Heart Rate Reduction by If-Channel Inhibition and its Potential Role in Heart Failure with Reduced and Preserved Ejection Fraction

Ivabradine in Septic Shock: A Narrative Review

In patients with septic shock, compensatory tachycardia initially serves to maintain adequate cardiac output and tissue oxygenation but may persist despite appropriate fluid and vasopressor resuscitation. This sustained elevation in heart rate and altered heart rate variability, indicative of autonomic dysfunction, is a well-established independent predictor of adverse outcomes in critical illness. Elevated heart rate exacerbates myocardial oxygen demand, reduces ventricular filling time, compromises coronary perfusion during diastole, and impairs the isovolumetric relaxation phase of the cardiac cycle, contributing to ventricular-arterial decoupling. This also leads to increased ventricular and atrial filling pressures, with a heightened risk of arrhythmias. Ivabradine, a highly selective inhibitor of the sinoatrial node's pacemaker current (If or "funny" current), mitigates heart rate by modulating diastolic depolarization slope without affecting contractility. By exerting a selective chronotropic effect devoid of negative inotropic properties, ivabradine shows potential for improving hemodynamics in septic shock patients with cardiac dysfunction. This review evaluates the plausible mechanisms and existing evidence regarding the utility of ivabradine in managing patients with septic shock.

Impact of heart rate, aortic compliance and stroke volume on the aortic regurgitation fraction studied in an ex vivo pig model

INTRODUCTION

Drug therapy to reduce the regurgitation fraction (RF) of high-grade aortic regurgitation (AR) by increasing heart rate (HR) is generally recommended. However, chronic HR reduction in HFREF patients can significantly improve aortic compliance and thereby potentially decrease RF. To clarify these contrasts, we examined the influence of HR, aortic compliance and stroke volume (SV) on RF in an ex vivo porcine model of severe AR.

METHODS

Experiments were performed on porcine ascending aorta with aortic valves (n=12). Compliance was varied by inserting a Dacron graft close to the aortic valve. Both tube systems were connected to a left heart simulator varying HR and SV. AR was accomplished by punching a 0.3 cm2 hole in one aortic cusp. Flow, RF, SV and aortic pressure were measured, aortic compliance with transoesophageal ultrasound probes.

RESULTS

Compliance of the aorta was significantly reduced after Dacron graft insertion (0.55%±0.21%/mm Hg vs 0.01%±0.007%/mm Hg, p<0.001, respectively). With increasing HR, RF was significantly reduced in each steady state of the native aorta (HR 40 bpm: 88%±7% vs HR 120 bpm: 42%±10%; p<0.001), but Dacron tube did not affect RF (HR 40 bpm: 87%±8%; p=0.79; HR 120 bpm: 42%±3%; p=0.86). Increasing SV also reduced RF independent of the stiff Dacron graft.

CONCLUSION

Aortic compliance did not affect AR in the ex vivo porcine model of AR. RF was significantly reduced with increasing HR and SV. These results affirm that HR lowering and negative inotropic drugs should be avoided to treat severe AR.

Optimal Heart Rate Control Improves Long-Term Prognosis of Decompensated Heart Failure with Reduced Ejection Fraction

Background and Objectives: An elevated heart rate is an independent risk factor for cardiovascular disease; however, the relationship between heart rate control and the long-term outcomes of patients with heart failure with reduced ejection fraction (HFrEF) remains unclear. This study explored the long-term prognostic importance of heart rate control in patients hospitalized with HFrEF. Materials and Methods: We retrieved the records of patients admitted for decompensated heart failure with a left ventricular ejection fraction (LVEF) of ≤40%, from 1 January 2005 to 31 December 2019. The primary outcome was a composite of cardiovascular death or hospitalization for heart failure (HHF) during follow-up. We analyzed the outcomes using Cox proportional hazard ratios calculated using the patients' heart rates, as measured at baseline and approximately 3 months later. The mean follow-up duration was 49.0 ± 38.1 months. Results: We identified 5236 eligible patients, and divided them into five groups on the basis of changes in their heart rates. The mean LVEFs of the groups ranged from 29.1% to 30.6%. After adjustment for all covariates, the results demonstrated that lesser heart rate reductions at the 3-month screening period were associated with long-term cardiovascular death, HHF, and all-cause mortality (p for linear trend = 0.033, 0.042, and 0.003, respectively). The restricted cubic spline model revealed a linear relationship between reduction in heart rate and risk of outcomes (p for nonlinearity > 0.2). Conclusions: Greater reductions in heart rate were associated with a lower risk of long-term cardiovascular death, HHF, and all-cause mortality among patients discharged after hospitalization for decompensated HFrEF.

Heart failure and atrial fibrillation: tachycardia-mediated acute decompensation

Aims

Tachycardia is a reversible event that may cause hemodynamic decompensation but may not necessarily cause direct damages to the myocardium. To evaluate the clinical outcomes of patients with heart failure (HF) and atrial fibrillation (AF), whose acute decompensation was tachycardia mediated.

Methods and results

The Korean Acute Heart Failure registry was a prospective registry that consecutively enrolled 5625 patients with acute HF. Patients were classified into three groups according to the rhythm and aggravating factor: (i) 3664 (65.1%) patients with sinus rhythm (SR), (ii) 1033 (18.4%) patients with AF whose decompensation was tachycardia‐mediated, AF‐TM (+), and (iii) N = 928 (16.5%) patients with AF whose decompensation was not tachycardia‐mediated, AF‐TM (−). The primary outcomes were in‐hospital and post‐discharge 1 year all‐cause mortality. At admission, the mean heart rate was 90.8 ± 23.4, 86.8 ± 26.8, and 106.3 ± 29.7 beats per minute for the SR, AF‐TM (−), and AF‐TM (+) groups, respectively. The AF‐TM (+) group had more favourable characteristics such as de novo onset HF, less diabetes, ischaemic heart disease, and higher blood pressure than the AF‐TM (−) group. In‐hospital mortality rates were 5.1%, 6.5%, and 1.7% for SR, AF‐TM (−), and AF‐TM (+) groups, respectively. In logistic regression analysis, the AF‐TM (+) group had lower in‐hospital mortality after adjusting the significant covariates (odds ratio, 0.49; 95% confidence interval, 0.26–0.93). The mortality rate did not differ between SR and AF‐TM (−) groups. During 1 year follow‐up, 990 (18.5%) patients died. In univariate and multivariate Cox proportional regression analyses, there was no difference in 1‐year all‐cause mortality between the three groups.

Conclusions

In patients with HF and AF, patients whose acute decompensation is tachycardia‐mediated have better in‐hospital, but similar post‐discharge outcomes compared with those with SR or those with AF whose decompensation is not tachycardia‐mediated.

Clinical Trial Registration: ClinicalTrial.gov NCT01389843.

Association of pulse rate with outcomes in heart failure with reduced ejection fraction: a retrospective cohort study

BACKGROUND

In a real-world setting, the effect of pulse rate measured at the time of diagnosis and serially during follow-up and management, on outcomes in heart failure with reduced ejection fraction (HFrEF), has not been well-studied. Furthermore, how beta-blockade use in a real-world situation modifies this relation between pulse rate and outcomes in HFrEF is not well-known. Hence, we identified a large, national, real-world cohort of HFrEF to examine the association of pulse rate and outcomes.

METHODS

Using Veterans Affairs (VA) national electronic health records we identified incident HFrEF cases between 2006 and 2012. We examined the associations of both baseline and serially measured pulse rates, with mortality and days hospitalized per year for heart failure and for any cause, using crude and multivariable Cox proportional hazards and Poisson or negative binomial models, respectively. The exposure was examined as continuous, dichotomous, and categorical. Post-hoc analyses addressed the interaction of pulse rate and beta-blocker target dose.

RESULTS

We identified 51,194 incident HFrEF cases (67 ± 12 years, 98% male, 77% white. A significant positive, near linear relationship was observed for both baseline and serially measured pulse rates with all-cause mortality, all-cause hospitalization and heart failure hospitalization after adjusting for covariates including beta-blocker use. Patients who had a pulse rate ≥ 70 bpm in the past 6 months had 36% (95% CI: 31-42%), 25% (95% CI: 19-32%), and 51% (95% CI: 33-72%) increased rates of mortality, all-cause hospitalization, and heart failure hospitalization, respectively, compared to patients with pulse rates < 70 bpm. A minority of subjects (15%) were treated with guideline directed beta blockade ≥50% of recommended target dose, among whom better outcomes were seen compared to those who did not achieve target dose in patients with pulse rates both above and below 70 beats per minute.

CONCLUSIONS

High pulse rate, both at the time of diagnosis and during follow-up, is strongly associated with increased risk of adverse outcomes in HFrEF patients, independent of the use of beta-blockers. In a real-world setting, the majority of HFrEF patients do not achieve target dose of beta-blockade; greater use of strategies to reduce heart rate may improve outcomes in HFrEF.

Differential Effect of β-Blockers According to Heart Rate in Acute Myocardial Infarction Without Heart Failure or Left Ventricular Systolic Dysfunction: A Cohort Study

OBJECTIVE

To evaluate the effect of β-blockers according to heart rate in patients with acute myocardial infarction (AMI) without heart failure (HF) or left ventricular systolic dysfunction (LVSD).

PATIENTS AND METHODS

We enrolled patients with AMI without HF or LVSD between June 1, 2003, and February 28, 2015, from Seoul National University Hospital Acute Myocardial Infarction Registry. Patients were categorized according to discharge heart rate recorded on electrocardiographs and β-blocker use. Low heart rate was defined as less than 75 beats/min. The primary end point was 5-year all-cause mortality according to discharge heart rate and β-blocker use.

RESULTS

Of 2271 patients, 1696 (74.7%) received β-blockers and 1427 (62.8%) had low heart rates. At 5 years after discharge, 205 patients died. Overall, patients with low heart rates (P<.001) and those with β-blocker treatment had lower mortality (P<.001). After adjustment for covariates, β-blocker use was associated with 48% reduced risk for 5-year mortality in patients with high heart rates (hazard ratio, 0.52; 95% CI, 0.35-0.76), but not in those with low heart rates (P=.97). In an inverse-probability treatment-weighted cohort, β-blocker use was also associated with improved mortality in those with a high heart rate. Findings were similar for 5-year cardiovascular mortality.

CONCLUSION

Among survivors with AMI without HF or LVSD, β-blocker use was associated with reduced 5-year all-cause mortality in patients who have high heart rates, but not in those with low heart rates.

β-Blockers and 1-Year Postdischarge Mortality for Heart Failure and Reduced Ejection Fraction and Slow Discharge Heart Rate

Background Many hospitalized patients with heart failure and reduced ejection fraction ( HF r EF ) have a slow heart rate at discharge, and the effect of β-blockers may be reduced in those patients. We sought to examine the variable effect of β-blockers on clinical outcomes according to the discharge heart rate of hospitalized HF r EF patients. Methods and Results The KorAHF (Korean Acute Heart Failure) registry consecutively enrolled 5625 patients hospitalized for acute heart failure. In this analysis, we included patients with HF r EF (left ventricular ejection fraction ≤40%). Slow heart rate was defined as <70 beats per minute regardless of the use of β-blockers. The primary outcome was 1-year all-cause postdischarge death according to heart rate. Among 2932 patients with HF r EF , 840 (29%) had a slow heart rate and 56% received β-blockers at discharge. Patients with slow heart rates were older and had lower 1-year mortality than those with high heart rates ( P<0.001). A significant interaction between discharge heart rate and β-blocker use was observed ( P<0.001 for interaction). When stratified, only patients without a β-blocker prescription and with a high heart rate showed higher 1-year mortality. In a Cox-proportional hazards regression analysis, β-blocker prescription at discharge was associated with 24% reduced risk for 1-year mortality in patients with high heart rates (hazard ratio: 0.76; 95% CI, 0.61-0.95) but not in those with slow heart rates (hazard ratio: 1.02; 95% CI, 0.68-1.55). Conclusions Many patients with acute heart failure have slow discharge heart rates, and β-blockers may have a limited effect on HF r EF and slow discharge heart rate. Clinical Trial Registration URL : http://www.clinicaltrial.gov . Unique identifier: NCT 01389843.

Heart failure with preserved ejection fraction: mechanisms, clinical features, and therapies

The clinical syndrome comprising heart failure (HF) symptoms but with a left ventricular ejection fraction (EF) that is not diminished, eg, HF with preserved EF, is increasingly the predominant form of HF in the developed world, and soon to reach epidemic proportions. It remains among the most challenging of clinical syndromes for the practicing clinician and scientist alike, with a multitude of proposed mechanisms involving the heart and other organs and complex interplay with common comorbidities. Importantly, its morbidity and mortality are on par with HF with reduced EF, and as the list of failed treatments continues to grow, HF with preserved EF clearly represents a major unmet medical need. The field is greatly in need of a more unified approach to its definition and view of the syndrome that engages integrative and reserve pathophysiology beyond that related to the heart alone. We need to reflect on prior treatment failures and the message this is providing, and redirect our approaches likely with a paradigm shift in how the disease is viewed. Success will require interactions between clinicians, translational researchers, and basic physiologists. Here, we review recent translational and clinical research into HF with preserved EF and give perspectives on its evolving demographics and epidemiology, the role of multiorgan deficiencies, potential mechanisms that involve the heart and other organs, clinical trials, and future directions.

Ivabradine, coronary artery disease, and heart failure: beyond rhythm control

Elevated heart rate could negatively influence cardiovascular risk in the general population. It can induce and promote the atherosclerotic process by means of several mechanisms involving endothelial shear stress and biochemical activities. Furthermore, elevated heart rate can directly increase heart ischemic conditions because of its skill in unbalancing demand/supply of oxygen and decreasing the diastolic period. Thus, many pharmacological treatments have been proposed in order to reduce heart rate and ameliorate the cardiovascular risk profile of individuals, especially those suffering from coronary artery diseases (CAD) and chronic heart failure (CHF). Ivabradine is the first pure heart rate reductive drug approved and currently used in humans, created in order to selectively reduce sinus node function and to overcome the many side effects of similar pharmacological tools (ie, β-blockers or calcium channel antagonists). The aim of our review is to evaluate the role and the safety of this molecule on CAD and CHF therapeutic strategies.

Relationship between stroke volume and pulse pressure during blood volume perturbation: a mathematical analysis

Arterial pulse pressure has been widely used as surrogate of stroke volume, for example, in the guidance of fluid therapy. However, recent experimental investigations suggest that arterial pulse pressure is not linearly proportional to stroke volume. However, mechanisms underlying the relation between the two have not been clearly understood. The goal of this study was to elucidate how arterial pulse pressure and stroke volume respond to a perturbation in the left ventricular blood volume based on a systematic mathematical analysis. Both our mathematical analysis and experimental data showed that the relative change in arterial pulse pressure due to a left ventricular blood volume perturbation was consistently smaller than the corresponding relative change in stroke volume, due to the nonlinear left ventricular pressure-volume relation during diastole that reduces the sensitivity of arterial pulse pressure to perturbations in the left ventricular blood volume. Therefore, arterial pulse pressure must be used with care when used as surrogate of stroke volume in guiding fluid therapy.

Efficacy and safety of ivabradine in patients with severe chronic systolic heart failure (from the SHIFT study)

A post hoc analysis of Systolic Heart failure treatment with the If inhibitor ivabradine Trial (SHIFT) explored the efficacy and safety of ivabradine in severe heart failure (HF) as denoted by left ventricular ejection fraction (LVEF) ≤20% and/or New York Heart Association (NYHA) class IV. The SHIFT population (LVEF ≤35%, heart rate ≥70 beats/min, and sinus rhythm) comprised 712 patients with severe (defined previously) and 5,973 with less severe (NYHA classes II or III and LVEF >20%) HF, all randomized to ivabradine or placebo on a background of guideline-defined standard care. The rate of primary composite end point of cardiovascular death or HF hospitalization with placebo was higher in severe (42%) than less severe (27%) HF (p <0.001). Treatment with ivabradine in severe HF was associated with relative risk reductions indistinguishable from those of less severe disease for the primary end point (16% reduction), all-cause death (22%), cardiovascular death (22%), HF death (37%), and HF hospitalization (17%; all p values for interaction: NS). NYHA class improved in 38% (n = 129) ivabradine-treated patients with severe HF versus 29% (n = 104) placebo-treated patients (p = 0.009). In the 272 patients with severe HF and baseline heart rate ≥75 beats/min (the indication approved by the European Medicines Agency), ivabradine reduced the primary end point by 25% (p = 0.045), HF hospitalization by 30% (p = 0.042), and cardiovascular death by 32% (p = 0.034). Ivabradine's safety profile in severe HF was indistinguishable from less severe. In conclusion, our analysis confirms that heart rate reduction with ivabradine can be safely used in severe HF and may improve clinical outcomes independently of disease severity.

The prognostic significance of heart rate in patients hospitalized for heart failure with reduced ejection fraction in sinus rhythm: insights from the EVEREST (Efficacy of Vasopressin Antagonism in Heart Failure: Outcome Study With Tolvaptan) trial

OBJECTIVES

The purpose of this study was to characterize the relationship between heart rate and post-discharge outcomes in patients with hospitalization for heart failure (HHF) with reduced ejection fraction (EF) in sinus rhythm.

BACKGROUND

A reduction in heart rate improves clinical outcomes in patients with chronic heart failure and in sinus rhythm, but the association between heart rate and post-discharge outcomes in patients with HHF is presently unclear.

METHODS

This post-hoc analysis of the EVEREST (Efficacy of Vasopressin Antagonism in Heart Failure: Outcome Study With Tolvaptan) trial examined 1,947 patients with HHF and EF ≤40% not in atrial fibrillation/flutter or pacemaker dependent.

RESULTS

The median follow-up period was 9.9 months. At baseline, patients with a higher heart rate tended to be younger with lower EF and were more likely to have worse New York Heart Association functional class and higher natriuretic peptide levels. After adjustment for clinical risk factors, baseline heart rate was not predictive of all-cause mortality (p ≥ 0.066). However, at ≥70 beats/min, every 5-beat increase in 1-week post-discharge heart rate was independently associated with increased all-cause mortality (hazard ratio: 1.13 [95% confidence interval: 1.05 to 1.22]; p = 0.002). Similarly, every 5-beat increase ≥70 beats/min in 4-week post-discharge heart rate was predictive of all-cause mortality (hazard ratio: 1.12 [95% confidence interval: 1.05 to 1.19]; p = 0.001).

CONCLUSIONS

In this large cohort of patients with HHF with reduced EF and in sinus rhythm, baseline heart rate did not correlate with all-cause mortality. In contrast, at ≥70 beats/min, higher heart rate in the early post-discharge period was independently predictive of death during subsequent follow-up. Further study of post-discharge heart rate as a potential therapeutic target in this high-risk population is encouraged.

Heart rate and heart failure: the role of ivabradine therapy

PURPOSE OF REVIEW

The clinical data about the impact of heart rate reduction in heart failure therapy will be reviewed.

RECENT FINDINGS

Clinical and experimental studies showed an association between elevated resting heart rate and mortality risk in heart failure patients. This review summarizes that heart rate level at rest and its extent of reduction is a sensitive indicator for outcome in heart failure. In addition to the nonspecific heart rate reducing drugs like β-blockers, cardiac glycosides and Ca(2+) antagonists, ivabradine is a highly selective heart rate reducing agent without modifying ventricular contractility and atrioventricular conduction in humans and animals, and has recently been shown to improve cardiovascular outcomes in patients with systolic heart failure by lowering the heart rate only. The present and future role of heart rate reduction in the spectrum of heart failure disease and therapy will be outlined and evaluated.

SUMMARY

Elevated heart rate at rest represents a key indicator of adverse outcome in heart failure and implies a major treatment target in these patients.

Selective heart rate reduction with ivabradine unloads the left ventricle in heart failure patients

OBJECTIVES

The study aimed to determine whether isolated heart rate (HR) reduction with ivabradine reduces afterload of patients with systolic heart failure.

BACKGROUND

The effective arterial elastance (Ea) represents resistive and pulsatile afterload of the heart derived from the pressure volume relation. HR modulates Ea, and, therefore, afterload burden.

METHODS

Among the patients with systolic heart failure (ejection fraction ≤35%) randomized to either placebo or ivabradine in the SHIFT (Systolic Heart Failure Treatment With the If Inhibitor Ivabradine Trial), 275 patients (n = 132, placebo; n = 143, ivabradine 7.5 mg twice a day) were included in the echocardiographic substudy. Ea, total arterial compliance (TAC), and end-systolic elastance (Ees) were calculated at baseline and after 8 months of treatment. Blood pressure was measured by arm cuff; stroke volume (SV), ejection fraction, and end-diastolic volume were assessed by echocardiography.

RESULTS

At baseline Ea, TAC, HR, and Ees did not differ significantly between ivabradine- and placebo-treated patients. After 8 months of treatment, HR was significantly reduced in the ivabradine group (p < 0.0001) and was accompanied by marked reduction in Ea (p < 0.0001) and improved TAC (p = 0.004) compared with placebo. Although contractility remained unchanged, ventricular-arterial coupling was markedly improved (p = 0.002), resulting in a higher SV (p < 0.0001) in the ivabradine-treated patients.

CONCLUSIONS

Isolated HR reduction by ivabradine improves TAC, thus reducing Ea. Because Ees is unaltered, improved ventricular-arterial coupling is responsible for increased SV. Therefore, unloading of the heart may contribute to the beneficial effect of isolated HR reduction in patients with systolic heart failure.

Heart failure in elderly: progress in clinical evaluation and therapeutic approach

Chronic heart failure (CHF) represents a major and growing health problem, due to its high incidence and prevalence, its poor prognosis and its impact on health-care costs. Although CHF patients are mainly elderly, few studies were aimed at testing the efficacy of diagnostic and therapeutic approaches in this population. The difficulty in CHF diagnosis among the elderly is related to different factors, such as: the frequent presence of co-morbidity conditions mimicking or masking heart failure signs and symptoms; the different diagnostic cut-offs of natriuretic peptides; and the need to correctly evaluate diastolic function in order to assess CHF with preserved ejection fraction. Furthermore, the therapy of elderly CHF patients has not been well defined, considering the few studies involving very aged patients and the absence of a therapeutic strategy demonstrated to improve prognosis of CHF patients with preserved ejection fraction. The aim of this review is to focus on the most recent issues concerning the diagnosis and therapy of elderly patients affected by CHF.

Haemodynamic effects of different basic heart rates in ambulatory heart failure patients treated with cardiac resynchronization therapy

AIMS

The impact of different basic paced heart rates (pHRs) in patients receiving cardiac resynchronization therapy (CRT) remains largely unknown. The aim of the present study was to investigate the haemodynamic effects of different pHRs (60 or 80 b.p.m.), using an implanted haemodynamic monitor (IHM), during a 2-week period in ambulatory CRT patients.

METHODS AND RESULTS

Ten CRT patients received an IHM (Chronicle(®), Medtronic Inc.) to continuously record right ventricular systolic (RVSP) and diastolic (RVDP) pressure, as well as estimated pulmonary artery diastolic pressure (ePAD) during a 2-week period at two basic pHR programming (60 and 80 b.p.m.). Cardiac output (CO) was calculated using a validated IHM algorithm. At the end of each period, 6 min walk test (6MWT), quality of life (QoL), and plasma levels of brain natriuretic peptide (BNP) were also assessed. Pacing at 80 b.p.m. significantly reduced the 2-week average of ePAD compared with 60 b.p.m. (23.4 ± 6.2 vs. 25.1 ± 6.5 mmHg, P = 0.03), whereas CO was increased (4.5 ± 1.3 vs. 4.2 ± 1.4 L/min; P = 0.01). Similarly ePAD, RVSP, and RVDP were significantly lower with a pHR of 80 b.p.m. (P < 0.05). The 6MWT, QoL score, and BNP were not affected by the pHR.

CONCLUSION

In CRT patients, a basic pHR of 80 b.p.m. compared with 60 b.p.m. reduces filling pressures and increases CO during a 2-week period of ambulatory living. This suggests that increasing the basic pHR may be considered to achieve short-term haemodynamic improvement. The long-term effects of differential pHR programming remain to be established.

Is heart rate a treatment target in heart failure?

Clinical and experimental studies confirmed an association between elevated resting heart rate and the risk of mortality in heart failure patients. Importantly, elevated heart rate at rest has been identified as a key finding in heart failure addressing a major treatment target. This review shows that heart rate level at rest and its extent of reduction is a sensitive indicator for successful therapy in heart failure patients demonstrating the specific influence of heart rate reduction on clinical outcome in the analyzed patients. Currently, experimental data provide convincing evidence of a pathophysiological concept of heart rate reduction; nevertheless, transition from experimental results to clinical evidence needs further clarification, especially in patients with diastolic heart failure. Since heart rate can be easily determined during physical examination, decrease in heart rate of patients allows a simple hint on prognosis and efficiency of heart failure therapy.

Heart rate reduction by If-inhibition improves vascular stiffness and left ventricular systolic and diastolic function in a mouse model of heart failure with preserved ejection fraction

AIMS

In diabetes mellitus, heart failure with preserved ejection fraction (HFPEF) is a significant comorbidity. No therapy is available that improves cardiovascular outcomes. The aim of this study was to characterize myocardial function and ventricular-arterial coupling in a mouse model of diabetes and to analyse the effect of selective heart rate (HR) reduction by If-inhibition in this HFPEF-model.

METHODS AND RESULTS

Control mice, diabetic mice (db/db), and db/db mice treated for 4 weeks with the If-inhibitor ivabradine (db/db-Iva) were compared. Aortic distensibility was measured by magnetic resonance imaging. Left ventricular (LV) pressure-volume analysis was performed in isolated working hearts, with biochemical and histological characterization of the cardiac and aortic phenotype. In db/db aortic stiffness and fibrosis were significantly enhanced compared with controls and were prevented by HR reduction in db/db-Iva. Left ventricular end-systolic elastance (Ees) was increased in db/db compared with controls (6.0 ± 1.3 vs. 3.4 ± 1.2 mmHg/µL, P < 0.01), whereas other contractility markers were reduced. Heart rate reduction in db/db-Iva lowered Ees (4.0 ± 1.1 mmHg/µL, P < 0.01), and improved the other contractility parameters. In db/db active relaxation was prolonged and end-diastolic capacitance was lower compared with controls (28 ± 3 vs. 48 ± 8 μL, P < 0.01). These parameters were ameliorated by HR reduction. Neither myocardial fibrosis nor hypertrophy were detected in db/db, whereas titin N2B expression was increased and phosphorylation of phospholamban was reduced both being prevented by HR reduction in db/db-Iva.

CONCLUSION

In db/db, a model of HFPEF, selective HR reduction by If-inhibition improved vascular stiffness, LV contractility, and diastolic function. Therefore, If-inhibition might be a therapeutic concept for HFPEF, if confirmed in humans.

Heart rate at baseline influences the effect of ivabradine on cardiovascular outcomes in chronic heart failure: analysis from the SHIFT study

BACKGROUND

We analysed the effect of ivabradine on outcomes in heart failure (HF) patients on recommended background therapies with heart rates ≥75 bpm and <75 bpm in the SHIFT trial. A cut-off value of ≥75 bpm was chosen by the EMEA for approval for the use of ivabradine in chronic heart failure.

METHODS

The SHIFT population was divided by baseline heart rate ≥75 or <75 bpm. The effect of ivabradine was analysed for primary composite endpoint (cardiovascular death or HF hospitalization) and other endpoints.

RESULTS

In the ≥75 bpm group, ivabradine reduced primary endpoint (HR 0.76, 95 % CI 0.68-0.85, P < 0.0001), all-cause mortality (HR 0.83, 95 % CI, 0.72-0.96, P = 0.0109), cardiovascular mortality (HR 0.83, 95 % CI, (0.71-0.97, P = 0.0166), HF death (HR 0.61, 95 % CI, 0.46-0.81, P < 0.0006), and HF hospitalization (HR 0.70, 95 % CI, 0.61-0.80, P < 0.0001). Risk reduction depended on heart rate after 28 days, with the best protection for heart rates <60 bpm or reductions >10 bpm. None of the endpoints was significantly reduced in the <75 bpm group, though there were trends for risk reductions in HF death and hospitalization for heart rate <60 bpm and reductions >10 bpm. Ivabradine was tolerated similarly in both groups.

CONCLUSION

The effect of ivabradine on outcomes is greater in patients with heart rate ≥75 bpm with heart rates achieved <60 bpm or heart rate reductions >10 bpm predicting best risk reduction. Our findings emphasize the importance of identification of high-risk HF patients by high heart rates and their treatment with heart rate-lowering drugs such as ivabradine.

β-blockers and their mortality benefits: underprescribed in heart failure and chronic obstructive pulmonary disease

This article discusses the most recent insights into the actions of β-blockers on the heart and lungs, highlighting that β-blockers should have a place in the treatment of patients with chronic obstructive pulmonary disease (COPD), especially in those with coexisting cardiovascular disease or arterial hypertension. Practical studies clearly show underutilization of β-blockers in patients with heart failure and COPD, which seems to be caused by an unnecessary fear for adverse effects on the lungs, and the ‘outdated’ adverse effects mentioned on instruction leaflets.

Heart rate as a risk factor in chronic heart failure (SHIFT): the association between heart rate and outcomes in a randomised placebo-controlled trial

BACKGROUND

Raised resting heart rate is a marker of cardiovascular risk. We postulated that heart rate is also a risk factor for cardiovascular events in heart failure. In the SHIFT trial, patients with chronic heart failure were treated with the selective heart-rate-lowering agent ivabradine. We aimed to test our hypothesis by investigating the association between heart rate and events in this patient population.

METHODS

We analysed cardiovascular outcomes in the placebo (n=3264) and ivabradine groups (n=3241) of this randomised trial, divided by quintiles of baseline heart rate in the placebo group. The primary composite endpoint was cardiovascular death or hospital admission for worsening heart failure. In the ivabradine group, heart rate achieved at 28 days was also analysed in relation to subsequent outcomes. Analysis adjusted to change in heart rate was used to study heart-rate reduction as mechanism for risk reduction by ivabradine directly.

FINDINGS

In the placebo group, patients with the highest heart rates (>or=87 beats per min [bpm], n=682, 286 events) were at more than two-fold higher risk for the primary composite endpoint than were patients with the lowest heart rates (70 to <72 bpm, n=461, 92 events; hazard ratio [HR] 2.34, 95% CI 1.84-2.98, p<0.0001). Risk of primary composite endpoint events increased by 3% with every beat increase from baseline heart rate and 16% for every 5-bpm increase. In the ivabradine group, there was a direct association between heart rate achieved at 28 days and subsequent cardiac outcomes. Patients with heart rates lower than 60 bpm at 28 days on treatment had fewer primary composite endpoint events during the study (n=1192; event rate 17.4%, 95% CI 15.3-19.6) than did patients with higher heart rates. The effect of ivabradine is accounted for by heart-rate reduction, as shown by the neutralisation of the treatment effect after adjustment for change of heart rate at 28 days (HR 0.95, 0.85-1.06, p=0.352).

INTERPRETATION

Our analysis confirms that high heart rate is a risk factor in heart failure. Selective lowering of heart rates with ivabradine improves cardiovascular outcomes. Heart rate is an important target for treatment of heart failure.

FUNDING

Servier, France.

I(f) inhibition in cardiovascular diseases

Heart rate (HR) is determined by the pacemaker activity of cells from the sinoatrial node (SAN), located in the right atria. Spontaneous electrical activity of SAN cells results from a diastolic depolarization (DD). Despite controversy in the exact contribution of funny current (I(f)) in pacemaking, it is a major contributor of DD. I(f) is an inward Na(+)/K(+) current, activated upon hyperpolarization and directly modulated by cyclic adenosine monophosphate. The f-proteins are hyperpolarization-activated cyclic nucleotide-gated channels, HCN4 being the main isoform of SAN. Ivabradine (IVA) decreases DD and inhibits I(f) in a use-dependent manner. Under normal conditions IVA selectively reduces HR and limits exercise-induced tachycardia, in animals and young volunteers. Reduction in HR with IVA both decreases myocardial oxygen consumption and increases its supply due to prolongation of diastolic perfusion time. In animal models and in human with coronary artery disease (CAD), IVA has anti-anginal and anti-ischemic efficacy, equipotent to classical treatments, β-blockers, or calcium channel blockers. As expected from its selectivity for I(f), the drug is safe and well tolerated with minor visual side effects. As a consequence, IVA is the first inhibitor of I(f) approved for the treatment of stable angina. Available clinical data indicate that IVA could improve the management of stable angina in all patients including those treated with β-blockers. As chronic elevation of resting HR is an independent predictor of mortality, pure HR reduction by inhibition of I(f) could, beyond the control of anti-anginal symptoms, improve the prognosis of CAD and heart failure; this therapeutic potential is currently under evaluation with IVA.