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Heart Failure Treatment (Part 1) (Digoxin (Mechanism of action: Blocks…
Heart Failure Treatment
(Part 1)
ACE inhibitors
Drugs:
Captopril, Enalapril, Fosinopril, Lisinopril, Perindopril, Quinapril, Ramipril, Trandolapril
Mechanism of action:
Inhibits angiotensin-converting enzyme, and therefore inhibits the conversion of angiotensin-I to angiotensin-II
This blocks angiotensin-II mediated vasoconstriction & aldosterone release (increased K+ reabsorption, decreased water & Na+ reabsorption leading to decreased blood volume)
Clinical effects:
Decreased BP
Reduced oedema
Adverse effects:
Hypotension, dizziness, hyperkalaemia, dry cough - due to bradykinin accumulation as ACE normally metabolises bradykinin)
AT-1 receptor antagonists
Drugs:
Candesartan, Eprosartan, Irbesartan, Losartan, Telmisartan
Mechanism of action:
Inhibits the action of angiotensin-II on AT-1 receptors
This blocks angiotensin-II mediated vasoconstriction & aldosterone release (increased K+ reabsorption, decreased water & Na+ reabsorption leading to decreased blood volume)
Clinical effects:
Decreased BP
Reduced oedema
Adverse effects:
Hypotension, dizziness, hyperkalaemia
Digoxin
Mechanism of action:
Blocks Na+/K+ pump on the cardiac cell membrane resulting in increased intracellular Ca2+
Also enhances vagal tone which slows SA node rate & AV node conduction
Clinical effects:
Slowed HR & AV conduction (allowing more time for ventricular filling)
Increased contractility
Clinical uses:
Atrial fibrillation (helps rate control)
Adverse effects:
Toxicity (narrow therapeutic index, also competes with K+ so hypokalaemia may worsen toxicity)
Toxicity may cause diarrhoea, vision disturbances, confusion, agitation, arrhythmias, AV block
Arrhythmias (Na+/K+ pump inhibition leads to increased intracellular Ca2+ which is pro-arrhythmic)
Pharmacokinetics:
70% renally cleared (important to think about with toxicity risk)
Beta blockers
Drugs:
Cardioselective are preferred (eg. Bisoprolol, Metoprolol,)
Mechanism of action:
Block beta-receptors thus opposing SNS action on the heart
Clinical effects:
Decreased HR (allowing more time for ventricular filling)
Adverse effects:
Bronchoconstriction, bradycardia & cardiac depression, fatigue, cold extremities, nightmares, hypoglycaemia (masks the warning signs)