Comprehensive Overview on Congestive Heart Failure (CHF) and Inotropic Drugs

Introduction to Congestive Heart Failure (CHF)

Definition: CHF is a chronic condition where the heart is unable to pump sufficient blood to meet the body's needs.
Epidemiology: Affects millions worldwide, commonly in elderly populations.
Pathophysiology: Results from conditions like hypertension, coronary artery disease, and cardiomyopathy.

Types of CHF

1. Left-Sided Heart Failure:

o Symptoms: Dyspnea, pulmonary congestion, fatigue.

o Causes: Hypertension, aortic valve disease, ischemic heart disease.

2. Right-Sided Heart Failure:

o Symptoms: Peripheral edema, hepatomegaly, ascites.

o Causes: Chronic lung disease, left-sided heart failure.

3. Biventricular Heart Failure:

o Symptoms of both left and right-sided failure.

Classification of CHF Drugs

Inotropic Drugs (e.g., Digoxin, Dobutamine) – Increase cardiac contractility.
Diuretics (e.g., Furosemide, Spironolactone) – Reduce fluid overload.
Vasodilators (e.g., ACE inhibitors, ARBs, Hydralazine) – Decrease afterload.
Beta-blockers (e.g., Metoprolol, Carvedilol) – Reduce myocardial oxygen demand.

Inotropic Drugs – Digoxin

Definition: A cardiac glycoside that increases myocardial contractility.
Source: Extracted from Digitalis purpurea (Foxglove plant).
Uses: Mainly for CHF and atrial fibrillation.

Pharmacokinetics of Digoxin

Absorption: 60-80% oral bioavailability.
Distribution: Large volume of distribution; binds to cardiac tissues.
Metabolism: Minimal hepatic metabolism.
Excretion: Primarily renal (unchanged form).
Half-life: ~36-48 hours.

Pharmacodynamics of Digoxin

Primary Action: Inhibition of Na+/K+ ATPase pump.
Effects:

Increases intracellular calcium leading to increased cardiac contractility.
Slows AV node conduction, beneficial in atrial fibrillation.
Increases vagal tone, reducing heart rate.

Mechanism of Action of Digoxin

1. Inhibits Na+/K+ ATPase → Increases intracellular Na+.

2. Na+/Ca2+ exchanger activity increases intracellular Ca2+.

3. Increased Ca2+ enhances myocardial contractility.

4. AV node depression leads to a slower heart rate.

Indications of Digoxin

Congestive heart failure (CHF) – Mainly in patients with systolic dysfunction.
Atrial fibrillation and atrial flutter – To control ventricular rate.

Adverse Effects of Digoxin

Cardiac Effects: Arrhythmias, bradycardia, heart block.
Gastrointestinal: Nausea, vomiting, diarrhea.
Neurological: Confusion, dizziness, visual disturbances (yellow vision).

Contraindications of Digoxin

Hypokalemia (increases toxicity risk).
AV block (risk of worsening conduction defects).
Ventricular fibrillation.
Digoxin hypersensitivity.

Drug Interactions of Digoxin

Increased Digoxin Toxicity:

Diuretics (cause hypokalemia → increase digoxin effect).
Calcium channel blockers (reduce renal clearance of digoxin).
Quinidine, Amiodarone (increase plasma digoxin levels).

Reduced Efficacy:

Rifampin, St. John’s Wort (increase digoxin metabolism).

Presentation for Congestive Heart Failure (CHF) and Inotropic Drugs

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