Ivabradine reduces heart rate by a novel mechanism and is used in stable angina and HFrEF with sinus tachycardia. Its mechanism of action is:

• A Beta-1 selective blockade in the sinoatrial node
• B Calcium channel blockade in the sinoatrial node, similar to verapamil
• C Muscarinic M2 agonism increasing vagal tone to the heart
• D Selective inhibition of the funny current (If) in sinoatrial node pacemaker cells ✓

Explanation

Ivabradine selectively blocks HCN (hyperpolarization-activated cyclic nucleotide-gated) channels responsible for the pacemaker 'funny current' (If) in the sinoatrial node. This current contributes to spontaneous diastolic depolarization that drives heart rate. By inhibiting If, ivabradine slows the rate of diastolic depolarization and thereby reduces heart rate without affecting myocardial contractility, conduction, or blood pressure. It is a pure heart rate-lowering agent, useful when beta-blockers are contraindicated (e.g., asthma) and in patients with HFrEF already on beta-blockers who remain tachycardic.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.