Ivabradine reduces heart rate in stable angina by blocking which ion channel?
- A L-type calcium channels in sinoatrial node pacemaker cells
- B Funny current (If) channels (HCN channels) in the sinoatrial node ✓
- C Potassium IKr channels, prolonging repolarisation
- D Beta-1 adrenoceptors, reducing cAMP
Correct answer: B. Funny current (If) channels (HCN channels) in the sinoatrial node
Explanation
Ivabradine selectively blocks the hyperpolarisation-activated cyclic nucleotide-gated (HCN) channels responsible for the 'funny current' (If) in sinoatrial pacemaker cells, slowing spontaneous diastolic depolarisation and thereby reducing heart rate without affecting myocardial contractility or AV conduction. This makes it useful in heart failure (HFrEF) and stable angina in patients who are beta-blocker intolerant. IKr blockade is the mechanism of amiodarone's Class III effect; beta-1 blockade is the mechanism of beta-blockers.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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