Lisinopril lowers cardiac adrenergic drive and increases beta-receptor density in the failing human heart

Acute effects of angiotensin-converting enzyme inhibition versus angiotensin II receptor blockade on cardiac sympathetic activity in patients with heart failure

The beneficial effects of angiotensin-converting enzyme (ACE) inhibitors and angiotensin II (ANG II) receptor antagonists in patients with heart failure secondary to reduced ejection fraction (HFrEF) are felt to result from prevention of the adverse effects of ANG II on systemic afterload and renal homeostasis. However, ANG II can activate the sympathetic nervous system, and part of the beneficial effects of ACE inhibitors and ANG II antagonists may result from their ability to inhibit such activation. We examined the acute effects of the ACE inhibitor captopril (25 mg, n = 9) and the ANG II receptor antagonist losartan (50 mg, n = 10) on hemodynamics as well as total body and cardiac norepinephrine spillover in patients with chronic HFrEF. Hemodynamic and neurochemical measurements were made at baseline and at 1, 2, and 4 h after oral dosing. Administration of both drugs caused significant reductions in systemic arterial, cardiac filling, and pulmonary artery pressures (P < 0.05 vs. baseline). There was no significant difference in the magnitude of those hemodynamic effects. Plasma concentrations of ANG II were significantly decreased by captopril and increased by losartan (P < 0.05 vs. baseline for both). Total body sympathetic activity increased in response to both captopril and losartan (P < 0.05 vs. baseline for both); however, there was no change in cardiac sympathetic activity in response to either drug. The results of the present study do not support the hypothesis that the acute inhibition of the renin-angiotensin system has sympathoinhibitory effects in patients with chronic HFrEF.

Physical training promotes similar effects to the blockade of angiotensin-converting enzyme on the cardiac morphology and function in old female rats subjected to premature ovarian failure

We investigated the effects of angiotensin-converting enzyme (ACE) inhibition and aerobic physical training on the heart of old female rats (82-wk-old) submitted to premature ovarian failure (10-wk.-old). We used different approaches: morphology and function by echocardiography, reactivity of the coronary bed and left ventricular contractibility (Langendorff Technique). Female Wistar ovariectomized (OVX) rats (n=42) were assigned to one of four groups: OVX, vehicle treated only; OVX-EM, Enalapril Maleate only (EM, 10mg·kg^-1·d^-1); OVX-T, aerobic trained only; and OVX-EMT, treated with Enalapril Maleate and aerobic trained. Both Enalapril Maleate treatment and aerobic training were done in the last 20weeks of the experimental protocol. When compared to the OVX group, the OVX-EM group showed lower values of wall thickness and left ventricular (LV) mass, lower values of coronary bed reactivity and reduced maximum response of LV contractility to dobutamine, while the OVX-T group showed lower values of LV wall thickness, increase in end-systolic volume, reduced maximum response of LV contractility to dobutamine, and left intraventricular pressure due to increased flow. The combination of treatments (EM and aerobic physical training) did not promote additional important effects on the parameters evaluated. Our results suggest similar beneficial effects of physical training and EM treatment on the morphology and cardiac function in old female rats submitted to premature ovarian failure. Although the causes of these benefits are still unknown, both treatments have promoted a decrease in cardiac contractility, and the reduced β1-adrenergic sensitivity suggests that both treatments may attenuate the sympathetic effect on the heart.

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.

Cardiac fibroblasts inhibit β-adrenoceptor-dependent connexin43 expression in neonatal rat cardiomyocytes

Cardiac fibroblasts play an important role in adverse cardiac remodelling. As in many cardiac diseases connexin43 (Cx43) is altered, we wanted to elucidate whether fibroblasts may influence cardiac Cx43 expression. We used four different cell culture systems of neonatal rat cardiomyocytes (CM) and fibroblasts (FB): type 1, pure CM culture; type 2, co-culture of CM/FB; type 3, pure FB culture; type 4, Transwell® system: CM/FB co-cultured but separated by a microporous membrane. Stimulation of types 1-3 cell culture models with isoprenaline significantly enhanced Cx43-protein and Cx43-mRNA expression as well as phosphorylation of ERK and translocation of AP1 and CREB only in the CM cultures; whereas, the CM/FB co-cultures and the FB cultures did not respond to isoprenaline. Similarly, if CM and FB were separated by a microporous membrane (Transwell® system) the isoprenaline-induced increase in CM Cx43 was completely suppressed, suggesting the existence of a soluble factor responsible for the suppressant effect of FB. Angiotensin II determination in types 1 and 2 cell culture supernatants revealed that the CM/FB co-cultures exhibited a significant higher angiotensin II release than the CM cultures. Furthermore, we aimed to inhibit angiotensin II signal transduction pathway: blockade of AT1 receptors or PKC inhibition restored the responsiveness of CM/FB co-cultures to isoprenaline. Moreover, external addition of angiotensin II to CM cultures also resulted in suppression of isoprenaline-stimulated Cx43 expression in an AT1-receptor- and PKC-dependent manner. Thus, our study indicates that cardiac fibroblasts inhibit β-adrenoceptor-dependent Cx43 signalling in CM involving angiotensin II.

Fast parameters estimation in medication efficacy assessment model for heart failure treatment

INTRODUCTION

Heart failure (HF) is a common and potentially fatal condition. Cardiovascular research has focused on medical therapy for HF. Theoretical modelling could enable simulation and evaluation of the effectiveness of medications. Furthermore, the models could also help predict patients' cardiac response to the treatment which will be valuable for clinical decision-making.

METHODS

This study presents a fast parameters estimation algorithm for constructing a cardiovascular model for medicine evaluation. The outcome of HF treatment is assessed by hemodynamic parameters and a comprehensive index furnished by the model. Angiotensin-converting enzyme inhibitors (ACEIs) were used as a model drug in this study.

RESULTS

Our simulation results showed different treatment responses to enalapril and lisinopril, which are both ACEI drugs. A dose-effect was also observed in the model simulation.

CONCLUSIONS

Our results agreed well with the findings from clinical trials and previous literature, suggesting the validity of the model.

The beta1-adrenergic receptor mediates the pharmacogenetic interaction of the ACE D allele and beta-blockers

The role of beta-receptor selectivity for the interaction between the angiotensin-converting enzyme (ACE) insertion/deletion polymorphism and beta-blocker therapy was investigated in 479 subjects with left ventricular dysfunction. Subjects were separated into no beta-blocker, beta1 -selective, and nonselective beta-blocker treatment groups. The D allele adversely affected transplant-free survival for subjects not on beta-blockers (p= 0.004). Treatment with selective beta1-blockers eliminated the impact of the D allele (p= 0.51) in a manner similar to nonselective beta1,2-blockers (p= 0.80). Treatment with beta1-blockers was sufficient to eliminate the adverse impact of the ACE D allele, suggesting this pharmacogenetic interaction is mediated through the beta1-receptor.

Neurohormonal inhibition in heart failure: insights from recent clinical trials

Heart failure (HF) is a clinical syndrome characterized by chronic, persistent activation of the neuroendocrine system, which has been assumed to be linked to disease progression and adverse outcomes. Clinical trials have shown that adrenergic modulators, such as angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, aldosterone blockers, and beta-blockers, improve long-term outcomes in patients with HF. These findings have led to the hypothesis that inhibition of a single neurohormonal or cytokine pathway may continue to provide incremental benefits. However, the results of recent clinical trials, using centrally acting agents--endopeptidase inhibitors or endothelin and cytokine antagonists--suggest that selective inhibition of neurohormonal systems may not be advantageous and actually may have serious adverse effects. The reasons for this lack of benefit may be ascribed to the fact that long-term mortality benefits in patients with chronic HF are primarily the result of treatment of the diseases that have caused HF in the first place rather than treatment of neurohormonal abnormalities.

Alterations in adrenergic receptor signaling in heart failure

In the failing heart, several changes occur in cardiac adrenergic receptor-signal transduction pathways. The most striking of these changes occur in beta-ARs, and of the changes in beta-adrenergic receptors, beta1-receptor down-regulation is the most prominent. Other changes include uncoupling of beta2-adrenergic receptors and increased activity of the inhibitory G-protein, Gi. Most of these changes appear to be related to increased activity of the adrenergic nervous system, i.e. increased exposure to norepinephrine. Antagonists of the adrenergic nervous system improve left ventricular function and outcome in patients with heart failure. This fact supports the notion that activation of these neurohormonal systems exerts a net long-term detrimental effect on the natural history of chronic heart failure and that myocardial adrenergic desensitization phenomena are at least partially adaptive in the setting of left ventricular dysfunction.

Mechanisms of neurohormonal activation in chronic congestive heart failure: pathophysiology and therapeutic implications

Patients with chronic congestive heart failure have a sequential and incessant activation of those neurohormonal systems, which control body fluids, cardiac output and systemic blood pressure. Neurohormonal activation is initially selective and regional. Generalized activation is a late event in the natural history of congestive heart failure. Although the ultimate stimulus responsible for the activation of these neurohormonal systems is unknown, a decreased cardiac output and diminished effective blood volume have been proposed as the responsible mechanisms. However, extensive clinical and experimental research suggest that cardiac remodeling and loading of low-pressure cardiac receptors with sympathetic afferents could be the triggering events followed by unloading of high-pressure carotid receptors by decreased cardiac output and diminished effective blood volume.

Angiotensin II and norepinephrine release: interaction and effects on the heart

BACKGROUND

Angiotensin (Ang) II may enhance the influence of the sympathetic nervous system at various levels by facilitating norepinephrine (NE) release. We investigated whether such an interaction is evident in the human heart and whether it has an impact on left ventricular (LV) structure.

METHODS AND RESULTS

Ang I and Ang II concentrations were determined in arterial and coronary sinus (CS) plasma samples in a group of normotensive (n = 10) and hypertensive (n = 18) subjects. Total systemic and cardiac NE spillover was measured using isotope dilution methodology and LV structure by echocardiography. Arterial and CS concentrations of Ang I and Ang II were similar in both groups (Ang II CS, 5.8 +/- 4.0 versus 3.7 +/- 3.1 fmol/ml; P = not significant), as was the Ang II/Ang I ratio (CS, 0.56 +/- 0.17 versus 0.54 +/- 0.22 fmol/fmol; P = not significant). Total systemic (223 +/- 145 versus 374 +/- 149 ng/min; P < 0.05) and cardiac NE spillover (11.7 +/- 6.3 versus 19.4 +/- 10.5 ng/min; P < 0.05) were increased in hypertensive patients, as was LV mass index (LVMI) (86.7 +/- 14.7 versus 117.2 +/- 19.4 g/m; P < 0.001). LVMI correlated with cardiac NE spillover (r = 0.47; P < 0.02). No correlation was evident between CS Ang II and cardiac NE spillover (r = 0.001; P = not significant) or LVMI (r = -0.20; P = not significant). Arterial Ang II tended to correlate with total systemic NE spillover (r = 0.34; P = 0.081). When hypertensive subjects were divided into two groups with either high or low CS Ang II concentration, cardiac NE spillover and LVMI did not differ between the two groups.

CONCLUSION

These findings suggest a growth-promoting effect of increased cardiac sympathetic tone on cardiomyocytes in hypertensive patients, but do not support the notion of a significant role of Ang II for norepinephrine release and LV hypertrophy in the hypertensive human heart.

The revised role of ACE-inhibition after myocardial infarction in the thrombolytic/primary PCI era

Many studies have investigated the process of left ventricular (LV) dilatation and the effects of angiotensin-converting enzyme (ACE) inhibitors after myocardial infarction (MI). It has been generally accepted that progression of LV dilatation is a major predictor of heart failure and death after MI. Also, attenuation of LV dilatation is thought to be one of the main mechanisms by which ACE inhibitors (ACE-Is) produce their beneficial effects. However, evidence for this hypothesis came from studies that were performed before thrombolytic therapy and primary percutaneous coronary intervention (PCI) were routinely used after acute MI. Nowadays, reperfusion is obtained much more frequently and LV dilatation after MI has become less prevalent. Nevertheless, ACE-Is proved effective in reducing cardiac morbidity and mortality. Therefore, mechanisms other than attenuation of LV dilatation, such as anti-atherosclerotic effects or plaque stabilisation, may explain the long-term beneficial effects of ACE-Is after MI. In the present overview, we evaluate the role of LV dilatation and the effects of ACE-Is after MI in the thrombolytic/primary PCI era and provide recommendations on ACE-I use in clinical practice.

Myocardial beta-adrenoceptor downregulation in idiopathic dilated cardiomyopathy measured in vivo with PET using the new radioligand (S)-[11C]CGP12388

PURPOSE

The beta-adrenoceptor (beta-AR) plays an important role in heart failure. Recently, the new tracer (S)-[11C]CGP12388 has been developed. It displays excellent properties for investigation of the cardiac beta-ARs in vivo with positron emission tomography (PET). Furthermore, the simple production method allows its use in a routine clinical setting. The aim of this study was to investigate whether decreased myocardial beta-AR density in patients with idiopathic dilated cardiomyopathy (IDC) can be estimated using (S)-[11C]CGP12388 PET.

METHODS

Myocardial beta-AR density was investigated in six patients with IDC and six age-matched healthy controls, using (S)-[11C]CGP12388 PET.

RESULTS

Beta-AR densities of 5.4+/-1.3 pmol/g (mean +/- SD) were observed in patients; these values were significantly lower than those observed in healthy controls (8.4+/-1.5 pmol/g, p<0.005).

CONCLUSION

This study indicates that PET with (S)-[11C]CGP12388 is applicable for the measurement of myocardial beta-AR density in patients. A highly significant reduction in beta-AR density was found in patients with IDC compared with healthy controls.

Cardiac neurotransmission SPECT imaging

The sympathetic nervous system has great influence on cardiovascular physiology. Cardiac neurotransmission single photon emission computed tomography (SPECT) imaging allows in vivo noninvasive assessment of presynaptic reuptake and storage of neurotransmitters, which offers characterization of the cardiac neuronal function in different diseases of the heart and other altered metabolic or functional conditions. Therefore assessment of the integrity of cardiac sympathetic innervation may help in the diagnosis of these disorders, as well as in prognostication, and will result in better therapy and outcome. At present, the most widely available SPECT tracer by which to assess cardiac neurotransmission is metaiodobenzylguanidine labeled with iodine 123. This article focuses on reviewing the characteristics of cardiac SPECT imaging with I-123 metaiodobenzylguanidine and its role in the assessment of pathophysiologic changes during relevant clinical conditions.

Beta-adrenergic receptor blockade and the angiotensin-converting enzyme deletion polymorphism in patients with chronic heart failure

BACKGROUND

Beta-adrenergic receptor blockade is an established treatment of chronic heart failure (HF). Previous studies have suggested a potential pharmacogenetic interaction between beta-blocker therapy and the angiotensin-converting enzyme (ACE) I/D polymorphism in patients with HF.

AIMS

We designed this study to analyze changes in myocardial function of HF patients in response to beta-blocker therapy as a function of the ACE I/D polymorphism.

METHODS AND RESULTS

We studied 199 consecutive patients with chronic HF not treated with beta-blockers. Before initiation of beta-blockers and 3 months after the maximal tolerated dose was reached, patients underwent echocardiography, radionuclide angiography, and a cardiopulmonary exercise test. We extracted genomic DNA from white blood cells and determined the ACE I/D polymorphism. Thirty-five (18%) patients had the II genotype, 86 (43%) the ID genotype and 78 (39%) the DD genotype. A significant and similar improvement in left ventricular ejection fraction (LVEF) was observed in II (from 0.30+/-0.10 to 0.41+/-0.13; P<0.0001), ID (from 0.29+/-0.11 to 0.39+/-0.13; P<0.0001) and DD patients (from 0.31+/-0.11 to 0.40+/-0.13; P<0.0001). Peak Vo(2) before and after beta-blockade was similar among the three groups. The proportion of responders to beta-blockers (patients without cardiac events during titration who had an increase in LVEF >5% after beta-blockers) was similar among the three groups (II: 65.9%%, ID: 60.6%%, DD: 65.9%; P=NS). During a median follow-up of 933 days, there was no evidence for any effect of ACE I/D polymorphism on cardiac survival.

CONCLUSIONS

We observed no evidence of pharmacogenetic interaction between the ACE I/D polymorphism and the effects of beta-blockade on LVEF and other prognostic parameters in patients with chronic HF. Our results support the initiation of beta-blockers in HF patients with the II or the ID genotype as well as in those with the DD genotype.

Twice-daily administration of a long-acting angiotensin-converting enzyme inhibitor has greater effects on neurohumoral factors than a once-daily regimen in patients with chronic congestive heart failure

Although many clinical trials have evaluated the use of long-acting angiotensin-converting enzyme (ACE) inhibitors in patients with chronic congestive heart failure (CHF), there are no data regarding whether a once-daily or twice-daily regimen is preferable with respect to effects on the neuroendocrine system. To address this issue, the authors evaluated the comparative effects of the administration schedule on neurohumoral factors and autonomic nervous activity in patients with CHF. Thirty-two patients with mild compensated CHF received lisinopril (5-20 mg/d) orally either once a day (n = 17) or twice a day (n = 15) for more than 3 months. After this initial therapy, patients receiving a once-daily regimen switched to a twice-daily regimen and vice-versa, and patients were followed for an additional 3 months. Neurohumoral factors and the coefficient of variance in the electrocardiographic R-R interval (CVRR) were measured. Hemodynamic parameters, renal function, plasma concentrations of brain natriuretic peptide and aldosterone, and CVRR did not differ between the two regimens. However, the plasma concentration of norepinephrine was significantly lower, and plasma renin activity tended to be lower with the twice-daily regimen. These findings suggest that twice-daily administration of long-acting ACE inhibitors may have better effects on the neuroendocrine system than a once-daily regimen in patients with mild CHF.

Adverse effects of ACE inhibitors in patients with chronic heart failure and/or ventricular dysfunction : meta-analysis of randomised clinical trials

BACKGROUND

The evidence-based benefit/risk evaluation of therapeutic interventions in randomised clinical trials should include both the assessment of the benefits and of the adverse outcomes. There is ample evidence that ACE inhibitors improve the symptoms and prognosis of chronic heart failure (CHF) and ventricular dysfunction. However, there is little systematic information on the tolerability and adverse effects associated with their use in these conditions.

OBJECTIVE

To estimate the adverse events related to ACE inhibitor use in the treatment of CHF and ventricular dysfunction.

DESIGN AND METHODS

Description of adverse events in reports of randomised clinical trials of ACE inhibitors in CHF or ventricular dysfunction was examined, and a meta-analysis was performed. Trials were included if they were placebo- or standard treatment-controlled, and if the treatment duration was at least 8 weeks. Relative risks and their 95% CIs were estimated with a random effects model.

RESULTS

Only 22 (43%) of 51 original reports contained information on the number of withdrawals and their causes. Missing information from the remaining 29 trials was obtained from the authors. The weighted mean duration of treatment was 100.2 weeks. After excluding administrative reasons, heart failure, myocardial infarction and hypertension, the withdrawal rates attributed to adverse events were 13.8% and 9.4% for the ACE inhibitor and control groups, respectively (RR = 1.54 [95% CI 1.30-1.83]; weighted difference = 3.1 per 100 treated patients [95% CI 1.8-4.4]). Cough, hypotension, renal dysfunction, dizziness, hyperkalaemia, and impotence were all significantly more prevalent among patients treated with ACE inhibitors than among those in the control groups.

CONCLUSIONS

Among patients with CHF or ventricular dysfunction enrolled in randomised clinical trials, treatment with an ACE inhibitor for an average of 2 years leads to an additional 3% of treatment withdrawals. In a significant proportion of the reports on these randomised clinical trials, information on adverse events leading to treatment withdrawal was inadequate. Proper evidence-based evaluation of the benefit/risk of therapeutic interventions needs a more systematic approach to reporting of adverse events experiences recorded in clinical trials.

Altered Effects of Angiotensin II Type 1 and Type 2 Receptor Blockers on Cardiac Norepinephrine Release and Inotropic Responses During Cardiac Sympathetic Nerve Stimulation in Aorto-Caval Shunt Rats

BACKGROUND

Inhibition of the sympathetic nervous and renin - angiotensin systems has become an important strategy in the treatment of chronic heart failure. However, direct evidence of how inhibition of the renin - angiotensin system alters sympathetic activity in a diseased heart is lacking.

METHODS AND RESULTS

Four weeks after abdominal aorto-caval (AV) shunting or sham operation in rats, the hearts were retrogradely perfused in vivo and the left ventricles contracted isovolumetrically at 300 beats/min. Sympathetic nerve stimulation (SNS) was performed in the baseline state and repeated with an infusion of the angiotensin II (A-II) type 1 receptor (AT(1)-R) blocker, losartan, the A-II type 2 receptor (AT(2)-R) blocker, PD123319, or A-II. Norepinephrine (NE) overflow and left ventricular (LV) inotropic responses during baseline SNS were lower in the AV shunt rats. Losartan did not change the NE overflow or the LV inotropic responses to SNS in the sham rats, but did increase them in the AV shunt rats. PD123319 changed neither parameter in the sham rats, but decreased both in the AV shunt rats. A-II enhanced the NE overflow but attenuated the LV inotropic responses to SNS in the sham rats, but attenuated both in the AV shunt rats.

CONCLUSIONS

The effects of A-II via the AT(1)-R and AT(2)-R on the adrenergic drive in the heart were altered significantly in volume overload hypertrophy induced by AV shunting.

Pharmacologic therapy for patients with chronic heart failure and reduced systolic function: review of trials and practical considerations

Heart failure (HF) is a complex clinical syndrome resulting from any structural or functional cardiac disorder impairing the ability of the ventricles to fill with or eject blood. The approach to pharmacologic treatment has become a combined preventive and symptomatic management strategy. Ideally, treatment should be initiated in patients at risk, preventing disease progression. In patients who have progressed to symptomatic left ventricular dysfunction, certain therapies have been demonstrated to improve survival, decrease hospitalizations, and reduce symptoms. The mainstay therapies are angiotensin-converting enzyme (ACE) inhibitors and beta-blockers (bisoprolol, carvedilol, and metoprolol XL/CR), with diuretics to control fluid balance. In patients who cannot tolerate ACE inhibitors because of angioedema or severe cough, valsartan can be substituted. Valsartan should not be added in patients already taking an ACE inhibitor and a beta-blocker. Spironolactone is recommended in patients who have New York Heart Association (NYHA) class III to IV symptoms despite maximal therapies with ACE inhibitors, beta-blockers, diuretics, and digoxin. Low-dose digoxin, yielding a serum concentration <1 ng/mL can be added to improve symptoms and, possibly, mortality. The combination of hydralazine and isosorbide dinitrate might be useful in patients (especially in African Americans) who cannot tolerate ACE inhibitors or valsartan because of hypotension or renal dysfunction. Calcium antagonists, with the exception of amlodipine, oral or intravenous inotropes, and vasodilators, should be avoided in HF with reduced systolic function. Amiodarone should be used only if patients have a history of sudden death, or a history of ventricular fibrillation or sustained ventricular tachycardia, and should be used in conjunction with an implantable defibrillator [corrected]. Finally, anticoagulation is recommended only in patients who have concomitant atrial fibrillation or a previous history of cerebral or systemic emboli.

Effects of the AT1-receptor antagonist eprosartan on the progression of left ventricular dysfunction in dogs with heart failure

1. We examined the effects of eprosartan, an AT(1) receptor antagonist, on the progression of left ventricular (LV) dysfunction and remodelling in dogs with heart failure (HF) produced by intracoronary microembolizations (LV ejection fraction, EF 30 to 40%). 2. Dogs were randomized to 3 months of oral therapy with low-dose eprosartan (600 mg once daily, n=8), high-dose eprosartan (1200 mg once daily, n=8), or placebo (n=8). 3. In the placebo group, LV end-diastolic (EDV) and end-systolic (ESV) volumes increased after 3 months (68+/-7 vs 82+/-9 ml, P<0.004, 43+/-1 vs 58+/-7 ml, P<0.003, respectively), and EF decreased (37+/-1 vs 29+/-1%, P<0.001). In dogs treated with low-dose eprosartan, EF, EDV, and ESV remained unchanged over the course of therapy, whereas in dogs treated with high-dose eprosartan, EF increased (38+/-1 vs 42+/-1%, P<0.004) and ESV decreased (41+/-1 vs 37+/-1 ml, P<0.006), Eprosartan also decreased interstitial fibrosis and cardiomyocyte hypertrophy. 4. We conclude that eprosartan prevents progressive LV dysfunction and attenuates progressive LV remodelling in dogs with moderate HF and may be useful in treating patients with chronic HF.

Effects of angiotensin-converting enzyme inhibition and angiotensin II type 1 receptor blockade on beta-adrenoceptor signaling in heart failure produced by myocardial Infarction in rabbits: reversal of altered expression of beta-adrenoceptor kinase and G i alpha

Both angiotensin-converting enzyme (ACE) inhibitors and angiotensin II type 1 (AT1) receptor blockers have been demonstrated to improve symptoms and prognosis in heart failure (HF). We compared the effects of ACE inhibition and AT1 receptor blockade on myocardial beta-adrenoceptor desensitization in rabbits with HF established 3 weeks after myocardial infarction (MI) with left circumflex coronary artery ligation. Rabbits with MI were randomized to no treatment, the ACE inhibitor temocapril (0.5 mg/kg/day) or AT1 receptor blocker valsartan (3 mg/kg/day). Echocardiographic examinations showed that, relative to rabbits with untreated MI, rabbits receiving temocapril or valsartan had a limitation of cardiac remodeling and prevention of the development of systolic dysfunction. Circulating plasma norepinephrine levels that were markedly elevated in MI animals were strongly inhibited by temocapril or valsartan therapy. beta-Adrenoceptor density, beta-adrenoceptor proportion showing high-affinity agonist binding, and basal and isoproterenol-stimulated adenylate cyclase activities were significantly reduced in MI rabbits. These defects were similarly reversed by temocapril or valsartan. Importantly, as found in human HF, myocardial protein levels of beta-adrenoceptor kinase 1 and G(i alpha) were significantly elevated in MI rabbits, suggesting that these molecules are contributing to the defects in myocardial beta-adrenoceptor signaling. The expression levels of these molecules were normalized equally by both treatments. The results suggest that pharmacologically different interventions in the renin-angiotensin system can equivalently improve the derangements in the beta-adrenoceptor signaling system in the failing heart. This may be important for the beneficial effects of these agents in HF.

Effects of the angiotensin-converting enzyme inhibitor enalapril on sympathetic neuronal function and beta-adrenergic desensitization in heart failure after myocardial infarction in rats

One of the beneficial effects of angiotensin-converting enzyme (ACE) inhibitors in the treatment of heart failure may derive from sympathoinhibition and the prevention of beta-adrenergic desensitization. However, the roles of these properties in the overall effects of ACE inhibitor are not clear. We studied the effects of chronic enalapril treatment (20 mg/L in drinking water for 12 weeks) on left ventricular (LV) function, cardiac norepinephrine (NE), sympathetic neuronal function assessed by 131I-metaiodobenzylguanidine (MIBG), beta-receptors, and isometric contraction of papillary muscle in rats with myocardial infarction (MI) induced by coronary artery ligation. Decreased LV function in the MI rats was associated with reduced cardiac NE content and MIBG uptake, and severely blunted responses of non-infarcted papillary muscle to isoproterenol, forskolin, and calcium. Enalapril attenuated LV remodeling in association with a reduction of the ventricular loading condition and restored baseline developed tension of non-infarcted papillary muscle to the level of sham-operated rats. However, enalapril did not improve cardiac NE content, MIBG uptake, or inotropic responsiveness to beta-agonists. These results suggest that the major effect of the ACE inhibitor enalapril in the treatment of heart failure is not due to sympathoinhibition or restoration of beta-adrenergic pathway in this model of heart failure.

Receptor crosstalk. Implications for cardiovascular function, disease and therapy

There are at least three well-defined signalling cascades engaged directly in the physiological regulation of cardiac circulatory function: the beta1-adrenoceptors that control the cardiac contractile apparatus, the renin-angiotensin-aldosterone system involved in regulating blood pressure and the natriuretic peptides contributing at least to the factors determining circulating volume. Apart from these pathways, other cardiac receptor systems, particularly the alpha1-adrenoceptors, adenosine, endothelin and opioid receptors, whose physiological role may not be immediately evident, are also important with respect to regulating cardiovascular function especially in disease. These and the majority of other cardiovascular receptors identified to date belong to the guanine nucleotide binding (G) protein-coupled receptor families that mediate signalling by coupling primarily to three G proteins, the stimulatory (Gs), inhibitory (Gi) and Gq/11 proteins to stimulate the adenylate cyclases and phospholipases, activating a small but diverse subset of effectors and ion channels. These receptor pathways are engaged in crosstalk utilizing second messengers and protein kinases as checkpoints and hubs for diverting, converging, sieving and directing the G protein-mediated messages resulting in different signalling products. Besides, the heart itself is endowed with the means to harmonize these signalling mechanisms and to fend off potentially fatal consequences of functional loss of the essential signalling pathways via compensatory reserve pathways, or by inducing some adaptive mechanisms to be turned on, if and when required. This receptor crosstalk constitutes the underlying basis for sustaining a coherently functional circulatory entity comprising mechanisms controlling the contractile apparatus, blood pressure and circulating volume, both in normal physiology and in disease.

Changes in vasoconstrictive hormones, natriuretic peptides, and left ventricular remodeling soon after anterior myocardial infarction

OBJECTIVE

Our purpose was to study the changes in vasoconstrictive neurohormones, N-terminal proatrial natriuretic peptide (Nt-proANP), and brain natriuretic peptide (BNP) and their relationship with left ventricular (LV) remodeling soon after anterior myocardial infarction (MI).

BACKGROUND

The Healing and Afterload Reducing Therapy (HEART) trial has shown that early use of ramipril improves left ventricular ejection fraction (LVEF) and attenuates LV remodeling when initiated soon after MI. This neurohumoral substudy of HEART investigates the changes in vasoconstrictive and natriuretic peptides and their relationship with LV remodeling.

METHODS

One hundred twenty-two patients had blood drawn for the measurement of catecholamines, endothelin-I, angiotensin II, Nt-proANP and BNP, and prostacyclins within 24 hours of an MI, and at 3, 14, and 90 days after the MI. Quantitative echocardiograms were performed at baseline and at 14 days.

RESULTS

All neurohormones except angiotensin II (P =.12) and prostaglandins were significantly elevated at baseline. Vasoconstrictive neurohormones decreased significantly over time but remained elevated at 14 days. Both Nt-proANP and BNP were elevated within the first 14 days. BNP decreased significantly by 90 days, whereas Nt-proANP exhibited no change between 14 and 90 days. Ramipril decreased plasma levels of angiotensin II at 3 days but had no effect on the other neurohormones.

CONCLUSIONS

Neurohumoral activation occurs and persists in patients with anterior MI and overall preserved LV function. Ramipril had only a modest impact on neurohormones despite its significant benefits on LV remodeling soon after MI.

Canine idiopathic dilated cardiomyopathy. Part II: pathophysiology and therapy

Dilated cardiomyopathy (DCM) in dogs is characterized by ventricular and atrial enlargement, and systolic and diastolic dysfunction, with congestive heart failure (CHF) often developing at some stage. With greater understanding of the impact of neuroendocrine stimulation in heart disease, the understanding of the pathophysiology for CHF has changed considerably. It is no longer considered only to be a simple haemodynamic consequence of pump dysfunction, but is now characterized as a complex clinical syndrome with release of many neurohormones, which are believed to have impact on the progression of disease. This change in our understanding of the pathophysiology of CHF has important therapeutic implications. There are strong indications, although not yet proven, that drugs designed to influence the neuroendocrine activity, such as Angiotensin Converting Enzyme (ACE) inhibitors and beta-receptors antagonists, are efficacious as adjunct therapy of heart failure attributable to DCM in dogs. The benefits of drugs designed to influence the myocardial contractile state (positive inotropes) have not been fully evaluated. However, evidence has emerged in recent years indicating that new types of positive inotropes may be beneficial in dogs with DCM. This review focuses on the neuroendocrine aspects of DCM and their possible therapeutic implications and the place for long-term inotropic support in dogs with DCM.

Heterogeneous cardiac sympathetic innervation in heart failure after myocardial infarction of rats

We examined cardiac neuronal function and beta-receptor with a dual-tracer method of [(131)I]meta-iodobenzylguanidine (MIBG) and [(125)I]iodocyanopindolol (ICYP) in rat heart failure after myocardial infarction (MI). In rats with MI, left ventricular (LV) systolic function decreased, and LV dimension and right ventricular (RV) mass increased gradually. MIBG accumulations of the noninfarcted LV (remote region) and RV decreased by 15% at 1 wk compared with sham-operated rats, and these accumulations were restored by 71% and 56%, respectively, at 24 wk compared with age-matched sham rats despite sustained depletion of myocardial norepinephrine contents in these regions. ICYP accumulation of the remote region and of the RV did not decrease at any stages. Myocardial MIBG distribution was heterogeneous at 1 wk when it was lower in the peri-infarcted region than in the remote region, associated with reduced ICYP accumulation in the peri-infarcted region. The heterogeneous distribution of both isotopes disappeared at 12 wk. Thus cardiac sympathetic neuronal alteration was coupled with downregulation of beta-receptors in rat heart failure after MI. The abnormal adrenergic signaling occurred heterogeneously in terms of ventricular distribution and time course after MI.

Cardiac afferents and neurohormonal activation in congestive heart failure

Cardiac chambers have afferent connections to the brainstem and to the spinal cord. Vagal afferents mediate depressor responses and become activated by volume expansion, increased myocardial contractility and atrial natriuretic factor. Sympathetic afferents, on the contrary, are activated by metabolic mediators, myocardial ischemia and cardiac enlargement. These opposite behaviors may lead to activation or suppression of the sympathetic nervous system and of the renin-angiotensin-aldosterone system. As cardiac diseases progress, the heart dilates, plasma norepinephrine increases, atrial natriuretic factor is released and the renin-angiotensin-aldosterone system is suppressed to maintain water and sodium excretion. This dissociation of the neurohormonal profile of cardiac patients, may be explained by coactivation of sympathetic afferents, by cardiac dilatation, and of vagal afferents by atrial natriuretic factor. In more advanced stages, atrial natriuretic factor suppression of the renin-angiotensin-aldosterone system is overridden by overt sympathetic activation and sodium and water retention ensues. Digitalis, angiotensin-converting enzyme inhibitors and beta-blockers selectively decrease cardiac adrenergic drive. A common mechanism of action, to all three groups of drugs, would be attenuation of sympathetic afferents and partial normalization of vagal afferents. Consequently, heart size and cardiac afferents emerge as the key factors to understand the pathophysiology and treatment of the syndrome of congestive heart failure.

Bradykinin regulates captopril-induced upregulation of beta-adrenergic receptor in cultured neonatal rat cardiomyocytes

The aim of this study was to elucidate the role of bradykinin in mediating captopril-induced upregulation of beta-adrenergic receptor (beta-AR). The density of beta-AR on the surface of cardiac myocytes was measured by binding assay using [(3)H]CGP-12177. Treatment of cultured neonatal rat cardiomyocytes with captopril resulted in a time-dependent elevation of bradykinin concentration in the culture medium. The increased bradykinin concentration was significant at 2, 3 and 6 h, but not at 12 h after exposure to captopril. This time-dependent effect of captopril on enhancement of bradykinin levels paralleled that of beta-AR upregulation. Exogenously applied bradykinin increased beta-AR density by 22, 30 and 35% at 0.01, 0.1 and 1 microm concentrations, respectively. Myocytes treated with 1 microm bradykinin responded to isoproterenol (ISP) in a dose-dependent manner, as demonstrated by acceleration of spontaneous beating frequency. These beating acceleration effects of bradykinin were abolished by Hoe 140. Stimulation of bradykinin B2 receptor by exogenously added bradykinin for 6 h was sufficient to produce beta-AR up-regulation to a level similar to that seen after 24 h. Our results indicate that bradykinin potentiation by ACE inhibitors regulates, at least in part, captopril-induced beta-AR up-regulation.

ACE inhibition improves cardiac NE uptake and attenuates sympathetic nerve terminal abnormalities in heart failure

Cardiac sympathetic nerve terminal dysfunction plays an important role in the downregulation of myocardial beta-adrenoceptors in heart failure. To determine whether chronic angiotensin-converting enzyme (ACE) inhibition improved cardiac sympathetic nerve terminal function and hence increased myocardial beta-adrenergic responsiveness, we administered ACE inhibitors to dogs with chronic right-sided heart failure (RHF) produced by tricuspid avulsion and pulmonary artery constriction. The RHF animals exhibited fluid retention, elevated right heart filling pressures, blunted inotropic response to isoproterenol, and reduced beta-adrenoceptor density. These changes were accompanied by decreases in right ventricular norepinephrine (NE) uptake and neuronal NE histofluorescence and tyrosine hydroxylase immunoreactive profiles. ACE inhibitors had no effect on the production of heart failure but greatly reduced the attenuation of cardiac NE uptake, neuronal NE histofluorescence, and tyrosine hydroxylase immunoreactive profiles. ACE inhibition also improved the inotropic response to isoproterenol and restored myocardial beta-adrenoceptor density. The changes probably are caused by reduction of cardiac NE release by ACE inhibition and may contribute to the beneficial effects of ACE inhibitor therapy in patients with chronic heart failure.

Angiotensin II and sympathoactivation in heart failure

Excessive activity of the sympathetic nervous system (SNS) contributes to the development and progression of the syndrome of congestive heart failure (CHF) in patients with decreased left ventricular function. The factors underlying chronic sympathoactivation are poorly understood, particularly in stable patients. This review summarizes both clinical and experimental data regarding the effects of angiotensin II (A-II) on the activity of the SNS. The focus is on both the direct effects of A-II on the SNS and an indirect effect medicated through alteration in function of the baroreflex. Available evidence is consistent with a potentially important effect of A-II on SNS activity, perhaps most likely via the baroreflex. Important issues regarding the direct effect of A-II on regional SNS activity, and on the physiological relevance of effects seen only at high plasma concentration of A-II remain to be fully elucidated.

Angiotensin II enhances the expression of Gialpha in A10 cells (smooth muscle): relationship with adenylyl cyclase activity

In the present studies, we have investigated the effect of angiotensin II (AII) on guanine nucleotide regulatory protein (G protein) expression and functions in A10 smooth muscle cells. AII treatment of A10 cells enhanced the levels of inhibitory guanine nucleotide regulatory protein (Gi) as well as Gi mRNA and not of stimulatory guanine nucleotide regulatory protein (Gs) in a concentration-dependent manner as determined by immunoblot and Northern blot analysis, respectively. AII-evoked increased expression of Gialpha-2 and Gialpha-3 was inhibited by actinomycin D treatment (RNA synthesis inhibitor). The increased expression of Gialpha-2 and Gialpha-3 by AII was not reflected in functions, because the GTPgammaS-mediated inhibition of forskolin-stimulated adenylyl cyclase and the receptor-mediated inhibition of adenylyl cyclase by AII and C-ANP4-23 [des(Gln18, Ser19, Gln20, Leu21, Gly22) ANP4-23-NH2] were not augmented but attenuated in AII-treated A10 cells. The attenuation was prevented by staurosporine (a protein kinase C inhibitor) treatment. On the other hand, AII treatment did not affect the expression and functions of stimulatory guanine nucleotide regulatory protein (Gs), however, the stimulatory effects of 5'-O-(3-thiotriphosphate), isoproterenol, and N-ethylcarboxamide adenosine (NECA) on adenylyl cyclase activity were inhibited to various degrees by AII treatment. Staurosporine reversed the AII-evoked attenuation of isoproterenol- and NECA-stimulated enzyme activity. From these results, it can be suggested that AII, whose levels are increased in hypertension, may be one of the possible contributing factors responsible for exhibiting an enhanced expression of Gi protein in hypertension.

Regulation of regional norepinephrine spillover in heart failure: the effect of angiotensin II and beta-adrenergic agonists in the forearm circulation

BACKGROUND

Prejunctional receptors for angiotensin II (A-II) and norepinephrine (NE) have been reported to facilitate NE release. If operative in patients with congestive heart failure (CHF), such receptors could participate in positive feedback cycles amplifying sympathoactivation.

METHODS AND RESULTS

A-II and isoproterenol (ISO) would increase regional NE spillover via facilitation of presynaptic release of NE in the forearm circulation of patients with chronic stable CHF. A-II, ISO, and nitroprusside (NP) were sequentially infused into the brachial arteries of 10 patients with chronic stable CHF, which was attributed to dilated cardiomyopathy. Forearm blood flow (FBF) was measured via plethysmography and regional spillover of NE was measured by using the isotope dilution method of Esler. A-II (5 ng/min) produced a nonsignificant decline in FBF (1.87+/-0.14 to 1.46+/-0.1 mL/100 g/min, P = .07) and did not change regional NE spillover (418+/-128 to 409+/-121 ng/min). ISO increased FBF from 1.6+/-0.12 to 4.3+/-0.7 mg/100 g/min (P < .001). Regional NE spillover increased from 337+/-86 to 856+/-300 ng/min (P < .001). Venous NE and regional extraction of NE did not change. NP increased FBF from 2.0+/-0.3 to 6.3+/-1.2 mL/100 g/min (P < .001; P = NS v change with ISO) and also increased regional NE spillover (301+/-99 to 712+/-288 ng/min, P < .001; P = NS v change with ISO). As with ISO, venous NE and extraction of NE were not altered.

CONCLUSIONS

Mild vasoconstrictor infusions of A-II do not increase regional NE spillover in the forearm circulation of patients with CHF. The beta-adrenergic agonist ISO does increase regional spillover, but the effect seems to be primarily related to flow rather than presynaptic stimulation of NE release. These data argue against an important positive feedback loop involving A-II and NE on sympathoactivation, at least with the dosages of the agonists studied and in the limb circulation in chronic stable CHF.

Evidence of phenotypic alteration as a cause of systolic dysfunction in the failing heart

This article describes the phenotype of dilated cardiomyopathy in humans and describes parallel studies in experimental models that support or refute the relevance of these changes to the development of the heart failure phenotype.

Medical therapy of chronic heart failure. Role of ACE inhibitors and beta-blockers

Heart failure has long been considered to have a progressive downhill course leading inexorably to an early demise. This course often occurs silently, in the absence of any obvious cardiac insults. The reason for this is a combination of cell loss, myocyte dysfunction, impaired energetics, and pathologic remodeling of the chamber. Improved clinical outcome should result from strategies that reduce the biologic signals responsible for myocyte growth, dysfunction, and loss and chamber remodeling. Clinicians should no longer attempt to treat chronic heart failure with pharmacologic growth and remodeling process. In time, it may be possible for the clinician to view the treatment of heart failure largely as a matter of improving the biologic function of the myocardium.

[The renin-angiotensin system in cardiovascular diseases]

BACKGROUND

The renin-angiotensin system is mainly involved in several cardiovascular diseases and in the pathophysiology of heart failure. It exists as a circulating and a local system which can be differently regulated. Interventions in this system by angiotensin-converting enzyme (ACE) antagonists or angiotensin-receptor antagonists slow the progression of heart failure and result in prolongation of life expectancy and improvement of hemodynamics.

MECHANISMS OF ACTION

The main underlying mechanisms are: 1. Heart failure results in activation of the renin-angiotensin system as a compensatory mechanism with elevation of circulating angiotensin II, norepinephrine and vasopressin. Antagonists of this compensatory mechanisms acutely result in improvement of the hemodynamic situation. 2. Elevated circulating and local renin-angiotensin systems cause chronic structural myocardial and vascular effects. Angiotensin-converting enzyme antagonists and angiotensin-receptor blockers modulate and partly antagonize these structural changes such as myocardial hypertrophy, myocardial fibrosis and vascular proliferative responses. Gene and receptor regulation of the system are currently not fully understood and are subject of intensive research. 3. The renin-angiotensin system is closely related to the bradykinin system and thus indirectly to nitric oxide and endothelial function. Bradykinin has multiple other effects on the hemostatic system as a well as on the myocardium and vascular system.

CONCLUSION

These complex interactions require further evaluation. Research with specific bradykinin antagonists will give new insights into this system.

The sympathetic nervous system in chronic heart failure

The sympathetic nervous system plays a pivotal role in the natural history of chronic heart failure (CHF). There is early activation of cardiac adrenergic drive, which is followed by an increasing magnitude of generalized sympathetic activation, with worsening heart failure. The adverse consequences predominate over the short-term compensatory effects and are mediated through downregulation of beta-receptor function and harmful biological effects on the cardiomyocyte. beta-blockers exert a beneficial effect on the natural history of CHF by attenuating the negative biological effects, restoring homogeneity of contractile/relaxant mechanisms, and reducing the risk of myocardial ischemia and arrhythmias. After pioneering work conducted over 20 years ago, numerous studies have shown the beneficial effects of beta-blockade on left ventricular function, and survival, morbidity, and mortality rates in CHF. Large-scale trials are underway to determine the overall benefits of beta-blockade in heart failure.

Differential effect of acute baroreceptor unloading on cardiac and systemic sympathetic tone in congestive heart failure

OBJECTIVES

The present study was designed to identify the hemodynamic factor or factors that reflexly contribute to activation of the cardiac sympathetic nerves in patients with severe congestive heart failure (CHF).

BACKGROUND

We and others have previously shown that activation of the sympathetic nervous system is a key feature of CHF in humans. Furthermore, the degree of sympathetic activation shows marked regional heterogeneity and is most pronounced in the heart. Recent studies have shown a significant positive relation between pulmonary artery pressure and the magnitude of cardiac sympathetic activation. Of particular importance, the degree of cardiac sympathoexcitation has also been shown to be strongly associated with mortality in CHF.

METHODS

We assessed total systemic and cardiac sympathetic activity (norepinephrine [NE] spillover method) in nine patients with severe CHF and significantly elevated pulmonary artery pressure (mean [+/-SEM] pulmonary artery pressure 46 +/- 3 mm Hg) at rest and during a titrated infusion of sodium nitroprusside (SNP).

RESULTS

SNP infusion significantly reduced mean arterial blood pressure, pulmonary artery pressure and pulmonary capillary wedge pressure. During SNP infusion, the total body NE spillover rate (NESR) increased (from 7.9 +/- 1.7 to 11.2 +/- 3.1 nmol/min, p < 0.01), whereas the cardiac NESR decreased (from 522 +/- 86 to 409 +/- 71 pmol/min, p < 0.05). The ratio of cardiac/total NE spillover was also substantially reduced (from 7.8 +/- 1.3 to 4.9 +/- 0.9%, p < 0.001).

CONCLUSIONS

There is a directionally opposite change in whole-body (increase) and cardiac (reduction) sympathetic nervous activity during SNP infusion, most likely due to unloading of arterial baroreceptors and specific cardiopulmonary baroreceptors, respectively, in severe CHF. These observations support the concept of a positive feedback relation between pulmonary artery pressure/filling pressure and cardiac sympathetic tone in CHF and serve to reinforce the importance of vasodilator therapy in this condition.

Mechanism of action of beta-blocking agents in heart failure

Antiadrenergic treatment is currently an emerging and very promising approach to the treatment of chronic heart failure. Although the adrenergic nervous system can be pharmacologically inhibited at multiple levels, it is the use of receptor-blocking agents that has generated the most interest and provided the most data for the "proof of concept" of this approach. In part because antiadrenergic treatment of chronic heart failure has developed in an atmosphere in which it was initially considered to be contraindicated (i.e., before Phase III clinical trials could be initiated), a large body of hypothesis-driven basic and clinical investigation was required to define the overall rationale and demonstrate feasibility. This article will review these data and propose a single primary mechanism of action to explain most of the clinical benefits of these agents.

Alterations in beta-adrenoceptor mechanisms in the aging heart. Relationship with heart failure

In chronic heart failure substantial and characteristic changes occur in the function of the adrenergic nervous system. Studies in isolated left ventricular muscle and in single cardiomyocytes from experimental models of aging and, recently, from humans show an age-related reduced contractile response to beta-adrenoceptor stimulation. "beta-adrenoceptor desensitization" is thought to be a general and common mechanism to explain the age- and heart failure-related decrease in beta-adrenoceptor response. The aim of this review is to compare alterations in beta-adrenoceptor mechanisms in physiological cardiovascular aging and chronic heart failure. From an analysis of the overall data on the role of aging in beta-adrenoceptor regulation in human and animal hearts, it is possible to conclude that the reduced response to beta-agonists is common to all species and all cardiac tissues. Moreover, the age-related changes are limited to beta-adrenoceptor-G-protein (s)-adenylyl cyclase system abnormalities, while the type and level of abnormalities change with species and tissues. The modifications shown in the aging heart are not very different from some observed in heart failure. In particular, both in aged and failing hearts we may see that the decrease in beta-adrenoceptor responsiveness is related to changes in G-protein function.

Acute and long-term effects of the angiotensin-converting enzyme inhibitor, enalapril, on adrenergic activity and sensitivity during exercise in patients with left ventricular systolic dysfunction

Patients with heart failure and left ventricular systolic dysfunction exhibit increased adrenergic activity but blunted adrenergic responsiveness. We studied patients enrolled in the Studies of Left Ventricular Dysfunction, examining exercise responses of heart rate (HR) and plasma norepinephrine (PNE). Eighty-seven patients were studied before randomization; 65 of these were examined 1 year after randomization to placebo or enalapril. Compared with prevention trial (asymptomatic) patients, patients in the treatment trial (symptomatic) had higher resting HR and PNE levels and less increase in HR with a greater increase in PNE with exercise. Acute administration of enalapril increased the resting HR in patients in the prevention trial only but had no significant effect on PNE. After 1 year of therapy, patients in the prevention trial exhibited no change. Within the treatment trial, the placebo group displayed both a higher peak PNE and increase in PNE with exercise than did the enalapril group, whose HR response was maintained in spite of a reduction of exercise PNE. We conclude that (1) compared with asymptomatic patients, symptomatic patients with reduced left ventricular ejection fraction manifest greater resting and exercise adrenergic activity, with blunted HR response; and (2) in symptomatic patients, 1 year of enalapril treatment effected an augmented HR response to adrenergic stimulation, supporting an interaction between the renin/angiotensin and adrenergic nervous systems. Normalization of adrenergic tone and response likely contributes to the benefits of long-term angiotensin-converting enzyme inhibitor therapy.

Angiotensin-converting enzyme inhibitor up-regulates cardiac beta-receptors in cultured neonatal rat myocytes

In patients with congestive heart failure (CHF), beta-receptor up-regulation is regarded as one of the mechanisms leading to improved function and prognosis. To clarify whether beta-receptor up-regulation is involved in the mechanisms underlying the beneficial effects of angiotensin-converting enzyme (ACE) inhibitors, we investigated the actions of ACE inhibitors and an angiotensin II type 1 receptor (AT1) antagonist on beta-receptors of neonatal rat cultured cardiac myocytes. Angiotensin II (A-II) increased the spontaneous beating frequency of the cells, and the effect was completely antagonized by the AT1 antagonist CV-11974. Under control conditions, beta-receptor density (Bmax) and affinity (Kd) were measured by radiobinding assay with the hydrophilic ligand [3H]CGP-12177, and were 103 +/- 11 fmol/mg protein and 3.4 +/- 0.4 nmol/L, respectively. Captopril increased the beta-receptor density of myocytes and augmented the response to isoproterenol. Bmax was increased by 34% after 24 h treatment with 10(-6) mol/L captopril. CV-3480, and ACE inhibitor that contains no sulfhydryl group, but neither A-II nor the AT1 antagonist, also up-regulated beta-receptors. The results suggest that beta-receptor up-regulation contributes at least partly to the beneficial cardiac effects of ACE inhibitors in patients with CHF. ACE inhibitors and AT1 antagonists seem to play different roles in clinical practice.

Lisinopril. A review of its pharmacology and clinical efficacy in elderly patients

Lisinopril, the lysine analogue of enalaprilat, is a long-acting angiotensin converting enzyme (ACE) inhibitor which is administered once daily by mouth. The efficacy of lisinopril in reducing blood pressure is well established in younger populations, and many trials now show it to be effective in lowering blood pressure in elderly patients with hypertension. In comparative and non-comparative clinical trials, 68.2 to 89.1% of elderly patients responded (diastolic pressure < or = 90 mm Hg) to > or = 8 weeks' lisinopril treatment. Age-related differences in antihypertensive efficacy do not appear to be clinically significant, and dosages effective in elderly patients tend to range from 2.5 to 40 mg/day. Dosages usually need to be lower in patients with significant renal impairment. In congestive heart failure, lisinopril 2.5 to 20 mg/day increases exercise duration, improves left ventricular ejection fraction and has no significant effect on ventricular ectopic beats. It is similar in efficacy to enalapril and digoxin and similar or superior to captopril on most end-points. Data from the GISSI-3 post-myocardial infarction trial show that lisinopril reduced mortality and left ventricular dysfunction when given for 42 days starting within 24 hours of the onset of infarction symptoms. Results at 6 weeks and 6 months were similar in elderly and younger patients. Elderly patients, however, among other subgroups, exhibited a strong reduction in risk of low ejection fraction after treatment (-25.5%). Economic studies suggest that lisinopril is cost saving compared with other ACE inhibitors in some markets. When given according to the GISSI-3 protocol, lisinopril appears to be one of the less expensive of the successful ACE inhibitor regimens for acute myocardial infarction. In other trials, patients with diabetic nephropathy and hypertension improved or did not deteriorate during lisinopril treatment. Blood pressure was controlled and reductions or trends towards reductions in albuminuria were observed. These reductions were similar to those in diltiazem, nifedipine and verapamil recipients, and greater than those in patients receiving atenolol. Lisinopril appears to reduce mortality in diabetic patients after myocardial infarction and may also improve neuropathy associated with diabetes. Lisinopril is well tolerated and the profile of adverse events seen is typical of ACE inhibitors as a class. There is a tendency for more elderly than younger patients to discontinue treatment, but this trend is not clearly related to the incidence of adverse events in these age groups. Drug interactions occur with few other agents and are usually clinically significant only between lisinopril and either diuretics or lithium. Lisinopril is, thus, an effective treatment for elderly patients with hypertension, congestive heart failure and acute myocardial infarction and has shown promising benefits in patients with diabetic nephropathy.

Hemodynamic predictors of early intolerance and long-term effects of propranolol in dilated cardiomyopathy

BACKGROUND

Fifty-six patients with dilated cardiomyopathy (DCM) (aged 14-68 years) and background therapy of angiotensin-converting enzyme inhibitors, diuretics, and digoxin were given an initial challenge of propranolol in gradually increasing doses. These patients were studied noninvasively and hemodynamically and subjected to right ventricle biopsy.

METHODS AND RESULTS

Forty-four patients tolerated propranolol and received the drug for 6 months; 12 patients deteriorated after starting the drug with worsening of congestive heart failure and/or hypotension. The patients who did not tolerate propranolol had higher left ventricular end-diastolic dimension (73 +/- 8 vs 66 +/- 8 mm, P < .05), and severe mitral regurgitation was more common. Hemodynamically these patients had higher heart rate, right ventricular end-diastolic pressure, mean pulmonary artery pressure, mean pulmonary artery wedge pressure, and left ventricular end-diastolic pressure (102 +/- 16 vs 89 +/- 12 beats/min, 15 +/- 7 vs 9 +/- 4, 39 +/- 16 vs 31 +/- 12, 28 +/- 8 vs 21 +/- 8, 28 +/- 8 vs 22 +/- 8 mmHg, respectively, P < .01). These patients had a significantly lower cardiac index (1.9 +/- 0.6 vs 2.5 +/- 0.6 L/min/m2, P < .01). Forty patients completed 6 months follow-up evaluation and were further subjected to repeat noninvasive and hemodynamic study. There was a significant improvement in New York Heart Association class, cardiothoracic ratio, and left ventricular end-diastolic dimension (68% vs 62%, 66 +/- 8 vs 62 +/- 7 mm, respectively, P < .01), while the ejection fraction (EF) rose from 23 to 35% (P < .001). Hemodynamically, there was a significant decrease in heart rate, right ventricular end-diastolic pressure, mean pulmonary artery pressure, mean pulmonary artery wedge pressure, and left ventricular end-diastolic pressure (91 +/- 14 vs 71 +/- 5 beats/min, 9 +/- 4 vs 5 +/- 3, 32 +/- 11 vs 22 +/- 7, 25 +/- 9 vs 17 +/- 8, 21 +/- 7 vs 14 +/- 4 mmHg, P < .05). The cardiac index rose from 2.3 +/- 0.6 to 3.2 +/- 0.7 L/min/m2 (P < .01).

CONCLUSIONS

Propranolol in dilated cardiomyopathy is associated with significant intolerance. Those who tolerate propranolol seem to have long-term beneficial effects. This study is limited as it is uncontrolled and nonrandomized.