Maximally recommended doses of angiotensin-converting enzyme (ACE) inhibitors do not completely prevent ACE-mediated formation of angiotensin II in chronic heart failure

Kinetics of lisinopril intramolecular cyclization in solid phase monitored by Fourier transform infrared microscopy

The solid-state intramolecular cyclization of lisinopril to diketopiperazine was investigated by in situ Fourier transform infrared (FT-IR) microscopy. Using a controllable heating cell, the isothermal transformation was monitored in situ at 147.5, 150, 152.5, 155, and 157.5 degrees C. The collected time-dependent FT-IR spectra at each isothermal temperature were preprocessed and analyzed using a multivariate chemometric approach. The pure component spectra of the observable component (lisinopril and diketopiperazine) were resolved and their time-dependent relative contributions were also determined. Model-free and various model fitting methods were implemented in the kinetic analysis to estimate the activation energy of the intramolecular cyclization reaction. Arrhenius plots indicate that the activation energy is circa 327 kJ/mol.

Current possibilities of ACE inhibitor and ARB combination in arterial hypertension and its complications

The renin-angiotensin-aldosterone system (RAAS) plays a crucial role in blood pressure regulation and hypertension-related complications. Angiotensin-converting enzyme inhibitors (ACEIs) were the first to be used to block the RAAS and now have many compelling indications in the treatment of hypertension and its cardiovascular and renal complications. Angiotensin II receptor blockers (ARBs), introduced 20 years later, have been shown to be equally as effective as antihypertensive treatment and are also associated with a lower number of side effects. Furthermore, in clinical trials ARBs and ACEIs were associated with comparable benefits for their most typical indications. This was confirmed in the 2007 New European Society of Hypertension/European Society of Cardiology (ESH/ESC) guidelines for the management of hypertension by comparable specific recommendations for ARB and ACEI treatment. There is sufficient theoretical background and, in some cases, also clinical evidence that combination therapy with ACEIs and ARBs may be more beneficial than monotherapy with either of the groups alone, both in uncomplicated hypertension and with concomitant heart failure or renal dysfunction. However, the combination of ACEI and ARB was not recommended in the ESH/ESC 2007 Guidelines. This may change after the publication of the Ongoing Telmisartan Alone and in Combination with Ramipril Global End point Trial (ONTARGET) study, the preliminary results of which have just been presented. In heart failure, recent studies have shown that the combination of ACEI and ARB decreases cardiovascular mortality and the number of hospitalizations due to aggravation of heart failure. These results have been reflected in the newest ESC guidelines of the heart failure treatment. Nephroprotective properties of the combination of ACEs and ARBs have been proved both in studies on nondiabetic and diabetic nephropathy. The potential benefits, indications in prespecified groups of patients, the most recent data from clinical trials and latest research regarding dual blockade of RAAS will be reviewed in this article.

Traditional and novel approaches to management of heart failure: successes and failures

Although considerable progress has been made in the pharmacologic and device management of chronic heart failure in recent decades, heart failure patients continue to remain symptomatic, with high hospitalization and mortality rates. A number of novel agents, including endothelin antagonists and tumor-necrosis factor blockers, have recently failed to improve the clinical outcomes of patients with heart failure. Have we reached a ceiling in preventing the progression of the disease? This article reviews successes and late-stage clinical trial disappointments in the treatment of patients with heart failure. Furthermore, the article discusses how agents that have beneficial effects in heart failure also generally attenuate or reverse ventricular remodeling, whereas the newer agents that have failed to improve clinical outcomes either had no effect on remodeling or have been associated with adverse remodeling.

Anti-angiotensin therapy: new perspectives

Activation of the renin-angiotensin system (RAS) plays an important role in the pathogenesis of heart failure. Thus, strategies for the treatment of heart failure have focused on agents that block the RAS. More recently, the role of angiotensin receptor blockers (ARBs) in heart failure therapy has been better defined. This article examines the rationale and role of ARBs in the treatment of patients with heart failure on the basis of evidence from clinical trials.

Losartan improves heart rate variability and heart rate turbulence in heart failure due to ischemic cardiomyopathy

BACKGROUND

Heart rate variability (HRV) and heart rate turbulence are known to be disturbed and associated with excess mortality in heart failure. The aim of this study was to investigate whether losartan, when added on top of beta-blocker and angiotensin-converting enzyme inhibitor (ACEI) therapy, could improve these indices in patients with systolic heart failure.

METHODS AND RESULTS

Seventy-seven patients (mean age 60.4 +/- 8.0, 80.5% male) with ischemic cardiomyopathy (mean ejection fraction 34.5 +/- 4.4%) and New York Heart Association Class II-III heart failure symptoms, already receiving a beta-blocker and an ACEI, were randomly assigned to either open-label losartan (losartan group) or no additional drug (control group) in a 2:1 ratio and the patients were followed for 12 weeks. The HRV and heart rate turbulence indices were calculated from 24-hour Holter recordings both at the beginning and at the end of follow-up. The baseline clinical characteristics, HRV, and heart rate turbulence indices were similar in the 2 groups. At 12 weeks of follow-up, all HRV parameters except pNN50 increased (SDNN: 113.2 +/- 34.2 versus 127.8 +/- 24.1, P = .001; SDANN: 101.5 +/- 31.7 versus 115.2 +/- 22.0, P = .001; triangular index: 29.9 +/- 11.1 versus 34.2 +/- 7.9, P = .008; RMSSD: 29.1 +/- 20.2 versus 34.3 +/- 23.0, P = .009; NN50: 5015.3 +/- 5554.9 versus 6446.7 +/- 6101.1, P = .024; NN50: 5.65 +/- 6.41 versus 7.24 +/- 6.99, P = .089; SDNNi: 45.1 +/- 13.3 versus 50.3 +/- 14.5, P = .004), turbulence onset decreased (-0. 61 +/- 1.70 versus -1.24 +/- 1.31, P = .003) and turbulence slope increased (4.107 +/- 3.881 versus 5.940 +/- 4.281, P = .004) significantly in the losartan group as compared with controls.

CONCLUSIONS

A 12-week-long losartan therapy significantly improved HRV and heart rate turbulence in patients with Class II-III heart failure and ischemic cardiomyopathy already on beta-blockers and ACEI.

Chronic ACE inhibitor treatment increases angiotensin type 1 receptor binding in vivo in the dog kidney

PURPOSE

PET imaging has been recently introduced for investigating the type 1 angiotensin II receptor (AT(1)R) in vivo. The goal of the present study was to investigate the effects of acute and chronic exposure to angiotensin converting enzyme inhibitors (ACEI) on the AT(1)R in the dog kidney.

METHODS

Animals were imaged at baseline, after acute intravenous ACEI treatment and after a chronic 2-week exposure to an oral ACEI. Control animals were imaged at identical time points in the absence of ACEI treatment.

RESULTS

In vivo AT(1)R binding expressed by K (i) was increased in the renal cortex by chronic ACEI treatment (p < 0.05). In vitro measurements of AT(1)R density (B (max)) also revealed significant increases in AT(1)R in isolated glomeruli (p < 0.05). Plasma renin activity was increased, but angiotensin II (Ang II) and the Ang II/Ang I ratio showed a weak correlation with chronic ACEI treatment, consistent with an Ang II escape phenomenon.

CONCLUSION

This study reveals, for the first time, that chronic ACEI treatment increases AT(1)R binding in vivo in the dog renal cortex.

Gradual reactivation of vascular angiotensin I to angiotensin II conversion during chronic ACE inhibitor therapy in patients with diabetes mellitus

AIMS/HYPOTHESIS

In chronic heart failure there is gradual reactivation of vascular tissue angiotensin I (AI) to angiotensin II (AII) conversion over time in patients taking chronic ACE inhibitor therapy. However, it remains unknown whether the same overall phenomenon occurs in other patients taking chronic ACE inhibitor therapy, such as patients with type 2 diabetes mellitus.

METHODS

We studied 30 patients with type 2 diabetes mellitus (mean age 43.5 +/- 10.8 years), all of whom received lisinopril (20 mg/day) as part of their normal treatment. Over the course of the 18 month study, we made measurements at 0, 9 and 18 months. These measurements included plasma values for components of the renin-angiotensin-aldosterone system. In addition, we infused AI and AII into the brachial arteries of patients to assess vascular tissue AI to AII conversion.

RESULTS

There were no significant changes in plasma renin activity, ACE, AI, AII or aldosterone during the study. In contrast, vascular AI to AII conversion was significantly (p = 0.01) greater at 18 months than at 0 months. There was no change over time in the response to infused AII.

CONCLUSIONS/INTERPRETATION

We have shown in vivo that vascular tissue AI to AII conversion gradually increases over time in patients with type 2 diabetes being treated with lisinopril. Further studies are required to determine whether this reactivation detracts from the cardioprotective effects of chronic ACE inhibitor therapy in diabetic patients, and if so, how best to overcome it.

Candesartan: from left ventricular hypertrophy to heart failure, a global approach

Cardiovascular disease is a continuum, starting with risk factors resulting from physiological changes and extending to vascular pathology associated with adverse clinical outcomes. The overactivation of the renin-angiotensin-aldosterone system has been related to the development and worsening of risk factors associated with cardiovascular diseases such as hypertension and heart failure. Treatment at each stage along the continuum may prevent, or at least delay, the next one, and so it is crucial to initiate therapy as early as possible in such patients so as to provide optimal care. Candesartan, a long-acting angiotensin receptor antagonist, has been shown to be an effective, and well-tolerated therapy, in both the early and late phases of cardiovascular disease (prehypertension, hypertension, left ventricular hypertrophy and heart failure). This article reviews the data supporting the use of candesartan in cardiovascular medicine, with a focus on left ventricular hypertrophy and ultimately heart failure. Particular emphasis is given to the Candesartan in Heart Failure Assessment of Reduction in Mortality and Morbidity (CHARM) program, which has shown a positive impact of candesartan in patients with chronic heart failure in terms of reducing the incidence of cardiovascular deaths and chronic heart failure hospitalizations.

Rationale for Combining Blockers of the Renin-Angiotensin System

Blockade of the renin-angiotensin system (RAS) with angiotensin I-converting enzyme (ACE) inhibitors and AT1-receptor (AT1R) blockers has become one of the most successful therapeutic approaches in medicine. The question is no longer whether RAS inhibition helps, but rather how we can optimize inhibition to achieve optimal cardiovascular and renal protection. Indeed, numerous data have shown that the RAS is not blocked fully over 24 hours with current doses of RAS blockers because they trigger a counter-regulatory renin release that can offset pharmacologic inhibition of the RAS. This absence of full blockade may have clinical implications. Combination therapy with ACE inhibitors and AT1R antagonists thus has been proposed to inhibit the biological effects of the reactive renin release triggered by single-site RAS inhibition. By using this approach, numerous experimental and clinical studies have suggested that this combination therapy has additive or synergistic effects on blood pressure and on the prevention of cardiovascular and renal lesions. Although similar intensity of RAS blockade can be achieved by either combination therapy or by using high doses of an AT1-receptor antagonist given alone, the ACE inhibitor present in the combination interferes with the bradykinin-nitric oxide pathway and the N-acetyl-Ser-Asp-Lys-Pro metabolism, which both may have additional biological effects.

Novel Drugs Targeting Hypertension: Renin Inhibitors

The first renin inhibitor, aliskiren, will soon enter the clinical arena. This review summarizes the potential differences between renin inhibitors and the currently existing blockers of the renin-angiotensin system (RAS) [ie, the ACE inhibitors and the angiotensin II type 1 (AT(1)) receptor antagonists], taking also into consideration the recently discovered (pro)renin receptor. This receptor not only activates the inactive precursor of renin, prorenin, but it also exerts direct renin/prorenin-induced effects, independently of angiotensin. The review ends with a brief overview of the available (pre)clinical aliskiren data and a description of its safety profile.

Combination Angiotensin-Converting Enzyme Inhibitor and Angiotensin Receptor Blocker Therapy: Its Role in Clinical Practice

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are commonly prescribed for the management of hypertension. In addition, each of these drug classes has been shown to be effective in the treatment of congestive heart failure, proteinuric chronic kidney disease, and most recently the high-cardiac-risk profile patient. The individual success of each of these drug classes has fueled the theory that given together, the overall biologic effect of both would surpass that of either given alone. The foundation of this premise, although biologically plausible, has yet to be proven in a compelling enough fashion to support the everyday use of these two drug classes in combination. Additional clarifying studies are required to establish whether specific patient subsets exist that might benefit from such combination therapy.

Comparison of angiotensin-converting enzyme inhibitor alone and in combination with irbesartan for the treatment of heart failure

OBJECTIVE

Angiotensin-converting enzyme inhibitor (ACEI) is beneficial in patients with congestive heart failure (CHF). Some, but not all, angiotensin receptor blocker (ARB) was demonstrated to be effective as "add-on" therapy. We investigated whether irbesartan is useful as an add-on therapy in CHF.

DESIGN

Randomized control trial.

SETTING

Single center.

PATIENTS

50 CHF patients on stable doses of ACEI.

INTERVENTIONS

Add-on therapy with irbesartan (300 mg/day) or continuation of conventional therapy (control group) for 1 year.

MAIN OUTCOME MEASURES

Serial clinical and echocardiographic assessment were performed as baseline, 3 months and 1 year after therapy.

RESULTS

There was no difference in clinical characteristics between 2 groups. Patients in the add-on therapy group had significant increase in 6-Minute Hall-Walk distance (351+/-89 to 392+/-84 m, P<0.01), achieved higher METs exercise time on treadmill test (3.9+/-1.1 to 4.6+/-1.3 METs, P=0.01), reduction of NYHA Class (2.4+/-0.5 to 2.0+/-0.8, P<0.005) and improvement of QOL score (28+/-19 to 17+/-18, P<0.05). These parameters were not improved in the control group and a worsening of exercise capacity was observed (P<0.05). A reduction of left ventricular end-systolic diameter (4.94+/-0.85 vs 4.30+/-1.17 cm, P<0.05) was observed in the add-on group. At the end of 1 year, more patients have normal or abnormal relaxation pattern in the add-on group than the control group (82% vs 53% chi(2)=7.1, P=0.02). Blood pressure and renal function were unchanged in both groups.

CONCLUSION

The addition of irbesartan to conventional ACEI therapy in CHF further improves symptoms, exercise capacity and quality of life without adverse effects on hemodynamics and renal function.

Valsartan in the treatment of heart attack survivors

Survivors of myocardial infarction (MI) are at high risk of disability and death. This is due to infarct-related complications such as heart failure, cardiac remodeling with progressive ventricular dilation, dysfunction, and hypertrophy, and arrhythmias including ventricular and atrial fibrillation. Angiotensin (Ang) II, the major effector molecule of the renin–angiotensin–aldosterone system (RAAS) is a major contributor to these complications. RAAS inhibition, with angiotensin-converting enzyme (ACE) inhibitors were first shown to reduce mortality and morbidity after MI. Subsequently, angiotensin receptor blockers (ARBs), that produce more complete blockade of the effects of Ang II at the Ang II type 1 (AT₁) receptor, were introduced and the ARB valsartan was shown to be as effective as an ACE inhibitor in reducing mortality and morbidity in high-risk post-MI suvivors with left ventricular (LV) systolic dysfunction and and/or heart failure and in heart failure patients, respectively, in two major trials (VALIANT and Val-HeFT). Both these trials used an ACE inhibitor as comparator on top of background therapy. Evidence favoring the use of valsartan for secondary prevention in post-MI survivors is reviewed.

What is the Optimal Angiotensin‐Converting Enzyme Inhibitor Dose in Heart Failure?

Doses of angiotensin-converting enzyme (ACE) inhibitors used in the landmark heart failure trials that demonstrated survival benefit are rarely reached in routine practice. The authors review the current literature regarding optimal dosing of ACE inhibitors in heart failure with specific focus on neurohormonal, functional capacity, and clinical outcomes. Neurohormonal studies have shown that lower ACE inhibitor dosing may provide inadequate suppression of the renin-angiotensin-aldosterone system. Higher doses of ACE inhibitors have resulted in greater increments in exercise and functional capacity. Clinically, patients on high-dose ACE inhibitor therapy had significant reductions in all-cause mortality or hospitalization, cardiovascular hospitalizations, and heart failure-specific hospitalizations. There is, however, conflicting evidence, and so continued uncertainty exists regarding optimal dosing. Despite underutilization of ACE inhibitors, there is insufficient evidence to support lower doses. Likewise, limited data exist for doses higher than those used in the landmark trials. Clinicians should therefore attempt to reach target doses in heart failure whenever possible.

Combination ACE Inhibitor and Angiotensin Receptor Blocker Therapy-Future Considerations

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are regularly prescribed for the management of hypertension. Each of these drug classes has also been shown to provide survival benefits for patients with heart failure, proteinuric chronic kidney disease, and/or a high cardiac risk profile. The individual gains seen with each of these drug classes have led to speculation that their combination might offer additive if not synergistic outcome benefits. The foundation of this hypothesis, although biologically possible, has thus far not been sufficiently well proven to support the everyday use of these 2 drug classes in combination. Additional outcomes trials, which are currently proceeding to their conclusion, may provide the necessary proof to support an expanded use of these 2 drug classes in combination.

The HF epidemic: the need for new treatment strategies

The incidence of heart failure is increasing, particularly in older patients. Clinical trials often do not reflect community practice where patients are older and have more co-morbid conditions. Therapeutic agents need to be at least neutral in their effects on these other conditions. Current therapy in heart failure includes angiotensin-converting enzyme (ACE) inhibitors, beta-blockers and diuretics, with advanced heart failure patients receiving spironolactone and possibly digitalis. Ongoing clinical trials are testing more effective inhibition of the renin-angiotensin-aldosterone system (RAAS) with highly selective angiotensin II (Ang II) receptor blockers (ARBs) such as valsartan. Future trials should study diverse racial groups and the elderly, particularly those with preserved systolic function. These should ideally be large multicentre studies with internal substudies to examine mechanisms of heart failure.

ACE phenotyping as a first step toward personalized medicine for ACE inhibitors. Why does ACE genotyping not predict the therapeutic efficacy of ACE inhibition?

Angiotensin (Ang)-converting enzyme (ACE) inhibitors are widely used for the treatment of cardiovascular diseases. Not all patients respond to ACE inhibitors, and it has been suggested that genetic variation might be a useful marker to predict the therapeutic efficacy of these drugs. In particular, the ACE insertion (I)/deletion (D) polymorphism has been investigated in this regard. Despite a decade of intensive research involving the genotyping of thousands of patients, we still do not know whether ACE genotyping helps in predicting the success of ACE inhibition. This review critically addresses the concept that predictive information on therapeutic efficacy of ACE inhibitors might be obtained based on ACE genotyping. It answers the following questions: Do higher ACE levels really result in higher Ang II levels? Is ACE the only converting enzyme in humans? Does ACE inhibition affect ACE expression? Why does ACE have 2 catalytically active domains? What is the relevance of ACE inhibitor-induced signaling through membrane-bound ACE? The review ends with the proposal that ACE phenotyping may prove to be a better first step toward personalized medicine for ACE inhibitors than ACE genotyping.

Redefining the ACE-inhibitor dose-response relationship: substantial blood pressure lowering after massive doses

OBJECTIVES

The blood pressure-lowering dose-response relationship for angiotensin converting enzyme (ACE) inhibitors is assumed to flatten at doses higher than those conventionally used in clinical practice. However, existing clinical trial data do not adequately address the haemodynamic effects of high ACE inhibitor dosages. Therefore, we examined the blood pressure responses in patients presenting to hospital following a deliberate ACE inhibitor overdose.

METHODS

The study design was a retrospective case review, and included all patients who presented to our hospital in the past 5 years after an ACE inhibitor overdose. The data collected were heart rate and systemic blood pressure at various times after ingestion and maximum haemodynamic derangement; these were compared to baseline or recovered values.

RESULTS

Data from 33 patients (24 men) were evaluated. The median (inter-quartile range, IQR) age of the patients was 49 years (IQR: 42-56 years). The median stated dose ingested was 140 mg (IQR: 60-280 mg), which is 20x (IQR: 7-42) the defined daily dose. The maximum fall in systolic blood pressure was 50 mmHg (IQR: 40-64 mmHg), diastolic blood pressure was 35 mmHg (IQR: 26-43 mmHg) and mean blood pressure was 39 mmHg (IQR: 30-47 mmHg).

CONCLUSIONS

The observed reduction in blood pressure following an overdose of an ACE inhibitor was greater than anticipated based on data from therapeutic doses. We conclude that a blood pressure-lowering dose-response relationship extends to higher ACE inhibitor doses than those conventionally used in clinical practice.

Carvedilol-induced antagonism of angiotensin II: a matter of alpha1-adrenoceptor blockade

OBJECTIVE

To investigate whether renin-angiotensin system blockade might underlie the favorable metabolic effects of the nonselective beta + alpha1-adrenoceptor blocker carvedilol as compared with the selective beta1-adrenoceptor blocker metoprolol.

METHODS

Human coronary microarteries (HCMAs), obtained from 32 heart valve donors, were mounted in myographs.

RESULTS

Angiotensin II and the alpha1-adrenoceptor agonist phenylephrine constricted HCMAs to maximally 63 +/- 10 and 46 +/- 15% of the contraction to 100 mmol/l K. Neither carvedilol, metoprolol, the nonselective beta-adrenoceptor antagonist propranolol, nor the alpha1-adrenoceptor antagonist prazosin affected the constrictor response to angiotensin II. alpha1-adrenoreceptors and beta-adrenoceptors are thus not involved in the direct constrictor effects of angiotensin II. When added to the organ bath at a subthreshold concentration, angiotensin II greatly amplified the response to phenylephrine. Both carvedilol and the angiotensin II type 1 (AT1) receptor antagonist irbesartan inhibited this angiotensin II-induced potentiation. Furthermore, carvedilol blocked the angiotensin II-induced amplification of phenylephrine-induced inositol phosphate accumulation in cardiomyocytes.

CONCLUSIONS

AT1-alpha1-receptor crosstalk, involving inositol phosphates, sensitizes HCMAs to alpha1-adrenoceptor agonists. Our results suggest that, in the presence of an increased sympathetic tone, carvedilol provides AT1 receptor blockade via its alpha1-adrenoceptor blocking effects. This could explain the favorable effects of carvedilol versus metoprolol.

Candesartan for the management of heart failure: more than an alternative

Candesartan is a long-acting angiotensin receptor antagonist that is well absorbed from the gastrointestinal tract, with insurmountable receptor binding abilities. Recent studies have shown candesartan to be an effective therapy for heart failure patients, producing a significant reduction in mortality and morbidity. Importantly, studies have demonstrated that candesartan is effective in heart failure patients who are intolerant to angiotensin-converting enzyme inhibitors, in patients already receiving angiotensin-converting enzyme inhibitors and for heart failure patients with preserved systolic function. The primary end point in the latter group failed to achieve statistical significance due to the small number of events. This paper will review the data supporting the use of candesartan to treat all heart failure patients, regardless of their ejection fraction.

Current and future uses of candesartan in the treatment of heart failure

Candesartan is an angiotensin receptor antagonist that is long acting, well absorbed from the gastrointestinal tract and demonstrates an insurmountable receptor antagonism. It is an effective once-daily antihypertensive therapy that maintains good control of blood pressure for over 24 h. More recently, candesartan was shown to be an effective therapy for heart failure patients, producing a significant reduction in mortality and morbidity. Importantly, the studies have demonstrated that candesartan is effective in heart failure patients intolerant to angiotensin-converting enzyme inhibitors (ACE-I), as well as in addition to ACE-I. This paper reviews the data supporting the use of candesartan to treat patients with clinical heart failure.

Effect of valsartan added to background ACE inhibitor therapy in patients with heart failure: results from Val-HeFT

AIMS

To investigate the effect of valsartan in the Valsartan-Heart Failure Trial (Val-HeFT) when added to angiotensin-converting enzyme inhibitor (ACEi) alone in patients with heart failure (HF).

METHODS

Subjects in Val-HeFT receiving ACEi but not beta-blocker at baseline were analysed; 1532 were assigned to valsartan and 1502 assigned to placebo. Primary outcome events (all-cause mortality, hospitalisation for adjudicated heart failure, sudden death with resuscitation and need for >4 h of parenteral therapy for worsening heart failure) were monitored.

RESULTS

Mortality was not affected by valsartan but morbidity endpoints were significantly reduced (36.3% in placebo, 31.0% in valsartan, p=0.002) in patients receiving an ACEi but no beta-blocker. Quality of life (QOL) was significantly improved, ejection fraction (EF) significantly increased, left ventricular (LV) diameter significantly reduced and plasma B-type natriuretic peptide, norepinephrine and aldosterone levels significantly reduced with valsartan compared to placebo. The morbidity benefit was significant in patients on ACEi doses below the median (22% reduction, p=0.003) and not statistically significant in those receiving ACEi doses above the median (14% reduction, p=0.143).

CONCLUSION

Valsartan reduces heart failure hospitalisations and slows LV remodelling in patients treated with an ACEi in the absence of beta-blockade, particularly in those on lower doses of ACEi.

Targeting the renin-angiotensin system for the reduction of cardiovascular outcomes in hypertension: angiotensin-converting enzyme inhibitors and angiotensin receptor blockers

Agents that counteract the negative impact of the renin-angiotensin-aldosterone system (RAAS) are effective antihypertensives and reduce the risk of developing Type 2 diabetes. Contrary to common perception, angiotensin-converting enzyme inhibitors do not share the apparent benefit of angiotensin II receptor blockers (ARBs) in reducing risk of cardiovascular-disease outcomes, particularly stroke, in randomised clinical trials. RAAS agents, especially ARBs, are well tolerated. Use of ARBs alone or in combination with other classes of antihypertensive agents to lower blood pressure and/or medications to control other conditions (e.g., insulin sensitivity) reduces risk of cardiovascular disease outcomes and Type 2 diabetes with excellent tolerability. Selected issues related to use of RAAS agents as antihypertensive therapies (e.g., Type 2 diabetes, global risk management, multiple drug therapy and coronary heart disease) are addressed.

Evaluation of enalapril+losartan treatment with cardiopulmonary exercise test in patients with left ventricular dysfunction

The aim of this study was to evaluate the effects of the combination of enalapril and losartan in patients with left ventricular systolic dysfunction by means of cardiopulmonary exercise test (CPET). Patients with left-ventricular systolic dysfunction and ejection fractions of 40% or less were included to the study. All patients were under the treatment of enalapril 20 mg once daily. The study group consisted of 20 patients (18 men, 2 women; mean age +/- standard deviation: 62.4 +/-6.5 years) and the comparison group consisted of 10 (8 men, 2 women; mean age 59.3 +/-11.9 years). The dose of 50 mg of losartan once daily was given additionally to the study patients. Breath-by-breath CPET was performed before administration of losartan and then 6-8 weeks later in the study group and 2 times with an interval of 6-8 weeks in the control group without any change in the treatment protocol. In the study group the average exercise times were 361 +/-192 and 454 +/-205 seconds (p = 0.001) before and after the study. Peak oxygen consumption ( VO2) values were 1,209 +/-366 and 1,284 +/-398 mL/minute before and after the study (p = 0.01). Anaerobic threshold VO2 values were 785 +/-187 and 855 +/-217 mL/minute before and after the study, respectively (p = 0.01). Peak heart rates (HR) were 141 +/-28 and 143 +/-22/minute (p = 0.35); peak VO2/HR values were 9.02 +/-3.1 and 9.3 +/-3 mL/minute (p = 0.4) before and after the study, respectively. On the other hand, in the control group, average exercise times were 556 +/-250 and 528 +/-251 seconds (p = 0.8); peak VO2 values were 1,502 +/-537 and 1,450 +/-501 mL/minute (p = 0.2); and anaerobic threshold VO2 values were 1,005 +/-338 and 975 +/-319 mL/min (p = 0.7), before and after the study respectively. At the highest comparable exercise stage for both tests in the study group the expired volume/oxygen consumption ( VE/ VO2) ratio declined from 35.1 +/-6.2 to 32.4 +/-5.6 (p = 0.007). VE values declined from 37.5 +/-10.9 to 33.9 +/-10.1 L (p = 0.02); heart rate declined from 140 +/-27 to 132 +/-21/minute (p = 0.02). No significant change was observed in the mentioned values for the control group. Addition of losartan to the standard therapy in patients with left ventricular systolic dysfunction improved exercise capacity and caused lower heart rate and ventilation requirements for the same exercise level.

Determinants of increased angiotensin II levels in severe chronic heart failure patients despite ACE inhibition

INTRODUCTION

The beneficial effects of ACE inhibitors are generally ascribed to blockade of neurohormonal activation. However, especially in chronic heart failure (CHF) patients plasma angiotensin II and aldosterone levels can be elevated despite ACE inhibition, the so-called ACE escape. In the present study, we aimed to identify the frequency and determinants of ACE escape in CHF patients.

METHODS

We studied 99 stable chronic heart failure patients (NYHA class III and IV, 66% ischemic etiology) receiving long-term therapy with ACE inhibitors. In all patients, cardiac, renal, and neurohormonal parameters were measured. ACE escape was defined as plasma angiotensin level > or = 16 pmol/L.

RESULTS

Mean (+/- SD) left ventricular ejection fraction of our 99 patients (79 men and 20 women, age 69 +/- 12 years) was 28 +/- 10%. In addition to an ACE inhibitor, 93% of patients received diuretics, 71% a beta-blocker, and 49% spironolactone. None of the patients used an angiotensin receptor blocker. In our population, 45% of the patients had an angiotensin II plasma concentration higher than 16 pmol/L (median concentration was 14.1 pmol/L). Spironolactone use was an independent predictor of elevated plasma angiotensin II levels. Furthermore, spironolactone users had significantly higher plasma active renin protein and aldosterone levels. Plasma angiotensin II concentration was positively correlated to active renin, plasma angiotensin I and plasma aldosterone. No correlation was found between plasma angiotensin II levels and serum ACE activity, dose of ACE inhibitor, or duration of use.

CONCLUSION

In a group of severe chronic heart failure patients, 45% had elevated plasma angiotensin II levels independent of serum ACE activity despite long-term ACE inhibitor use. Although a causal link could not be proven, an association was found between spironolactone use and active renin protein, angiotensin II and aldosterone levels, suggesting that escape from ACE is mainly caused by a feedback mechanism.

Advanced glycation end products activate a chymase-dependent angiotensin II-generating pathway in diabetic complications

BACKGROUND

Angiotensin II is a key mediator of diabetes-related vascular disease. It is now recognized that in addition to angiotensin-converting enzyme, chymase is an important alternative angiotensin II-generating enzyme in hypertension and diabetes. However, the mechanism of induction of chymase in diabetes remains unknown.

METHODS AND RESULTS

Here, we report that chymase is upregulated in coronary and renal arteries in patients with diabetes by immunohistochemistry. Upregulation of vascular chymase is associated with deposition of advanced glycation end products (AGEs), an increase in expression of the receptor for AGEs (RAGE), and activation of ERK1/2 MAP kinase. In vitro, AGEs can induce chymase expression and chymase-dependent angiotensin II generation in human vascular smooth muscle cells via the RAGE-ERK1/2 MAP kinase-dependent mechanism. This is confirmed by blockade of AGE-induced vascular chymase expression with a neutralizing RAGE antibody and an inhibitor to ERK1/2 and by overexpression of the dominant negative ERK1/2. Compared with angiotensin-converting enzyme, chymase contributes to the majority of angiotensin II production (>70%, P<0.01) in response to AGEs. Furthermore, AGE-induced angiotensin II production is blocked by the anti-RAGE antibody and by inhibition of ERK1/2 MAP kinase activities.

CONCLUSIONS

AGEs, a hallmark of diabetes, induce chymase via the RAGE-ERK1/2 MAP kinase pathway. Chymase initiates an important alternative angiotensin II-generating pathway in diabetes and may play a critical role in diabetic vascular disease.

Suppression of the Renin–Angiotensin–Aldosterone System in Chronic Heart Failure

Chronic heart failure (CHF) has taken on epidemic proportions in the United States, with approximately 550,000 new cases annually. With the evolution of pharmacotherapy targeting neurohormonal pathways over the past 2 decades, the annual mortality in subjects with New York Heart Association (NYHA) class IV has dramatically improved from 52% in the seminal CONSENSUS trial to less than 20% in more recent trials in CHF. Suppression of the renin-angiotensin system (RAS) with various angiotensin-converting enzyme (ACE) inhibitors has been proven to save lives in several large-scale trials of CHF, and all of them can be used at doses tested in clinical trials without clear preference of one over another. Angiotensin receptor blockers (ARBs) can be used in place of ACE inhibitors in the case of ACE inhibitor intolerance with comparable results. However, some inconsistencies exist between trials with ARBs, and it is uncertain if the ARBs tested in clinical trials provide comparable clinical benefit whether used in place of or in combination with ACE inhibitors. Once ACE inhibition has been started, beta blockade should follow for all subjects with symptomatic CHF. Triple neurohormonal blockade can then be accomplished with the addition of an aldosterone receptor or ARB. Regardless of the exact agent used or sequence of initiation, the critical importance of careful monitoring of neurohormonal blockade cannot be overstated. Renal failure and hyperkalemia are the most important complications of suppression of the renin-angiotensin-aldosterone system (RAAS), and an increase in hospital admissions and death from hyperkalemia after publication of the RALES trial illustrates the danger of "casual" use of neurohormonal blockers. In light of the tremendous benefits of neurohormonal blockade, the only conclusion from these data is to initiate RAAS-blocking agents following the safety precautions tested in the respective clinical trials.

Angiotensin-converting enzyme inhibition intervention in elderly persons: effects on body composition and physical performance

The disablement process is often accompanied by sarcopenia or muscle loss, which is associated with virtually all identified disability risk factors. Clinically, the association between body composition and physical performance has been documented by several studies. However, loss of strength is greater than loss of muscle mass with age implying that the quality of remaining muscle may be reduced. Although there are limited data explaining potential physiological mechanisms that contribute to muscle quality, sarcopenia is frequently associated with fat accumulation, and the percentage of body fat increases with age even if weight does not. However, the relationship between fat and muscle function may not be linear, suggesting that there may be an optimal ratio of lean to fat mass for physical function. There are no definitive pharmacological interventions proven to prevent decline in physical function either by modulating body composition or by other means. One exception may be angiotensin-converting enzyme inhibitors (ACEIs). ACE is an important component of the renin-angiotensin system, the central hormonal regulator of blood pressure. Recent evidence suggests that ACEIs may improve physical function by means of direct effects on body composition in older persons, rather than through its blood-pressure-lowering effects. Clinical and genetic studies in humans and experimental evidence in animals suggest that modulation of the renin-angiotensin system is associated with metabolic and biochemical changes in skeletal muscle and fat, changes that are associated with declining physical function. ACEIs may modulate this process through a variety of molecular mechanisms including their influence on oxidative stress and on metabolic and inflammation pathways. This review describes potential biological mechanisms of ACE inhibition and its contribution to declining physical performance and changing body composition. Promising pharmacoepidemiological studies and experimental evidence in animals suggest that there are appropriate models in which to study this effect.

Candesartan in heart failure

Candesartan cilexetil is a nonpeptide selective blocker of the angiotensin II receptor sub-type 1. It is a prodrug that is converted to its active metabolite during its variable absorption. It is highly protein bound with a small volume of distribution and a nine-hour half-life. Candesartan is one of two angiotensin receptor blockers approved for use in heart failure. MEDLINE was searched using OVID and PubMed to evaluate the evidence for using candesartan in patients with heart failure. Pharmacologic and pharmacokinetic evaluations, as well as clinical trials, were selected and are presented in this review. Clinical evidence supports the indication for use in systolic heart failure. Results for use in patients with diastolic heart failure were non-significant. Candesartan was well tolerated in the trials, with hyperkalemia, renal dysfunction, and hypotension being the most common adverse events. Use of angiotensin receptor blockers with angiotensin-converting enzyme inhibitors needs further study; however, candesartan appears to provide added benefit in this setting. Candesartan is a safe and effective option for patients with systolic heart failure. Data regarding other angiotensin receptor blockers is underway.

Comparative effect of aspirin and clopidogrel on arterial function in CHF

BACKGROUND

By inhibiting prostaglandins, aspirin may be deleterious in congestive heart failure (CHF) and/or partially counteract the efficacy of angiotensin-converting enzyme inhibitors (ACEI). Conversely, clopidogrel has no effect on prostaglandin metabolism. The aim of this study was to prospectively investigate the effect of aspirin and clopidogrel on arterial functional properties in CHF patients treated with ACEI.

METHODS

Forty-five patients with stable NYHA class II-IV CHF (64.0+/-15.5 years), ejection fraction <40%, were included in this prospective double-blind study and randomized to receive aspirin 325 mg/day or clopidogrel 75 mg/day for 14 days. Reflected wave assessed by radial applanation tonometry and pulse wave velocity (PWV) were measured at day 0 and day 14.

RESULTS

Aspirin resulted in an increase in the augmentation index of the reflected wave (Delta=+3.5+/-5.2%, p=0.005) and the height above the shoulder of the reflected wave (Delta=+1.7+/-3.1 mm Hg, p=0.023), without statistically variation in PWV. Conversely, clopidogrel had no effect on the same parameters (p=0.512, p=0.677 and 0.801, respectively). Overall, variations in the augmentation index of reflected wave significantly differed when compared aspirin with clopidogrel (p=0.0261).

CONCLUSION

This study demonstrates the existence of a negative effect of aspirin 325 mg/day when compared to clopidogrel 75 mg/day on arterial functional properties in CHF patients treated with ACEI.

Angiotensin-converting enzyme inhibitors and angiotensin II type I receptor blockers in the management of congestive heart failure patients: what have we learned from recent clinical trials?

PURPOSE OF REVIEW

Angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers and aldosterone antagonists have all been shown to decrease the morbidity and mortality related to heart failure. The population of patients with a diagnosis of heart failure represents a heterogeneous group, ranging from asymptomatic left ventricular dysfunction to chronic decompensation with advanced heart failure; and the clinical roles of these agents can vary within this diverse heart failure population. This article will review the recent developments pertaining to renin-angiotensin-aldosterone system modulation therapy and help to clarify some of the relevant issues surrounding the role and relevance of these drugs in the currently established multi-drug regimen of heart failure patients.

RECENT FINDINGS

Clinical trials such as OPTIMAAL, VALIANT and EPHESUS have added insight into the role of angiotensin II receptor blockers and aldosterone in the post-myocardial infarct heart failure patient. The CHARM series has provided new information into the role of angiotensin II receptor blocker therapy in patients who are angiotensin-converting enzyme intolerant and those with heart failure and normal ejection fraction. In addition further data is now available about the benefits and risks when considering a strategy of either angiotensin-converting enzyme plus angiotensin II receptor blocker or angiotensin-converting enzyme plus aldactone in chronic heart failure patients.

SUMMARY

Important recent clinical trials have helped to add insight on the role of renin-angiotensin-aldosterone system in heart failure. Choosing between a class of drug or particular strategy depends on knowledge of the patient populations studied in clinical trials as well as the inherent risks involved.

Addition of an angiotensin receptor blocker to full-dose ACE-inhibition: controversial or common sense?

Both angiotensin-converting enzyme (ACE)-inhibitors and angiotensin receptor blockers (ARBs) interfere with the activity of the renin-angiotensin system (RAS) in a different way. Theoretically, one might expect beneficial effects when they are used in combination, as a more complete suppression of the RAS can be achieved. But can this additional effect still be seen in patients on full-dose ACE-inhibition? Several controlled trials demonstrated that combination therapy can have additional benefits in hypertensive patients, in chronic heart failure patients, and in both diabetic and non-diabetic nephropathy patients. However, the clinical benefit was not always as pronounced as expected and not every patient will benefit from dual blockade of the RAS. There is some evidence of a less pronounced effect of combination therapy when a full dose of the ACE-inhibitor is given. However, it is well known that ACE-inhibitors cannot completely suppress the formation of angiotensin II, in particular, when the RAS is activated. Indeed, clinical trials indicated that add-on therapy with an ARB was especially of use when the RAS remained activated despite full-dose ACE-inhibitor treatment. In summary, combination of a full-dose ACE-inhibitor and an ARB can be a rational choice in selected patients.

Rationale for the use of angiotensin ii receptor blockers in patients with left ventricular dysfunction (part I of II)

Almost 5 million individuals in the United States are diagnosed with chronic heart failure (HF), and the prevalence is increasing. Angiotensin-converting enzyme (ACE) inhibitors and beta blockers, neurohormonal antagonists that block the renin-angiotensin system (RAS) and the sympathetic nervous system, respectively, have been shown in clinical trials to reduce morbidity and mortality in patients with HF, and these therapies are now integral components of standard HF treatment. Yet, morbidity and mortality rates in HF remain unacceptably high, and the limitations of current standard therapies are becoming increasingly apparent. About 10% of patients with HF are unable to tolerate ACE inhibitors, often because of cough. In addition, ACE inhibition may not completely block the RAS because angiotensin II, the main end product of the RAS, can be generated via non-ACE enzymatic pathways. Angiotensin II receptor blockers (ARBs) may exert more complete RAS blockade than ACE inhibitors by interfering with the binding of angiotensin II at the receptor level, regardless of the enzymatic pathway of production. They are also better tolerated than ACE inhibitors and have been shown to improve symptoms and function in clinical trials in patients with HF. These factors provide a strong rationale for the study of the clinical effects of ARBs in patients with HF.

Valsartan for the treatment of heart failure

Heart failure (HF) still has a discouraging prognosis. Therapeutic strategies aim to reduce mortality as well as slow the progression of the disease, improve symptoms and reduce the frequency of hospital admission. Activation of the renin-angiotensin-aldosterone system (RAAS) is a hallmark of several cardiocirculatory diseases, including HF. Drugs for evidence-based therapy of HF are angiotensin-converting enzyme inhibitors (ACEIs), beta-blockers and aldosterone antagonists. A promising alternative is a more complete action on the RAAS through selective blockade of the angiotensin type 1 (AT(1)) receptors, taking into account not only physiopathological issues but also pharmacological, experimental and clinical data. The effect of valsartan, an orally-active, selective antagonist of AT(1) receptors, on the outcome in patients with chronic and symptomatic HF was evaluated in a large-scale, international, placebo-controlled clinical study, the Valsartan in Heart Failure Trial (Val-HeFT). In this study, overall mortality was similar in the valsartan and placebo groups (19.7 and 19.4%, respectively). However, valsartan, in addition to recommended therapy of HF including an ACEI, significantly reduced the combined end point of mortality and morbidity, with a significant reduction in the risk of hospitalisation, paralleled by improvements in New York Heart Association (NYHA) functional class, signs and symptoms and quality of life. Valsartan also improved left ventricular anatomy and function and significantly reduced neurohormonal activation. These results were confirmed and extended by the CHARM trial, where the benefits of candesartan were proved not only in all 7599 patients with HF, but also in the 2548 given an ACEI, the 2028 not given an ACEI and in the 3023 patients with an ejection fraction of > 40%. In conclusion, the first choice for HF remains an ACEI with a beta-blocker, but two new options are emerging. In patients intolerant to ACEI, the combination of valsartan or candesartan with a beta-blocker is proposed, whereas an ACEI with either valsartan or candesartan can be considered in patients intolerant to or with contraindications to beta-blockers.

Angiotensin Receptor Blockers versus ACE Inhibitors: Prevention of Death and Myocardial Infarction in High-Risk Populations

OBJECTIVE:

To determine, through a review of the medical literature, whether there is adequate evidence to support the use of angiotensin receptor blockers (ARBs) in place of angiotensin-converting enzyme (ACE) inhibitors in high-risk populations, focusing on the prevention of death and myocardial infarction (MI).

DATA SOURCES:

Original investigations, reviews, and meta-analyses were identified from the biomedical literature via a MEDLINE search (1966–August 2004). Published articles were also cross-referenced for pertinent citations, and recent meeting abstracts were searched for relevant data.

STUDY SELECTION AND DATA EXTRACTION:

All articles identified during the search were evaluated. Preference was given to prospective, randomized, controlled trials that evaluated major cardiovascular endpoints and compared ARBs with ACE inhibitors, active controls, or placebo.

DATA SYNTHESIS:

The renin—angiotensin system plays a pivotal role in the continuum of cardiovascular disease and represents a major therapeutic target in the treatment of patients at risk for vascular events. While ACE inhibitors have been definitively shown to prevent death and MI, studies with ARBs in similar populations have not reduced these endpoints. In clinical trials that enrolled patients with heart failure, post-MI, diabetes, and hypertension, ARBs did not prevent MI or prolong survival compared with ACE inhibitors, other antihypertensives, or placebo.

CONCLUSIONS:

ACE inhibitors and ARBs should not be considered interchangeable, even among patients with a documented history of ACE inhibitor intolerance. ARBs can be considered a second-line alternative in such patients with the realization that they have not been shown to prevent MI or prolong survival.

The use of angiotensin receptor blockers in the treatment of chronic heart failure

Angiotensin receptor blockers (ARBs) have a pharmacological role in the treatment of heart failure through their blockade of the effects of angiotensin II. ARBs, however, lack the potential benefits of inhibiting the breakdown of bradykinin that is seen with ACE-Is. Historically, the medical literature assessing ARBs in the treatment of chronic heart failure have been short in duration and primarily focused on surrogate markers of disease severity. Recent, well-designed clinical trials have shed new light on the potential roles of ARBs in the treatment of chronic heart failure and their effects on mortality in this patient population. In comparison to captopril, losartan has been shown to have similar benefits in cardiovascular mortality and morbidity. In patients with systolic dysfunction who are intolerant to ACE-Is, candesartan has been shown to reduce cardiovascular mortality and hospital admissions for heart failure. In combination with ACE-Is, candesartan and valsartan have been shown to improve heart failure morbidity and, with candesartan, reduced cardiovascular mortality in those with systolic dysfunction. These 2 trials show conflicting mortality information regarding the use of triple therapy with ACE-Is, ARBs, and beta-blockers for systolic dysfunction. In patients with heart failure but preserved systolic dysfunction, candesartan showed no effects on mortality and only modest effects on morbidity.

Valsartan in Chronic Heart Failure

OBJECTIVE:

To evaluate the evidence for valsartan in the treatment of heart failure and determine its need for formulary inclusion.

DATA SOURCES:

OVID and PubMed databases were searched (1983–June 2004) using the key words angiotensin-receptor blocker, heart failure, valsartan, Diovan, and angiotensin-converting enzyme inhibitor. Only English-language literature was selected.

STUDY SELECTION AND DATA EXTRACTION:

Pharmacology and pharmacokinetic evaluations for valsartan were selected. Prospective, randomized clinical trials investigating the use of valsartan and other angiotensin-receptor blockers (ARBs) in chronic heart failure were evaluated.

DATA SYNTHESIS:

Valsartan, a selective antagonist for angiotensin receptor subtype 1, is the first ARB to be approved for use in chronic heart failure. Clinical trial data support valsartan as an alternative to angiotensin-converting enzyme (ACE) inhibitors in ACE inhibitor—intolerant patients with chronic heart failure. Valsartan is generally well tolerated, with renal impairment, elevated serum creatinine and potassium levels, and dizziness being the most common adverse effects; consequently, patients experiencing those adverse events while taking ACE inhibitors are likely to experience them with valsartan. Although further study is needed, differences in effectiveness among races may exist with use of valsartan; however, at this time, valsartan is recommended as an alternative to ACE inhibitors regardless of race. Candesartan and losartan have been studied in similar settings. Candesartan's data support its use in heart failure; however, losartan's data have been less consistent.

CONCLUSIONS:

Valsartan is a safe and effective alternative for heart failure patients intolerant of ACE inhibitors. Valsartan has not been shown to be safe and effective when used in combination with ACE inhibitors.

Arterial stiffness and the renin-angiotensin-aldosterone system

Arterial stiffness has recently been recognised as an independent risk factor for cardiovascular morbidity and mortality in hypertension. Many of the complications seen with angiotensin II (Ang II) excess or hyperaldosteronism--an increased event rate, left ventricular hypertrophy, endothelial dysfunction and target organ damage--are also associated with arterial stiffness. It is possible that reduced arterial compliance may be one mechanism whereby increased activity of the renin-angiotensin-aldosterone system (RAAS) produces adverse vascular effects. Common pathophysiological processes, altered collagen turnover and increased fibrosis may underlie both arterial stiffness and RAAS-associated vascular damage. While it is recognised that patients with hyperaldosteronism have increased arterial stiffness, the role of the RAAS in modulating arterial compliance in essential hypertension and in normotensive subjects is less clear cut. There is, however, more consistent data which show that drugs that interfere with Ang II or aldosterone, namely angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs) and aldosterone antagonists, all reduce arterial stiffness. In many cases, this is to a greater extent than predicted from the extent of reduction in blood pressure (BP), suggesting a role for RAAS in vascular stiffness in hypertensive subjects. There is also evidence that combined ACE inhibitors (ACE-Is) and ARBs may have an additive effect in reducing stiffness. The reduction in cardiovascular mortality in end-stage renal disease patients treated with ACE-Is was preferentially seen in those who had reduced arterial stiffness. These data suggest that, in addition to regulation of vascular biology and BP, the RAAS is an important determinant of arterial stiffness in health and, more particularly, in disease.

Combined angiotensin receptor blocker and ACE inhibitor on myocardial fibrosis and left ventricular stiffness in dogs with heart failure

Angiotensin receptor blocker (ARB) and angiotensin-converting enzyme (ACE) inhibitor (ACEI) each act in a different manner to prevent myocardial fibrosis and left ventricular (LV) stiffness in animals with pathways in the heart for generating ANG II as well as ACE. A model of pacing-induced congestive heart failure (CHF) was used to test the central hypothesis that ARB + ACEI prevents myocardial fibrosis and decreases LV stiffness to a greater extent than ARB or ACEI alone. Thirty-five dogs were assigned to the following treatment protocols on the 8th day of a 4-wk pacing schedule: 1) rapid ventricular pacing, 2) ARB (candesartan cilexetil, 1.5 mg.kg(-1).day(-1)) with pacing, 3) ACEI (enalapril, 1.9 mg.kg(-1).day(-1)) with pacing, 4) ARB (candesartan cilexetil, 0.75 mg.kg(-1).day(-1)) + ACEI (enalapril, 0.95 mg.kg(-1).day(-1)) with pacing, and 5) sham operation. The LV stiffness coefficient was significantly increased after rapid pacing but was significantly lower with ARB + ACEI than with ARB or ACEI alone. The collagen volume fraction and mRNA levels of collagen I and III, which were increased by rapid pacing, were significantly lower with ARB + ACEI than with ARB or ACEI alone. Thus ARB + ACEI prevents myocardial fibrosis and decreases LV stiffness during the progression of CHF compared with ARB or ACEI alone.

ACE inhibitors in heart failure: what more do we need to know?

ACE inhibitors have significantly decreased cardiovascular mortality, myocardial infarction (MI), and hospitalizations for heart failure (HF) in patients with asymptomatic or symptomatic left ventricular (LV) systolic dysfunction. Furthermore, the extended 12-year study of the SOLVD (Studies Of Left Ventricular Dysfunction) Prevention and Treatment trials (X-SOLVD) demonstrated a significant benefit with a reduction of cumulative all-cause death compared with placebo (50.9% vs 56.4%) [hazard ratio (HR) 0.86; 95% CI 0.79, 0.93; p < 0.001]. The survival benefits and significant reductions in cardiovascular morbidity related to treatment with ACE inhibitors are likely achieved by titrating the dose of ACE inhibitors to the target dose achieved in clinical trials. Although the ATLAS (Assessment of Treatment with Lisinopril And Survival) study, which randomly allocated HF patients to low- or high-dose lisinopril, showed no significant difference between groups for the primary outcome of all-cause mortality (HR 0.92; 95% CI 0.82, 1.03), the predetermined secondary combined outcome of all-cause mortality and HF hospitalization was reduced by 15% for the patients receiving high-dose lisinopril compared with low-dose (p < 0.001) with a 24% reduction in HF hospitalization (p = 0.002). Despite the use of ACE inhibitors, blockade of the renin angiotensin aldosterone system (RAAS) remains incomplete, with evidence of continued production of angiotensin II by non-ACE-dependent pathways. The safety and potential benefits of angiotensin receptor antagonists (angiotensin receptor blockers [ARBs]) in patients with impaired systolic function have been assessed in moderate to large clinical trials. In patients with impaired LV systolic function and HF, combination therapy with ARBs with recommended HF therapy including ACE inhibitors in patients who remain symptomatic may be considered for its morbidity benefit. Based on the CHARM (Candesartan in Heart failure: Assessment of Reduction in Mortality and morbidity)-Added data, candesartan cilexetil in addition to standard HF therapy results in a further reduction of cardiovascular mortality. Close monitoring of renal function and serum potassium levels is needed in this setting. The VALIANT (VALsartan In Acute myocardial iNfarction Trial) results suggest that valsartan is as effective as captopril in patients following an acute MI with HF and/or LV systolic dysfunction and may be used as an alternative treatment in ACE inhibitor-intolerant patients. There was no survival benefit with valsartan-captopril combination compared with captopril alone in this trial. Despite these results, ACE inhibitors remain the first-choice therapeutic agent in post-MI patients, and ARBs can be used in patients with clear intolerance. Although the use of ACE inhibitors may be appealing in patients with HF and preserved LV systolic function, there is currently no evidence from large clinical trials to support this.

Comparison of suppression of the circulating and vascular renin-angiotensin system by enalapril versus trandolapril in chronic heart failure

Experimental studies suggest that angiotensin-converting enzyme (ACE) inhibitors with high tissue affinity confer a greater degree of vascular renin-angiotensin system suppression than those with low tissue affinity despite similar suppression of the circulating renin-angiotensin system. To test this hypothesis in a clinical setting, we randomized subjects with chronic heart failure to receive the low tissue affinity ACE inhibitor enalapril or the high tissue affinity ACE inhibitor trandolapril, and assessed the degree of circulating and vascular renin-angiotensin system suppression. Vascular renin-angiotensin system suppression was determined by measuring the pressor response to intravenous injections of angiotensin I. Circulating renin-angiotensin system suppression was determined by measuring plasma angiotensin II. Vascular and circulating renin-angiotensin system suppression, endothelial function (flow-mediated vasodilation), and maximal exercise capacity (peak oxygen uptake) were assessed after a 4-week run-in period on open-label enalapril 40 mg/day and after 8 weeks of randomized double-blind treatment with enalapril 40 mg/day or trandolapril 4 mg/day. Twenty-six men and 4 women (mean age 52 +/- 11 years; mean left ventricular ejection fraction 25 +/- 9%; New York Heart Association class II [n = 16] and III [n = 14]) were studied. After a 2-month randomized treatment period, vascular renin-angiotensin system suppression, circulating renin-angiotensin system suppression, endothelial function, and exercise capacity did not differ between subjects treated with enalapril and those treated with trandolapril. Despite substantial differences in the tissue affinity of enalapril and trandolapril, the degree of vascular renin-angiotensin system suppression achieved with these agents did not differ in subjects with chronic heart failure during long-term therapy.