Effects of ivabradine on allograft function and exercise performance in heart transplant recipients with permanent sinus tachycardia

Five-year results of heart rate control with ivabradine or metoprolol succinate in patients after heart transplantation

Background

Cardiac graft denervation causes inadequate sinus tachycardia in patients after heart transplantation (HTX) which is associated with reduced survival. This study investigated the 5-year results of heart rate control with ivabradine or metoprolol succinate in patients after HTX.

Methods

This registry study analyzed 104 patients receiving either ivabradine (n = 50) or metoprolol succinate (n = 54) within 5 years after HTX. Analysis included patient characteristics, medication, echocardiographic features, cardiac catheterization data, cardiac biomarkers, heart rates, and post-transplant survival including causes of death.

Results

Demographics and post-transplant medication revealed no significant differences except for ivabradine and metoprolol succinate use. At 5-year follow-up, patients with ivabradine had a significantly lower heart rate (73.3 bpm) compared to baseline (88.6 bpm; P < 0.01) and to metoprolol succinate (80.4 bpm; P < 0.01), a reduced left ventricular mass (154.8 g) compared to baseline (179.5 g; P < 0.01) and to metoprolol succinate (177.3 g; P < 0.01), a lower left ventricular end-diastolic pressure (LVEDP; 12.0 mmHg) compared to baseline (15.5 mmHg; P < 0.01) and to metoprolol succinate (17.1 mmHg; P < 0.01), and a reduced NT-proBNP level (525.4 pg/ml) compared to baseline (3826.3 pg/ml; P < 0.01) and to metoprolol succinate (1038.9 pg/ml; P < 0.01). Five-year post-transplant survival was significantly better in patients with ivabradine (90.0%) versus metoprolol succinate (68.5%; P < 0.01).

Conclusion

Patients receiving ivabradine showed a superior heart rate reduction and a better left ventricular diastolic function along with an improved 5-year survival after HTX.

Beyond Heart Failure and Ischemic Heart Disease: A Scoping Review of Novel Uses of Ivabradine in Adults

Ivabradine lowers heart rate by inhibiting the hyperpolarization-activated current in pacemaker cells, and its use for the treatment of heart failure (HF) and ischemic heart disease (IHD) is well described. Ivabradine may be an attractive treatment option for other conditions for which a reduction in heart rate is desirable but less is known about its role in these settings. The primary objective was to perform a scoping review summarizing the literature evaluating novel uses for ivabradine other than HF and IHD in adults. PubMed and EMBASE were searched for articles for all dates through September 2019. Search strategies combined terms generic, commercial/trade, and international names for ivabradine. Manual search of references was also performed to identify additional articles. Studies were included if they were published in English, evaluated the efficacy of ivabradine for indications other than HF or IHD in patients aged 18 years or older, and the primary outcome included clinically relevant end points. Articles were screened first by title and abstract followed by full-text screening of the remaining articles. After removal of duplicates, 1807 records were screened for inclusion and 84 studies were included in this scoping review. Novel uses of ivabradine were reported for various tachyarrhythmias, valvular heart disease, premedication for coronary computed tomography angiography, perioperative risk reduction, sepsis with and without multi-organ dysfunction syndrome, cor pulmonale, reactive airway disease, and erectile dysfunction. This scoping review identified several potential novel uses for ivabradine in adults. This review may help to identify existing gaps where further research is needed to elucidate the role of ivabradine for indications beyond HF and IHD.

Is there a role for ivabradine beyond its conventional use?

Results of recent clinical trials in patients with stable angina and chronic heart failure have successfully demonstrated a beneficial role of use of ivabradine in addition to the conventional therapy. Based on the results of these trials, the aim of our review was to give an overview of the literature about the use of ivabradine in clinical settings outside its usual purpose.

Exercise limitation following transplantation

Organ transplantation is one of the medical miracles or the 20th century. It has the capacity to substantially improve exercise performance and quality of life in patients who are severely limited with chronic organ failure. We focus on the most commonly performed solid-organ transplants and describe peak exercise performance following recovery from transplantation. Across all of the common transplants, evaluated significant reduction in VO2peak is seen (typically renal and liver 65%-80% with heart and/or lung 50%-60% of predicted). Those with the lowest VO2peak pretransplant have the lowest VO2peak posttransplant. Overall very few patients have a VO2peak in the normal range. Investigation of the cause of the reduction of VO2peak has identified many factors pre- and posttransplant that may contribute. These include organ-specific factors in the otherwise well-functioning allograft (e.g., chronotropic incompetence in heart transplantation) as well as allograft dysfunction itself (e.g., chronic lung allograft dysfunction). However, looking across all transplants, a pattern emerges. A low muscle mass with qualitative change in large exercising skeletal muscle groups is seen pretransplant. Many factor posttransplant aggravate these changes or prevent them recovering, especially calcineurin antagonist drugs which are key immunosuppressing agents. This results in the reduction of VO2peak despite restoration of near normal function of the initially failing organ system. As such organ transplantation has provided an experiment of nature that has focused our attention on an important confounder of chronic organ failure-skeletal muscle dysfunction.

Heart rate reduction for 36 months with ivabradine reduces left ventricular mass in cardiac allograft recipients: a long-term follow-up study

Background

Due to graft denervation, sinus tachycardia is a common problem after heart transplantation, underlining the importance of heart rate control without peripheral effects. However, long-term data regarding the effects of ivabradine, a novel I_f channel antagonist, are limited in patients after heart transplantation.

Methods

In this follow-up analysis, the resting heart rate, left ventricular mass indexed to body surface area (LVMI), tolerability, and safety of ivabradine therapy were evaluated at baseline and after 36 months in 30 heart transplant recipients with symptomatic sinus tachycardia versus a matched control group.

Results

During the study period, ivabradine medication was stopped in three patients (10% of total). Further analysis was based on 27 patients with 36 months of drug intake. The mean patient age was 53.3±11.3 years and mean time after heart transplantation was 5.0±4.8 years. After 36 months, the mean ivabradine dose was 12.0±3.4 mg/day. Resting heart rate was reduced from 91.0±10.7 beats per minute before initiation of ivabradine therapy (ie, baseline) to 81.2±9.8 beats per minute at follow-up (P=0.0006). After 36 months of ivabradine therapy, a statistically significant reduction of LVMI was observed (104.3±22.7 g at baseline versus 93.4±18.4 g at follow-up, P=0.002). Hematologic, renal, and liver function parameters remained stable during ivabradine therapy. Except for a lower mycophenolate mofetil dose at follow-up (P=0.02), no statistically significant changes in immunosuppressive drug dosage or blood levels were detected. No phosphenes were observed during 36 months of ivabradine intake despite active inquiry.

Conclusion

In line with previously published 12-month data, heart rate reduction with ivabradine remained effective and safe in chronic stable patients after heart transplantation, and also during 36-month long-term follow-up. Further, a significant reduction of LVMI was observed only during ivabradine therapy. Therefore, ivabradine may have a sustained long-term beneficial effect with regard to left ventricular remodeling in heart transplant patients.

Long-term prognostic value of elevated heart rate one year after heart transplantation

BACKGROUND

Elevated heart rate (HR) is associated with adverse cardiovascular outcome in the general population and in patients with cardiovascular disease. Elevated HR due to graft denervation is often found in heart transplantation (HTx) patients; the effect on graft survival and vasculopathy is unclear. Thus, the aim of this study was to evaluate the role of elevated HR at 12 months post-HTx and its power to predict HTx long-term outcome.

METHODS

We evaluated retrospectively a prospective database of 312 patients undergoing HTx at two centers. HR was registered at 12 months post-HTx. The median HR was used as a cutoff point. Cox regression analysis was performed with variables known to be clinically relevant to mortality and those selected from the univariate analysis.

RESULTS

During a mean follow-up of 5.5 ± 2.8 years there were 58 deaths (19%). Patients with a HR ≥ 90 bpm (median HR) at 12 months had an increased risk for all-cause mortality (Hazard Ratio=2.4, 95% CI 1.2 to 4.5, p=0.009) and mortality related to coronary allograft vasculopathy (CAV) (Hazard Ratio=3.0, 95% CI 1.25-7.14, p=0.01). Multivariate analysis showed that a HR ≥ 90 bpm independently predicted mortality (HR 3.2, 95% CI 1.4-7.1, p=0.004).

CONCLUSIONS

Elevated HR measured at 12 months after HTx is an independent predictor of all-cause mortality in HTx recipients. A HR ≥ 90 bpm identifies a group of patients at high risk of death and CAV-related mortality at mid- to long-term.

HCN channels expressed in the inner ear are necessary for normal balance function

HCN1-4 subunits form Na+/K+-permeable ion channels that are activated by hyperpolarization and carry the current known as I(h). I(h) has been characterized in vestibular hair cells of the inner ear, but its molecular correlates and functional contributions have not been elucidated. We examined Hcn mRNA expression and immunolocalization of HCN protein in the mouse utricle, a mechanosensitive organ that contributes to the sense of balance. We found that HCN1 is the most highly expressed subunit, localized to the basolateral membranes of type I and type II hair cells. We characterized I(h) using the whole-cell, voltage-clamp technique and found the current expressed in 84% of the cells with a mean maximum conductance of 4.4 nS. I(h) was inhibited by ZD7288, cilobradine, and by adenoviral expression of a dominant-negative form of HCN2. To determine which HCN subunits carried I(h), we examined hair cells from mice deficient in Hcn1, 2, or both. I(h) was completely abolished in hair cells of Hcn1⁻/⁻ mice and Hcn1/2⁻/⁻ mice but was similar to wild-type in Hcn2⁻/⁻ mice. To examine the functional contributions of I(h), we recorded hair cell membrane responses to small hyperpolarizing current steps and found that activation of I(h) evoked a 5-10 mV sag depolarization and a subsequent 15-20 mV rebound upon termination. The sag and rebound were nearly abolished in Hcn1-deficient hair cells. We also found that Hcn1-deficient mice had deficits in vestibular-evoked potentials and balance assays. We conclude that HCN1 contributes to vestibular hair cell function and the sense of balance.

Ivabradine: recent and potential applications in clinical practice

INTRODUCTION

published data indicate that heart rate is an independent strong predictor of cardiovascular and all-cause mortality in men and women of all ages, with and without cardiovascular disease, including atherosclerosis, ventricular arrhythmias, and left ventricular dysfunction. Ivabradine is a pure heart-rate-lowering agent with well-documented antianginal and anti-ischemic properties comparable to well-established anti-anginal agents.

AREAS COVERED

this short review explores recent results with ivabradine, a new medication that lowers heart rate by selectively inhibiting the I (f) current. This review also describes future potential applications.

EXPERT OPINION

measurement of heart rate represents an important component of the assessment of patients with coronary artery disease and chronic heart failure, and should be viewed in the same light as other risk factors, because a high heart rate has direct detrimental effects not only on myocardial ischemia but also on the progression of atherosclerosis, ventricular arrhythmias and left ventricular function. Ivabradine has anti-ischemic and antianginal efficacy equivalent to that of β-blockers and calcium channel antagonists in the treatment of chronic stable angina pectoris. Recently ivabradine has been shown to improve cardiac outcomes in stable coronary artery disease and left ventricular systolic dysfunction in patients who have heart rates of ≥ 70 bpm and in patients with stable angina.

The usefulness of chronic heart failure treatments in chronic cardiac graft failure

Following cardiac transplantation, registry data has demonstrated a gradual improvement in survival over the last several decades, which is testament to continual improvement in aftercare strategy. However, a significant number of patients will eventually develop a new syndrome of chronic heart failure, owing to the multitude of physiological processes that occur after transplantation. This condition, referred to as chronic graft failure (CGF) should be regarded as a unique illness rather than one that is simply analogous with chronic heart failure. In particular, the unique pathophysiological (and pharmacological) environment in the setting of CGF presents a challenging situation to the transplant physician. There is uncertainty over which treatments to offer given a paucity of clinical trial data to support the use of standard heart failure treatments in CGF. In this review, we discuss which chronic heart failure treatments could be considered in the setting of CGF based on their mechanisms of action, benefits within the native heart failure setting, and the relevant issues within the posttransplant environment.

Ivabradine: beyond heart rate control

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