Physiological effects of ivabradine in heart failure and beyond

Ivabradine is a pharmacologic agent that inhibits the funny current responsible for determining heart rate in the sinoatrial node. Ivabradine's clinical potential has been investigated in the context of heart failure since it is associated with reduced myocardial oxygen demand, enhanced diastolic filling, stroke volume, and coronary perfusion time; however, it is yet to demonstrate definitive mortality benefit. Alternative effects of ivabradine include modulation of the renin-angiotensin-aldosterone system, sympathetic activation, and endothelial function. Here, we review key clinical trials informing the clinical use of ivabradine and explore opportunities for leveraging its potential pleiotropic effects in other diseases, including treatment of hyperadrenergic states and mitigating complications of COVID-19 infection.

Effects of dapagliflozin according to QRS duration across the spectrum of left ventricular ejection fraction: An analysis of DAPA-HF and DELIVER

AIMS

The primary aim was to evaluate the effect of dapagliflozin according to QRS duration across the spectrum of left ventricular ejection fraction (LVEF), given that prolongation of QRS duration is associated with less favourable ventricular remodelling with pharmacological therapy and worse outcomes.

METHODS AND RESULTS

A pooled analysis of the DAPA-HF and DELIVER trials, excluding patients with a paced rhythm and cardiac resynchronization therapy. Overall, 4008 patients had heart failure (HF) with reduced ejection fraction (HFrEF), and 5816 had HF with mildly reduced/preserved ejection fraction (HFmrEF/HFpEF). QRS duration was <120 ms in 7039 patients (71.7%), 120-149 ms in 1725 (17.6%), and ≥150 ms in 1060 patients (10.8%). The median follow-up time was 23 months. The rate of the primary composite outcome of cardiovascular death or worsening HF was 9.2 (95% confidence interval [CI] 8.7-9.7), 14.3 (13.0-15.7), and 15.9 (14.1-17.9) per 100 patient-years in the <120, 120-149, and ≥150 ms groups, respectively. This gradient in event rates was observed both in HFrEF and HFmrEF/HFpEF. Dapagliflozin, compared with placebo, reduced the risk of the primary outcome consistently across the QRS duration subgroups (hazard ratio [95% CI] 0.75 [0.67-0.85], 0.79 [0.65-0.96], and 0.89 [0.70-1.13] in the <120, 120-149, and ≥150 ms groups, respectively; p for interaction = 0.28). The effect of dapagliflozin on the primary outcome was consistent across the QRS duration regardless of HF phenotype that is, HFrEF or HFmrEF/HFpEF.

CONCLUSIONS

Prolongation of QRS duration is associated with worse outcomes irrespective of HF phenotype. Dapagliflozin reduced the risk of the primary outcome, regardless of QRS duration, in DAPA-HF and DELIVER.

Ivabradine in patients with heart failure: a systematic literature review

Background: Heart failure is a chronic disease linked with significant morbidity and mortality, and uncontrolled resting heart rate is a risk factor for adverse outcomes. This systematic literature review aimed to assess the efficacy, safety, and patient-reported outcomes (PROs) of ivabradine in patients with heart failure (HF) with reduced ejection fraction (HFrEF) in randomized controlled trials (RCTs) and observational studies. Methods: We searched electronic databases from their inception to July 2021 to include studies that reported on efficacy, safety, or PROs of ivabradine in patients with HFrEF. Results: Of 1947 records screened, 51 RCTs and 6 observational studies were identified. Ivabradine on top of background therapy demonstrated a significant reduction in composite outcomes including hospitalization for HF or cardiovascular death. In addition, observational studies suggested that ivabradine was associated with a significant reduction in mortality. Across all studies, ivabradine use on top of background therapy was associated with greater reductions in heart rate, improved EF, and improved health-related quality of life (QoL) and comparable risk of total adverse events compared to those treated with background therapy alone. Conclusions: Ivabradine on top of background therapy is beneficial for heart rate, hospitalization risk for HF, mortality, EF, and patients' QoL. Moreover, these benefits were achieved with no significant increase in the overall risk of total adverse events.

Therapeutic Use and Molecular Aspects of Ivabradine in Cardiac Remodeling: A Review

Cardiac remodeling can cause ventricular dysfunction and progress to heart failure, a cardiovascular disease that claims many lives globally. Ivabradine, a funny channel (I_f) inhibitor, is used in patients with chronic heart failure as an adjunct to other heart failure medications. This review aims to gather updated information regarding the therapeutic use and mechanism of action of ivabradine in heart failure. The drug reduces elevated resting heart rate, which is linked to increased morbidity and mortality in patients with heart failure. Its use is associated with improved cardiac function, structure, and quality of life in the patients. Ivabradine exerts several pleiotropic effects, including an antiremodeling property, which are independent of its principal heart-rate-reducing effects. Its suppressive effects on cardiac remodeling have been demonstrated in animal models of cardiac remodeling and heart failure. It reduces myocardial fibrosis, apoptosis, inflammation, and oxidative stress as well as increases autophagy in the animals. It also modulates myocardial calcium homeostasis, neurohumoral systems, and energy metabolism. However, its role in improving heart failure remains unclear. Therefore, elucidating its molecular mechanisms is imperative and would aid in the design of future studies.

Effects of heart rate reduction with ivabradine on vascular stiffness and endothelial function in chronic stable coronary artery disease

INTRODUCTION

Epidemiological and clinical studies have shown a relevant association between heart rate and cardiovascular mortality. Experimental studies identified vascular effects of heart rate reduction with the If channel inhibitor ivabradine. Therefore, the effects of heart rate reduction on endothelial function and indices of arterial stiffness were examined in patients with stable coronary artery disease in a prospective, placebo-controlled clinical crossover study.

METHODS AND RESULTS

Twenty-three patients (18 men and 5 women) with a resting heart rate (HR) of at least 70 beats per minute (bpm) and stable coronary artery disease were enrolled in this study. In a cross-over design, all patients were treated with ivabradine (Iva, 7.5 mg b.i.d.) and placebo for 6 months each. Iva reduced heart rate by 11.4 bpm (Iva 58.8 ± 8.2 bpm vs. placebo 70.2 ± 8.3 bpm, P < 0.0001). Augmentation index (AIx75), carotid-femoral pulse wave velocity (cfPWV) and central aortic blood pressure were measured using applanation tonometry (SphygmoCor). HRR by Iva increased AIx75 by 12.4% (Iva 24.3 ± 10.5% vs. placebo 21.3 ± 10.1%, P < 0.05) and reduced cfPWV by 14.1% (Iva 6.3 ± 1.7 m/s vs. placebo 7.3 ± 1.4 m/s, P < 0.01). Iva increased mean central blood pressure by 7.8% (Iva 107.5 ± 15.4 mmHg vs. placebo 99.1 ± 12.2 mmHg, P < 0.001). Endothelial function was determined measuring the flow-mediated vasodilation (FMD) of the brachial artery. HRR by Iva increased FMD by 18.5% (Iva 7.3 ± 2.2% vs. placebo 6.0 ± 2.0%, P < 0.001). Aortic distensibility was characterized by MRI. HRR by Iva increased aortic distensibility by 33.3% (Iva 0.003 ± 0.001/mmHg vs. placebo 0.002 ± 0.010/mmHg, P < 0.01) and circumferential cyclic strain by 37.1% (Iva 0.062 ± 0.027 vs. placebo 0.039 ± 0.018, P < 0.0001).

CONCLUSION

Heart rate reduction with Iva increased endothelium-dependent vasodilation and reduced arterial stiffness in patients with stable CAD. These findings corroborate and expand the results collected in experimental studies and indicate the importance of heart rate as a determinant of vascular function.

Optimization of Heart Failure Treatment by Heart Rate Reduction

Heart failure (HF) treatment should be optimized in addition to guideline-directed and recommended drugs to achieve an appropriate heart rate (i.e. 50−60 bpm) by ivabradine in patients with a heart rate >70 bpm in sinus rhythm and with an ejection fraction ≤35%. Heart rate reduction was to reduce cardiovascular death and HF hospitalization dependent on baseline resting heart rate. In particular in patients at a heart rate >75 bpm, a reduction in cardiovascular death, all-cause death, HF death, HF hospitalization and all-cause hospitalization has been observed. The optimal heart rate achieved appears to be between 50−60 bpm, if well tolerated as in these patients the lowest event rate is observed on treatment. Heart rate reduction is, therefore, a treatable risk factor in chronic HF. Observational studies support the concept that it is a risk indicator in other cardiovascular and non-cardiovascular conditions. Whether heart rate reduction is also modifying risk in other conditions than chronic HF should be explored in prospective clinical trials.

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.

Heart rate reduction after ivabradine might be associated with reverse electrical remodeling in patients with cardiomyopathy and left bundle branch block

Left bundle branch block increases the risk of death in patients with chronic heart failure. We herein report four clinical cases of patients with chronic heart failure caused by nonischemic cardiomyopathy with left bundle branch block that occurred when adding ivabradine to optimal medical therapy, resulting in reverse electrical and mechanical remodeling. This phenomenon might be explained by the effect of ivabradine on reverse remodeling of the left ventricle with improvement of intraventricular conduction.

Role of ivabradine and heart rate lowering in chronic heart failure: guideline update

INTRODUCTION

This review summarizes the current management of heart failure (HF) in patients with reduced ejection fraction and the potential role of heart rate lowering agents in select populations, as recommended in the updated guidelines. Areas covered: PubMed was searched for studies that evaluated the role of heart rate lowering or ivabradine in HF management. Expert commentary: Targeting heart rate may offer benefit when added to renin-angiotensin aldosterone antagonists, and beta-blockers. Ivabradine is a heart rate lowering agent that acts on the funny current (I_f) in the sinoatrial node, thereby reducing heart rate without directly affecting cardiac contraction and relaxation. Clinical data from a phase III trial demonstrated that ivabradine reduced the composite end point of cardiovascular death or hospital admission for worsening systolic HF, while maintaining an acceptable safety profile in patients receiving standard of care therapy. These data, in addition to more recently published guidelines, suggest ivabradine as a promising new treatment option for lowering heart rate after optimizing standard therapy in select patients with chronic HF.

Benefits of Heart Rate Slowing With Ivabradine in Patients With Systolic Heart Failure and Coronary Artery Disease

Heart rate (HR) is a risk factor in patients with chronic systolic heart failure (HF) that, when reduced, provides outcome benefits. It is also a target for angina pectoris prevention and a risk marker in chronic coronary artery disease without HF. HR can be reduced by drugs; however, among those used clinically, only ivabradine reduces HR directly in the sinoatrial nodal cells without other known effects on the cardiovascular system. This review provides current information regarding the safety and efficacy of HR reduction with ivabradine in clinical studies involving >36,000 patients with chronic stable coronary artery disease and >6,500 patients with systolic HF. The largest trials, Morbidity-Mortality Evaluation of the I_f Inhibitor Ivabradine in Patients With Coronary Disease and Left Ventricular Dysfunction and Study Assessing the Morbidity-Mortality Benefits of the I_f Inhibitor Ivabradine in Patients With Coronary Artery Disease, showed no effect on outcomes. The Systolic Heart Failure Treatment With the I_f Inhibitor Ivabradine Trial, a randomized controlled trial in >6,500 patients with HF, revealed marked and significant HR-mediated reduction in cardiovascular mortality or HF hospitalizations while improving quality of life and left ventricular mechanical function after treatment with ivabradine. The adverse effects of ivabradine predominantly included bradycardia and atrial fibrillation (both uncommon) and ocular flashing scotomata (phosphenes) but otherwise were similar to placebo. In conclusion, ivabradine improves outcomes in patients with systolic HF; rates of overall adverse events are similar to placebo.

The Prognostic Impact of New-Onset Persistent Left Bundle Branch Block Following Transcatheter Aortic Valve Implantation: A Meta-analysis

New-onset persistent left bundle branch block (NOP-LBBB) is one of the most common conduction disturbances after transcatheter aortic valve implantation (TAVI). We hypothesized that NOP-LBBB may have a clinically negative impact after TAVI. To find out, we conducted a systematic literature search of the MEDLINE/PubMed and Embase databases. Observational studies that reported clinical outcomes of NOP-LBBB patients after TAVI were included. The random-effects model was used to combine odds ratios, risk ratios, or hazard ratios (HRs) with 95% confidence intervals. Adjusted HRs were utilized over unadjusted HRs or risk ratios when available. A total of 4049 patients (807 and 3242 patients with and without NOP-LBBB, respectively) were included. Perioperative (in-hospital or 30-day) and midterm all-cause mortality and midterm cardiovascular mortality were comparable between the groups. The NOP-LBBB patients experienced a higher rate of permanent pacemaker implantation (HR: 2.09, 95% confidence interval: 1.12-3.90, P = 0.021, I(2) = 83%) during midterm follow-up. We found that NOP-LBBB after TAVI resulted in higher permanent pacemaker implantation but did not negatively affect the midterm prognosis. Therefore, careful observation during the follow-up is required.

Clinical outcomes according to QRS duration and morphology in the Eplerenone in Mild Patients: Hospitalization and SurvIval Study in Heart Failure (EMPHASIS-HF)

AIMS

We examined the relationship between different degrees of QRS prolongation and different QRS morphologies and clinical outcomes in patients with heart failure, reduced ejection fraction (HF-REF), and mild symptoms in the Eplerenone in Mild Patients Hospitalization and SurvIval Study in Heart Failure trial (EMPHASIS-HF). We also evaluated the effect of eplerenone in these patients according to QRS duration/morphology.

METHODS AND RESULTS

Patients were categorized as: QRS duration (ms) (i) <120 (n = 1375); (ii) 120-149 (n = 517); and (iii) ≥150 (n = 383), and QRS morphology (i) normal (n = 1252); (ii) left bundle branch block (BBB) (n = 608); and (iii) right BBB/intraventricular conduction defect (IVCD) (n = 415). The outcomes examined were the composite of cardiovascular death or heart failure hospitalization and all-cause mortality. Both abnormal QRS duration and QRS morphology were associated with higher risk, e.g. the rates of the composite outcome were: 10.2, 17.6, and 15.5 per 100 patient-years in the <120, 120-149, and ≥150 ms groups, respectively. Eplerenone reduced the risk of the primary outcome and mortality, compared with placebo, consistently across the QRS duration/morphology subgroups.

CONCLUSION

We found that even moderate prolongation of QRS duration and right BBB/IVCD were associated with a high risk of adverse outcomes in HF-REF. Eplerenone was similarly effective, irrespective of QRS duration/morphology.

Update on ivabradine for heart failure

Despite dramatic advances in therapy for heart failure (HF) during the past 3 decades, hospitalization and mortality rates remain relatively high. In recent decades, it has become apparent that HF is divisible into two equally lethal but pathophysiologically different sub-classes, the first comprising patients with LV systolic dysfunction [heart failure with reduced ejection fraction (HFrEF)] and the other, approximately equal in size, involving patients with "preserved" systolic function [heart failure with preserved ejection fraction (HFpEF)]. Evidence-based event reducing therapy currently is available only for HFrEF. With the completion of seminal trials of beta blockers, now part of standard therapy for HFrEF, it was apparent that heart rate slowing is an underlying basis of clinical effectiveness of HFrEF therapy. With the discovery of the "f current" that modulates the slope of spontaneous diastolic depolarization of the sino-atrial node, a non-beta blockade approach to heart rate slowing became available. Ivabradine, the first FDA-approved f-current blocker for HFrEF, markedly reduces hospitalizations for worsening heart failure, while also progressively reducing mortality as pre-therapy heart rate increases, and also promotes beneficial left ventricular remodeling, improves health-related quality of life and is effective despite a wide range of comorbidities. The drug is well tolerated and adverse effects are relatively few. Ivabradine represents an important addition to the armamentarium for mitigation of HFrEF.

Heart Rate Control With If Inhibitor, Ivabradine, in Japanese Patients With Chronic Heart Failure - A Randomized, Double-Blind, Placebo-Controlled Phase II Study

BACKGROUND

Elevated heart rate (HR) is an independent risk factor for cardiovascular outcomes in various cardiac diseases, including heart failure (HF).

METHODS AND RESULTS

Randomized placebo-controlled study was conducted to evaluate the effects of ivabradine, an Ifinhibitor, on the resting HR in 126 Japanese symptomatic HF patients with left ventricular ejection fraction ≤35%, resting HR ≥75 beats/min in sinus rhythm, and stable, optimal background treatment. Patients were randomly allocated into 3 groups: placebo; starting dose of ivabradine 2.5 mg twice daily (BID; 2.5 mg group); 5 mg BID group. The dose was increased up to 7.5 mg BID according to dose-adjustment criteria. After the 6-week treatment, the reductions in resting HR were significant in both the 2.5-mg (16.6±8.1 beats/min) and 5-mg (16.4±9.6 beats/min) groups (P<0.0001 for both groups) compared with placebo (1.7±8.7 beats/min). The most frequent side effect of ivabradine was phosphenes, but all were mild. Treatment was discontinued in 1 patient due to HF in the 5 mg group.

CONCLUSIONS

Ivabradine starting at 2.5 or 5 mg BID effectively reduced resting HR in Japanese HF patients. Ivabradine at the starting dose of 2.5 mg BID could be safer than 5 mg BID. (Circ J 2016; 80: 668-676).

Ivadradine

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Gender and outcomes after primary prevention implantable cardioverter-defibrillator implantation: Findings from the National Cardiovascular Data Registry (NCDR)

BACKGROUND

Clinical trials have demonstrated the benefit of implantable cardioverter-defibrillators (ICDs) for the primary prevention of sudden cardiac death in selected high-risk individuals. Because of small numbers of women enrolled in these trials, outcomes for women after hospital discharge have not been well described. We compared procedure-related complications and outcomes after hospital discharge between men and women undergoing single- or dual-chamber ICD implantation for primary prevention.

METHODS

In patients 65 years or older with Medicare fee-for-service coverage, we identified 38,912 initial implants (25% women) who received single- or dual-chamber ICDs for primary prevention between January 2006 and December 2009 in the NCDR and evaluated gender differences in outcomes.

RESULTS

Women had greater comorbidity and more advanced heart failure (HF) at the time of ICD implantation than did men. Device-related complications, death at 6 months, all-cause readmissions, and HF readmissions at 6 months were significantly more common in women (7.2% vs 4.8%, 6.5% vs 5.6%, 37.2% vs 31.7%, and 14.0% vs 10.0% respectively; P < .001 for all). Women continued to have higher odds of procedural complications (odds ratio [OR] 1.39, 95% CI 1.26-1.53, P < .001), 6-month all-cause readmission (OR 1.22, 95% CI 1.16-1.28, P < .001), and 6-month HF readmission (OR 1.32, 95% CI 1.23-1.42, P < .001), with a trend toward higher 6-month mortality (OR 1.08, 95% CI 0.98-1.20, P = .123), compared with men, after adjusting for differences in baseline characteristics and device type (single vs dual chamber).

CONCLUSIONS

Among older patients receiving ICDs for primary prevention in clinical practice, women experience worse outcomes than do men. Reasons for gender differences in outcomes are poorly understood and require further investigation.

Resting heart rate: risk indicator and emerging risk factor in cardiovascular disease

Resting heart rate is central to cardiac output and is influenced by changes occurring in numerous diseases. It predicts longevity and cardiovascular diseases, and current evidence suggests that it is also an important marker of outcome in cardiovascular disease, including heart failure. Beta-blockers improve outcomes in heart failure; however, they have effects outside reducing heart rate. Ivabradine has demonstrated efficacy in reducing rehospitalizations and mortality in heart failure and in improving exercise tolerance and reducing angina attacks in patients with coronary artery disease, whereas selective heart rate reduction may also prove to be beneficial in therapeutic areas outside those in which ivabradine has already demonstrated clinical efficacy. This review provides an update on the associations between heart rate and cardiovascular outcomes in various conditions, the experimental effects of heart rate reduction with ivabradine, and the potential new indications in cardiovascular disease.

Stochasticity intrinsic to coupled-clock mechanisms underlies beat-to-beat variability of spontaneous action potential firing in sinoatrial node pacemaker cells

Recent evidence indicates that the spontaneous action potential (AP) of isolated sinoatrial node cells (SANCs) is regulated by a system of stochastic mechanisms embodied within two clocks: ryanodine receptors of the "Ca(2+) clock" within the sarcoplasmic reticulum, spontaneously activate during diastole and discharge local Ca(2+) releases (LCRs) beneath the cell surface membrane; clock crosstalk occurs as LCRs activate an inward Na(+)/Ca(2+) exchanger current (INCX), which together with If and decay of K(+) channels prompts the "M clock," the ensemble of sarcolemmal-electrogenic molecules, to generate APs. Prolongation of the average LCR period accompanies prolongation of the average AP beating interval (BI). Moreover, the prolongation of the average AP BI accompanies increased AP BI variability. We hypothesized that both the average AP BI and AP BI variability are dependent upon stochasticity of clock mechanisms reported by the variability of LCR period. We perturbed the coupled-clock system by directly inhibiting the M clock by ivabradine (IVA) or the Ca(2+) clock by cyclopiazonic acid (CPA). When either clock is perturbed by IVA (3, 10 and 30 μM), which has no direct effect on Ca(2+) cycling, or CPA (0.5 and 5 μM), which has no direct effect on the M clock ion channels, the clock system failed to achieve the basal AP BI and both AP BI and AP BI variability increased. The changes in average LCR period and its variability in response to perturbations of the coupled-clock system were correlated with changes in AP beating interval and AP beating interval variability. We conclude that the stochasticity within the coupled-clock system affects and is affected by the AP BI firing rate and rhythm via modulation of the effectiveness of clock coupling.