Ivabradine reduces heart rate in heart failure by selectively blocking the If (funny) current. Compared to beta-blockers, ivabradine's mechanism of action is clinically distinct because it:
- A Lowers heart rate without reducing myocardial contractility or blood pressure ✓
- B Blocks L-type calcium channels in the SA node in addition to the If current
- C Prolongs atrioventricular conduction time benefiting patients with accessory pathways
- D Reduces heart rate by increasing vagal tone rather than direct SA node suppression
Correct answer: A. Lowers heart rate without reducing myocardial contractility or blood pressure
Explanation
Ivabradine selectively inhibits the HCN (hyperpolarization-activated cyclic nucleotide-gated) channel in SA node pacemaker cells that carries the If current, slowing spontaneous depolarization and reducing heart rate (pure chronotropic effect). Unlike beta-blockers, it has no effect on myocardial contractility (no negative inotropic effect) or peripheral vascular tone, making it particularly useful in heart failure with reduced ejection fraction when heart rate exceeds 70 bpm on maximally tolerated beta-blocker doses.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.