Ongoing clinical trials of angiotensin-converting enzyme inhibitors for treatment of coronary artery disease in patients with preserved left ventricular function

Angiotensin converting enzyme (ACE) inhibitory, antihypertensive and antihyperlipidaemic activities of protein hydrolysates from Rhopilema esculentum

Angiotensin-converting enzyme (ACE) inhibitory, antihypertensive and antihyperlipidaemic activities of protein hydrolysates (RPH) from the jellyfish Rhopilema esculentum were investigated. R. esculentum was hydrolysed sequentially with pepsin and papain, and then the hydrolysate was ultrafiltered with a 2000 Da cut-off membrane. It was found that RPH contained high levels of Gly, Glu, Pro, Asp and Ala, having potential ACE inhibitory activity in vitro with an IC(50) of 1.28 mg/ml. It was also found that systolic blood pressure was reduced markedly in spontaneously hypertensive rats after single and chronic oral administration of RPH, indicating that RPH had an antihypertensive effect. In addition, oral administration of RPH decreased total serum cholesterol and triglyceride, and increased high-density lipoprotein cholesterol in rats fed with high-fat diet. These results indicate that RPH may prove to be a promising functional food for the prevention and treatment of hypertension and hyperlipidaemia.

Pathophysiologic bases for adjunctive therapies in the treatment and secondary prevention of acute myocardial infarction

Postmyocardial infarction (MI) survival has been steadily improving. This improvement has been due, in part, to the actions of the adjunctive medical therapies for the treatment of MI. Aspirin, beta blockers, angiotensin-converting enzyme (ACE) inhibitors, and lipid-lowering agents have been shown to improve survival in the treatment and secondary prevention of MI. Nitrates have beneficial effects as well. These medications complement the reperfusion strategies through different mechanisms. Other adjunctive medical therapies, namely magnesium, antiarrhythmic agents, and calcium-channel blockers, have not been shown to improve mortality with routine post-MI use despite their theoretical benefits.

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers in atherosclerosis

Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) effectively interfere with the renin-angiotensin system and exert various beneficial actions on cardiac and vascular structure and function, beyond their blood pressure-lowering effects. Randomized, controlled clinical trials have shown that ACE inhibitors improve endothelial function, cardiac and vascular remodeling, retard the anatomic progression of atherosclerosis, and reduce the risk of myocardial infarction, stroke, and cardiovascular death. Therefore, these agents are recommended in the treatment of a wide range of patients at risk for adverse cardiovascular outcomes, including those with coronary disease, prior stroke, peripheral arterial disease, high-risk diabetes, hypertension, and heart failure. ARBs are effective blood pressure- lowering and renoprotective agents and can be used in heart failure in patients who do not tolerate ACE inhibitors. The role of ARBs in the prevention of atherosclerosis and its sequelae is currently under investigation. The use of combined ACE inhibitor plus ARB therapy offers theoretical advantages over the use of each of these agents alone and is also under investigation in large, randomized clinical trials.

The Quinapril Ischemic Event Trial (QUIET): evaluation of chronic ace inhibitor therapy in patients with ischemic heart disease and preserved left ventricular function

Angiotensin-converting enzyme inhibitors improve endothelial function, inhibit experimental atherogenesis, and decrease ischemic events. The Quinapril Ischemic Event Trial was designed to test the hypothesis that quinapril 20 mg/day would reduce ischemic events (the occurrence of cardiac death, resuscitated cardiac arrest, nonfatal myocardial infarction, coronary artery bypass grafting, coronary angioplasty, or hospitalization for angina pectoris) and the angiographic progression of coronary artery disease in patients without systolic left ventricular dysfunction. A total of 1,750 patients were randomized to quinapril 20 mg/day or placebo and followed a mean of 27 +/- 0.3 months. The 38% incidence of ischemic events was similar for both groups (RR 1.04; 95% confidence interval 0.89 to 1.22; p = 0.6). There was also no significant difference in the incidence of patients having angiographic progression of coronary disease (p = 0.71). The rate of development of new coronary lesions was also similar in both groups (p = 0.35). However, there was a difference in the incidence of angioplasty for new (previously unintervened) vessels (p = 0.018). Quinapril was well tolerated in patients after angioplasty with normal left ventricular function. Quinapril 20 mg did not significantly affect the overall frequency of clinical outcomes or the progression of coronary atherosclerosis. However, the absence of the demonstrable effect of quinapril may be due to several limitations in study design.

Vasopeptidase inhibition: a new direction in cardiovascular treatment

The development of new antihypertensive agents is becoming even more important. We need better blood pressure control and also agents that treat hypertension as a disease of the vascular endothelium. Recently, it has been shown that blocking the renin-angiotensin system with angiotensin converting enzyme (ACE) inhibitors reduces blood pressure and decreases the incidence of vascular disease. Another peptide system, the natriuretic peptide system, has also been shown to be important in blood pressure control and volume homeostasis. Because ACE and neutral endopeptidase, the enzyme responsible for the degradation of the natriuretic peptides, are both zinc metalloproteases, new pharmaceuticals that inhibit both enzymes have been developed. The first of these, omapatrilat, has been shown to be an effective antihypertensive agent and to have great potential for treating congestive heart failure.

Effect of enalaprilat on nitric oxide activity in coronary artery disease

Atherosclerosis is associated with vascular endothelial dysfunction and reduced nitric oxide (NO) activity. Enhancement of NO activity may have an antiatherogenic action. This study was performed to determine whether angiotensin-converting enzyme (ACE) inhibition improves peripheral vascular NO activity in patients with atherosclerosis. In the femoral circulation of 43 patients with atherosclerosis and 10 controls, we studied endothelium-dependent vasodilation with bradykinin and acetylcholine, and endothelium-independent vasodilation with sodium nitroprusside before and after enalaprilat. In 22 patients, we repeated these infusions in the presence of L-N(G) monomethyl arginine (L-NMMA). Doppler-femoral artery flow velocity was measured. Before ACE inhibition, acetylcholine responses were depressed in patients with atherosclerosis compared with controls (p = 0.03). Enalaprilat did not alter femoral vascular tone at rest or vasodilation with sodium nitroprusside, but potentiated bradykinin-mediated vasodilation in patients (p<0.001) and controls (p = 0.02). Acetylcholine-mediated vasodilation was augmented only in patients (p<0.001), but not in control subjects. L-NMMA inhibited the potentiation by enalaprilat of acetylcholine and bradykinin responses. This study demonstrates that ACE inhibition selectively improves endothelial dysfunction in human atherosclerosis by enhancing NO activity. The antithrombotic and antiproliferative effects of NO may reduce adverse manifestations related to atherosclerosis during long-term therapy.

Treatment of stable angina

Severe atherosclerotic narrowing of one or more coronary arteries is responsible for myocardial ischemia and angina pectoris in most patients with stable angina pectoris. The coronary arteries of patients with stable angina also contain many nonobstructive plaques, which are prone to fissures or rupture resulting in presentation of acute coronary syndromes (unstable angina, myocardial infarction, sudden ischemic death). In addition to symptomatic relief of symptoms and an increase in angina-free walking time with antianginal drugs or revascularization procedures, the recent emphasis of treatment has been to reduce adverse clinical outcomes (coronary death and myocardial infarction). The role of smoking cessation, aspirin, treatment of elevated lipids, and treatment of high blood pressure in all patients and of beta-blockers and angiotensin-converting enzyme inhibitors in patients with diminished systolic left ventricular systolic function in reducing adverse outcomes has been well established. What is unknown, however, is whether any anti-anginal drugs (beta-blockers, long-acting nitrates, calcium channel blockers) effect adverse outcomes in patients with stable angina pectoris. Recent trials evaluated the usefulness of suppression of ambulatory ischemia in patients with stable angina pectoris, but it remains to be established whether suppression of ambulatory myocardial ischemia with antianginal agents or revascularization therapy is superior to pharmacologic therapy targeting symptom relief. Patients who have refractory angina despite optimal medical treatment and are not candidates for revascularization procedures may be candidates for newer techniques of transmyocardial revascularization, enhanced external counterpulsation, spinal cord stimulation, or sympathectomy. The usefulness of these techniques, however, needs to be confirmed in large randomized clinical trials.

Patterns of prescribing ACE inhibitors after myocardial infarction

We attempted to determine physician prescribing patterns of angiotensin-converting enzyme (ACE) inhibitors in patients who experienced a myocardial infarction, stratified by left ventricular function. We retrospectively reviewed drug therapy at discharge in 534 patients to assess prescription of ACE inhibitor therapy, including dosage. Thirty-four percent of patients were discharged taking an ACE inhibitor, of whom only 11% received recommended dosages. The drugs were prescribed more often for patients who had an ejection fraction below 40% than for those with an ejection fraction of 40% or above (54% vs 28%, p<0.05). We conclude that ACE inhibitors are underprescribed for patients who experienced a myocardial infarction, illustrating the gap between clinical research and clinical practice, and the need for programs to ensure optimal medical management.

Abnormal flow-mediated epicardial vasomotion in human coronary arteries is improved by angiotensin-converting enzyme inhibition: a potential role of bradykinin

OBJECTIVES

This study was performed to determine whether angiotensin converting enzyme (ACE) inhibition improves endothelium-dependent flow-mediated vasodilation in patients with atherosclerosis or its risk factors and whether this is mediated by enhanced bradykinin activity.

BACKGROUND

Abnormal coronary vasomotion due to endothelial dysfunction contributes to myocardial ischemia in patients with atherosclerosis, and its reversal may have an antiischemic action. Previous studies have shown that ACE inhibition improves coronary endothelial responses to acetylcholine, but whether this is accompanied by improved responses to shear stress remains unknown.

METHODS

In 19 patients with mild atherosclerosis, metabolic vasodilation was assessed during cardiac pacing. Pacing was repeated during separate intracoronary infusions of low-dose bradykinin (BK) and enalaprilat. Endothelium-dependent and -independent vasodilation was estimated with intracoronary BK and sodium nitroprusside respectively.

RESULTS

Enalaprilat did not alter either resting coronary vascular tone or dilation with sodium nitroprusside, but potentiated BK-mediated dilation. Epicardial segments that constricted abnormally with pacing (-5+/-1%) dilated (3+/-2%) with pacing in the presence of enalaprilat (p = 0.002). Similarly, BK at a concentration (62.5 ng/min) that did not alter resting diameter in the constricting segments also improved the abnormal response to a 6+/-1% dilation (p < 0.001). Cardiac pacing-induced reduction in coronary vascular resistance of 27+/-4% (p < 0.001) remained unchanged after enalaprilat.

CONCLUSIONS

Thus ACE inhibition: A) selectively improved endothelium-dependent but not-independent dilation, and B) abolished abnormal flow-mediated epicardial vasomotion in patients with endothelial dysfunction, in part, by increasing endogenous BK activity.

How to standardize vasomotor tone in serial studies based on quantitation of coronary dimensions?

In patients with coronary artery disease including those after coronary bypass graft operation and heart transplantation intervention studies based on serial quantitative coronary angiography, in part combined with intravascular ultrasound, are of increasing relevance. Since vasomotor tone of epicardial coronary arteries is influenced by a variety of factors, angiographic follow-up studies require standardization of coronary tone by induction of maximal dilation. We reviewed the effects of the most potent coronary vasodilatory drug groups, calcium antagonists and nitrocompounds, on coronary diameters. Intravenous or intracoronary injections of verapamil, diltiazem, nifedipine, nicardipine, and nisoldipine can cause profound coronary dilation which has been shown to be maximal with verapamil and nisoldipine. Shortcomings of calcium antagonists include short or unknown duration of action after bolus administration, severe drop in blood pressure, and lack of commercial availability of solutions for injection of many substances. Isosorbide dinitrate induces profound coronary dilation; however, after sublingual administration marked blood pressure decrease can occur, and the duration of action and ideal dose of intracoronary isosorbide dinitrate has not been investigated yet. Injections of molsidomine and its active metabolite, SIN-1, cause longlasting, reproducible, maximal coronary dilation, although only after a waiting period of at least 10 minutes; unfortunately, SIN-1 is only commercially available in France. Nitroglycerin induces reproducible maximal coronary dilation and is easy to administer sublingually or as intracoronary bolus injection with rapid onset of action and no major side effects. The short duration of action may require repeated administrations. To date, repeated intracoronary bolus injections of 0.1 mg nitroglycerin every 10 minutes seem to be the optimal known regimen for standardization of coronary vasomotor tone in serial angiographic studies. Further investigations in this field with old and new vasodilatory drugs are recommendable.

Influence of prior ACE inhibitor therapy on morbidity and mortality following acute myocardial infarction

BACKGROUND

Angiotensin-converting enzyme inhibitor (ACE-I) therapy reduces complications of acute myocardial infarction (MI) even when the therapy is started very early after an acute event. This study sought to determine whether administration of ACE-I therapy prior to acute MI is related to subsequent patient morbidity and mortality.

METHODS

Chart review of 318 consecutive patients admitted between September 1995 and December 1996 with a diagnosis of acute MI. Outcome data were compared between patient groups receiving ACE-I therapy prior to infarction and those who were not.

RESULTS

Sixty-four patients (20%) were receiving prior ACE-I therapy. They experienced smaller MIs, as determined by peak creatine kinase elevation (1066 +/- 134 vs. 1510 +/- 95 IU; p < 0.05), and fewer Q-wave infarctions (p < 0.05) than did patients who were not receiving prior treatment. The severity of coronary artery disease, defined by an angiographic score, was similar for the two groups. Mortality rates, including patients resuscitated from ventricular fibrillation, were similar within the first 72 hours of admission (3% vs. 2%; p = NS), but patients receiving prior ACE-I therapy showed a greater long-term in-hospital mortality rate (14% vs. 5%; p < 0.05) related to more heart failure deaths. Multivariate logistic regression analysis identified age, treatment with digoxin prior to acute MI, and left ventricular ejection fraction after infarction, but not ACE-I therapy taken prior to infarction, as significant independent predictors of mortality and combined morbidity and mortality.

CONCLUSIONS

In a group of patients experiencing an acute MI, those receiving prior ACE-I therapy were more likely to sustain fewer transmural MIs and smaller infarcts. Chronic ACE-I therapy may have cardioprotective effects during acute myocardial ischemia.

Combination of fosinopril and pravastatin decreases platelet response to thrombin receptor agonist in monkeys

Both angiotensin-converting enzyme (ACE) inhibitors and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors have been shown to decrease cardiovascular morbidity and mortality. Results from clinical trials have suggested that HMG-CoA reductase inhibition might exert a beneficial effect independent of its lipid-lowering effect, and ACE inhibition may exert a benefit independent of blood-pressure lowering. To test the hypothesis that such an effect might be mediated by alteration in platelet reactivity, we studied 55 monkeys receiving both, 1, or neither of the ACE inhibitor fosinopril and the HMG-CoA reductase inhibitor pravastatin. Platelet responsiveness to collagen and to the thrombin receptor agonist (TRA) SFLRRN-NH2 was determined by aggregometry. For each agonist, the maximum rate and extent of aggregation were measured for each dose, and the concentration required for half-maximal response (C50) was determined. Each drug, when given alone, slightly decreased the dose of agonist required to produce 50% response in the rate and extent of platelet aggregation relative to control. The combination of the 2 drugs, however, produced a significant increase in the dose of TRA required to produce 50% response in the rate and extent of aggregation relative to either drug alone or the control group. This was not true for collagen. The magnitude of the change relative to the control group, 47% for rate and 30% for extent of aggregation, could confer considerable protection by changing the threshold for thrombin-induced platelet aggregation and, thus, decrease thrombosis.

Role of angiotensin-converting enzyme inhibition in reversal of endothelial dysfunction in coronary artery disease

Angiotensin-converting enzyme (ACE) inhibitors have shown unexpected benefits in the prevention of ischemic events in patients with hypertension and congestive heart failure. In addition to these clinical observations, there is a growing body of knowledge about the molecular and cellular effects of ACE inhibitors. For example, ACE inhibition prevents stimulation of smooth muscle cell angiotensin II receptors, thereby blocking both contractile and proliferative actions. Angiotensin II blockade also diminishes the production of superoxide anion, which inactivates ambient nitric oxide. ACE inhibition of kininase II inhibits the breakdown of bradykinin, a direct stimulant of nitric oxide release from the intact endothelial cell. Thus, at the cellular level within the vasculature, ACE inhibition shifts the balance of ongoing mechanisms in favor of those promoting vasodilatory, antiaggregatory, antithrombotic, and antiproliferative effects. These effects underlie the potential benefits of ACE inhibition in the therapy of ischemia and atherosclerosis. Some data is available in humans to show that these effects can be sustained for months, thereby maintaining improved endothelial function and, presumably, allowing the initiation of steps that might alter the progression of atherosclerosis. Definitive information is not yet available in humans to show that ACE inhibition clearly alters the progression of atherosclerosis or diminishes coronary events in uncomplicated coronary disease. This promising area of investigation is, however, the subject of multiple clinical trials, which should provide clarification of this important question in coming years.

Inhibitors of the renin angiotensin system: implications for the anaesthesiologist

The major long-term benefits of angiotensin-converting enzyme (ACE) inhibitors have now clearly been demonstrated in patients with arterial hypertension, cardiac insufficiency, coronary artery disease and several renal diseases. Such long-term treatment markedly alters the cardiovascular response to anaesthesia and surgery, whereas preliminary data suggest that short-term renin angiotensin system blockade might provide perioperative organ protection and improved circulatory conditions. Besides the classic view that the conversion of angiotensin I to angiotensin II is mainly due to ACE, alternative pathways have recently been identified, including cathepsin G as well as chymostatin- and aprotinin-sensitive serine proteases that are released from mastocytes and endothelial cells and which are insensitive to the effects of ACE inhibitors. These proteases are thought to contribute to tissue perfusion under hypoxic conditions and to structural remodelling. In clinical practice, ACE inhibitors may be preferred to angiotensin II receptor antagonists since the former, besides reducing angiotensin II synthesis, also lead to an accumulation of kinins (e.g. bradykinin), which have important cardio- and renal protective effects through liberation of prostacyclin and nitric oxide in endothelial cells and through stimulation of guanylate cyclase to form cyclic GMP.

[Therapeutic options for improvement of myocardial perfusion in coronary atherosclerosis]

The combination of morphological atherosclerotic alterations of coronary vessels and disturbance of coronary vasomotor control of epicardial and resistance vessels determines the amount of myocardial oxygen supply. The endothelium plays a crucial role for functional alterations of the coronary vessels in patients with early atherosclerosis or risk factors for coronary artery disease. A therapy which aims to ameliorate endothelium-dependent vasodilator capacity improves myocardial perfusion in patients with coronary artery disease. Thereby, even in patients with angiographically normal or minimally diseased coronary vessels who develop myocardial ischemia due to microvascular disease, symptomatic improvement might be achieved. Control of coronary vasomotor tone and proliferation processes within the vessel wall are both determined by the redox equilibrium of nitric oxide (NO) and superoxide radicals (O2-), induced by angiotensin II. Thus, vasomotor control and vessel wall proliferation is closely related to each other. Aim of a therapeutic intervention to enhance NO bioactivity is either to increase NO production in the endothelium or to decrease O2- production, which rapidly inactivates NO. NO bioactivity can be ameliorated by ACE-inhibitors, increase of shear stress on the endothelium by physical exercise, estrogens or L-arginine. For these therapies clinically an improvement of endothelial vasodilator function could be shown. In addition, improvement of endothelial vasodilator function can be achieved by a treatment which reduced oxidative stress in the vascular wall such as antioxidants and, especially, lipid lowering drugs. Endothelin-antagonists and angiotensin II receptor-blockers are promising to improve endothelial dysfunction. However, these therapies have to be validated. Most therapy strategies, which have shown to ameliorate endothelial dysfunction, are also able to improve prognosis of the patients. Whether endothelial dysfunction alone--without evidence of overt coronary atherosclerosis--is sufficient to justify a long-term therapy to improve prognosis, still has to be clarified.

Do ACE inhibitors provide protection for the heart in the clinical setting of acute myocardial infarction?

Large randomised clinical trials have shown ACE inhibitors to improve survival after acute myocardial infarction (AMI). The precise mechanism underlying this benefit is not fully established, despite extensive research. There is also controversy with regard to the clinical use of these drugs, particularly the need for selection of patients prior to treatment and the timing of drug initiation and withdrawal for maximum benefit. Animal models of AMI used to assess drug effects are of limited value in understanding the mechanisms of benefit because they involve significantly different pathophysiology from that which occurs in humans. Here we propose that the benefit of ACE inhibitor therapy is largely confined, post-AMI, to those with evidence of left ventricular dysfunction clinically or on investigation, and suggest the continuing importance of treatment distant from the acute event. We argue that the beneficial effects are, at least in part, related to a reduction in the direct toxic effects of angiotensin II and catecholamines on cardiomyocytes resulting from the long term excess stimulation of the renin-angiotensin and sympathetic systems in these patients. Importantly, we believe that for some patients after AMI there is little or no benefit to be gained from treatment and that, in fact, careful analysis of the trials suggests that ACE inhibitors may be associated with adverse outcomes in some individuals. Finally, since ACE inhibitors also potentiate bradykinin and other peptides, their beneficial action may not simply be due to reducing the formation of angiotensin II. The proportion of the benefit that may be via bradykinin is difficult to assess, especially in humans. However, the advent of the angiotensin receptor antagonists has provided the opportunity to investigate this important issue.

Current perspective on the use of angiotensin-converting enzyme inhibitors in the management of coronary (atherosclerotic) artery disease

OBJECTIVE

To review the pathophysiology of atherosclerosis, the role of the renin-angiotensin system in atherogenesis, and studies supporting the potential beneficial effects of angiotensin-converting enzyme (ACE) inhibitors in reducing cardiovascular events with long-term use.

BACKGROUND

Through its action in converting angiotensin I to angiotensin II and by degrading bradykinin, local tissue ACE exerts many effects that can contribute to the development of atherosclerosis. Therefore, the use of ACE inhibitors can possibly result in antiatherogenic effects. Possible mechanisms for antiatherogenic effects of ACE inhibitors include: (1) reduction of blood pressure; (2) antiproliferative and antimigratory effects on vascular smooth muscle cells, neutrophils, and monocytes; (3) restoration of endothelial function; (4) stabilization of fatty plaque by preventing vasoconstriction; (5) antiplatelet effects; and (6) enhancement of endogenous fibrinolysis.

DATA SOURCES

English-language clinical studies, abstracts, and review articles pertaining to the use of ACE inhibitors and atherosclerosis.

STUDY SELECTION AND DATA EXTRACTION

Relevant human studies examining the role of ACE inhibitors and atherosclerosis.

DATA SYNTHESIS

Studies evaluating the possible beneficial effects of ACE inhibitors in the development of atherosclerosis are reviewed and critiqued. Design of ongoing studies with clinical and surrogate end points are discussed.

CONCLUSIONS

Based on current published studies, recommendations are made regarding the use of ACE inhibitors in atherosclerosis. Therapeutic monitoring parameters for efficacy and adverse effects are also reviewed.

The potential use of angiotensin-converting enzyme inhibitors in patients with hyperlipidemia

New evidence suggests an interaction between hyperlipidemia, activation of the renin-angiotensin system, and atherosclerotic disease. In patients with atherosclerosis and hyperlipidemia, coronary endothelial dysfunction is usually diffuse and affects vasomotor tone, platelet activity, thrombosis, fibrinolysis, and regulation of inflammatory cells. Angiotensin II, an important oxidant, alters the binding of low-density-lipoprotein (LDL) cholesterol to its receptors and increases endothelial uptake of LDL. Endothelial dysfunction is worsened by the suppression of nitric oxide production and/or release via angiotensin II-associated degradation of bradykinin and oxygen free radical production, resulting in inadequate vasorelaxation. Therapy with angiotensin-converting enzyme (ACE) inhibitors appears to eliminate these untoward effects and may ameliorate the tendency for myocardial infarction associated with elevated plasma levels of angiotensin II. Although the role of ACE inhibitors in the prevention and/or treatment of coronary artery disease in patients without left ventricular dysfunction remains to be established, the capacity of ACE inhibition to correct endothelial dysfunction offers promise. The ability of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors to improve endothelial function, prevent the progression of coronary atherosclerosis, reduce the incidence of ischemic events, and improve survival is well known. Potentially, ACE inhibitors may have an additive or synergistic effect on the development of atherosclerosis and the clinical consequences of this disease when used in combination therapy with lipid-lowering strategies.

Angiotensin-converting enzyme inhibitor therapy affects left ventricular mass in patients with ejection fraction > 40% after acute myocardial infarction

OBJECTIVES

We tested the hypothesis that angiotensin-converting enzyme (ACE) inhibitor therapy decreases left ventricular (LV) mass in patients with a left ventricular ejection fraction (LVEF) > 40% and no evidence of heart failure after their first acute Q wave myocardial infarction (MI).

BACKGROUND

Recently, ACE inhibitor therapy has been shown to have an early mortality benefit in unselected patients with acute MI, including patients without heart failure and a LVEF > 35%. However, the effects on LV mass and volume in this patient population have not been studied.

METHODS

Thirty-five patients with a LVEF > 40% after their first acute Q wave MI were randomized to titrated oral ramipril (n = 20) or conventional therapy (control, n = 15). Magnetic resonance imaging (MRI) performed an average of 7 days and 3 months after MI provided LV volumes and mass from summated serial short-axis slices.

RESULTS

Left ventricular end-diastolic volume index did not change in ramipril-treated patients (62 +/- 16 [SD] to 66 +/- 17 ml/m2) or in control patients (62 +/- 16 to 68 +/- 17 ml/m2), and stroke volume index increased significantly in both groups. However, LV mass index decreased in ramipril-treated patients (82 +/- 18 to 73 +/- 19 g/m2, p = 0.0002) but not in the control patients (77 +/- 15 to 79 +/- 23 g/m2). Systolic arterial pressure did not change in either group at 3-month follow-up.

CONCLUSIONS

In patients with a LVEF > 40% after acute MI, ramipril decreased LV mass, and blood pressure and LV function were unchanged after 3 months of therapy. Whether the decrease in mass represents a sustained effect that is associated with a decrease in morbid events requires further investigation.

Angiotensin-converting enzyme inhibition after acute myocardial infarction with special reference to the Fourth International Study of Infarct Survival (ISIS-4)

Role of ACE inhibitors in the management of asymptomatic or symptomatic left ventricular (LV) dysfunction after acute myocardial infarction (AMI) is well established. More recently, large clinical trials have evaluated the use of angiotensin-converting enzyme (ACE) inhibitors early after AMI, ie, within 24 hours of symptom onset. This concept has emerged with the understanding of pathophysiological changes occurring after AMI. Neurohormonal activation and ventricular remodelling after AMI form the basis of these changes, whereas the extent of LV dysfunction remains strongly predictive of poor outcome. The large clinical trials with mortality end point have shown modest benefit with early use of ACE inhibitors in an unselected population. However, the generalized use of ACE inhibitors remains controversial because of an overall small benefit. We review the pathophysiological changes occurring after AMI, the rationale for early use of ACE inhibitors, and the data available from the large clinical trials. We recommend consideration of early ACE inhibitor in all but the lowest risk patients. Clinical features of such a low-risk population would include small and nonanterior infarctions in patients less than 65 years of age and with LV ejection fractions greater than 50%. Objective assessment of LV function is warranted during hospitalization for AMI to appropriately select patients for ACE inhibitor therapy. Dosing should be started carefully to avoid hypotension and should be titrated to the goal of doses used in the large trials. Duration of therapy in patients at high risk for death or ventricular enlargement should be indefinite. Further large-scale secondary prevention trials with long-term treatment are underway to assess the effect of ACE inhibition on coronary disease progression and reinfarction.