Prospects for cardioreparation

Kidney Is Essential for Blood Pressure Modulation by Dietary Potassium

Eating more potassium may reduce blood pressure and the occurrence of other cardiovascular diseases by actions on various systems, including the vasculature, the sympathetic nervous system, systemic metabolism, and body fluid volume. Among these, the kidney plays a major role in the potassium-rich diet-mediated blood pressure reduction. PURPOSE OF REVIEW: To provide an overview of recent discoveries about the mechanisms by which a potassium-rich diet leads to natriuresis. RECENT FINDINGS: Although the distal convoluted tubule (DCT) is a short part of the nephron that reabsorbs salt, via the sodium-chloride cotransporter (NCC), it is highly sensitive to changes in plasma potassium concentration. Activation or inhibition of NCC raises or lowers blood pressure. Recent work suggests that extracellular potassium concentration is sensed by the DCT via intracellular chloride concentration which regulates WNK kinases in the DCT. High-potassium diet targets NCC in the DCT, resulting in natriuresis and fluid volume reduction, which are protective from hypertension and other cardiovascular problems.

Mechanisms of remodelling: a question of life (stem cell production) and death (myocyte apoptosis)

Remodeling myocytes show a typical switch between the embryonic and classical features of apoptosis and/or hypertrophy representing a signal of death (ie, apoptosis) and a signal of life (ie, hypertrophy). The adult myocyte, however, is a terminal cell; usually it is unable to reproduce and death is not genetically programmed (apoptosis), but occurs by necrosis. The reinstatement of apoptosis and development of hypertrophy during remodeling could be part of the switch forward to the embryonic phenotype with reinstatement of the early embryonic genetic program. Hypertrophy and apoptosis are "sons" of the same "mother": the local, tissue neuroendocrine-neurohumoral response to a mechanical stretch of the myocytes consequent to the geometric changes imposed on the viable myocytes by the necrotic ones. As expected, the life and death cycle is very closely regulated by several autocrine systems, one of which is linked to the interleukin-6 family via a regulatory protein named GP-130. Activation of the GP-130 slows down the death signals, thus favoring hypertrophy and reducing fibrosis.

Effects of sustained-release moxonidine, an imidazoline agonist, on plasma norepinephrine in patients with chronic heart failure

BACKGROUND

In chronic heart failure, sympathetic activation is increased. Moxonidine acts on central nervous system receptors to decrease sympathetic activation. We investigated the dose-response relationship of a new sustained-release (SR) preparation of moxonidine and the plasma concentration of norepinephrine in patients with chronic heart failure.

METHODS AND RESULTS

A total of 268 patients with chronic heart failure in NYHA functional class II to IV on optimal standard therapy were randomized to placebo or 1 of 5 doses of moxonidine SR: 0.3, 0.6, 0.9, 1.2, or 1.5 mg BID. After a dose-titration phase (7 weeks), patients were followed up for another 12 weeks at their maximally tolerated dose. Blood samples for plasma norepinephrine were collected at baseline and weekly during the initial 7 weeks, at week 19, and at the end of the study. At baseline and 7 and 19 weeks, sampling was also done 4 hours after the dose. After the active phases of the study, plasma norepinephrine was evaluated for an additional 3 days. A marked, statistically significant dose-related decrease in plasma norepinephrine was observed for predose levels as well as 4 hours after the dose at week 19. At the highest dose (1.5 mg BID), the trough reduction in norepinephrine was 52%. These reductions were accompanied by a modest decrease in heart rate, a modest increase in left ventricular ejection fraction, and a dose-related increase in adverse events.

CONCLUSIONS

Plasma norepinephrine was markedly reduced in a dose-related manner by moxonidine SR. This reduction was accompanied by evidence of reverse remodeling, but also by an increase in adverse events.

Identification, synthesis and pharmacological activity of moxonidine metabolites

The metabolism of moxonidine, 4-chloro-N-(4,5-dihydro-1H-imidazol-2-yl)-6-methoxy-2-methyl-5-pyrimidinamine, LY326869, in rats, mice, dogs, and humans has been examined. At least 17 metabolites were identified or tentatively identified in the different species by HPLC, LC/MS and LC/MS/MS. The identities of seven of the major metabolites have been verified by independent synthesis. The metabolites are generally derived from oxidation and conjugation pathways. Oxidation occurred at the imidazolidine ring as well as the methyl at the 2 position of the pyrimidine ring. All seven metabolites were examined in the spontaneously hypertensive rats (3 mg kg(-1), i.v.) for pressure and heart rate. Only one, 2-hydroxymethyl-4-chloro-5-(imidazolidin-2-ylidenimino)-6-methoxypyrimidine, exerted a short-lasting decrease in blood pressure, albeit attenuated in magnitude compared to moxonidine.

Pathophysiology of pediatric heart failure

Our understanding of the syndrome of heart failure has undergone several revisions, most importantly in the second half of the 20th century. New insights into the mechanisms of diseases offer new, challenging, controversial and sometimes counterintuitive forms of therapy. The development and progression of heart failure results from a complex interplay of hemodynamic and neurohormonal, cellular and genetic factors, rather than simply changes in cardiac function. It is because of this reason that our therapeutic focus can no longer be solely based on supply and demand models. Since the description of the pulsatile nature of the heart function and the flow of blood around a circuit by W. Harvey, numerous new paradigms have been put forward to explain the nature of heart failure. However, no single new model thus far proposed has been able to displace previous ones and successfully dictate therapy. It is the purpose of this manuscript to review the overall current understanding of the heart failure syndrome and how these new ideas may affect our therapeutic approach.

Overview of the management of pediatric heart failure

For the most part of this the century heart failure syndrome was understood as a pump failure disorder with hemodynamic consequences stemming from the same myocardial dysfunction. In addition supply and demand theories were used to explain the nature of symptoms. As a result, therapeutic strategies were directed at correcting the abnormal hemodynamic conditions and normalizing the delivery of the much needed nutrients. Improvement of cardiac pump function with inotropic drugs and abnormal circulatory conditions with afterload and preload modifications became therapeutic goals and standards of care. However, while vasodilators and inotropic drugs immediately improved symptoms, hemodynamics and functional status, in the long term they either did not affect or worsen the natural history of heart failure. In pediatrics, this is further complicated by the lack of large scale trials addressing issues pertinent to the particularities that affect heart failure in children. In the late 1980s and 1990s heart failure has evolved into a more complex, multiple and interactive pathophysiologic disorder. Today not only the abnormal hemodynamics but also the biological disorders are pharmacologic targets. The reversal or slowing of myocardial maladaptation has become one of the most important therapeutic goals. With this end in mind therapeutic strategies may seem counterintuitive and paradoxical, such as the use of beta-blockers. This review will address the current thinking and therapeutic modalities used today in the treatment of heart failure syndrome in the adult population. We also discuss some of the issues why we think that these principles can be extrapolated to the pediatric population.

Cardiac remodeling--concepts and clinical implications: a consensus paper from an international forum on cardiac remodeling. Behalf of an International Forum on Cardiac Remodeling

Cardiac remodeling is generally accepted as a determinant of the clinical course of heart failure (HF). Defined as genome expression resulting in molecular, cellular and interstitial changes and manifested clinically as changes in size, shape and function of the heart resulting from cardiac load or injury, cardiac remodeling is influenced by hemodynamic load, neurohormonal activation and other factors still under investigation. Although patients with major remodeling demonstrate progressive worsening of cardiac function, slowing or reversing remodeling has only recently become a goal of HF therapy. Mechanisms other than remodeling can also influence the course of heart disease, and disease progression may occur in other ways in the absence of cardiac remodeling. Left ventricular end-diastolic and end-systolic volume and ejection fraction data provide support for the beneficial effects of therapeutic agents such as angiotensin-converting enzyme (ACE) inhibitors and beta-adrenergic blocking agents on the remodeling process. These agents also provide benefits in terms of morbidity and mortality. Although measurement of ejection fraction can reliably guide initiation of treatment in HF, opinions differ regarding the value of ejection fraction data in guiding ongoing therapy. The role of echocardiography or radionuclide imaging in the management and monitoring of HF is as yet unclear. To fully appreciate the potential benefits of HF therapies, clinicians should understand the relationship between remodeling and HF progression. Their patients may then, in turn, acquire an improved understanding of their disease and the treatments they are given.

The effects of moxonidine, a novel imidazoline, on plasma norepinephrine in patients with congestive heart failure. Moxonidine Investigators

OBJECTIVE

To evaluate the dose response relationship of moxonidine on plasma concentration of norepinephrine during acute and chronic administration in patients with congestive heart failure (CHF).

BACKGROUND

Sympathetic activation is increased in heart failure. Moxonidine is an imidazoline ligand acting on the central nervous system (CNS) receptors to decrease sympathetic activation.

METHODS

Ninety-seven patients with heart failure and New York Heart Association class II-III symptoms and ejection fraction <40% were randomized to placebo or one of three target doses of moxonidine, 0.1, 0.2 or 0.3 mg administered twice daily. An initial dose of moxonidine 0.1 mg twice a day (b.i.d.) was followed by weekly increments of 0.1 mg b.i.d. until target dose. The second and third study days occurred after four weeks (at target dose) and after 12 weeks, respectively. At each study day, repeated blood samples were drawn.

RESULTS

There was a significant dose-related decrease of systolic blood pressure across all three study days. Heart rate decreased significantly on study day 3 in a dose-related manner. The acute 2 h decrease in plasma norepinephrine in response to all three doses of moxonidine was significantly different compared with placebo after four and 12 weeks. There was a significant linear relation between dose and plasma norepinephrine after four and 12 weeks in both 2 h peak and the time averaged effect (>8 h). The number of adverse events was similar in the moxonidine and placebo groups.

CONCLUSIONS

The increased sympathetic activation in CHF can be reduced by moxonidine through CNS inhibition.

Catecholamine Cardiomyopathy: An Autopsy Study

Pheochromocytoma, an uncommon intra-abdominal tumor of the sympathetic nervous system, is associated with episodic hypertension. Cardiac complications infrequently occur as the principal presenting symptoms and may account for the morbidity and mortality. The role of catecholamines, mainly noradrenaline, in ventricular hypertrophy and cardiac dysfunction is well documented. This report documents two autopsy cases, one of adrenal pheochromocytoma and the other of extra-adrenal pheochromocytoma, with manifestations primarily of cardiac etiology. The changes described indicate catecholamine cardiomyopathy.

Prolonged Captopril Therapy in Murine Viral Myocarditis

BACKGROUND: Acute myocarditis can progress to chronic heart muscle disease and cardiomyopathy. In the coxsackievirus B(3) (CB(3)) mouse model of myocarditis, early administration of captopril, an angiotensin-converting enzyme (ACE) inhibitor, ameliorated histopathological changes in inflammation, necrosis, and calcification and reduced heart weight. Late administration of captopril reduced heart weight but did not affect the histological findings. In this study, we investigated the effects of prolonged captopril treatment in the chronic phase of this model. METHODS AND RESULTS: Three-week-old male CD(1) mice were infected with CB(3) and then randomized to receive placebo or captopril starting on day 7 of infection. Captopril, 2 g/L, was given as the drinking water daily for up to 6 months. Autopsies were performed at 6 and 10 months. Heart-to-body weight ratios were obtained, and deaths were tallied. Myocardial fibrosis was graded according to a score system. In addition, picrosirius red stain (PSR) also was used for assessment of collagen deposition. Mean heart weights were similar in both groups. Mean body weight was significantly lower in captopril-treated mice (40.7 g) than in the untreated group (43.6 g) at 6 months (P =.0155), and mortality was higher (8.7 vs 0.87%; P =.009). At 6 months, the mean myocardial fibrosis score in treated mice (0.12) was significantly less than in untreated animals (0.35; P =.035). With PSR, the mean myocardial fibrosis score in the captopril group (1.20) was also significantly less than in the untreated group (1.58; P =.045). At 10 months, fibrosis scores were similar in both groups. CONCLUSIONS: Chronic captopril treatment in CB(3) myocarditis reduces myocardial fibrosis.

The sympathetic nervous system and the renin-angiotensin-aldosterone system in cardiovascular disease

Both the sympathetic nervous system and the renin-angiotensin-aldosterone system (RAAS) have central roles in vascular adaptive processes. Stimulation of the 2 systems has been demonstrated in a range of cardiovascular disorders, including congestive heart failure and hypertension. However, elucidation regarding the interactions of the many factors involved in these 2 systems is lacking. Angiotensin-converting enzyme inhibitors have been used to reveal the contribution of some elements in the RAAS. Until relatively recently, little was known about the specific disturbances of the sympathetic nervous system in cardiovascular disease. Plasma norepinephrine levels, an indicator of sympathetic activity, have limited value because they are affected by various physiologic processes in addition to sympathetic activation. Newer approaches to the assessment of neurohormonal activity include the determination of the power content of heart-rate variability. More specific probes may lead to a better comprehension of neurohormonal physiology in health and disease and underlie future therapeutic advances targeted to prevention and treatment of specific syndromes.

Remodeling after myocardial infarction in humans is not associated with interstitial fibrosis of noninfarcted myocardium

OBJECTIVES

This study was specifically designed to evaluate whether noninfarcted hypertrophic myocardium in patients with end-stage heart failure after myocardial infarction (MI) is associated with an increase in interstitial fibrous tissue.

BACKGROUND

Postinfarction remodeling consists of complex alterations that involve both infarcted and noninfarcted myocardium. The question arises whether ventricular dysfunction is due to physical events, such as inadequate myocardial hypertrophy to compensate for increased tangential wall stress, or is caused by the development of progressive interstitial fibrosis in noninfarcted myocardium.

METHODS

Fifteen hearts were obtained as cardiac explants (n = 13) or at autopsy (n = 2) from patients with end-stage coronary artery disease. Sixteen normal hearts served as reference hearts. Samples were taken from the left ventricular (LV) wall that contained the infarcted area, the border area and noninfarcted myocardium remote from scar areas. Collagen was quantified biochemically and microdensitophotometrically. Collagen type I and III ratios were analyzed by using the cyanogen bromide method and immunohistochemical staining, followed by microdensitophotometric quantification.

RESULTS

In noninfarcted myocardium remote from the scar areas, total collagen levels and collagen type I/III ratios did not differ statistically from those in reference hearts. These observations contrasted with high total collagen content and high collagen type I/III ratios in scar and border areas.

CONCLUSIONS

Remodeling of LV myocardium after MI in patients with end-stage heart failure is not necessarily associated with interstitial fibrosis in noninfarcted hypertrophic myocardium remote from scar areas. This finding raises questions regarding therapeutic interventions designed to prevent or retard the development of interstitial fibrosis.

The integrated effects of angiotensin II

In recent years, a prodigious amount of information has been gathered regarding the relationship between vascular biology and the mechanisms underlying cardiovascular disease. Activation of elements of the reninangiotensin system (RAS) appear to play an important role in the development and progression of conditions such as hypertension, coronary artery disease, and heart failure. Indeed, converging lines of evidence indicate that angiotensin-converting enzyme (ACE) regulates a delicate balance among a multitude of factors responsible for vascular tone, cellular growth promotion and inhibition, and pro- and anti-inflammatory effects. Because angiotensin II inhibits fibronectin, stimulates expression of plasminogen activator inhibitors, and degrades bradykinin, thereby impairing production of nitric oxide, ACE and the RAS are also involved in thrombosis and fibrinolysis. The favorable effects of ACE inhibition on endothelial function and, potentially, on cardiovascular morbidity and mortality are believed to result not only from angiotensin II suppression but also its consequent bradykinin preservation and nitric oxide production.

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.

Lisinopril. A review of its pharmacology and clinical efficacy in the early management of acute myocardial infarction

Following establishment of its efficacy in hypertension and congestive heart failure, the ACE inhibitor lisinopril has now been shown to reduce mortality and cardiovascular morbidity in patients with myocardial infarction when administered as early treatment. The ability of lisinopril to attenuate the detrimental effects of left ventricular remodelling is a key mechanism; however, additional cardioprotective and vasculoprotective actions are postulated to play a role in mediating the early benefit. The GISSI-3 trial in > 19 000 patients has demonstrated that, when given orally within 24 hours of symptom onset and continued for 6 weeks, lisinopril (with or without nitrates) produces measurable survival benefits within 1 to 2 days of starting treatment. Compared with no lisinopril treatment, reductions of 11% in risk of mortality and 7.7% in a combined end-point (death plus severe left ventricular dysfunction) were evident at 6 weeks. Advantages were apparent in all types of patients. Thus, those at high risk-women, the elderly, patients with diabetes mellitus and those with anterior infarct and/or Killip class > 1 -also benefited. These gains in combined end-point events persisted in the longer term, despite treatment withdrawal after 6 weeks in most patients. At 6 months, the incidence rate for the combined end-point remained lower than with control (a 6.2% reduction). The GISSI-3 results concur with those from recent large investigations (ISIS-4, CCS-1, SMILE) of other ACE inhibitors as early management in myocardial infarction. However, the results of the CONSENSUS II trial (using intravenous enalaprilat then oral enalapril) were unfavourable in some patients. These findings, together with the development of persistent hypotension and, to a lesser extent, renal dysfunction among patients in the GISSI-3 trial, have prompted considerable debate over optimum treatment strategies. Present opinion generally holds that therapy with lisinopril or other ACE inhibitors shown to be beneficial may be started within 24 hours in haemodynamically stable patients with no other contraindications; current labelling in the US and other countries reflects this position. There is virtually unanimous agreement that such therapy is indicated in high-risk patients, particularly those with left ventricular dysfunction. The choice of ACE inhibitor appears less important than the decision to treat; it seems likely that these benefits are a class effect. Lisinopril has a tolerability profile resembling that of other ACE inhibitors, can be given once daily and may be less costly than other members of its class. However, present cost analyses are flawed and this latter points remains to be proven in formal cost-effectiveness analyses. In conclusion, early treatment with lisinopril (within 24 hours of symptom onset) for 6 weeks improves survival and reduces cardiovascular morbidity in patients with myocardial infarction, and confers ongoing benefit after drug withdrawal. While patients with symptoms of left ventricular dysfunction are prime candidates for treatment, all those who are haemodynamically stable with no other contraindications are also eligible to receive therapy. Lisinopril and other ACE inhibitors shown to be beneficial should therefore be considered an integral part of the early management of myocardial infarction in suitable patients.

Long-term treatment with angiotensin I-converting enzyme inhibitors attenuates the loss of cardiac beta-adrenoceptor responses in rats with chronic heart failure

BACKGROUND

Cardiac contractile force in response to beta-adrenoceptor agonists and beta-adrenergic receptor density are decreased in failing human hearts. The effects of angiotensin I-converting enzyme (ACE) inhibitor on cardiac responsiveness to beta-adrenergic stimulation in failing hearts are not established. The present study was undertaken to determine whether ACE inhibitor may improve cardiac beta-adrenergic responsiveness in animals with chronic heart failure (CHF).

METHODS AND RESULTS

CHF was induced by left coronary artery ligation in rats. Cardiac output and stroke volume indices decreased 12 weeks after the operation. In sham-operated rats, dobutamine and isoprenaline increased cardiac output and stroke volume indices. In contrast, cardiac output and stroke volume responses to dobutamine and isoprenaline were severely blunted in the CHF rat. Cardiac beta 1-adrenergic receptor density was decreased while its dissociation constant (Kd) was not altered in the viable tissue of the left ventricle of the CHF rat, which is consistent with beta-adrenergic receptor downregulation. Cardiac norepinephrine content decreased in the CHF rats. Rats were treated orally with ACE inhibitors, 3 mg/kg trandolapril or 10 mg/kg enalapril once daily, or 5 mg/kg captopril twice daily from the 2nd to the 12th weeks after the operation. Treatment with ACE inhibitors attenuated the reduction in cardiac output and stroke volume indices and improved the inotropic response to dobutamine and isoprenaline and reversed partially the cardiac norepinephrine content in the CHF rat. ACE inhibitor treatment also attenuated the reduction in beta 1-adrenergic receptor density in the viable tissue of the left ventricle of the CHF rat.

CONCLUSIONS

The results suggest that ACE inhibitor treatment attenuates the blunting of cardiac responses to beta-adrenergic agonists in the CHF rat and that one of the mechanisms underlying this effect is prevention of cardiac beta 1-adrenergic receptor downregulation.

Angiotensin-converting enzyme inhibitors in the clinical setting of chronic congestive heart failure

The addition of an angiotensin-converting enzyme (ACE) inhibitor to digitalis and diuretics in chronic congestive heart failure (CHF) prolongs survival and improves the clinical condition of patients. These actions depend on the inhibition of ACE and are, therefore, common to all ACE inhibitors. Thus, the inclusion of an ACE inhibitor in the therapeutic regimen of chronic CHF is mandatory, whenever feasible. The use of ACE inhibitors in chronic CHF should avoid symptomatic hypotension and inordinate decreases in renal function. To this end, ACE inhibitor therapy should progress by gradually increasing doses, and sodium intake and dosages of diuretics and ACE inhibitors should be adjusted in the light of changing circumstances. ACE inhibitors with short elimination half-lives should be preferred in chronic CHF, since they allow quicker dose adjustment than their longer-acting congeners, and given that compliance with once and twice daily dosing would be similar.

Cardioreparation and the concept of modulating cardiovascular structure and function

Hypertension and atherosclerotic cardiovascular disease represent major global health problems. Practising physicians are challenged daily by patients suffering adverse cardiovascular events, such as myocardial infarction, stroke, heart failure and sudden cardiac death. Major risk factors have been identified of which the most important is left ventricular hypertrophy. In recent years, growth factors, regulatory peptides and effector hormones of the renin-angiotensin-aldosterone system have been identified as important modulators of cell growth and behaviour. It therefore follows that a major emphasis has been placed on the importance of abnormalities in organ structure as the primary basis for impaired function of the heart and vasculature, including large and medium sized arteries and resistance vessels, or arterioles. The concept of reparation recognizes the importance of abnormalities in tissue structure to the functional basis of disease. It suggests that the structurally remodelled heart and vasculature can be restored to, or toward, normal structure and function by suitable therapy. Experimental and clinical trials which address this premise are reviewed herein.