Ivabradine reduces heart rate in stable angina without affecting myocardial contractility or blood pressure. Its mechanism is:

• A Selective blockade of the beta-1 adrenoceptor in the SA node
• B Blockade of L-type calcium channels in the SA node pacemaker cells
• C Inhibition of the hyperpolarisation-activated cyclic nucleotide-gated (HCN) channel (If current) in the SA node ✓
• D Activation of inward rectifier K+ channels, hyperpolarising the SA node

Explanation

Ivabradine selectively inhibits the funny current (If) carried by HCN channels in the SA node. If is a mixed Na+/K+ inward current activated by hyperpolarisation that drives the diastolic depolarisation slope (phase 4). By slowing If, ivabradine lengthens the interval between action potentials, reducing heart rate without negative inotropy or blood pressure effects.

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

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Written and medically reviewed by the StethoPrep medical team.