The role of heart rate may differ according to pathophysiological setting: from SHIFT to SIGNIFY

Ivabradine in Cardiovascular Disease Management Revisited: a Review

Ivabradine is a unique agent that is distinct from beta-blockers and calcium channel blockers as it reduces heart rate without affecting myocardial contractility or vascular tone. Ivabradine is a use-dependent inhibitor targeting the sinoatrial node. It is approved for use in the United States as an adjunct therapy for heart rate reduction in patients with heart failure with reduced ejection fraction. In this scenario, ivabradine has demonstrated improved clinical outcomes due to reduction in heart failure readmissions. However, there has been conflicting evidence from prospective studies and randomized controlled trials for its use in stable ischemic heart disease regarding efficacy in symptom reduction and mortality benefit. Ivabradine may also play a role in the treatment of patients with inappropriate sinus tachycardia, who often cannot tolerate beta-blockers and/or calcium channel blockers. In this review, we highlight the evidence for the nuances of using ivabradine in heart failure, stable ischemic heart disease, and inappropriate sinus tachycardia to raise awareness for its vital role in the treatment of select populations.

Resting heart rate and relation to disease and longevity: past, present and future

Assessment of heart rate has been used for millennia as a marker of health. Several studies have indicated that low resting heart rate (RHR) is associated with health and longevity, and conversely, a high resting heart to be associated with disease and adverse events. Longitudinal studies have shown a clear association between increase in heart rate over time and adverse events. RHR is a fundamental clinical characteristic and several trials have assessed the effectiveness of heart rate lowering medication, for instance beta-blockers and selective sinus node inhibition. Advances in technology have provided new insights into genetic factors related to RHR as well as insights into whether elevated RHR is a risk factor or risk marker. Recent animal research has suggested that heart rate lowering with sinus node inhibition is associated with increased lifespan. Furthermore, genome-wide association studies in the general population using Mendelian randomization have demonstrated a causal link between heart rate at rest and longevity. Furthermore, the development in personal digital devices such as mobile phones, fitness trackers and eHealth applications has made heart rate information and knowledge in this field as important as ever for the public as well as the clinicians. It should therefore be expected that clinicians and health care providers will be met by relevant questions and need of advice regarding heart rate information from patients and the public. The present review provides an overview of the current knowledge in the field of heart rate and health.

Ivabradine for the Treatment of Cardiovascular Diseases

Higher heart rate (HR) is independently related to worse outcomes in various cardiac diseases, including hypertension, coronary artery disease, and heart failure (HF). HR is determined by the pacemaker activity of cells within the sinoatrial node. The hyperpolarization-activated cyclic nucleotide-gated (HCN) 4 channel, one of 4 HCN isoforms, generates the I_f current and plays an important role in the regulation of pacemaker activity in the sinoatrial node. Ivabradine is a novel and only available HCN inhibitor, which can reduce HR and has been approved for stable angina and chronic HF in many countries other than Japan. In this review, we summarize the current knowledge of the HCN4 channel and ivabradine, including the function of HCN4 in cardiac pacemaking, the mechanism of action of I_f inhibition by ivabradine, and the pharmacological and clinical effects of ivabradine in cardiac diseases as HF, coronary artery disease, and atrial fibrillation.

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.

Clinical presentation and management of stable coronary artery disease in Austria

Background

Cardiovascular disease is the main cause of death in Austria. However, no systematic information exists regarding characteristics and treatments of contemporary patients with stable coronary artery disease (CAD) in Austria. We assembled two retrospective physicians’ databases to describe demographics, clinical profiles, and therapeutic strategies in patients with stable CAD. In addition, we compared patient profiles of secondary care internists and hospital-based cardiologists with those of general practitioners in a primary care setting outside of hospital.

Methods

The study population was identified from retrospective chart review of 1020 patients from 106 primary care physicians in Austria (ProCor II registry), and was merged with a previous similar database of 1280 patients under secondary care (ProCor I registry) to yield a total patient number of 2300.

Results

Female patients with stable CAD were older, had more angina and/or heart failure symptoms, and more depression than males. Female gender, type 2 diabetes mellitus, higher CCS class and asthma/COPD were predictors of elevated heart rate, while previous coronary events/revascularization predicted a lower heart rate in multivariate analysis. There were no significant differences with regard to characteristics and management of patients of general practitioners in the primary care setting versus internists in secondary care.

Conclusions

Characteristics and treatments of unselected patients with stable ischemic heart disease in Austria resemble the pattern of large international registries of stable ischemic heart disease, with the exception that diabetes and systemic hypertension were more prevalent.

Ivabradine: Do the Benefits Outweigh the Risks?

Ivabradine is a selective I _f current inhibitor that is used to lower the heart rate (HR) of patients with angina and/or heart failure. It is approved for use in several countries, including the United Kingdom, Australia, Saudi Arabia, and the United States. The drug was studied in several clinical trials, and it exhibited beneficial effects on the approved indicators. However, there are some concerns with the safety profile of this drug, especially its effect in reducing HR and causing severe bradycardia. Therefore, the current review assessed the benefit-risk balance of ivabradine. A literature review of the major published studies that assessed the efficacy and safety of ivabradine was performed. The online VigiBase adverse drug reaction (ADR) reporting system was also accessed to investigate reports associated with this drug. A full benefit-risk assessment was performed using the collected data from the above-mentioned resources. Most of the reviewed studies concluded that ivabradine exerted beneficial effects with a tolerable safety profile. Specifically, a favorable benefit-risk profile was found when ivabradine was used for patients with an HR ≥70 beats per minute. Reports revealed that the most common ADR was bradycardia, which was expected. Other safety risks or ADRs were comparable to other prescribed drugs. This review presents an up-to-date analysis of ivabradine from the latest literature and reports. These studies suggest that ivabradine exhibits an acceptable and favorable benefit-risk profile, and this drug should be considered as a viable option in patients with angina pectoris and chronic heart failure.

Efficacy Profile of Ivabradine in Patients with Heart Failure plus Angina Pectoris

Objectives: In the Systolic Heart Failure Treatment with the If Inhibitor Ivabradine Trial (SHIFT), slowing of the heart rate with ivabradine reduced cardiovascular death or heart failure hospitalizations among patients with systolic chronic heart failure (CHF). Subsequently, in the Study Assessing the Morbidity-Mortality Benefits of the If Inhibitor Ivabradine in Patients with Coronary Artery Disease (SIGNIFY) slowing of the heart rate in patients without CHF provided no benefit for cardiovascular death or nonfatal myocardial infarction (primary composite end point), with secondary analyses suggesting possible harm in the angina subgroup. Therefore, we examined the impact of ivabradine in the patients with CHF plus angina in SHIFT. Methods: SHIFT enrolled adults with stable, symptomatic CHF, a left ventricular ejection fraction ≤35% and a sinus rhythm with a resting heart rate ≥70 bpm. Outcomes were the SHIFT and SIGNIFY primary composite end points and their components. Results: Of 6,505 patients in SHIFT, 2,220 (34%) reported angina at randomization. Ivabradine numerically, but not significantly, reduced the SIGNIFY primary composite end point by 8, 11 and 11% in the SHIFT angina subgroup, nonangina subgroup and overall population, respectively. Ivabradine also reduced the SHIFT primary composite end point in all 3 subgroups. Conclusions: In SHIFT, ivabradine showed consistent reduction of cardiovascular outcomes in patients with CHF; similar results were seen in the subgroup of SHIFT patients with angina.

Selective Heart Rate Reduction With Ivabradine Increases Central Blood Pressure in Stable Coronary Artery Disease

Abstract—

Heart rate (HR) lowering by β-blockade was shown to be beneficial after myocardial infarction. In contrast, HR lowering with ivabradine was found to confer no benefits in 2 prospective randomized trials in patients with coronary artery disease. We hypothesized that this inefficacy could be in part related to ivabradine’s effect on central (aortic) pressure. Our study included 46 patients with chronic stable coronary artery disease who were randomly allocated to placebo (n=23) or ivabradine (n=23) in a single-blinded fashion for 6 months. Concomitant baseline medication was continued unchanged throughout the study except for β-blockers, which were stopped during the study period. Central blood pressure and stroke volume were measured directly by left heart catheterization at baseline and after 6 months. For the determination of resting HR at baseline and at follow-up, 24-hour ECG monitoring was performed. Patients on ivabradine showed an increase of 11 mm Hg in central systolic pressure from 129±22 mm Hg to 140±26 mm Hg ( P =0.02) and in stroke volume by 86±21.8 to 107.2±30.0 mL ( P =0.002). In the placebo group, central systolic pressure and stroke volume remained unchanged. Estimates of myocardial oxygen consumption (HR×systolic pressure and time-tension index) remained unchanged with ivabradine.The decrease in HR from baseline to follow-up correlated with the concomitant increase in central systolic pressure ( r =−0.41, P =0.009) and in stroke volume ( r =−0.61, P <0.001). In conclusion, the decrease in HR with ivabradine was associated with an increase in central systolic pressure, which may have antagonized possible benefits of HR lowering in coronary artery disease patients.

Clinical Trials—URL:

http://www.clinicaltrials.gov . Unique identifier NCT01039389.

Heart Rate Reduction With Ivabradine Protects Against Left Ventricular Remodeling by Attenuating Infarct Expansion and Preserving Remote-Zone Contractile Function and Synchrony in a Mouse Model of Reperfused Myocardial Infarction

BACKGROUND

Ivabradine selectively inhibits the pacemaker current of the sinoatrial node, slowing heart rate. Few studies have examined the effects of ivabradine on the mechanical properties of the heart after reperfused myocardial infarction (MI). Advances in ultrasound speckle-tracking allow strain analyses to be performed in small-animal models, enabling the assessment of regional mechanical function.

METHODS AND RESULTS

After 1 hour of coronary occlusion followed by reperfusion, mice received 10 mg/kg per day of ivabradine dissolved in drinking water (n=10), or were treated as infarcted controls (n=9). Three-dimensional high-frequency echocardiography was performed at baseline and at days 2, 7, 14, and 28 post-MI. Speckle-tracking software was used to calculate intramural longitudinal myocardial strain (Ell) and strain rate. Standard deviation time to peak radial strain (SD Tpeak Err) and temporal uniformity of strain were calculated from short-axis cines acquired in the left ventricular remote zone. Ivabradine reduced heart rate by 8% to 16% over the course of 28 days compared to controls (P<0.001). On day 28 post-MI, the ivabradine group was found to have significantly smaller end-systolic volumes, greater ejection fraction, reduced wall thinning, and greater peak Ell and Ell rate in the remote zone, as well as globally. Temporal uniformity of strain and SD Tpeak Err were significantly smaller in the ivabradine-treated group by day 28 (P<0.05).

CONCLUSIONS

High-frequency ultrasound speckle-tracking demonstrated decreased left ventricular remodeling and dyssynchrony, as well as improved mechanical performance in remote myocardium after heart rate reduction with ivabradine.

Current Role of Ivabradine in Stable Coronary Artery Disease Without Heart Failure

Increase in heart rate represents a significant contribution in the pathophysiology of coronary artery disease and heart failure, by promoting atherosclerotic process and endothelial dysfunction. Thus, it negatively influences cardiovascular risk in the general population. The aim of this review is to analyze the current, controversial, and future role of ivabradine as an anti-anginal agent in the setting of coronary artery disease without heart failure. Ivabradine represents a selective heart rate-lowering agent that increased diastolic perfusion time and improving energetics in the ischemic myocardium.