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

Differences in the Effects of Beta-Blockers Depending on Heart Rate at Discharge in Patients With Heart Failure With Preserved Ejection Fraction and Atrial Fibrillation

Background and Objectives

Beta-blockers (BBs) improve prognosis in heart failure (HF), which is mediated by lowering heart rate (HR). However, HR has no prognostic implication in atrial fibrillation (AF) and also BBs have not been shown to improve prognosis in heart failure with preserved ejection fraction (HFpEF) with AF. This study assessed the prognostic implication of BB in HFpEF with AF according to discharge HR.

Methods

From the Korean Acute Heart Failure Registry, 687 patients with HFpEF and AF were selected. Study subjects were divided into 4 groups based on 75 beats per minute (bpm) of HR at discharge and whether or not they were treated with BB at discharge.

Results

Of the 687 patients with HFpEF and AF, 128 (36.1%) were in low HR group and 121 (36.4%) were in high HR group among those treated with BB at discharge. In high HR group, HR at discharge was significantly faster in BB non-users (85.5±9.1 bpm vs. 89.2±12.5 bpm, p=0.005). In the Cox model, BB did not improve 60-day rehospitalization (hazard ratio, 0.93; 95% confidence interval [95% CI], 0.35-2.47) or mortality (hazard ratio, 0.77; 95% CI, 0.22-2.74) in low HR group. However, in high HR group, BB treatment at discharge was associated with 82% reduced 60-day HF rehospitalization (hazard ratio, 0.18; 95% CI, 0.04-0.81), but not with mortality (hazard ratio, 0.77; 95% CI, 0.20-2.98).

Conclusions

In HFpEF with AF, in patients with HR over 75 bpm at discharge, BB treatment at discharge was associated with a reduced 60-day rehospitalization rate.

Pulmonary and Systemic Hemodynamics in Patients with Hyperthyroidism

BACKGROUND

There is an association between hyperthyroidism and pulmonary hypertension. However, the prevalence of pulmonary hypertension in hyperthyroidism and the underlying mechanisms are incompletely defined.

METHODS

Consecutive patients with severe hyperthyroidism, mostly due to Graves disease, were included in this single-center study. Echocardiographic assessment of pulmonary hemodynamics was performed at the time of hyperthyroidism diagnosis (baseline) and after normalization of thyroid hormones (follow-up; median 11 months). In a subset of patients, right heart catheterization and noninvasive assessment of central hemodynamics was performed.

RESULTS

Among all 99 patients, 31% had pulmonary hypertension at baseline. The estimated systolic pulmonary artery pressure correlated significantly with the estimated left ventricular filling pressure (E/e'). The invasively measured systolic pulmonary artery pressure correlated well with the estimated systolic pulmonary artery pressure. Cardiac output, E/e', left and right ventricular dimensions were significantly reduced from baseline to follow-up, whereas the estimated pulmonary vascular resistance did not differ. Diastolic blood pressure was significantly higher at follow-up, with no change in systolic blood pressure. The central systolic blood pressure, however, exhibited a trend for a reduction at follow-up, while the pulse wave velocity was significantly lower at follow-up.

CONCLUSIONS

Approximately one-third of patients with hyperthyroidism have evidence of pulmonary hypertension. Our data suggest that an increased cardiac output and left ventricular filling pressure are the main mechanisms underlying the elevated systolic pulmonary artery pressure in hyperthyroidism, whereas there is no evidence of significant pulmonary vascular disease.

Personalized accelerated physiologic pacing

Heart failure with preserved ejection fraction (HFpEF) is increasingly prevalent with a high socioeconomic burden. Pharmacological heart rate lowering was recommended to improve ventricular filling in HFpEF. This article discusses the misperceptions that have resulted in an overprescription of beta-blockers, which in all likelihood have untoward effects on patients with HFpEF, even if they have atrial fibrillation or coronary artery disease as a comorbidity. Directly contradicting the lower heart rate paradigm, faster heart rates provide haemodynamic and structural benefits, amongst which lower cardiac filling pressures and improved ventricular capacitance may be most important. Safe delivery of this therapeutic approach is feasible with atrial and ventricular conduction system pacing that aims to emulate or enhance cardiac excitation to maximize the haemodynamic benefits of accelerated pacing. This conceptual framework was first tested in the myPACE randomized controlled trial of patients with pre-existing pacemakers and preclinical or overt HFpEF. This article provides the background and path towards this treatment approach.

Lower heart rates and beta-blockers are associated with new-onset atrial fibrillation

Background

Lower heart rates (HRs) prolong diastole, which increases filling pressures and wall stress. As a result, lower HRs may be associated with higher brain natriuretic peptide (BNP) levels and incident atrial fibrillation (AF). Beta-blockers may increase the risk for AF due to suppression of resting HRs.

Objective

Examine the relationships of HR, BNP, beta-blockers and new-onset AF in the REVEAL-AF and SPRINT cohort of subjects at risk for developing AF.

Methods

In REVEAL-AF, 383 subjects without a history of AF and a mean CHA₂DS₂VASC score of 4.4 ± 1.3 received an insertable cardiac monitor and were followed up to 30 months. In SPRINT, 7595 patients without prior history of AF and a mean CHA₂DS₂VASC score of 2.3 ± 1.2 were followed up to 60 months.

Results

The median daytime HR in the REVEAL-AF cohort was 75bpm [IQR 68-83]. Subjects with below-median HRs had 2.4-fold higher BNP levels compared to subjects with above-median HRs (median BNP [IQR]: 62 pg/dl [37-112] vs. 26 pg/dl [13-53], p < 0.001). HRs <75bpm were associated with a higher incidence of AF: 37% vs. 27%, p < 0.05. This was validated in the SPRINT cohort after adjusting for AF risk factors. Both a HR < 75bpm and beta-blocker use were associated with a higher rate of AF: 1.9 vs 0.7% (p < 0.001) and 2.5% vs. 0.6% (p < 0.001), respectively. The hazard ratio for patients on beta-blockers to develop AF was 3.72 [CI 2.32, 5.96], p < 0.001.

Conclusions

Lower HRs are associated with higher BNP levels and incident AF, mimicking the hemodynamic effects of diastolic dysfunction. Suppression of resting HR by beta-blockers could explain their association with incident AF.

Effect of Personalized Accelerated Pacing on Quality of Life, Physical Activity, and Atrial Fibrillation in Patients With Preclinical and Overt Heart Failure With Preserved Ejection Fraction: The myPACE Randomized Clinical Trial

Importance

Patients with heart failure with preserved ejection fraction (HFpEF) with a pacemaker may benefit from a higher, more physiologic backup heart rate than the nominal 60 beats per minute (bpm) setting.

Objective

To assess the effects of a moderately accelerated personalized backup heart rate compared with 60 bpm (usual care) in patients with preexisting pacemaker systems that limit pacemaker-mediated dyssynchrony.

Design, Setting, and Participants

This blinded randomized clinical trial enrolled patients with stage B and C HFpEF from the University of Vermont Medical Center pacemaker clinic between June 2019 and November 2020. Analysis was modified intention to treat.

Interventions

Participants were randomly assigned to personalized accelerated pacing or usual care and were followed up for 1 year. The personalized accelerated pacing heart rate was calculated using a resting heart rate algorithm based on height and modified by ejection fraction.

Main Outcomes and Measures

The primary outcome was the serial change in Minnesota Living with Heart Failure Questionnaire (MLHFQ) score. Secondary end points were changes in N-terminal pro-brain natriuretic peptide (NT-proBNP) levels, pacemaker-detected physical activity, atrial fibrillation from baseline, and adverse clinical events.

Results

Overall, 107 participants were randomly assigned to the personalized accelerated pacing (n = 50) or usual care (n = 57) groups. The median (IQR) age was 75 (69-81) years, and 48 (48%) were female. Over 1-year follow-up, the median (IQR) pacemaker-detected heart rate was 75 (75-80) bpm in the personalized accelerated pacing arm and 65 (63-68) bpm in usual care. MLHFQ scores improved in the personalized accelerated pacing group (median [IQR] baseline MLHFQ score, 26 [8-45]; at 1 month, 15 [2-25]; at 1 year, 9 [4-21]; P < .001) and worsened with usual care (median [IQR] baseline MLHFQ score, 19 [6-42]; at 1 month, 23 [5-39]; at 1 year, 27 [7-52]; P = .03). In addition, personalized accelerated pacing led to improved changes in NT-proBNP levels (mean [SD] decrease of 109 [498] pg/dL vs increase of 128 [537] pg/dL with usual care; P = .02), activity levels (mean [SD], +47 [67] minutes per day vs -22 [35] minutes per day with usual care; P < .001), and device-detected atrial fibrillation (27% relative risk reduction compared with usual care; P = .04) over 1-year of follow-up. Adverse clinical events occurred in 4 patients in the personalized accelerated pacing group and 11 patients in usual care.

Conclusions and Relevance

In this study, among patients with HFpEF and pacemakers, treatment with a moderately accelerated, personalized pacing rate was safe and improved quality of life, NT-proBNP levels, physical activity, and atrial fibrillation compared with the usual 60 bpm setting.

Trial Registration

ClinicalTrials.gov Identifier: NCT04721314.

Sustained-Release Ivabradine Hemisulfate in Patients With Systolic Heart Failure

BACKGROUND

Ivabradine has potent actions in reducing heart rate and improving clinical outcomes of chronic heart failure with reduced ejection fraction (HFrEF). At present, only the short-acting formulation of ivabradine is available that needs to be administered twice daily.

OBJECTIVES

This study sought to evaluate the role of ivabradine hemisulfate sustained release (SR), a novel long-acting formulation of ivabradine dosed once daily, in stable patients with HFrEF.

METHODS

Patients with stabilized HFrEF in New York Heart Association functional class II-IV were enrolled and randomized to receive placebo or ivabradine SR in addition to standard medications. The primary endpoint was the change of left ventricular (LV) end-systolic volume index from baseline to week 32.

RESULTS

We randomly assigned 181 patients to placebo and 179 patients to ivabradine SR. After 32 weeks, a significant improvement of LV end-systolic volume index from baseline was observed in both arms with a greater effect in the ivabradine SR arm. Ivabradine SR therapy also exhibited superiority in improving LV end-diastolic volume index, LV ejection fraction, resting heart rate, the Kansas City Cardiomyopathy Questionnaire score, and hospital admission for heart failure worsening and cardiovascular disease in comparison to placebo. Overall adverse events showed no difference between the treatment arms. There were fewer occurrences of worsening heart failure in the ivabradine SR arm.

CONCLUSIONS

The present study demonstrates that ivabradine SR once daily in addition to optimum standard therapy improved heart function in patients with HFrEF. (Clinical Trial of Systolic Heart Failure Treatment of IvabRadine Hemisulfate Sustained-release Tablets [FIRST]; NCT02188082).

[Therapy of Heart Failure with Reduced Ejection Fraction: What's New in the 2021 Guidelines?]

Therapy of Heart Failure with Reduced Ejection Fraction: What's New in the 2021 Guidelines? Abstract. The spectrum of treatment options for patients with heart failure with reduced ejection fraction (HFrEF) has substantially expanded over the last years. The 2021 guidelines of the European Society of Cardiology propose a new treatment algorithm for patients with HFrEF and define the role of the currently available drugs, interventions and devices in this context. The new standard is a basic therapy consisting of four drugs with different mechanisms of action for all patients with HFrEF: an angiotensin-converting enzyme inhibitor, a betablocker, a mineralocorticoid antagonist, and a sodium glucose co-transporter-2 inhibitor. Additional drugs and/or interventions/devices are indicated depending on the response to the four-drug basic therapy (which has to be up-titrated to the maximally tolerated doses) and the clinical phenotype. In the present article, we discuss the available drugs and devices, their role in the proposed HFrEF treatment algorithm and clinically relevant practical aspects.

Treatment with angiotensin receptor neprilysin inhibitor for Taiwan heart failure patients: Rationale and baseline characteristics of the TAROT-HF study

BACKGROUND

This study used a real-world database to investigate the prescription patterns of sacubitril/valsartan (Sac/Val) among Taiwanese patients with heart failure with reduced ejection fraction (HFrEF).

METHODS

The Treatment with Angiotensin Receptor neprilysin inhibitor fOr Taiwan Heart Failure patients (TAROT-HF) study is a principal investigator-initiated, multicenter, observational, retrospective study on Taiwanese HFrEF patients. A total of 1772 patients with HFrEF (mean age 62.5 years, 75.3% male, mean left ventricular ejection fraction [LVEF] 29.3%) who received Sac/Val at 10 hospitals between 2017 and 2018 were enrolled at the date of Sac/Val initiation. Among these patients, 585 (33%) initially received Sac/Val during acute decompensated heart failure (HF) hospitalization (TAROT-AHF arm), whereas 1187 (67%) initially received the same at the outpatient clinic (TAROT-CHF arm).

RESULTS

A total of 1343 (75.8%) patients received an initial dose of 50 mg twice daily or fewer, whereas 422 (23.8%) received the standard initiation dose (100 mg twice daily). During outpatient Sac/Val initiation, the mean dosages were significantly higher than that following hospitalization (117 ± 55 mg vs 109 ± 57 mg; p = 0.014). Multivariate analysis identified younger age, higher systolic blood pressure, higher LVEF, prior use of renin-angiotensin system inhibitors, use of ivabradine, and a history of diabetes mellitus as independent factors for initiating a standard Sac/Val dose. Over a follow-up period of 18 months, incidences of cardiovascular death or first unplanned HF hospitalization were 18.69 and 33.11 per 100-person years for the TAROT-CHF and TAROT-AHF arms, respectively.

CONCLUSION

The TAROT-HF study provided an opportunity to describe the clinical features of patients with HFrEF who received Sac/Val, assess the real-world utilization and efficacy of Sac/Val, and compare these patients with those included in prior registries.

Two cases of dilated cardiomyopathy with blood pressure-limited tolerability of cardioprotective agents improved by ivabradine

The titration of cardioprotective agents is essential for successful treatment of heart failure (HF) patients with reduced left ventricular ejection fraction. However, hypotension is one of the limiting factors for titration. Ivabradine reduces heart rate without compromising systolic function by prolonging diastolic filling time. Herein two cases of dilated cardiomyopathy (DCM) are presented in which ivabradine improved blood pressure (BP)-limited tolerability and allowed for further titration of cardioprotective agents. In both cases, the introduction of ivabradine raised the BP, which permitted further increase of the dose of renin-angiotensin system inhibitors or beta-blockers. One major hypothesized mechanism of ivabradine-induced BP elevation has been postulated to be an increase in stroke volume due to prolonged ventricular diastolic filling time. However, ivabradine is not expected to increase BP for all HF patients. In those with small and poorly compliant ventricles with severe diastolic or restricted dysfunction, decreased heart rate and prolonged diastole may excessively suppress compensatory mechanisms, and thus may not lead to increased cardiac output and BP. In contrast, ivabradine potentially increases BP and improves BP-limited tolerability of cardioprotective agents in DCM patients with a large and compliant heart. In addition, subsequent titration of cardioprotective agents may provide additional cardiac reverse remodeling. Learning objective: Ivabradine is usually used for heart failure patients with reduced ejection fraction when the tolerability of cardioprotective agents is maximized. This agent has no direct cardiac contractility-suppressing action. It potentially increases blood pressure and improves tolerability of cardioprotective agents in patients with a large and compliant heart such as dilated cardiomyopathy. Furthermore, subsequent titration of cardioprotective agents may provide additional cardiac reverse remodeling.

Combination of ivabradine and sacubitril/valsartan in patients with heart failure and reduced ejection fraction

AIMS

Ivabradine and sacubitril/valsartan are second-line therapies for patients with heart failure and reduced ejection fraction (HFrEF) based on guideline recommendations. We aimed to evaluate the synergistic effects of these two medications.

METHODS AND RESULTS

Patients' data were extracted from a multicentre database between 2016 and 2018. Patients were classified into (1) Simultaneous group: simultaneous prescription of ivabradine and sacubitril/valsartan within 6 weeks; (2A) Sequential group, ivabradine-first: ivabradine was prescribed first, followed by sacubitril/valsartan; and (2B) Sequential group, sacubitril/valsartan-first: sacubitril/valsartan was prescribed first, followed by ivabradine. A total of 464 patients with HFrEF were enrolled. Cardiovascular death and/or unplanned re-hospitalizations for HF were less frequent (28.6% vs. 44.8%, P = 0.01), and the improvement of left ventricular ejection fraction (LVEF) was significantly greater in patients from the Simultaneous group than those from the Sequential group (∆LVEF 12.8 ± 12.9% vs. 9.3 ± 12.6%, P = 0.007). Among Sequential subgroups, the ivabradine-first treatment decreased heart rate and increased systolic blood pressure (SBP) compared with sacubitril/valsartan-first treatment (∆heart rate -9.1 ± 12.9 b.p.m. vs. 2.6 ± 16.0 b.p.m., P < 0.001; ∆SBP 4.6 ± 16.5 mmHg vs. -4.8 ± 17.2 mmHg, P < 0.001), whereas sacubitril/valsartan-first treatment showed a higher degree of LVEF improvement (∆LVEF 3.6 ± 7.8% vs. 0.7 ± 7.7%, P = 0.002) than ivabradine-first treatment. At the end of follow-up, SBP, LVEF, and left ventricular volume were comparable between two Sequential subgroups.

CONCLUSIONS

Among patients with HFrEF, simultaneous rather than sequential treatment with sacubitril/valsartan and ivabradine was a better strategy to reduce adverse events and achieve left ventricular reverse remodelling. Ivabradine treatment had a more significant benefit on improving haemodynamic stability, whereas sacubitril/valsartan treatment showed a more significant effect on improving LVEF.

The Influence of Resting Heart Rate on Central Pulse Pressure is Age-Dependent

INTRODUCTION

Low resting heart rate (RHR) increases augmentation pressure (AP) and central pulse pressure (central PP) and decreases peripheral pressure wave amplification. Given that the contribution of AP to central PP increases with age we hypothesized that the influence of RHR on AP, central PP and peripheral amplification varies with age.

AIM

To evaluate the interaction between age and RHR on the forward and backward components of central PP.

METHODS

A cohort of 1249 ambulatory hypertensive patients with good quality radial wave recordings was stratified into age groups and quartiles of RHR (< 61, 61-68, 69-76 and > 76 bpm). Central aortic pressure was estimated from radial applanation tonometry.

RESULTS

Forward wave (FW) and AP showed opposite changes until midlife, mutually canceling their effect on central PP, whereas both components of central PP increased in parallel after the fifth decade. The initial fall in FW was expressed in the brachial artery as a corresponding decrease in PP and in peripheral amplification. After midlife there was a further decrease in peripheral amplification at the expense of the rise in central PP. A lower RHR exaggerated the age-related increase in left ventricular ejection time (LVET), AP, central PP, and the decrease in peripheral amplification (P < 0.001, for all the interactions between decades and quartiles of RHR). Multivariable regression analyses (n = 1249) confirmed a significant interaction between age and RHR on central PP (P < 0.001), AP (P < 0.001), LVET (P < 0.001), AIx (P < 0.035), and peripheral amplification (P < 0.001). Multivariable regression analyses stratified by age groups (< 30, 30-59 and ≥ 60 years) showed an increasing strength in the relationship of RHR with AP, independently of sex, mean arterial pressure, pulse wave velocity and beta-blockers use. The average increase in AP for a decrease in 10 bpm was 1.4 mmHg before age < 30 years; 2.5 mmHg between age 30-59 years; and 5.4 mmHg at 60 years and older.

CONCLUSIONS

A lower heart rate exaggerated AP and central PP in an age dependent fashion, being the effect particularly relevant in older patients.

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.

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.

Atenolol's Inferior Ability to Reduce Central vs Peripheral Blood Pressure Can Be Explained by the Combination of Its Heart Rate-Dependent and Heart Rate-Independent Effects

OBJECTIVE

Whether the inferior ability of atenolol to reduce central (aortic) compared to peripheral (brachial) blood pressure (BP) is related to its heart rate (HR)-dependent or -independent effects, or their combination, remains unclear. To provide further mechanistic insight into this topic, we studied the acute effects of atenolol versus nebivolol and ivabradine on systolic blood pressure amplification (SBPA; peripheral systolic BP minus central systolic BP) in a model of sick sinus syndrome patients with a permanent dual-chamber cardiac pacemaker in a nonrandomized single-blind single-group clinical trial.

METHODS

We determined hemodynamic indices noninvasively (Sphygmocor XCEL) before and at least 3 h after administration of oral atenolol 50 or 100 mg, nebivolol 5 mg, or ivabradine 5 or 7.5 mg during atrial pacing at a low (40 bpm), middle (60 bpm), and high (90 bpm) HR level in 25 participants (mean age 65.5 years, 12 men).

RESULTS

At the low HR level, i.e., when the drugs could exert their HR-dependent and HR-independent effects on central BP, only atenolol produced a significant decrease in SBPA (mean change 0.74 ± 1.58 mmHg (95% CI, 0.09-1.40; P = 0.028)), indicating inferior central vs peripheral systolic BP change. However, we observed no significant change in SBPA with atenolol at the middle and high HR levels, i.e., when HR-dependent mechanisms had been eliminated by pacing.

CONCLUSION

The findings of our trial with a mechanistic approach to the topic imply that the inferior ability of atenolol to reduce central vs peripheral BP can be explained by the combination of its heart rate-dependent and -independent effects. This trial is registered with NCT03245996.

Increased sarcoplasmic/endoplasmic reticulum calcium ATPase 2a activity underlies the mechanism of the positive inotropic effect of ivabradine

NEW FINDINGS

What is the central question of this study? The therapeutic effect of ivabradine on patients with chronic heart failure and chronic stable angina pectoris is mediated through a reduction in heart rate: what are the haemodynamic characteristics and the mechanism of the inotropic effect? What is the main finding and its importance? Ivabradine has a positive inotropic effect and lowers the heart rate both in vivo and in vitro. These effects are likely mediated by ivabradine's significant increase of the fast component rate constant mediated by sarcoplasmic/endoplasmic reticulum calcium ATPase 2a and decrease of the slow component rate constant that is mediated by the Na⁺ /Ca²⁺ exchanger and sarcolemmal Ca²⁺ -ATPase during the Ca²⁺ transient decay phase.

ABSTRACT

Ivabradine's therapeutic effect is mediated by a reduction of the heart rate; however, its haemodynamic characteristics and the mechanism of its inotropic effect are poorly understood. We aimed to investigate the positive inotropic effect of ivabradine and its underlying mechanism. The results demonstrated that ivabradine increased the positive inotropy of the rat heart in vivo by increasing the stroke work, cardiac output, stroke volume, end-diastolic volume, end-systolic pressure, ejection fraction, ±dP/dt_max , left ventricular end-systolic elastance and systolic blood pressure without altering the diastolic blood pressure and arterial elastance. This inotropic effect was observed in both non-paced and paced rat isolated heart. Ivabradine increased the Ca²⁺ transient amplitude and the reuptake rates of sarcoplasmic/endoplasmic reticulum calcium ATPase 2a (SERCA2a), lowered the diastolic Ca²⁺ level and suppressed the combined extrusion rate of the Na⁺ /Ca²⁺ exchanger and the sarcolemmal Ca²⁺ -ATPase. In addition, ivabradine widened the action potential duration, hyperpolarized the resting membrane potential, increased sarcoplasmic reticulum Ca²⁺ content and reduced Ca²⁺ leak. Overall, ivabradine had a positive inotropic effect brought about by enhanced SERCA2a activity, which might be mediated by increased phospholamban phosphorylation. The positive inotropic effect along with the lowered heart rate underlies ivabradine's therapeutic effect in heart failure.

Central blood pressure for the management of hypertension: Is it a practical clinical tool in current practice?

Since noninvasive central blood pressure (BP) measuring devices are readily available, central BP has gained growing attention regarding its clinical application in the management of hypertension. The disagreement between central and peripheral BP has long been recognized. Some previous studies showed that noninvasive central BP may be better than the conventional brachial BP in association with target organ damages and long-term cardiovascular outcomes. Recent studies further suggest that the central BP strategy for confirming a diagnosis of hypertension may be more cost-effective than the conventional strategy, and guidance of hypertension management with central BP may result in less use of medications to achieve BP control. Despite the use of central BP being promising, more randomized controlled studies comparing central BP-guided therapeutic strategies with conventional care for cardiovascular events reduction are required because noninvasive central and brachial BP measures are conveniently available. In this brief review, the rationale supporting the utility of central BP in clinical practice and relating challenges are summarized.

Pharmacokinetic profile of ivabradine hemisulfate sustained-release tablets administered in Chinese healthy volunteers: An open-label, randomized, single-dose, three-period crossover study

We aimed to determine the pharmacokinetics and safety of three single oral doses (5, 10 and 15 mg) of ivabradine hemisulfate sustained-release tablets in healthy Chinese volunteers. A total of 12 volunteers (six males and six females) were randomized to receive a single oral dose of ivabradine hemisulfate sustained-release tablets 5, 10 or 15 mg, with a 1-week washout between periods. Blood samples were collected at regular intervals from 0 to 48 h after drug administration, and the concentrations of ivabradine and N-desmethyl ivabradine were determined by HPLC-tandem mass spectrometry. Pharmacokinetic parameters were estimated by non-compartmental analysis. After administering single doses of 5, 10 and 15 mg, the mean maximum concentration (C_max ) levels of ivabradine were 4.36, 7.29 and 12.62 ng/mL, and the mean area under the curve from time 0 to 48 h (AUC_0-48 ) values were 55.66, 101.16 and 182.09 h·ng/mL, respectively. The mean C_max levels of N-desmethyl ivabradine were 1.05, 2.03 and 3.16 ng/mL, and the mean AUC_0-48 values were 20.61, 39.44 and 65.72 h·ng/mL, respectively. The median time of maximum concentration (T_max ) levels of ivabradine and N-desmethyl ivabradine were 5 h for all three doses tested. The pharmacokinetic properties of ivabradine hemisulfate sustained-release tablets were linear at doses from 5 to 15 mg. Ivabradine hemisulfate sustained-release tablet appears to be well tolerated in these healthy volunteers.

Acute Tachycardia Increases Aortic Distensibility, but Reduces Total Arterial Compliance Up to a Moderate Heart Rate

Background: The differential effects of rapid cardiac pacing on small and large vessels have not been well-established. The objective of this study was to investigate the effect of pacing-induced acute tachycardia on hemodynamics and arterial stiffness.

Methods: The pressure and flow waves in ascending aorta and femoral artery of six domestic swine were recorded simultaneously at baseline and heart rates (HR) of 135 and 155 beats per minutes (bpm) and analyzed by the models of Windkessel and Womersley types. Accordingly, the flow waves were simultaneously measured at carotid and femoral arteries to quantify aortic pulse wave velocity (PWV). The arterial distensibility was identified in small branches of coronary, carotid and femoral arteries with diameters of 300–600 μm by ex vivo experiments.

Results: The rapid pacing in HR up to 135 bpm reduced the total arterial compliance, stroke volume, systemic pulse pressure, and central systolic pressure by 36 ± 17, 38 ± 26, 29 ± 16, and 23 ± 12%, respectively, despite no statistical difference of mean aortic pressure, cardiac output, peripheral resistance, and vascular flow patterns. The pacing also resulted in a decrease of distensibility of small muscular arteries, but an increase of aortic distensibility. Pacing from 135 to 155 bpm had negligible effects on systemic and local hemodynamics and arterial stiffness.

Conclusions: There is an acute mismatch in the response of aorta and small arteries to pacing from basal HR to 135 bpm, which may have important pathological implications under chronic tachycardia conditions.

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.

Pharmacological heart rate lowering in patients with a preserved ejection fraction-review of a failing concept

Epidemiological studies have demonstrated that high resting heart rates are associated with increased mortality. Clinical studies in patients with heart failure and reduced ejection fraction have shown that heart rate lowering with beta-blockers and ivabradine improves survival. It is therefore often assumed that heart rate lowering is beneficial in other patients as well. Here, we critically appraise the effects of pharmacological heart rate lowering in patients with both normal and reduced ejection fraction with an emphasis on the effects of pharmacological heart rate lowering in hypertension and heart failure. Emerging evidence from recent clinical trials and meta-analyses suggest that pharmacological heart rate lowering is not beneficial in patients with a normal or preserved ejection fraction. This has just begun to be reflected in some but not all guideline recommendations. The detrimental effects of pharmacological heart rate lowering are due to an increase in central blood pressures, higher left ventricular systolic and diastolic pressures, and increased ventricular wall stress. Therefore, we propose that heart rate lowering per se reproduces the hemodynamic effects of diastolic dysfunction and imposes an increased arterial load on the left ventricle, which combine to increase the risk of heart failure and atrial fibrillation. Pharmacologic heart rate lowering is clearly beneficial in patients with a dilated cardiomyopathy but not in patients with normal chamber dimensions and normal systolic function. These conflicting effects can be explained based on a model that considers the hemodynamic and ventricular structural effects of heart rate changes.

Modeling Arterial Pulse Pressure From Heart Rate During Sympathetic Activation by Progressive Central Hypovolemia

Heart rate (HR) has an impact on the central blood pressure (BP) wave shape and is related to pulse wave velocity and therefore to timing and duration of systole and diastole. This study tested the hypothesis that in healthy subjects both in rest and during sympathetic stimulation the relation between HR and pulse pressure (PP) is described by a linear effect model. Forty-four healthy volunteers were subjected to sympathetic stimulation by continuous lower body negative pressure (LBNP) until the onset of pre-syncopal symptoms. Changes in PP and HR were tracked non-invasively and modeled by linear mixed effect (LME) models. The dataset was split into two groups: the first was used for creating a model and the second for its evaluation. Models were created on the data obtained during LBNP. Model performance was expressed as absolute median error (1st; 3rd quantiles) and bias with limits of agreement (LOA) between modeled and measured PP. From rest to sympathetic stimulation, mean BP was maintained while HR increased (~30%) and PP decreased gradually (~20%). During baseline, PP could be modeled with an absolute error of 6 (4; 10) mm Hg and geometric mean ratio of the bias was 0.97 (LOA: 0.8–1.1). During LBNP, absolute median model error was 5 (4; 8) mmHg with geometric mean ratio 1.02 (LOA: 0.8–1.3). In conclusion, both during rest and during sustained sympathetic outflow induced by progressive central hypovolemia, a LME model of HR provides for an estimate of PP in healthy young adults.

Current Pharmacological Therapies in Heart Failure Patients

Heart failure (HF) is a major problem of public health. More than 23 million patients worldwide are affected by heart failure. Despite incidence and prevalence of heart failure may vary according to real world or randomized trials database, advancing age is a major determinant of heart failure. Heart failure is also characterized by an elevated rate of morbidity and mortality and represents one of the leading causes of hospitalization. A major consequence of heart failure is the frequent hospital admissions and related costs. Guidelines have clearly indicated evidence-based treatments in patients with heart failure, and the adherence to these indications has translated in an improvement of patient's prognosis. Nevertheless, the use of recommended treatments at the recommended dosages is still lower than expected. In the last year in Europe new guidelines on the diagnosis and treatment of heart failure and in USA an update on pharmacological treatment of heart failure were published, pointing the attention on the use of new available pharmacological and non-pharmacological treatments. HF syndrome reflects the interaction between hemodynamic dysregulation (alterations in myocardial preload, afterload, and contractility and a neurohormonal disarray those results in the development of symptoms and in the progression of the disease. Current treatment approaches target both hemodynamic alterations and the neurohumoral elements to slow disease progression as well as to improve symptoms and outcomes.

Effect of ivabradine on central aortic blood pressure in patients with stable coronary artery disease: What do we know?

Treatment of hypertensive patients with beta-blockers decreases central blood pressure (CBP) less than other antihypertensive drugs, which is believed to account for their lesser cardiovascular protection in this setting. Some authors have suggested that decreasing heart rate (HR) with beta-blockers would increase CBP. In contrast to beta-blockers, the anti-anginal agent ivabradine reduces HR without other hemodynamic effects, and represents an attractive tool for exploring the direct relationship between HR and CBP. Here, we review the available clinical data assessing the effect of selective HR reduction with ivabradine on CBP in patients with stable coronary artery disease (CAD). We collected data from five studies which report either increase, decrease, or neutral effects of ivabradine on CBP. Further studies are needed to clarify the exact role of ivabradine on CBP. However, as supported by its pharmacodynamic effect in patients with stable CAD, available evidence to date suggests that ivabradine does not negatively impact CBP when associated with beta-blocker. HR reduction with both beta-blockers and ivabradine remains well-established treatments for the symptomatic treatment of angina patients.