From the Guidelines
Ivabradine primarily affects the electrocardiogram (ECG) by causing a dose-dependent reduction in heart rate, with the most characteristic ECG change being bradycardia, as ivabradine selectively inhibits the funny current (If) in the sinoatrial node, reducing heart rate without affecting cardiac contractility or blood pressure 1.
Effects of Ivabradine on ECG
The effects of ivabradine on the electrocardiogram (ECG) are primarily related to its mechanism of action, which involves the selective inhibition of the funny current (If) in the sinoatrial node. This results in a reduction in heart rate without affecting cardiac contractility or blood pressure. Key effects on the ECG include:
- Reduction in heart rate: Ivabradine causes a dose-dependent decrease in heart rate, which is the most characteristic ECG change associated with this medication 1.
- Increase in PR interval: There may be a slight increase in the PR interval due to the effects of ivabradine on the atrioventricular node, although this is not as pronounced as the reduction in heart rate 1.
- Prolongation of the QT interval: Ivabradine can cause a prolongation of the QT interval, although this is typically corrected for heart rate and is not considered a significant risk factor for arrhythmias 1.
Clinical Considerations
When monitoring patients on ivabradine, clinicians should be aware of the potential for excessive bradycardia (heart rate below 50 beats per minute), which may require dose reduction. Additionally, ivabradine should be used cautiously in patients with pre-existing conduction disorders or in combination with other medications that affect heart rate or QT interval. The visual phosphenes (luminous phenomena) caused by ivabradine do not correlate with ECG changes and are typically transient and well-tolerated 1.
Key Points
- Ivabradine reduces heart rate without affecting cardiac contractility or blood pressure.
- The most characteristic ECG change is bradycardia.
- Ivabradine can cause a slight increase in PR interval and prolongation of the QT interval.
- Clinicians should monitor for excessive bradycardia and use ivabradine cautiously in patients with pre-existing conduction disorders or in combination with other medications that affect heart rate or QT interval.
From the FDA Drug Label
Ivabradine blocks the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel responsible for the cardiac pacemaker I fcurrent, which regulates heart rate. In clinical electrophysiology studies, the cardiac effects were most pronounced in the sinoatrial (SA) node, but prolongation of the AH interval has occurred as has PR interval prolongation There was no effect on ventricular repolarization and no effects on myocardial contractility Ivabradine increases the uncorrected QT interval with heart rate slowing but does not cause rate-corrected prolongation of QT.
The effects of ivabradine on electrocardiogram (ECG) include:
- Heart rate reduction: approximately 10 bpm at rest and during exercise
- Prolongation of the AH interval: occurred in clinical electrophysiology studies
- Prolongation of the PR interval: occurred in clinical electrophysiology studies
- No effect on ventricular repolarization: no changes observed
- No effects on myocardial contractility: no changes observed
- Increase in uncorrected QT interval: occurs with heart rate slowing, but no rate-corrected prolongation of QT 2
From the Research
Effects of Ivabradine on ECG
The effects of ivabradine on electrocardiogram (ECG) can be understood by analyzing its mechanism of action and the results from various studies.
- Ivabradine is a heart rate-lowering agent that selectively inhibits the I(f) current in sinoatrial node cells, reducing diastolic depolarization rate and heart rate 3.
- At therapeutic concentrations, ivabradine has no action on other cardiac or vascular ion channels or receptors, which means it does not affect the ECG parameters other than heart rate 3.
- The heart rate reduction with ivabradine is dose-dependent and tends to a maximum or plateau level at high doses, which can be observed on an ECG as a decrease in heart rate without any significant changes in other parameters 3.
- Ivabradine lowers heart rate without any negative inotropic or lusitropic effect, thus preserving ventricular contractility, and it does not modify any major electrophysiological parameters not related to heart rate 4.
- In patients with inappropriate sinus tachycardia, ivabradine significantly reduced maximum and mean heart rate, and improved symptoms without significant changes in minimum heart rate 5.
ECG Parameters Affected by Ivabradine
The ECG parameters that can be affected by ivabradine include:
- Heart rate: Ivabradine reduces heart rate by inhibiting the I(f) current in sinoatrial node cells 3, 4.
- PR interval: There is no direct effect of ivabradine on the PR interval, as it only affects the sinoatrial node and not the atrioventricular node 3.
- QT interval: Ivabradine does not affect the QT interval, as it does not affect the ventricular repolarization 3, 4.
Clinical Implications
The effects of ivabradine on ECG have important clinical implications, including:
- Reduction in myocardial oxygen demand and improvement in coronary blood flow, which can be beneficial in patients with angina pectoris or heart failure 6, 7.
- Improvement in symptoms and quality of life in patients with inappropriate sinus tachycardia or heart failure 7, 5.
- Potential role in the treatment of other cardiovascular conditions, such as heart failure or coronary artery disease 4, 6.