Effect of enalapril on mortality and the development of heart failure in asymptomatic patients with reduced left ventricular ejection fractions

Hypertension in the elderly: age- and disease-related complications and therapeutic implications

Effective treatment of hypertension in the elderly requires an understanding of both the progressive course of the disease and the impact of aging on the cardiovascular system, including physiological, genetic, lifestyle, and environmental factors. Review of the literature that has attempted to define the impact of an "aging process" on cardiovascular structure and function reveals a diversity of findings and interpretations. However, in general, normotensive elderly subjects exhibit the heart and vascular characteristics of "muted" hypertension, including many features of younger hypertensive patients: cardiac hypertrophy, diminution in resting left ventricular early diastolic filling rate, increased arterial stiffness and aortic impedance, diminution in the baroreceptor reflex, a diminished response to catecholamines and diminished renal blood flow, and an increase in peripheral vascular resistance (PVR). Treatment of elderly hypertensives is more challenging because of the greater likelihood of the presence of concomitant diseases, most importantly, coronary and peripheral atherosclerosis, renal dysfunction, and diabetes mellitus. Isolated systolic hypertension (ISH), the most common form of hypertension in the elderly, has also been clearly shown to be an important predictor of cardiovascular morbidity and mortality, including coronary artery disease, congestive heart failure, and stroke. Treatment of ISH has been shown to lower systolic pressure safely and effectively in the elderly. By reducing PVR, and possibly the arterial stiffness, and thus the early reflected pulse waves, vasodilators, including calcium antagonists, may lower these three components of arterial impedance, and hence lower the arterial load on the heart. The cardiac hypertrophy and reduced left ventricular filling rate associated with hypertension in older individuals can also be ameliorated, to some extent, by calcium channel blockers.

Effects of lisinopril on electromechanical properties and membrane currents in guinea-pig cardiac preparations

1. The effects of the angiotensin-converting enzyme inhibitor, lisinopril, were studied in guinea-pig atria and papillary muscles and in single isolated ventricular cells. 2. In isolated right atria, lisinopril (0.001-10 microM) decreased the amplitude and rate of the spontaneous contractions. In electrically driven left atria this negative inotropic effect was accompanied by a shortening of the time to peak tension and time for total contraction. 3. Lisinopril did not modify the electrophysiological characteristics of the ventricular action potentials recorded in papillary muscles perfused with normal Tyrode solution or elicited by isoprenaline in papillary muscles perfused with 27 mM K Tyrode solution. 4. In single ventricular cells, lisinopril (10 microM) had no effect on the inward L-type Ca2+ (ICa,L), the inward rectifier (IK1) or the delayed rectifier K+ currents (IK). However, it abolished the stimulation-dependent facilitation of the L-type Ca2+ current. 6. These results indicate that the negative inotropic effect of lisinopril cannot be explained by a decrease in Ca2+ entry through L-type channels and suggest that lisinopril may possibly act at an intracellular site to reduce contractile force.

Angioedema in the emergency department: the impact of angiotensin-converting enzyme inhibitors

Angiotensin-converting enzyme (ACE) inhibitors have been reported to cause angioedema. The purpose of this study was to establish what proportion of patients who present to the emergency department (ED) with angioedema were concomitantly taking any of the ACE inhibitors and to show how this group differed in presentation and response to treatment from the larger population of patients with non-ACE inhibitor-related angioedema. An 8-year retrospective chart review of all patients with the diagnosis of angioedema observed from January 1, 1984 to December 31, 1991 was undertaken in the ED of an urban teaching hospital. Forty-nine patients ranging from 12 to 88 years of age with symptoms and physical examination that was consistent with the diagnosis of angioedema were entered onto the study. Twelve cases of ACE inhibitor-related angioedema were identified, all occurring in the last 4 years of the review, and when compared with the non-ACE inhibitor-related group were older (mean age, 63.3 vs 43.0 years), had less of an allergic history (0% vs 49%; P = .013), but demonstrated the same severity of symptoms and response to medical therapy. No case required an artificial or surgical airway. ACE inhibitor related angioedema is becoming a common type of angioedema observed in this ED. These patients are older and free of other allergic disease and respond well to traditional therapy.

Hemodynamic effects of captopril and isosorbide mononitrate started early in acute myocardial infarction: a randomized placebo-controlled study

OBJECTIVES

The aim of this study was to study the hemodynamic effects of orally administered captopril and isosorbide mononitrate in suspected acute myocardial infarction.

BACKGROUND

Early treatment with converting enzyme inhibitors and nitrates in acute myocardial infarction may limit infarct expansion and prevent left ventricular dilation.

METHODS

In a double-blind study, 81 patients were randomized within 36 h of the onset of symptoms of suspected acute myocardial infarction to 1 month of oral captopril (6.25 mg initial dose, followed 2 h later by 12.5 mg and continuing with 12.5 mg three times daily), isosorbide mononitrate (initial dose 20 mg followed by 20 mg three times daily) or matching placebo. The effects of treatment on changes from baseline in mean arterial blood pressure, heart rate, stroke volume, cardiac output and systemic vascular resistance were assessed noninvasively using Doppler echocardiography 1 h after the first dose, 1 week after infarction and at 6 weeks (that is, 2 weeks after the scheduled end of trial treatment).

RESULTS

One hour after the start of treatment, blood pressure was reduced by approximately 10% with both captopril and isosorbide mononitrate, but this difference did not persist at 1 week. Captopril was associated with a significant increase in cardiac output compared with placebo of 13 +/- 3% at 1 h (p < 0.01), 23 +/- 5% at 1 week (p < 0.001) and 22 +/- 6% (p < 0.05) at 6 weeks (2 weeks after the end of trial treatment). This increase in cardiac output with captopril was mainly due to a substantial and sustained increase in stroke volume, although there was also a small increase in heart rate at 1 week. Both captopril and isosorbide mononitrate reduced systemic vascular resistance within 1 h of the start of treatment, but only the effect of captopril was sustained (perhaps because the three-times daily nitrate regimen induced tolerance). Study treatment was well tolerated, and the incidence of withdrawal of study treatment for hypotension was not significantly different from that with placebo.

CONCLUSIONS

This study indicates that the hemodynamic effects of both captopril and isosorbide mononitrate are well tolerated in the acute phase of myocardial infarction and that captopril favorably influences cardiac function.

The treatment of heart failure--what next?

1. Despite demonstrable benefits in terms of symptomatic relief and improvement in prognosis, even the best treatments of heart failure currently available fall short of being ideal. We review the basis for newer approaches to the treatment of heart failure and discuss some of the agents which capitalize on current understanding of the underlying patho-physiology. 2. Several drugs, old and new, are presently being investigated by major clinical trials. We also consider some of the difficulties related to the design and conduct of such trials and suggest how drugs might be better assessed in the future.

Effects of lisinopril on cardiorespiratory, neuroendocrine, and renal function in patients with asymptomatic left ventricular dysfunction

OBJECTIVE

To determine the cardiac, renal, and neuroendocrine effects of lisinopril in men with untreated, symptom free left ventricular systolic dysfunction.

DESIGN

A randomised, double blind cross over trial with six week treatment periods to compare lisinopril (10 mg/day) and matching placebo.

SETTING

Hospital outpatient department.

PATIENTS

Patients with pronounced systolic dysfunction on cross sectional echocardiography due to myocardial infarction at least six months previously, without angina and with no or minimal breathlessness. Eighteen men were identified of whom 15 completed the study.

INTERVENTIONS

Lisinopril (10 mg) or placebo given once daily by mouth.

MAIN OUTCOME MEASURES

Primary: oxygen consumption at peak exercise. Secondary: resting cardiac function as measured by radionuclide ventriculography and echocardiography, renal function estimated radioisotopically, and plasma indices of neuroendocrine activity.

RESULTS

Compared with placebo, lisinopril increased (mean (SD)) peak oxygen consumption during exercise (19.8(3.1) ml/kg/min v 21.4(3.2) ml/kg/min; p < 0.003). Lisinopril did not improve indices of cardiac function at rest. It reduced plasma concentrations of angiotensin II (median values 7 pg/ml to 5 pg/ml; p < 0.02), aldosterone (median values 113 pg/ml to 66 pg/ml; p < 0.05) and atrial natriuretic peptide (median values 69 pg/ml to 40 pg/ml; p < 0.04), but noradrenaline and antidiuretic hormone concentrations did not change. Renal blood flow increased and glomerular filtration rate declined.

CONCLUSIONS

Even before the onset of heart failure lisinopril improves the cardiopulmonary response to exercise in patients with systolic ventricular dysfunction.

Heart failure: drug therapy in the nineties and beyond

The lesson learned from recent advances in the understanding of congestive heart failure is that it is too complex a process to be managed in a simple fashion. At present, incremental improvement such as that provided by ACE inhibitors, and now possibly by new agents such as flosequinan, are what we have to offer our patients, short of transplantation, to control symptoms and increase exercise tolerance. No one knows what the future holds for these patients, but one can hope that the current therapy and those drugs being studied in clinical trials will provide agents that will continue to reduce the morbidity and mortality associated with current therapies. However, only so much can be done with drugs in the failing heart, and research must continue in the area of cardiac transplantation as well as in the area of totally implantable ventricular assist devices.

Circulating N-terminal atrial natriuretic peptide as a marker for symptomless left-ventricular dysfunction

Early identification of patients with symptomless left-ventricular dysfunction and early pharmacologic intervention may have an impact on the outlook of patients with heart failure. Atrial natriuretic peptide (ANP) is a cardiac hormone that is released as a C-terminal (C-ANP) and an N-terminal peptide (N-ANP). Since N-ANP has reduced clearance rates compared with C-ANP, N-ANP circulates at higher concentrations. Based on the known increased concentration of C-ANP in symptomatic congestive heart failure, our study was designed to evaluate prospectively N-ANP profile and left-ventricular function in subjects with symptomless and symptomatic heart failure, and the role of plasma N-ANP as a marker for early identification of patients with heart failure. 180 patients who were referred for rest and exercise radionuclide angiography for evaluation of left-ventricular function were studied. Blood was taken for measurement of C-ANP and N-ANP before angiography. Patients were grouped according to New York Heart Association (NYHA) heart failure classification and left-ventricular function. Mean (SD) plasma N-ANP concentration in patients with symptomless left-ventricular dysfunction (NYHA class I, n = 70) was 243 (256) pmol/L (range 27-922 pmol/L), and was higher (p < 0.001) than in 25 control subjects (28 pmol/L). A plasma N-ANP concentration above 54 pmol/L (mean +/- 1.96SD of the control group) had a sensitivity of 90% and a specificity of 92% for detection of patients with symptomless left-ventricular dysfunction. We have shown that plasma N-ANP concentrations are significantly increased in patients with symptomless left-ventricular dysfunction and that this peptide can serve as a marker for diagnosis of such patients.

Plasma brain natriuretic peptide as an indicator for angiotensin-converting-enzyme inhibition after myocardial infarction

Brain natriuretic peptide (BNP) is a cardiac ventricular hormone that may be a sensitive and specific marker of changes in ventricular function. In a prospective, randomised open trial with 16 patients followed for 6 months after first Q wave anterior myocardial infarction we set out to determine: whether BNP concentrations are raised acutely, the effect on circulating BNP of angiotensin-converting enzyme (ACE) inhibition, how BNP and atrial natriuretic peptide (ANP) concentrations compared as correlates of left-ventricular ejection fraction, and whether plasma BNP concentrations could distinguish patients with low (< 40%) and relatively preserved (> 40%) ejection fractions. Plasma concentrations of BNP measured on days 2, 7, 8, 42, and 180 postinfarction were significantly raised in patients compared with normal controls and to a proportionately greater degree than ANP concentrations. Treatment with placebo (n = 8) or oral captopril (n = 8) from day 8 resulted in significantly lower BNP concentrations at days 42 (p = 0.05) and 180 (p < 0.05) in the captopril-treated group. Compared with ANP, BNP concentrations were much more strongly correlated with radionuclide-measured left-ventricular ejection fraction at days 2, 42, and 180. All 8 patients with baseline (day 2) ejection fractions of 40% or above had plasma BNP concentrations less than 10 pmol/L, whereas the 8 patients with ejection fractions less than 40% had BNP concentrations greater than 10 pmol/L. Our findings suggest that measurements of circulating BNP may identify those patients with significant left-ventricular dysfunction who have been highlighted by the Survival and Ventricular Enlargement study as likely to benefit from long-term ACE inhibition after myocardial infarction.

Newer concepts in the medical management of patients with congestive heart failure

Congestive heart failure (CHF) remains a major cause of morbidity and mortality in the United States, especially among the elderly. Although an underlying disturbance in cardiac function can be identified in most patients, manifestations of the disease are greatly influenced by other factors, particularly neurohumoral and peripheral adaptive responses which occur secondary to impaired cardiac function. The renin-angiotensin system (RAS) is integrally involved in the pathophysiology of CHF. Originally considered a humoral system, the RAS is now known to exist and operate within cardiac and vascular tissues. The importance of tissue-specific renin-angiotensin systems in CHF is presently under investigation. Most patients with symptomatic CHF benefit from the administration of an ACE inhibitor. Certain asymptomatic patients, such as those with severe left ventricular (LV) dysfunction and those who are at high risk for LV remodeling after anterior wall myocardial infarction, may also benefit from ACE inhibitor therapy. Diuretics and nitrates improve symptoms and often cardiac output in many patients with CHF. Although many new inotropic agents have been tested in CHF patients, none appear clinically superior to digitalis glycosides. The efficacy of digitalis glycosides in CHF may in part result from sympathoinhibitory properties such as the activation of baroreceptor mechanisms. Despite the fact that many CHF patients die from arrhythmias, treatment of asymptomatic ventricular arrhythmias in these patients is not recommended. Patients with symptomatic or sustained ventricular arrhythmias are best treated by a physician experienced in cardiac electrophysiology. Therapy with beta-blocking drugs for CHF patients is controversial. Anticoagulants are recommended for selected patients with CHF. Finally, exercise therapy may improve functional capacity in some patients with CHF through its effects on peripheral blood vessels and skeletal muscle tissues.

Sudden death in idiopathic dilated cardiomyopathy: role of ventricular arrhythmias

Sudden cardiac death (SCD) is associated with idiopathic congestive cardiomyopathy (IDCM) and most commonly is due to ventricular tachyarrhythmias. The recurrence rate of SCD in the absence of specific therapy is thought to be around 20%-30% per year. Asymptomatic and symptomatic ventricular arrhythmias are common in patients with IDCM and the direct causal link of such arrhythmias with SCD in IDCM patients remains to be established. Furthermore, therapy directed at suppressing these ventricular arrhythmias has not been shown to decrease the incidence of SCD. Various approaches such as ambulatory monitoring, electrophysiological testing, signal-averaged electrocardiogram, and hemodynamics have met with variable success in identifying patients prone to SCD. Additionally, therapeutic approaches to prevent SCD in IDCM patients have produced equivocal results. This article reviews the published studies addressing the causal link of ventricular arrhythmias to sudden death in patients with IDCM and the attempts to decrease the incidence of sudden.

Progressive left ventricular dysfunction and remodeling after myocardial infarction. Potential mechanisms and early predictors

BACKGROUND

Left ventricular enlargement and the development of chronic heart failure are potent predictors of survival in patients after myocardial infarction. Prospective studies relating progressive ventricular enlargement in individual patients to global and regional cardiac dysfunction and the onset of late chronic heart failure are not available. It was the aim of this study to define the relation between left ventricular dilatation and global and regional cardiac dysfunction and to identify early predictors of enlargement and chronic heart failure in patients after myocardial infarction.

METHODS AND RESULTS

Left ventricular volumes, regional area shrinkage fraction in 18 predefined sectors (gated single photon emission computed tomography), global ejection fraction, and hemodynamics at rest and during exercise (supine bicycle, 50 W, 4 minutes, Swan-Ganz catheter) were assessed prospectively 4 days, 4 weeks, 6 months, and 1.5 and 3 years after first myocardial infarction. Seventy patients were assigned to groups with progressive, limited, or no dilatation. Patients without dilatation (n = 38) maintained normal volumes and hemodynamics until 3 years. With limited dilatation (n = 18), left ventricular volume increased up to 4 weeks after infarction and stabilized thereafter; depressed stroke volume was restored 4 weeks after infarction and then remained stable at rest. Wedge pressure during exercise, however, progressively increased. With progressive dilatation (n = 14), depressed cardiac and stroke indexes were also restored by 4 weeks but progressively deteriorated thereafter. Area shrinkage fraction as an estimate of regional left ventricular function in normokinetic sectors at 4 days gradually deteriorated during 3 years, but hypokinetic and dyskinetic sectors remained unchanged. Global ejection fraction fell after 1.5 years, whereas right atrial pressure, wedge pressure, and systemic vascular resistance increased. By multivariate analysis, ejection fraction and stroke index at 4 days, ventriculographic infarct size, infarct location, and Thrombolysis in Myocardial Infarction trial grade of infarct artery perfusion were significant predictors of progressive ventricular enlargement and chronic dysfunction.

CONCLUSIONS

Almost 26% of patients may develop limited left ventricular dilatation within 4 weeks after first infarction, which helps to restore cardiac index and stroke index at rest and to preserve exercise performance and therefore remains compensatory. A somewhat smaller group (20%) develops progressive structural left ventricular dilatation, which is compensatory at first, then progresses to noncompensatory dilatation, and finally results in severe global left ventricular dysfunction. In these patients, depression of global ejection fraction probably results from impairment of function of initially normally contracting myocardium. Early predictors from multivariate analysis allow identification of patients at high risk for progressive left ventricular dilatation and chronic ventricular dysfunction within 4 weeks after acute infarction.

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.

The NHLBI model: a 25 year history

Although newer techniques and procedures have been developed, many of the clinical trial design and monitoring concepts used today in the NHLBI were implemented 25 years ago. Among these are the organizational structure of multicentre trials and the use of an independent data monitoring committee. Examples of data monitoring committee discussions and decisions are provided.

The role of phosphodiesterase inhibitors in heart failure

Myocardial contractility is dependent on available intracellular calcium and this can be enhanced by increasing intracellular cyclic adenosine monophosphate. One way of achieving this is by inhibiting the phosphodiesterase III enzyme. Over the last 15 years, a number of new drugs with this mechanism of action have been studied in man and have been found not only to have a positive inotropic action on the heart but also a vasodilating action on peripheral blood vessels. This combination of effects produces favourable haemodynamic improvement in patients with chronic heart failure. While some smaller studies showed that this did translate into an improvement in symptoms and functional capacity, a large well-designed and controlled clinical trial showed that survival was decreased when milrinone was used in target daily doses of 40 mg. For this reason, chronic long-term oral therapy with phosphodiesterase III inhibitors is not currently being actively pursued. They may still have a role as acute short-term therapy in severely ill patients who do not respond adequately to optimal standard drug therapy. Milrinone has been one of the most widely studied drugs in this regard. Even during short-term administration, its use should be closely monitored for any evidence of an increase in ventricular arrhythmias or decrease in ventricular function.

Angiotensin-converting enzyme inhibitors in the treatment of clinical heart failure

During the last decade, angiotensin-converting enzyme inhibitors (ACE-I) have become cornerstones in the treatment of clinical congestive heart failure. There is convincing evidence that they improve survival and that, in this respect, they are superior to ordinary vasodilators. ACE-I administration also improves New York Heart Association functional class and the left-ventricular function, but their long-term effects on exercise tolerance and quality of life appear modest. During prolonged administration to patients with ischemic left-ventricular dysfunction, ACE-I also significantly reduce the incidence of new ischemic events (myocardial infarction, unstable angina).

Ventricular remodeling after myocardial infarction. Experimental and clinical studies

Changes of ischemic myocardium following coronary occlusion, including active and passive functions, and adaptive changes of non-ischemic surviving myocardium have been summarized under the term "left ventricular remodeling" post myocardial infarction. An increase in left ventricular volume may be a consequence, and associated with an adverse prognosis. Although left ventricular dilatation may increase stroke volume and, thus, be compensatory at first, in about one-fifth of patients it ultimately results in progressive dysfunction and heart failure. Major determinants of this process are time, infarct size, infarct location, global left ventricular function assessed 4 days after infarction by radionuclide ejection fraction and right heart catheter (stroke volume), and morphology of the infarct-associated coronary artery. The surviving myocardium hypertrophies and may also dilate structurally. Depression of left ventricular ejection fraction chronically after the infarct is due to deterioration of wall motion of chamber segments initially classified normal by radionuclide analysis. Biochemical changes may also occur, including reduction of phosphocreatine, prolongation of time to peak Cai2+, and changes in myosin isoforms. Systemic or local humoral factors may be involved in these changes, however, clear evidence is still lacking. Perfusion of surviving myocardium may be altered under various conditions due to morphologic and functional changes of coronary vasculature. Successful prevention of heart failure and death by angiotensin converting enzyme inhibitors in asymptomatic patients with left ventricular dysfunction post-myocardial infarction has supported the pathophysiologic concepts of remodeling.

ACE-inhibitors in coronary artery disease?

Angiotensin converting enzyme (ACE)-inhibitors are established in the treatment of arterial hypertension and heart failure. In recent years ACE-inhibitors have also been used in the treatment of patients with coronary artery disease (CAD), since from experimental data an antiischemic action of these agents is suggested. Antiischemic effects of ACE-inhibitors may be exerted through a reduction of myocardial oxygen demand, by a reduction of angiotensin-mediated coronary vasoconstriction, by an interaction with bradykinin and the prostaglandin system, by a modulation of endothelial control of vascular tone, and by an interaction with the sympathetic nervous system. However, clinical findings on potential beneficial effects of ACE-inhibitors in patients with CAD are inconsistent and controversial. While in hypertensive patients with CAD ACE-inhibitors generally seem to attenuate myocardial ischemia at rest and during exercise, a significant fraction of about 30% of normotensive patients with CAD does not benefit or even deteriorates. Lowering of coronary perfusion pressure and alteration of transmural blood flow distribution may be responsible for this. In patients with left ventricular dysfunction (SOLVD) or congestive heart failure (CONSENSUS, SOLVD) ACE-inhibitors have been proven to prevent progressive deterioration in left ventricular function and to reduce mortality. In patients with asymptomatic left ventricular dysfunction after myocardial infarction (SAVE), long-term administration of captropril was associated with an improvement in survival and reduced morbidity and mortality due to major cardiovascular events. Therefore, from a prognostic viewpoint patients with CAD and left ventricular dysfunction or congestive heart failure should be treated with ACE-inhibitors, although the clinical use of ACE-inhibitors in patients with ongoing angina pectoris may be limited by an aggravation of angina, presumably due to critically lowering coronary perfusion pressure. Finally, ACE-inhibitors failed to prevent restenosis after successful PTCA. In conclusion, from a prognostic viewpoint patients with CAD and congestive heart failure or left ventricular dysfunction should be treated with ACE-inhibitors. In hypertensive patients ACE-inhibitors generally seem to attenuate myocardial ischemia. In normotensive patients with CAD and angina pectoris but without left ventricular dysfunction ACE-inhibitors cannot generally be recommended at present, unless the patients, which may have benefit from ACE-inhibitor treatment can be better defined.

Local expression and pathophysiological role of renin-angiotensin in the blood vessels and heart

While the circulating renin-angiotensin system (RAS) plays an important role in short-term maintenance of cardiovascular homeostasis, recent studies point to a role in long-term cardiovascular regulation for endogenous RAS in target tissues. This article focuses on the multiple effects of tissue angiotensin enzyme (ACE) and angiotensin II (Ang II), its active peptide product. Ang II has been shown to be a potent growth factor in vascular smooth muscle cells. Depending on the local conditions, the vascular response may be either hypertrophy or hyperplasia. The molecular mechanisms involved in the interactions of Ang II with endothelium- and smooth muscle-derived cell products may play important roles in the modulation of vascular structure in hypertension and vascular injury. Evidence also points to a role for Ang II in the development of left ventricular hypertrophy in hypertension. In addition, cardiac RAS may contribute to the pathophysiology of heart failure. Experimental and clinical studies with ACE inhibitors point to a role for tissue ACE activity in the development of atherosclerosis, as well as cardiac hypertrophy and remodeling.

Pathophysiology of heart failure and the renin-angiotensin-system

For more than a decade, the inhibition of the renin-angiotensin system in heart failure has been regarded as pure vasodilator therapy. Consequently, the role of the renin-angiotension system has been seen as contributing to hemodynamic overload by vasoconstriction and volume retention. Meanwhile, clinical experience was indicated that important additional aspects of ACE-inhibition in heart failure are attenuation of the enhanced neuroendocrine activity and reversal or prevention of inappropriate trophic reactions of the overloaded myocardium. In overloaded hearts there is enhanced intracardiac formation of angiotensin due to enhanced expression of angiotensinogen and ACE, and due to accumulation of circulating, nephrogenic active renin. In human hearts, a mast-cell-derived chymase, which is not blocked by ACE-inhibition, contributes to intracardiac angiotensin formation. The enhanced intracardiac angiotensin-II formation in overloaded hearts is involved in coronary constriction, impairment of diastolic relaxation, myocyte enlargement and interstitial fibrosis, which aggravate the diastolic impairment. The major problem in overloaded, hypertrophied cardiocytes is the dedifferentiation with instabilization of Ca(++)-homeostasis due to an altered program of gene expression. Dedifferentiated cardiocytes have a reduced expression of sarcoplasmic reticulum Ca(++)-ATPase and an enhanced expression of the sarcolemmal Na+/Ca(++)-exchanger, resulting in an attenuation of active diastole (Ca(++)-reaccumulation into the sarcoplasmic reticulum), a depressed force-frequency relation, and an enhanced susceptibility for fatal arrhythmias. Furthermore, an enhanced local renin-angiotensin system in distensible coronary and systemic arteries seems to contribute to a reduced releasability of endothelium-derived relaxing factor, probably by reducing bradykinin availability. This modulation of endothelial function appears to contribute to the localization and progression of atheroma development in presence of risks factors for atherosclerosis.

Angiotensin-converting enzyme inhibitors as cardioprotective agents

This discussion of documented and possible cardioprotective effects of angiotensin-converting enzyme (ACE) inhibitors examines the variety of sites along the pathway to end-stage heart disease at which they might intervene. In addition to their antihypertensive activity, their effects on left ventricular hypertrophy, lipid profiles, and insulin sensitivity are discussed in comparison to the effects of other classes of antihypertensive agents on these risk factors. The ability of ACE inhibitors to prevent the progression of congestive heart failure and reduce mortality is documented and a summary of data demonstrating benefits of their use in postmyocardial infarction patients with low ejection fraction is presented.

Effect of enalapril on myocardial infarction and unstable angina in patients with low ejection fractions

An association between raised renin levels and myocardial infarction has been reported. We studied the effects of enalapril, an angiotensin-converting enzyme (ACE) inhibitor, on the development of myocardial infarction and unstable angina in 6797 patients with ejection fractions < or = 0.35 enrolled into the two Studies of Left Ventricular Dysfunction (SOLVD) trials. Patients were randomly assigned to placebo (n = 3401) or enalapril (n = 3396) at doses of 2.5-20 mg per day in two concurrent double-blind trials with the same protocol. Patients with heart failure entered the treatment trial (n = 2569) and those without heart failure entered the prevention trial (n = 4228). Follow-up averaged 40 months. In each trial there were significant reductions in the number of patients developing myocardial infarction (treatment trial: 158 placebo vs 127 enalapril, p < 0.02; prevention trial: 204 vs 161 p < 0.01) or unstable angina (240 vs 187 p < 0.001; 355 vs 312, p < 0.05). Combined, there were 362 placebo group patients with myocardial infarction compared with 288 in the enalapril group (risk reduction 23%, 95% CI 11-34%; p < 0.001). 595 placebo group patients developed unstable angina compared with 499 in the enalapril group (risk reduction 20%, 95% CI 9-29%, p < 0.001). There was also a reduction in cardiac deaths (711 placebo, 615 enalapril; p < 0.003), so that the reduction in the combined endpoint of deaths, myocardial infarction, and unstable angina was highly significant (20% risk reduction, 95% CI 14-26%; p < 0.0001). Enalapril treatment significantly reduced myocardial infarction, unstable angina, and cardiac mortality in patients with low ejection fractions.

Effect of amiodarone on mortality after myocardial infarction: a double-blind, placebo-controlled, pilot study

OBJECTIVES

The goal of this study was to evaluate the effect of amiodarone on mortality, ventricular arrhythmias and clinical complications in high risk postinfarction patients.

BACKGROUND

No therapy has been shown to reduce sudden death in patients ineligible to receive beta-adrenergic blocking agents after myocardial infarction.

METHODS

Patients who were not eligible to receive beta-blockers were randomized to receive amiodarone (n = 305) or placebo (n = 308) for 1 year.

RESULTS

There were 21 deaths in the amiodarone group compared with 33 in the placebo group (odds ratio 0.62, 95% confidence interval [CI] 0.35 to 1.08, p = 0.095). There were two noncardiac deaths in the amiodarone group and none in the placebo group; thus, the difference in cardiac mortality (19 vs. 33, respectively) was statistically significant (odds ratio 0.55, 95% CI 0.32 to 0.99, p = 0.048). There was a significant decrease in Lown class 4 ventricular arrhythmias (7.5% vs. 19.7%, respectively, p < 0.001). Adverse effects developed in 30% of amiodarone-treated patients and 10% of placebo-treated patients. Pulmonary toxicity, which was mild and reversible, occurred in only one patient in the amiodarone group but in no patient in the placebo group.

CONCLUSIONS

This trial demonstrated a significant reduction in cardiac mortality and ventricular arrhythmias with amiodarone treatment. However, given the wide confidence intervals and borderline statistical significance of our trial, larger trials are needed to confirm or refute this view.

Effects of the early administration of enalapril on mortality in patients with acute myocardial infarction. Results of the Cooperative New Scandinavian Enalapril Survival Study II (CONSENSUS II)

BACKGROUND

Long-term administration of angiotensin-converting--enzyme (ACE) inhibitors has been shown to improve survival in patients with symptomatic left ventricular failure and to attenuate left ventricular dilatation in patients with myocardial infarction. We studied whether mortality could be reduced during the 6 months after an acute myocardial infarction with use of the ACE inhibitor enalapril.

METHODS

At 103 Scandinavian centers patients with acute myocardial infarctions and blood pressure above 100/60 mm Hg were randomly assigned to treatment with either enalapril or placebo, in addition to conventional therapy. Therapy was initiated with an intravenous infusion of enalapril (enalaprilat) within 24 hours after the onset of chest pain, followed by administration of oral enalapril.

RESULTS

Of the 6090 patients enrolled, 3046 were assigned to placebo and 3044 to enalapril. The life-table mortality rates in the two groups at one and six months were not significantly different (6.3 and 10.2 percent in the placebo group vs. 7.2 and 11.0 percent in the enalapril group, P = 0.26). The relative risk of death in the enalapril group was 1.10 (95 percent confidence interval, 0.93 to 1.29). Death due to progressive heart failure occurred in 104 patients (3.4 percent) in the placebo group and 132 (4.3 percent) in the enalapril group (P = 0.06). Therapy had to be changed because of worsening heart failure in 30 percent of the placebo group and 27 percent of the enalapril group (P less than 0.006). Early hypotension (systolic pressure less than 90 mm Hg or diastolic pressure less than 50 mm Hg) occurred in 12 percent of the enalapril group and 3 percent of the placebo group (P less than 0.001).

CONCLUSIONS

Enalapril therapy started within 24 hours of the onset of acute myocardial infarction does not improve survival during the 180 days after infarction.

Effect of electrical stimulus parameters on the development and propagation of action potentials in short excitable fibres

Intracellular action potentials (IAPs) produced by short fibres in response to their electrical stimulation were analysed. IAPs were calculated on the basis of the Hodgkin-Huxley (1952) model by the method described by Joyner et al. (1978). Principal differences were found in processes of activation of short (semilength L less than 5 lambda) and long fibres under near-threshold stimulation. The shorter the fibre, the lower was the threshold value (Ithr). Dependence of the latency on the stimulus strength (Ist) was substantially non-linear and was affected by the fibre length. Both fibre length and stimulus strength influenced the IAP amplitude, the instantaneous propagation velocity (IPV) and the site of the first origin of the IAP (and, consequently, excitability of the short fibre membrane). With L less than or equal to 2 lambda and Ithr less than or equal to Ist less than or equal to 1.1Ithr, IPV could reach either very high values (so that all the fibre membrane fired practically simultaneously) or even negative values. The latter corresponded to the first origin of the propagated IAP, not at the site of stimulation but at the fibre termination or at a midpoint. The characters of all the above dependencies were unchanged irrespective of the manner of approaching threshold (variation of stimulus duration or its strength). Reasons for differences in processes of activation of short and long fibres are discussed in terms of electrical load and latency. Applications of the results to explain an increased jitter, velocity recovery function and velocity-diameter relationship are also discussed.