase cAMP, producing both inotropic and vasodilator effects (“inodilators”). Used in severe heart failure but not for long-term therapy.

7. Vasopressin Receptor Antagonists

Examples: Tolvaptan, Conivaptan

Help in CHF patients with severe fluid overload and low sodium levels.

8. Brain Natriuretic Peptide (BNP)

Example: Nesiritide

Given IV in acute decompensated CHF. It dilates blood vessels and reduces breathlessness. Hypotension is a common side effect.

Detailed Notes:

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