American Board of Internal Medicine (ABIM) Certification Practice Exam

In patients with HFrEF, what is the target resting heart rate before starting ivabradine?

1. 70 beats per minute or higher

2. 60 beats per minute or higher

3. 80 beats per minute or higher

4. 50 beats per minute or lower

The correct answer is: 70 beats per minute or higher

The target resting heart rate for initiating ivabradine in patients with heart failure with reduced ejection fraction (HFrEF) is set at 70 beats per minute or higher. This is because ivabradine is specifically indicated for patients who are in sinus rhythm and have a resting heart rate of 70 beats per minute or more to effectively reduce heart rate and improve outcomes. Ivabradine works by selectively inhibiting the If current in the sinoatrial node, leading to decreased heart rate without affecting myocardial contractility or overall hemodynamics. The drug is ideally used in patients who have not achieved adequate heart rate control with beta-blockers or are intolerant to them. Having a baseline heart rate of 70 or higher ensures that there is sufficient room for ivabradine to exert its effects, allowing for potential improvement in symptoms and reduction in hospitalizations due to heart failure. If the heart rate is below this threshold, initiating therapy with ivabradine may not be appropriate, as it could lead to bradycardia or other complications without providing the intended therapeutic benefit.