Losartan in heart failure. Hemodynamic effects and tolerability. Losartan Hemodynamic Study Group

Angiotensin-II drives changes in microglia-vascular interactions in rats with heart failure

Activation of microglia, the resident immune cells of the central nervous system, leading to the subsequent release of pro-inflammatory cytokines, has been linked to cardiac remodeling, autonomic disbalance, and cognitive deficits in heart failure (HF). While previous studies emphasized the role of hippocampal Angiotensin II (AngII) signaling in HF-induced microglial activation, unanswered mechanistic questions persist. Evidence suggests significant interactions between microglia and local microvasculature, potentially affecting blood-brain barrier integrity and cerebral blood flow regulation. Still, whether the microglial-vascular interface is affected in the brain during HF remains unknown. Using a well-established ischemic HF rat model, we demonstrate the increased abundance of vessel-associated microglia (VAM) in HF rat hippocampi, along with an increased expression of AngII AT1a receptors. Acute AngII administration to sham rats induced microglia recruitment to brain capillaries, along with increased expression of TNFα. Conversely, administering an AT1aR blocker to HF rats prevented the recruitment of microglia to blood vessels, normalizing their levels to those in healthy rats. These results highlight the critical importance of a rather understudied phenomenon (i.e., microglia-vascular interactions in the brain) in the context of the pathophysiology of a highly prevalent cardiovascular disease, and unveil novel potential therapeutic avenues aimed at mitigating neuroinflammation in cardiovascular diseases.

Exploring Hypertension: The Role of AT1 Receptors, Sartans, and Lipid Bilayers

The rational design of AT1 receptor antagonists represents a pivotal approach in the development of therapeutic agents targeting cardiovascular pathophysiology. Sartans, a class of compounds engineered to inhibit the binding and activation of Angiotensin II on the AT1 receptor, have demonstrated significant clinical efficacy. This review explores the multifaceted role of sartans in mitigating hypertension and related complications. We highlight the integration of crystallography, computational simulations, and NMR spectroscopy to elucidate sartan-AT1 receptor interactions, providing a foundation for the next-generation antagonist design. The review also delves into the challenges posed by the high lipophilicity and suboptimal bioavailability of sartans, emphasizing advancements in nanotechnology and novel drug delivery systems. Additionally, we discuss the impact of lipid bilayers on the AT1 receptor conformation and drug binding, underscoring the importance of the lipidic environment in receptor-drug interactions. We suggest that optimizing drug design to account for these factors could enhance the therapeutic potential of AT1 receptor antagonists, paving the way for improved cardiovascular health outcomes.

Angiotensin-II drives changes in microglia-vascular interactions in rats with heart failure

Activation of microglia, the resident immune cells of the central nervous system, leading to the subsequent release of pro-inflammatory cytokines, has been linked to cardiac remodeling, autonomic disbalance, and cognitive deficits in heart failure (HF). While previous studies emphasized the role of hippocampal Angiotensin II (AngII) signaling in HF-induced microglial activation, unanswered mechanistic questions persist. Evidence suggests significant interactions between microglia and local microvasculature, potentially affecting blood-brain barrier integrity and cerebral blood flow regulation. Still, whether the microglial-vascular interface is affected in the brain during HF remains unknow. Using a well-established ischemic HF rat model, we demonstrate increased vessel-associated microglia (VAM) in HF rat hippocampi, which showed heightened expression of AngII AT1a receptors. Acute AngII administration to sham rats induced microglia recruitment to the perivascular space, along with increased expression of TNFa. Conversely, administering an AT1aR blocker to HF rats prevented the recruitment of microglia to the perivascular space, normalizing their levels to those in healthy rats. These results highlight the critical importance of a rather understudied phenomenon (i.e., microglia-vascular interactions in the brain) in the context of the pathophysiology of a highly prevalent cardiovascular disease, and unveil novel potential therapeutic avenues aimed at mitigating neuroinflammation in cardiovascular diseases.

Angiotensin II-Mediated Neuroinflammation in the Hippocampus Contributes to Neuronal Deficits and Cognitive Impairment in Heart Failure Rats

BACKGROUND

Heart failure (HF) is a debilitating disease affecting >64 million people worldwide. In addition to impaired cardiovascular performance and associated systemic complications, most patients with HF suffer from depression and substantial cognitive decline. Although neuroinflammation and brain hypoperfusion occur in humans and rodents with HF, the underlying neuronal substrates, mechanisms, and their relative contribution to cognitive deficits in HF remains unknown.

METHODS

To address this critical gap in our knowledge, we used a well-established HF rat model that mimics clinical outcomes observed in the human population, along with a multidisciplinary approach combining behavioral, electrophysiological, neuroanatomical, molecular and systemic physiological approaches.

RESULTS

Our studies support neuroinflammation, hypoperfusion/hypoxia, and neuronal deficits in the hippocampus of HF rats, which correlated with the progression and severity of the disease. An increased expression of AT1aRs (Ang II [angiotensin II] receptor type 1a) in hippocampal microglia preceded the onset of neuroinflammation. Importantly, blockade of AT1Rs with a clinically used therapeutic drug (Losartan), and delivered in a clinically relevant manner, efficiently reversed neuroinflammatory end points (but not hypoxia ones), resulting in turn in improved cognitive performance in HF rats. Finally, we show than circulating Ang II can leak and access the hippocampal parenchyma in HF rats, constituting a possible source of Ang II initiating the neuroinflammatory signaling cascade in HF.

CONCLUSIONS

In this study, we identified a neuronal substrate (hippocampus), a mechanism (Ang II-driven neuroinflammation) and a potential neuroprotective therapeutic target (AT1aRs) for the treatment of cognitive deficits in HF.

Arterial stiffness and its associations with left ventricular diastolic function according to heart failure types

BACKGROUND

Little is known about the characteristics of arterial stiffness in heart failure (HF). This study was performed to compare the degree of arterial stiffness and its association with left ventricular (LV) diastolic function among three groups: control subjects, patients with HF with reduced ejection fraction (HFrEF), and patients with HF with preserved ejection fraction (HFpEF).

METHODS

A total of 83 patients with HFrEF, 68 patients with HFpEF, and 84 control subjects were analyzed. All HF patients had a history of hospitalization for HF treatment. Brachial-ankle pulse wave velocity (baPWV) measurement and transthoracic echocardiography were performed at the same day in a stable condition.

RESULTS

The baPWV was significantly higher in patients with both HFrEF and HFpEF compared to control subjects (1,661 ± 390, 1,909 ± 466, and 1,477 ± 296 cm/sec, respectively; P < 0.05 for each). After adjustment of age, baPWV values were similar between patients with HFrEF and HFpEF (P = 0.948). In the multiple linear regression analysis, baPWV was significantly associated with both septal e' velocity (β = -0.360, P = 0.001) and E/e' (β = 0.344, P = 0.001). However, baPWV was not associated with either of the diastolic indices in HFrEF group. The baPWV was associated only with septal e' velocity (β = -0.429, P = 0.002) but not with E/e' in the HFpEF group in the same multivariable analysis.

CONCLUSIONS

Although arterial stiffness was increased, its association with LV diastolic function was attenuated in HF patients compared to control subjects. The degree of arterial stiffening was similar between HFrEF and HFpEF.

Benefit from sacubitril/valsartan is associated with hemodynamic improvement in heart failure with reduced ejection fraction: An echocardiographic study

BACKGROUND

Sacubitril/valsartan improves outcome in patients with heart failure (HF) with reduced left ventricular (LV) ejection fraction (EF, HFrEF). However, little is known about possible mechanisms underlying this favourable effect.

PURPOSE

To assess changes in echocardiographically-derived hemodynamic profiles induced by sacubitril/valsartan and their impact on outcome.

METHODS

In this multicenter, open-label study, 727 HFrEF outpatients underwent comprehensive echocardiography at baseline (before starting sacubitril/valsartan) and after 12 months. Estimated LV filling pressure (E/e') and cardiac index (CI, l/min/m²) were combined to determine 4 hemodynamic profiles: profile-A (normal-flow/normal-pressure); profile-B (low-flow/normal-pressure); profile-C: (normal-flow/high-pressure); profile-D: (low-flow/high-pressure). Changes among categories were recorded, and their associations with rates of the composite of death/HF-hospitalization were assessed by multivariable Cox analysis.

RESULTS

At baseline, 29% had profile-A, 15% had profile-B, 32% profile-C, and 24% profile-D. After 12 months, the hemodynamic profile improved in 53% of patients (all profile-A achievers, or profile-D patients achieving either C or B profile), while it remained unchanged in 39% patients and worsened in 9%. Prevalence of improved profile progressively increased with increasing dose of sacubitril/valsartan (P < 0.0001). After the second echocardiography, patients were followed up 12.6 ± 7.6 months: event-rate was lower in patients with improved profile (12.3%, 95%CI: 9.4-16.1) compared to patients in whom hemodynamic profile remained unchanged (29.9%, 24.0-37.3) or worsened (31.2%, 20.7-46.9, P < 0.0001). Improved hemodynamic profile was associated with favourable outcome independent of LVEF and other covariates (HR 0.65, 95%CI: 0.45-0.95, P < 0.05).

CONCLUSION

In HFrEF patients, the beneficial prognostic effects of sacubitril/valsartan are associated with improvement in hemodynamic conditions.

Angiotensin Type 1 Receptor Blockers in Heart Failure

Homeostasis in the cardiovascular system is maintained by physiological functions of the Renin Angiotensin Aldosterone System (RAAS). In pathophysiological conditions, over activation of RAAS leads to an increase in the concentration of Angiotensin II (AngII) and over activation of Angiotensin Type 1 Receptor (AT1R), resulting in vasoconstriction, sodium retention and change in myocyte growth. It causes cardiac remodeling in the heart which results in left ventricular hypertrophy, dilation and dysfunction, eventually leading to Heart Failure (HF). Inhibition of RAAS using angiotensin converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARBs) has shown to significantly reduce morbidity and mortality due to HF. ACEi have been shown to have higher drug withdrawal rates due to discomfort when compared to ARBs; therefore, ARBs are the preferred choice of physicians for the treatment of HF in combination with other anti-hypertensive agents. Currently, eight ARBs have been approved by FDA and are clinically used. Even though they bind to the same site of AT1R displacing AngII binding but clinical outcomes are significantly different. In this review, we described the clinical significance of each ARB in the treatment of HF and their clinical outcome.

Testing the Translational Power of the Zebrafish: An Interspecies Analysis of Responses to Cardiovascular Drugs

The zebrafish is rapidly emerging as a promising alternative in vivo model for the detection of drug-induced cardiovascular effects. Despite its increasing popularity, the ability of this model to inform the drug development process is often limited by the uncertainties around the quantitative relevance of zebrafish responses compared with nonclinical mammalian species and ultimately humans. In this test of concept study, we provide a comparative quantitative analysis of the in vivo cardiovascular responses of zebrafish, rat, dog, and human to three model compounds (propranolol, losartan, and captopril), which act as modulators of two key systems (beta-adrenergic and renin–angiotensin systems) involved in the regulation of cardiovascular functions. We used in vivo imaging techniques to generate novel experimental data of drug-mediated cardiovascular effects in zebrafish larvae. These data were combined with a database of interspecies mammalian responses (i.e., heart rate, blood flow, vessel diameter, and stroke volume) extracted from the literature to perform a meta-analysis of effect size and direction across multiple species. In spite of the high heterogeneity of study design parameters, our analysis highlighted that zebrafish and human responses were largely comparable in >80% of drug/endpoint combinations. However, it also revealed a high intraspecies variability, which, in some cases, prevented a conclusive interpretation of the drug-induced effect. Despite the shortcomings of our study, the meta-analysis approach, combined with a suitable data visualization strategy, enabled us to observe patterns of response that would likely remain undetected with more traditional methods of qualitative comparative analysis. We propose that expanding this approach to larger datasets encompassing multiple drugs and modes of action would enable a rigorous and systematic assessment of the applicability domain of the zebrafish from both a mechanistic and phenotypic standpoint. This will increase the confidence in its application for the early detection of adverse drug reactions in any major organ system.

Efficacy of losartan as add-on therapy to prevent aortic growth and ventricular dysfunction in patients with Marfan syndrome: a randomized, double-blind clinical trial

BACKGROUND

Marfan syndrome (MFS) is a multisystemic hereditary connective tissue disease. Aortic root aneurysms and dissections are the most common and life-threatening cardiovascular disorders affecting these patients. Other cardiac manifestations include mitral valve prolapse, ventricular dysfunction and arrhythmias. Medical treatment of cardiovascular features is ultimately aimed at slowing down aortic root growth rate and preventing dissection. Losartan has been proposed as a new therapeutic tool for this purpose. To which extent losartan affects cardiac function has not been studied previously.

METHODS

We designed a prospective, double-blind, randomized placebo-controlled trial to evaluate the effect of losartan added to beta-blocker therapy on aortic growth and ventricular function in patients with MFS. Secondary outcomes were aortic dissection, prophylactic aortic surgery and death.

RESULTS

Twenty-two patients were enrolled in the trial. There was a mild and similar increase in the aortic root during the 3 years of follow-up in both groups (median 1 mm, IQR [-1-1.5] and 1 mm, IQR [-0.25-1] in the losartan and placebo group, respectively, p = 1). Diastolic and systolic ventricular function was normal at baseline in both groups and remained stable during the study. One patient in the placebo group presented a subclavian artery dissection during follow-up.

CONCLUSION

Losartan on top of beta-blocker therapy has no additional effect on aortic growth or on cardiac function in patients with MFS. Our results are underpowered but are in line with the result from other groups. In order to have a better insight on whether a group of patients could benefit more from losartan therapy, the outcome of an on-going meta-analysis should be awaited.

Varying effects of recommended treatments for heart failure with reduced ejection fraction: meta-analysis of randomized controlled trials in the ESC and ACCF/AHA guidelines

The aim of this paper is to evaluate the treatment effects of recommended drugs and devices on key clinical outcomes for patients with heart failure with reduced ejection fraction (HFREF). Randomized controlled trials (RCTs) listed in the 2012 HF guideline from the European Society of Cardiology as well as the 2013 HF guideline from the American College of Cardiology Foundation and American Heart Association were evaluated for use in the meta‐analysis. RCTs written in English evaluating recommended drugs and devices for the treatment of patients with HFREF were included. Meta‐analyses, based on the outcomes of all‐cause mortality and hospitalization because of HF, were performed with relative risk ratio as the effect size. In the identified 47 RCTs, patients were on average 63 years old and 22% were female. Drugs targeting the renin‐angiotensin‐aldosterone system, beta‐blockers, cardiac resynchronization therapy (CRT), and intracardiac defibrillator devices (ICDs) significantly reduced the risk of death with reductions of 14–19, 23, 20, and 20%, respectively. Drugs targeting the renin‐angiotensin‐aldosterone system, beta‐blockers, digoxin, and CRT significantly reduced the risk of HF hospitalization with reductions of 24–37, 22, 60, and 36%, respectively, while ICDs significantly increased the risk with 34%. Ivabradine showed no significant effects on either outcome. As such, the majority of recommended HFREF treatments offered significant treatment benefits. However, many of the included studies were from the 1990s or earlier, and one must therefore be cautious when extrapolating these results to contemporary patients with HF.

Pharmacologic Management of Chronic Heart Failure: A Review

Standard drug therapy of systolic heart failure has been evaluated in large-scale randomized clinical trials and includes angiotensin-converting enzyme (ACE) inhibi tors, which should be used as first-line therapy, diuret ics for the management of extracellular fluid volume excess, and digoxin. In combination with ACE inhibitors and diuretics, with or without digoxin, some β-adrener gic receptor blockers attenuate disease progression and improve outcome in mild-to-moderate systolic heart failure. The pharmacologic management of chronic dia stolic heart failure is largely empirical and directed at reducing symptoms. Symptoms caused by increased ventricular filling pressures may be diminished by diuret ics and nitrovasodilators. Some calcium channel antago nists and most β-blockers prolong diastolic filling time by slowing heart rate, thereby improving the symptoms of diastolic heart failure.

Impaired neuronal and vascular responses to angiotensin II in a rabbit congestive heart failure model

Congestive heart failure (CHF) is characterised by activation of the renin-angiotensin-aldosterone system (RAAS) and the sympathetic nervous system (SNS). Both systems are known to interact and to potentiate each other's activities. We recently demonstrated that angiotensin II (Ang II) enhances sympathetic nerve traffic via prejunctionally-located AT1-receptors. At present, little is known about the effects of Ang II at the level of the sympathetic neurones in CHF.

Accordingly, we investigated the effect of Ang II in the presence and absence of the AT1-receptor antagonist, eprosartan, on stimulation-induced nerve traffic in isolated thoracic aorta preparations obtained from rabbits suffering from experimentally-induced CHF. Control-preparations were obtained from age-matched animals. Sympathetic activity was assessed by a [3H]noradrenaline spill-over model. Additionally, Ang II constrictor responses were compared between CHF and control vessels in the presence and absence of eprosartan. Additionally, to study postjunctional facilitation, the effects of Ang II on postsynaptic α-adrenoceptor-mediated responses were studied using noradrenaline.

Stimulation-evoked SNS-neurotransmission was similar in both groups (CHF versus control). Ang II (0.1 nM—0.1 µM) caused a concentration-dependent increase of the stimulation-evoked sympathetic outflow in both groups, with a maximum at 10 nM (control [n=7], FR2/FR12.03±0.11 and CHF-preparations [n=7], FR2/FR11.71±0.07). The enhancement by Ang II was decreased in CHF-preparations compared with controls (p<0.05). Eprosartan concentration-dependently attenuated the Ang II-enhanced (10 nM) sympathetic outflow in both CHF- and control preparations. The sympathoinhibitory potency of eprosartan was similar in both groups (control pIC508.81±0.31; CHF 8.65±0.42).

Ang II (1 nM—0.3 µM) concentration-dependently increased the contractile force in control preparations (Emax21.64±3.86 mN, pD27.63±0.02, n=7). Eprosartan (1 nM—0.1 µM) influenced the Ang IIcontractions via a mixed form of antagonism. In CHF-preparations, Ang II caused impaired vascular contraction. The KCl-induced contraction was decreased in the CHF- compared with control preparations (13.02±0.64 mN versus 30.40±0.89 mN). The relative Ang II contraction (% of KCl) was also decreased (2.3% vs. 58.0%). Concentration-response curves to noradrenaline (%KCl) were similar (control pD26.93±0.05, Emax131.0±2.7; CHF pD27.00±0.05, Emax136.7±2.6) (p>0.05) and were not affected by Ang II.

We conclude that Ang II-enhanced sympathetic neurotransmission is mediated by the prejunctional AT1-receptor in both control and CHF-preparations. The decreased facilitation of SNS effects by Ang II may be explained by down-regulation or desensitisation of the neuronal AT1-receptor. Additionally, the aortic contractile capacity in heart failure rabbits appears to be decreased, probably as a result of heart failure-associated neuroendocrine and functional changes.

ACE Inhibition versus Angiotensin-II Antagonism in Heart Failure

Heart failure is becoming increasingly frequent. Once diagnosed, 5-year survival is less than 50% and a substantial percentage of patients (25% to 50%) die suddenly. Angiotensin-converting enzyme inhibitors are the only agents shown to reduce mortality in heart failure. All angiotensin-converting enzyme inhibitors appear to have similar clinical benefits in heart failure. Therapy should be started with a low dose and titrated up to the target dosage in major trials. Although angiotensin-I receptor antagonists provide more complete inhibition of angiotensin-II effects, they have not been found to be superior to long-acting angiotensin-converting enzyme inhibitors in reducing morbidity and mortality in heart failure. Therefore, in current clinical practice, angiotensin-II antagonists should be used as an alternative to angiotensin-converting enzyme inhibitors when the latter are not tolerated. The combined use of angiotensin-converting enzyme inhibitors and angiotensin-II antagonists is not currently recommended in the treatment of heart failure.

Under-Utilization of Implantable Cardioverter Defibrillators in Patients with Heart Failure - The Current State of Sudden Cardiac Death Prophylaxis

Background

Despite ACC/AHA guidelines indicating implantable cardioverter defibrillator (ICD) as class I therapy for primary prevention of sudden cardiac death in patients with EF≤35%, ICD utilization rates in real world practice have been low.

Objective

To determine the rate of ICD implantation at a tertiary care academic center and to assess the reasons for under-utilization of the same.

Methods

Review of a prospectively collected database which included all patients diagnosed with an EF≤35% was performed to assess the rate of ICD implantation and mortality. Reasons for non-implantation of ICD were then assessed from detailed chart review.

Results

A total of 707 patients (age 69.4 ± 14.1 years) with mean EF of 26±7% were analyzed. Only 28% (200/707) of patients had ICDs implanted. Mortality was lower in the group with ICD (25% vs 37%, p=0.004). When patients who either died or were lost to follow-up prior to 2005 were excluded, ICD utilization rate was still low at 37.6%. The most common reason for non-implantation of ICD was physicians not discussing this option with their patients. Patient refusal was the second most common reason.

Conclusions

ICD Implantation rates for primary prevention of SCD in patients with EF≤35% is low. Physician and patient education should be addressed to improve the utilization rates.