Ivabradine reduces heart rate in stable angina by a mechanism distinct from beta-blockers. It specifically inhibits which cardiac channel?

• A Funny current (If) channels (HCN4) in the SA node ✓
• B Voltage-gated L-type calcium channels in the SA node
• C IKr (hERG) rapid delayed rectifier potassium channels
• D INa persistent late sodium current in cardiomyocytes

Explanation

Ivabradine selectively inhibits the hyperpolarisation-activated cyclic nucleotide-gated (HCN4/If 'funny') current in the sinoatrial node, which is responsible for spontaneous diastolic depolarisation (pacemaker potential). By reducing the rate of this depolarisation, ivabradine slows the sinus rate without affecting myocardial contractility, blood pressure, or conduction. Unlike beta-blockers, it is therefore useful in patients where chronotropic reduction is desired without negative inotropy.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.