Clinical Results of If Current Inhibition by Ivabradine

Ivabradine: Evidence and current role in cardiovascular diseases and other emerging indications

Increased heart rate (HR) is associated with deleterious effects on several disease conditions. Chronic heart failure (CHF) is one of the cardiovascular diseases with recurrent hospitalization burden and an ongoing drain on health-care expenditure. Despite advancement in medicine, management of CHF remains a challenge to health-care providers. Ivabradine selectively and specifically inhibits the pacemaker I(f) ionic current which reduces the cardiac pacemaker activity. The main effect of ivabradine therapy is the substantial lowering of HR. It does not influence intracardiac conduction, contractility, or ventricular repolarization. As shown in numerous clinical studies, ivabradine improves clinical outcomes and quality of life and reduces the risk of death from heart failure (HF) or other cardiovascular causes. Recently updated HF guidelines recommend ivabradine as a class II indication for reduction of HF hospitalizations. Based on the principle of benefits of reduced HR, the ivabradine in patients with ischemic heart disease, sepsis, and multiple organ dysfunction syndrome has also been studied. It can also be a useful agent for HR reduction in patients with contraindications to use beta-blockers or those who cannot tolerate them. In this review, we provide an overview of efficacy and safety of ivabradine and its combination with currently recommended pharmacological therapy in different conditions.

If Channel as an Emerging Therapeutic Target for Cardiovascular Diseases: A Review of Current Evidence and Controversies

In 2015, non-communicable diseases accounted for 39.5 million (70%) of the total 56.4 million deaths that occurred globally, of which 17.7 million (45%) were due to cardiovascular diseases. An elevated heart rate is considered to be one of the independent predictors and markers of future cardiovascular diseases. A variety of experimental and epidemiological studies have found that atherosclerosis, heart failure, coronary artery disease, stroke, and arrhythmia are linked to elevated heart rate. Although there are established drugs to reduce the heart rate, these drugs have undesirable side effects. Hence, the development of new drugs that selectively inhibit the heart rate is considered necessary. In the search for such drugs, almost four decades ago the I_f channel, also known as the “funny channel,” emerged as a novel site for the selective inhibition of heart rate. These I_f channels, with a mixed sodium and potassium inward current, have been identified in the sinoatrial node of the heart, which mediates the slow diastolic depolarization of the pacemaker of the spontaneous rhythmic cells. The hyperpolarization-activated cyclic nucleotide-gated (HCN) subfamily is primarily articulated in the heart and neurons that are encoded by a family of four genes (HCN1-4) and they identify the funny channel. Of these, HCN-4 is the principal protein in the sinoatrial node. Currently, funny channel inhibition is being targeted for the treatment and prevention of cardiovascular diseases such as atherosclerosis and stroke. A selective I_f channel inhibitor named ivabradine was discovered for clinical use in treating heart failure and coronary artery disease. However, inconsistencies regarding the clinical effects of ivabradine have been reported in the literature, suggesting the need for a rigorous analysis of the available evidence. The objective of this review is therefore to assess the current advances in targeting the I_f channel associated with ivabradine and related challenges.

The role of Ivabradine in Diastolic Heart Failure with preserved Ejection Fraction. A Doppler-Echocardiographic study

Background:

Ivabradine (IVA) is effective in patients with coronary artery disease (CAD) or systolic heart failure in sinus rhythm. Its action consists in reducing heart rate (HR) and improving the time of left ventricular (LV) diastolic filling. The aim of this study was to evaluate the effects of IVA added to conventional therapy on patients with diastolic heart failure (DHF) and preserved ejection fraction (HFpEF).

Methods:

We evaluated 25 patients with DHF in the New York Heart Association (NYHA) Class II-III and sinus rhythm. In these, IVA per os (5 mg/twice a day) was added to the conventional medical therapy and given for 12 weeks. Immediately before the beginning of IVA therapy and 3 months later, patients underwent echocardiographic evaluation by two-dimensional (2D) ultrasound and tissue Doppler imaging (TDI). The patterns of diastolic mitral inflow and pulmonary venous flow were recorded using 2D echocardiography, while the diastolic phase of mitral flow was recorded by TDI, from the lateral mitral annulus.

Results:

Three months after the addition of IVA to conventional treatment, HR significantly decreased in comparison to the baseline values. On the contrary, the echocardiographic indexes of LV diastolic dysfunction improved.

Conclusions:

These results testify that the addition of IVA to conventional therapy in patients with HFpEF can improve LV diastolic function evaluated by 2D and tissue Doppler-echocardiographic patterns. These Doppler-echocardiographic results match with the clinical improvement of patients evaluated.

Stable angina pectoris: the medical management of symptomatic myocardial ischemia

Coronary artery disease (CAD) remains an important cause of morbidity and mortality and is a serious public health problem. Over the last 4 decades there have been dramatic advances in the both the prevention and treatment of CAD. The management of CAD was revolutionized by the development of effective surgical and percutaneous revascularization techniques. In this review we discuss the importance of the medical management of symptomatic, stable angina. Medical management approaches to both the treatment and prevention of symptomatic myocardial ischemia are summarized. In Canada, organic nitrates, β-adrenergic blocking agents, and calcium channel antagonists have been available for the therapy of angina for more than 25 years. All 3 classes are of proven benefit in the improvement of symptoms and exercise capacity in patients with stable angina. Although there is no clear first choice within these classes of anti-anginal agents, the presence of prior or concurrent conditions (for example, prior myocardial infarction and/or hypertension) plays an important role in the choice of anti-anginal class in individual patients. For some patients, combinations of different anti-anginal agents can be effective; however it is recommended that this approach be individualized. Although not currently available in Canada, other classes of anti-anginal agents have been developed; their mechanism of action and clinical efficacy is discussed. Patients with stable angina have an excellent prognosis. Patients in this category who obtain relief from symptomatic myocardial ischemia may do well without invasive intervention.

Pharmacodynamic effects of ivabradine, a negative chronotropic agent, in healthy cats

OBJECTIVE

To determine the pharmacodynamic effects of oral ivabradine in cats.

ANIMALS

Eight healthy, adult domestic short hair cats.

METHODS

Each cat underwent four study periods of 24 h, receiving either one dose of placebo or ivabradine (0.1 mg/kg, 0.3 mg/kg, and 0.5 mg/kg) in a single-blind randomized crossover study. Clinical tolerance was assessed hourly for the first 8 h, at 12 h, and at the end of the 24-h study period. Heart rate and blood pressure were monitored continuously for 18-24 h via radiotelemetry after each treatment. Response to stress (acoustic startle) was studied before (t = 0) and after treatment (t = 4 h). Statistical comparisons were made using a linear mixed models and 1-way and 2-way repeated measures ANOVA.

RESULTS

Heart rate (min(-1)) decreased significantly (P < 0.05) in a dose-dependent manner with peak negative chronotropic effects observed 3 h after ivabradine (mean ± SD; placebo, 144 ± 20; ivabradine 0.1 mg/kg, 133 ± 22; ivabradine 0.3 mg/kg, 112 ± 20; and ivabradine 0.5 mg/kg, 104 ± 11). Heart rate (min(-1)) was still reduced (P < 0.05) 12 h after ivabradine (0.3 mg/kg; 128 ± 18 and 0.5 mg/kg; 124 ± 16) compared to placebo (141 ± 21). The tachycardic response to acoustic startle was significantly (P < 0.01) blunted at all 3 doses of ivabradine. Myocardial oxygen consumption estimated by the rate-pressure product was significantly reduced (P < 0.05) for all doses of ivabradine. No effect of ivabradine on systolic, diastolic, and mean blood pressure was identified and no clinically discernable side effects were observed.

CONCLUSION

These findings indicate that a single oral dose of ivabradine predictably lowers heart rate, blunts the chronotropic response to stress, and is clinically well tolerated in healthy cats. This makes ivabradine potentially interesting in the treatment of feline heart disease where ischemia is of pathophysiologic importance.

The Contribution of HCN4 to normal sinus node function in humans and animal models

Although sinus node bradycardia is a very common clinical condition, the cellular mechanisms contributing to abnormal sinus node function are not clearly delineated. In recent publications, mutations in the hyperpolarization-activated, cyclic nucleotide-gated (HCN) 4 channels have been associated with sinus bradycardia. These channels are thought to be crucial in generating the spontaneous sinus node action potential, in accelerating the heart rate during sympathetic drive, and decelerating heart rate during vagal stimulation. Humans carrying HCN4 mutations indeed display significant bradycardia. Recent studies generating HCN4 knock out mice suggested that although HCN4 is crucial in early development, other mechanisms may also play a role in the accelerated heat rate achieved during sympathetic drive. In this review, we focus on genotype-phenotype correlation of these mutations and discuss the relative contribution of various ion channels to sinus node function. We also discuss the importance of HCN in treating clinical conditions such as brady- and tachycardia.

Treatment of stable angina pectoris by ivabradine in every day practice: the REDUCTION study

BACKGROUND

The antianginal efficacy of ivabradine was studied in controlled clinical trials. Strict patient selection criteria may cause a discrepancy between the results of highly controlled clinical trials and everyday routine practice. The objective of this study was to evaluate the efficacy and safety of ivabradine in everyday routine practice.

METHODS

In this multicenter study, 4,954 patients with stable angina pectoris received ivabradine in everyday routine practice and underwent follow-up for 4 months. The heart rate (HR), angina pectoris attacks, nitrate consumption, overall efficacy, and tolerance were evaluated.

RESULTS

Within 4 months of treatment with ivabradine, HR was reduced by 12.4 +/- 12.2 beat/min from 82.9 +/- 15.3 to 70.4 +/- 9.2 beat/min (P < .0001). Angina pectoris attacks were reduced from 2.4 +/- 3.1 to 0.4 +/- 1.5 per week (P < .0001). Consumption of short-acting nitrates was reduced from 3.3 +/- 4.4 to 0.6 +/- 1.6 U/wk (P < .0001). Seventy-eight cases of adverse drug reactions were reported. The most common adverse drug reactions were nausea (n = 11, 0.22%) and dizziness (n = 9, 0.18%). Efficacy and tolerance were graded by physicians as being "excellent/very good" for 97% and 98% of the patients treated.

CONCLUSION

Ivabradine reduces the HR and is highly effective and well tolerated in the treatment of patients with symptomatic coronary artery disease. The results confirm the findings of controlled clinical trials in a broad patient population in everyday routine practice.

Impact of a pure reduction in heart rate for the treatment of left ventricular dysfunction: clinical benefits of ivabradine in the BEAUTIFUL trial

Ivabradine is an I(f) current inhibitor, that has documented antianginal efficacy. The BEAUTIFUL trial tested ivabradine against placebo in a large population of 10,917 patients in sinus rhythm, with coronary artery disease and left ventricular dysfunction, defined as left ventricular ejection fraction < or =35%. Overall, there was no impact of ivabradine on the primary end-point of the trial (cardiovascular mortality, hospitalisation for myocardial infarction, new onset or worsening heart failure). In the placebo arm of the trial, baseline heart rate > or = 70 bpm was associated with an increased risk of cardiovascular mortality, myocardial infarction, heart failure and coronary revascularisation. In the subgroup of patients with a baseline heart rate > or =70 bpm, treatment with ivabradine resulted in a significant, 36% reduction in the risk of myocardial infarction and a 20% reduction in the need for coronary revascularisation. Ivabradine was well tolerated, with an increased rate of treatment discontinuation, mainly due to bradycardia, compared with placebo. Because of its safety and efficacy to control angina, ivabradine should be considered first-line antianginal treatment in coronary artery disease patients with left ventricular dysfunction and increased heart rate, already receiving beta-blocker therapy or in whom these medications are not tolerated.

Ivabradine: beyond heart rate control

Chronic stable angina pectoris (CSAP) usually occurs in patients with coronary artery disease (CAD) that affects one or more large epicardial arteries. It results when myocardial perfusion is insufficient to meet cardiac metabolic demand. Elevated heart rate (HR) is an important factor in the development of myocardial ischemia and angina pectoris. The pharmacologic agents most commonly administered in the treatment of CSAP are beta-blockers and calcium channel blockers (CCBs). However, the use of beta-blockers is limited by poor compliance related to contraindications and comorbidities, especially in elderly patients. Ivabradine is a new selective HR-lowering agent that selectively inhibits the pacemaker current I (f) in the sinus atrial node. In several randomized controlled trials, ivabradine 5-10 mg twice daily has demonstrated equivalent anti-ischemic and anti-anginal activity to beta-blockers and CCBs, with a good safety and tolerability profile. Although ivabradine has been shown not to improve cardiac outcomes in patients with stable CAD and left ventricular systolic dysfunction, it may be used to reduce the incidence of CAD outcomes in a subgroup of patients with HR > or =70 bpm. The aim of this short review is to summarize the use of ivabradine in the treatment of CSAP, and its potential utility in atherosclerosis, primitive and dilatative cardiomyopathy, and arrhythmias, such as postural tachycardia syndrome and inappropriate sinus tachycardia, where exclusive lowering of elevated HR may prove beneficial.