Calcium channel blockers in heart failure

Effects of selective calcium channel blockers on ions' permeation through the human Cav1.2 ion channel: A computational study

Selective calcium channel antagonists are widely used in the treatment of cardiovascular disorders. They are mainly classified into 1,4-dihydropyridine (1,4-DHPs) and non-DHPs. The non-DHPs class is further classified into phenylalkylamines (PAAs) and benzothiazepines (BZTs) derivatives. These blockers are used for the treatment of hypertension, angina pectoris, and cardiac arrhythmias. Despite their well-established efficiency, the structural basis behind their activity is not very clear. Here we report the use of a near-open confirmation (NOC) model of the Cav1.2 cardiac ion channel to examine the mode of binding of these antagonists within the pore domain as well as the fenestration of the pore-forming domains. Effects of calcium ion permeation in the presence of drug molecules were assessed using steered molecular dynamics (SMD) simulations. These studies reveal that nicardipine, a DHP derivative, shows a strong Cav1.2 blocking activity, requiring more 2500 pN force to pull calcium ion towards the channel's pore in the presence of the compound. Similar blocking activity was observed for verapamil, a PAA derivative, requiring almost 2300 pN of force. The least blocking activity was observed for Diltiazem, a BZT derivative. Our results explain the structural basis and the binding details of 1,4-DHPs, PAAs and BZTs at their distinct Cav1.2 sites and offer detailed insights into their mechanism of action in modulating the Cav1.2 channel.

RBM20 Mutations Induce an Arrhythmogenic Dilated Cardiomyopathy Related to Disturbed Calcium Handling

Background:

Mutations in RBM20 (RNA-binding motif protein 20) cause a clinically aggressive form of dilated cardiomyopathy, with an increased risk of malignant ventricular arrhythmias. RBM20 is a splicing factor that targets multiple pivotal cardiac genes, such as Titin (TTN) and CAMK2D (calcium/calmodulin-dependent kinase II delta). Aberrant TTN splicing is thought to be the main determinant of RBM20-induced dilated cardiomyopathy, but is not likely to explain the increased risk of arrhythmias. Here, we investigated the extent to which RBM20 mutation carriers have an increased risk of arrhythmias and explore the underlying molecular mechanism.

Methods:

We compared clinical characteristics of RBM20 and TTN mutation carriers and used our previously generated Rbm20 knockout (KO) mice to investigate downstream effects of Rbm20-dependent splicing. Cellular electrophysiology and Ca 2+ measurements were performed on isolated cardiomyocytes from Rbm20 KO mice to determine the intracellular consequences of reduced Rbm20 levels.

Results:

Sustained ventricular arrhythmias were more frequent in human RBM20 mutation carriers than in TTN mutation carriers (44% versus 5%, respectively, P =0.006). Splicing events that affected Ca 2+ - and ion-handling genes were enriched in Rbm20 KO mice, most notably in the genes CamkIIδ and RyR2. Aberrant splicing of CamkIIδ in Rbm20 KO mice resulted in a remarkable shift of CamkIIδ toward the δ-A isoform that is known to activate the L-type Ca 2+ current ( I Ca,L ). In line with this, we found an increased I Ca,L , intracellular Ca 2+ overload and increased sarcoplasmic reticulum Ca 2+ content in Rbm20 KO myocytes. In addition, not only complete loss of Rbm20, but also heterozygous loss of Rbm20 increased spontaneous sarcoplasmic reticulum Ca 2+ releases, which could be attenuated by treatment with the I Ca,L antagonist verapamil.

Conclusions:

We show that loss of Rbm20 disturbs Ca 2+ handling and leads to more proarrhythmic Ca 2+ releases from the sarcoplasmic reticulum. Patients that carry a pathogenic RBM20 mutation have more ventricular arrhythmias despite a similar left ventricular function, in comparison with patients with a TTN mutation. Our experimental data suggest that RBM20 mutation carriers may benefit from treatment with an I Ca,L blocker to reduce their arrhythmia burden.

Pregabalin and heart failure: A population-based study

PURPOSE

The anticonvulsant pregabalin is increasingly prescribed for pain, seizures, and psychiatric disorders. Although evidence suggests pregabalin can cause edema and heart failure, its cardiac safety profile in clinical practice is unknown. We sought to examine the risk of heart failure among older patients receiving pregabalin compared to those receiving gabapentin.

METHODS

We conducted a population-based cohort study of Ontarians aged 66 and older with a history of seizure who received pregabalin or gabapentin between April 2013 and March 2014. We used propensity scores to match patients commencing pregabalin to those commencing gabapentin. The primary outcome was an emergency department visit or hospitalization for heart failure within 90 days.

RESULTS

We studied 9855 patients who initiated pregabalin and an equal number treated with gabapentin. In the primary analysis, we found no difference in the risk of heart failure with pregabalin compared to gabapentin (1.2% versus 1.3%, hazard ratio of 0.77; 95% CI 0.58-1.03). Secondary analyses stratified for baseline history of heart failure yielded similar findings.

CONCLUSION

In a large cohort of older patients with a seizure disorder, pregabalin was not associated with an increased risk of heart failure relative to gabapentin.

Flunarizine rescues reduced lifespan in CLN3 triple knock-out Caenorhabditis elegans model of batten disease

CLN3 disease (Spielmeyer-Vogt-Sjogren-Batten disease, previously known as classic juvenile neuronal ceroid lipofuscinosis, NCL) is a pediatric-onset progressive neurodegenerative disease characterized by progressive vision loss, seizures, loss of cognitive and motor function, and early death. While no precise biochemical mechanism or therapies are known, the pathogenesis of CLN3 disease involves intracellular calcium accumulation that may trigger apoptosis. Our prior work in in vitro cell models of CLN3 deficiency suggested that FDA-approved calcium channel antagonists may have therapeutic value. To further evaluate the potential efficacy of this approach in an otherwise untreatable disorder, we sought to compare the therapeutic effects and underlying mechanisms in an animal model of CLN3 disease. Here, we used the well-characterized XT7 complete cln-3 knockout strain of C. elegans to evaluate the therapeutic efficacy of calcium channel antagonist therapy in a living animal model of Batten disease. Therapeutic effects of five calcium channel antagonists were evaluated on XT7 animal lifespan and in vivo mitochondrial physiology. Remarkably, maximal therapeutic efficacy in this model animal was observed with 1 μM flunarizine, the identical concentration previously identified in cell-based neuronal models of CLN3 disease. Specifically, flunarizine rescued the short lifespan of XT7 worms and prevented their pathophysiologic mitochondrial accumulation. These results confirm the treatment efficacy and dosing of flunarizine in cln-3 disease in a translational model organism. Clinical treatment trials in CLN3 human patients are now needed to test the dosing regimen and efficacy of flunarizine in individuals suffering with this otherwise untreatable and ultimately lethal neurologic disease.

Mechanism of vasoselective action of mebudipine, a new calcium channel blocker

In previous studies, mebudipine, a newly synthesized dihydropyridine calcium channel blocker, showed a considerable vasoselective action. To investigate the mechanism of this property, the pattern of inhibitory action on the KCl-induced contraction in isolated rat aortic rings and the effect of changing resting membrane potential on the potency of this compound were considered. In addition, its chronotropic and inotropic actions were also studied. Mebudipine inhibited KCl-induced contractions. Its inhibitory effect was progressive and needed time to reach maximum. Incubation of the aortic rings in depolarizing physiological solution (high potassium, zero calcium) resulted in the augmentation of mebudipine effect. The potency of mebudipine in inhibiting aortic contractions and its time- and voltage-dependent action were significantly greater than those of nifedipine. In comparison with nifedipine, mebudipine showed a greater negative chronotropic effect, but in the case of negative inotropism, the reverse relation was observed. It is concluded that mebudipine has a greater time- and voltage-dependent inhibitory effect, as compared to nifedipine and this property could explain its prominent vasoselective action. It has also marked negative chronotropic effect and minor negative inotropic action. With regard to the above findings, mebudipine might have a selective and protective calcium channel blocking effect in ischemic regions (ischemia-selectivity), and the potential to be used in cardiovascular diseases without causing harmful effects such as reflex tachycardia and heart failure which have sometimes been seen with the older agents.

Chronic angina pectoris: inadequacies of current therapy

Chronic angina is a major medical problem in the United States with more than 6 million patients affected, a number that will increase substantially because of the progressive aging of the population. The annual mortality rate for patients with chronic angina is approximately 2%, but is much higher in certain subsets of patients, particularly the elderly. Angina is also associated with major social and economic burdens. Because of poor symptom control and hemodynamic, as well as other drug side effects, angina is commonly associated with a poor quality of life. No new class of drug has been available for angina treatment in more than two decades, and current medications frequently fail to provide adequate symptom control. Thus, the majority of patients are taking two or three antianginal medications. New agents that modulate myocardial metabolism have shown antianginal efficacy, a favorable side-effect profile, and an absence of hemodynamic effects.

Drug treatment of stable angina pectoris in the elderly: defining the place of calcium channel antagonists

Chronic stable angina pectoris (CSAP) resulting from coronary artery disease (CAD) is common in elderly patients, and significantly reduces their quality of life. Myocardial revascularisation procedures in this age group entail significant risks, largely related to comorbidities rather than advanced age itself. Coronary artery anatomy is more likely to be technically unsuitable for revascularisation and angina more resistant to drug treatment. Therefore, elderly patients often take combinations of antianginal drugs. Calcium channel antagonists (CCAs) are effective antianginal drugs first introduced for clinical use in the late 1970's. They reduce myocardial ischaemia by both causing vasodilatation of coronary resistance vessels and reducing cardiac workload (negative inotropic effect). However, adverse effects related to abrupt arterial vasodilatation limited the tolerability of these short acting 'first generation' drugs (nifedipine, verapamil and diltiazem). Furthermore, short acting nifedipine may occasionally increase both the frequency of angina pectoris and mortality in patients with CAD. Since then, long acting formulations of first generation agents and new chemical entities (second and third generation drugs) have been developed. These are well tolerated and effective at attenuating both myocardial ischaemia and the frequency and severity of angina pectoris in most patients with stable CAD. Current guidelines on the drug treatment of CSAP propose that beta-adrenoceptor antagonists (beta-blockers) should be used as first line medication primarily for their prognostic benefits, and that CCAs need only be introduced if beta-blockers are not tolerated, contraindicated or ineffective. Despite this, there is a wealth of evidence from clinical trials that demonstrate equal antianginal efficacy for CCAs and beta-blockers. The presence of chronic heart failure and prior myocardial infarction are clear indications for the use of beta-blockers in preference to CCAs for the treatment of CSAP. However, in patients with both CSAP and hypertension, second and third generation CCAs may offer prognostic benefits of similar magnitude to those provided by beta-blockers. Therefore, antianginal drug therapy must be tailored to the individual needs and comorbidities of each elderly patient.

Pharmacological modulators of voltage-gated calcium channels and their therapeutical application

Calcium channels (CCs) play an important role in the transduction of action potential to the cytosol. An influx of Ca(2+) is essential for muscle contraction, neurotransmitter, and hormonal release. Level of cytosolic Ca(2+) controls activities of many enzymes and regulatory proteins. Voltage-gated calcium channels (VGCCs) serve as sensors for membrane depolarization. Blood pressure reduction is due to relaxation of actomyosine filaments in vascular smooth muscles. Calcium channel blockers (CCBs) are traditionally used for treatment of cardiovascular diseases. Neurotransmitter release from presynaptic neurons is triggered by Ca(2+) influx. Blockers of neuronal CCs may be applied for pain treatment. Overload of neurons by Ca(2+) is toxic. CCBs may be applied for prevention of some neurodegenerative disorders.

Effects of amlodipine on sympathetic nerve traffic and baroreflex control of circulation in heart failure

Short-acting calcium antagonists exert a sympathoexcitation that in heart failure further enhances an already elevated sympathetic activity. Whether this is also the case for long-acting formulations is not yet established, despite the prognostic importance of sympathetic activation in heart failure. It is also undetermined whether in this condition long-acting calcium antagonists favorably affect a mechanism potentially responsible for the sympathetic activation, ie, the baroreflex impairment. In 28 heart failure patients (NYHA functional class II) under conventional treatment we measured plasma norepinephrine and efferent postganglionic muscle sympathetic nerve activity (microneurography) at rest and during arterial baroreceptor stimulation and deactivation induced by stepwise intravenous infusions of phenylephrine and nitroprusside, respectively. Measurements were performed at baseline and after 8 weeks of daily oral amlodipine administration (10 mg/d, 14 patients) or before and after an 8-week period without calcium antagonist administration (14 patients). Amlodipine caused a small and insignificant blood pressure reduction. Heart rate, left ventricular ejection fraction, and plasma renin and aldosterone concentrations were not affected. This was the case also for plasma norepinephrine (from 2.43+/-0.41 to 2.50+/-0.34 nmol/L, mean+/-SEM), muscle sympathetic nerve activity (from 54.4+/-5.9 to 51.0+/-4.3 bursts/min), and arterial baroreflex responses. No change in the above-mentioned variables was seen in the control group. Thus, in mild heart failure amlodipine treatment does not adversely affect sympathetic activity and baroreflex control of the heart and sympathetic tone. This implies that in this condition long-acting calcium antagonists can be administered without untoward neurohumoral effects anytime conventional treatment needs to be complemented by drugs causing additional vasodilatation.

The clinical significance of neurohormonal activation

Progressive heart disease after the onset of left ventricular dysfunction has typically been attributed to hemodynamic factors. As left ventricular function declines, decreased cardiac output and tissue hypoperfusion lead to compensatory increases in afterload, preload, and heart rate. The purpose of these compensatory responses is to increase cardiac output and maintain tissue perfusion; however, they may also create hemodynamic stress for the failing heart. However, this does not explain the progression of heart failure despite hemodynamic maintenance with pharmacologic therapy. Activation of neurohormonal systems that are essential for homeostasis in the normal heart plays a key role in the progression of heart failure. In acute heart failure, these systems have beneficial effects, but in chronic heart failure their activation produces deleterious effects by increasing the load on the left ventricle and promoting structural remodeling, which may further impair left ventricular function. The issue of neurohormonal activation is an important one in cardiovascular medicine, not only for patients with heart failure but also for patients with hypertension and ischemic heart disease when left ventricular dysfunction is present. As neurohormonal activation may play a pathogenic role in the long-term outcome of patients, interventions that have favorable hemodynamic but unfavorable neurohormonal effects can actually exacerbate cardiac disease and may increase cardiovascular morbidity and mortality. As neurohormonal activation appears to parallel the severity of heart failure, whether assessed according to symptoms or prognosis, an understanding of neurohormonal activation and its interaction with hemodynamic factors is essential for optimizing pharmacologic therapy for cardiovascular disease.

Safety of calcium antagonists in patients with congestive heart failure

Continuing high morbidity and mortality have spurred an ongoing search for new therapeutic agents for patients with congestive heart failure. Calcium antagonists (CAs) have been under active investigation in patients with heart failure since their introduction into clinical medicine, because their anti-ischemic and vasodilator properties were thought to be of potential benefit in this patient population. However, review of published clinical trials of CAs in patients with heart failure reveals that some of these drugs are associated with detrimental effects, including acute hemodynamic deterioration, increased symptoms of heart failure, and increased mortality. The adverse effects of short-acting CAs in patients with heart failure include negative inotropic effects and neurohormonal activation. Long-acting CAs, such as amlodipine and felodipine, had fewer negative inotropic effects, showed less evidence of neurohormonal activation, and were better tolerated in clinical trials. Amlodipine, in combination with an angiotensin-converting enzyme inhibitor, had a neutral effect in patients with ischemic heart failure and an unexplained benefit in a subgroup of patients with non-ischemic cardiomyopathy. Although the preliminary experience with long-acting dihydropyridine CAs in heart failure has been encouraging, safety concerns raised by past trials dictate that no CA can be recommended for the treatment of heart failure at this time.

Effects of nisoldipine and/or enalapril on left ventricular function and exercise capacity in patients with recent anterior myocardial infarction and mild cardiac dysfunction

Treatment of abnormal remodeling and dysfunction of left ventricle after myocardial infarction is one of the major goals of recent therapeutic interventions. The current study, the Nisoldipine Enalapril Anterior Myocardial infarction Study pilot investigation, was designed to investigate the effects of 12 weeks of treatment with enalapril or nisoldipine or their combination on left ventricular (LV) function and exercise capacity in patients with recent (< 1 month) anterior myocardial infarction and mild LV dysfunction (LV ejection fraction [EF] 38% to 48%). Forty-six patients were studied and received, by random assignment, enalapril (5 mg once per day) plus placebo (n = 14) or nisoldipine (10 mg two times per day) plus placebo (n = 18) or enalapril (5 mg once per day) plus nisoldipine (10 mg two times per day) (n = 14). All patients received aspirin (325 mg) throughout the study. Data on LV EF and peak filling rate at rest and LV EF during exercise were collected during radionuclide ventriculography. In addition, the product of heart rate and systolic blood pressure (rate-pressure product) and exercise time were determined during exercise stress testing. The analyzed parameters were not significantly modified after treatment with enalapril or with nisoldipine. In contrast, the combination of enalapril and nisoldipine significantly raised LV EF at rest (from 43% +/- 3% to 48% +/- 6%, p < 0.01) and during exercise (from 45% +/- 8% to 50% +/- 9%, p < 0.01) and raised peak filling rate at rest (fraction of end-diastolic volume per second) from 1.57 +/- 0.3 to 1.67 +/- 0.3 (p < 0.05). In addition, the combined administration of the two drugs increased the rate-pressure product (values x 10(3)) (from 20.7 +/- 5 to 22.7 +/- 4, p < 0.05) and increased exercise time (from 573 +/- 173 seconds to 668 +/- 178 seconds, p < 0.05). These results show that in patients with recent anterior myocardial infarction and mild LV dysfunction, the combination of the angiotensin-converting enzyme inhibitor enalapril and the dihydropyridine nisoldipine improves resting LV systolic and diastolic function and exercise LV systolic function and exercise capacity.

Effect of mibefradil on left ventricular diastolic function in patients with congestive heart failure

Calcium antagonists have antihypertensive and antianginal properties. In heart failure, however, their use can be hazardous, as systolic function can deteriorate. This may not be true of the new calcium antagonist mibefradil, which has a new chemical structure. Calcium antagonists may also be beneficial for diastolic left ventricular function in coronary artery disease. To investigate the possible effects of mibefradil on diastolic left ventricular function, we performed the present study as a multicenter, double-blind,placebo-controlled, multiple-dose safety trial. Fifteen patients with New York Heart Association (NYHA) class II or III for dyspnea and depressed ejection fraction (<40%) due to a previous myocardial infarction were investigated. The measured nuclear angiographic parameters included ejection fraction (EF), peak ejection rate (PER), and peak filling rate (PFR). Systolic and diastolic blood pressure (SBP, DBP) and heart rate (HR) were also obtained. Group I (5 patients) received placebo medication; group IIA (6 patients) received mibefradil 6.25, 12.5, or 25 mg/day; and group IIB (4 patients) received mibefradil 50 or 100 mg/day. Measurements were made before and after the first dose and after 1 week of treatment before and after the final dose. Mibefradil clearly decreased HR (repeated-measures analysis of variance p < 0.05). No statistically significant effects of mibefradil were noted on SBP or DBP or on systolic and diastolic left ventricular function. In our study conditions, mibefradil caused no worsening of systolic function and preserved diastolic function in short-term treatment of patients with decreased EF and heart failure.

Acute hemodynamic and long-term clinical effects of isradipine in patients with coronary artery disease and chronic heart failure. A double-blind, placebo-controlled study

To assess the acute hemodynamic and long-term clinical effects of isradipine, a calcium antagonist of the dihydropyridine class, we performed a double-blind, placebo-controlled parallel study in 19 patients with coronary artery disease (CAD) and stable chronic heart failure (CHF). Their mean age was 56 +/- 5 years, and left ventricular ejection fraction (LVEF) was 0.18 +/- 0.05. Patients were treated with diuretics and digoxin only. All were clinically stable and in sinus rhythm. The acute hemodynamic study showed that (intravenous) isradipine increased cardiac index (+36%) and stroke volume index (+30%) (both P < 0.001), while systemic vascular resistance (-33%) and mean arterial pressure (-10%) decreased (both P < 0.005). Filling pressures and heart rate were not affected. Of the 19 patients, 17 completed the 12 week study; 2 patients on placebo (1 death, 1 side-effects) but no patient on isradipine (5 mg 3 times daily) dropped out. After 12 weeks, peak oxygen consumption (VO2), LVEF, echocardiographic indices, and other clinical parameters were unaffected by treatment. Repeat invasive hemodynamic measurements showed that the initial improvement by isradipine was not present anymore. In conclusion, despite a beneficial acute hemodynamic effect, isradipine has no favorable clinical influence during prolonged treatment in patients with mild to moderate CHF.

New drugs in the treatment of heart failure

1. Current therapy of heart failure relies on diuretics, positive inotropic compounds and vasodilators. The short-term haemodynamic benefits, especially of the cAMP generators, may be compromised by long-term limitations leading to an increased mortality. In contrast, some vasodilators, especially angiotensin converting enzyme inhibitors, improve survival even in severe heart failure. 2. Modulation of Na(+)- or K(+)-channels and calcium sensitization are positive inotropic mechanisms whose promise in treatment of heart failure needs to be fully explored. 3. The introduction of vasodilator therapy has been a significant advance. Newer compounds act to inhibit the endogenous vasoconstrictors angiotensin II and endothelin, or to potentiate the endogenous vasodilators atrial natriuretic factor and nitric oxide. The full potential of these compounds is yet to be realised.

Diagnosis and outpatient management of congestive heart failure

Congestive heart failure causes substantial patient morbidity and mortality in the United States. Symptoms and physical findings can be helpful in diagnosis but have limited sensitivity and specificity. Objective measurement of ventricular function is essential in virtually all patients in whom a diagnosis of heart failure is suspected. Reversible causes of heart failure must be sought. Outpatient management includes education and counseling, emphasis on and assessment of compliance with diet, and pharmacologic treatment. Angiotensin-converting enzyme inhibitors are the mainstay of treatment but are underused, and maximal doses are not given apparently because of concern about side effects. Diuretic therapy should be administered only as needed to manage fluid overload. Calcium channel blockers are relatively contraindicated in patients with impaired ventricular function. Patient follow-up should be guided by the results of the medical history and physical examination. Routine serial testing of ventricular function and exercise performance is discouraged.

Calcium antagonist use in congestive heart failure: still a bridge too far?

Calcium antagonists continue to be used to treat congestive heart failure (CHF), despite clinical evidence that they may exacerbate the disease. The systemic vasodilatory actions of these drugs make them potentially attractive for use as afterload reducing agents in patients with CHF. Newer calcium antagonists of the 1,4-dihydropyridine class, with claims of little or no negative inotropic properties and minimal effects on the sympathetic nervous system, seem a promising treatment of this disease. All calcium antagonists, however, consistent with their ability to block transmembrane calcium transport in cardiac muscle cells, are intrinsically negative inotropes. Moreover, clinical trial data are inconclusive about the ability of these newer calcium antagonists to activate the sympathetic nervous system. The relatively small numbers of patients with CHF, the differing degrees of CHF in different patient groups, and the variation in route of administration, dosage, and schedule of hemodynamic measurements make analyses of published data difficult. Although some patients with CHF respond positively to treatment with calcium antagonists, there is great individual variability of response, and the majority of patients show deterioration of myocardial function when taking calcium antagonists. Until conclusive clinical evidence of the safety and effectiveness of calcium antagonists in the treatment CHF is available, they should not be used to treat this disease unless individual patient characteristics clearly indicate a positive benefit/risk ratio.

Calcium antagonists and left ventricular dysfunction

Calcium antagonists are used in the management of a variety of cardiovascular disorders. Ischemia leads to left ventricular dysfunction, which is the clinical entity on which the calcium antagonists are expected to have their effect as a result of their anti-ischemic action. This article reviews the efficacy of calcium antagonists in several different settings of left ventricular dysfunction due to ischemia and reperfusion.

Reduction of ischemic events with angiotensin-converting enzyme inhibitors: lessons and controversy emerging from recent clinical trials

Angiotensin-converting enzyme (ACE) inhibitor therapy has been associated with a substantial (> or = 20%) reduction in the risk of major ischemic events in two recent clinical trials with long-term follow-up: Studies of Left Ventricular Dysfunction (SOLVD) and the Survival and Ventricular Enlargement (SAVE) study. Participants in these studies included patients with a low ejection fraction (< or = 0.35 in SOLVD and < or = 0.40 in SAVE), generally without symptoms of congestive heart failure. Approximately 80% of patients enrolled in SOLVD and all participants in SAVE had histories of ischemic heart disease or acute myocardial infarction (SAVE). In both SOLVD and SAVE the risk of experiencing a major ischemic event such as myocardial infarction was reduced significantly following prolonged ACE inhibitor therapy. In the SOLVD trial, this effect was evident across a range of patient subgroups, including varying concomitant drug therapies. In both studies, several months elapsed before this benefit became apparent, suggesting an effect on underlying ischemic pathophysiology. A third trial of ACE inhibitor therapy postinfarction, the Acute Infarction Ramipril Efficacy (AIRE) Study, demonstrated a 27% reduction in all cause mortality but no effect on myocardial infarction after a 15-month mean follow-up. No effect of ACE inhibition on risk of survival or reinfarction was reported in the Cooperative New Scandinavian Enalapril Survival Study (CONSENSUS-II), which began the drug within 24 hours of infarction and terminated follow-up at 6 months, a time not likely to demonstrate infarction reduction benefit based on the SOLVD and SAVE observations. Neither AIRE nor CONSENSUS-II had objectively determined left ventricular dysfunction as an entry criterion, as did SOLVD and SAVE, but AIRE mandated "clinical" congestive heart failure prior to randomization. More recently, preliminary results from the third Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto Miocardico (GISSI-3), the Fourth International Study of Infarct Survival (ISIS-4), and the Chinese Captopril Trial suggested that angiotensin-converting enzyme (ACE) inhibitor mortality benefits post-myocardial infarction would be detected in these megatrials as early as 35 days after the event.(ABSTRACT TRUNCATED AT 400 WORDS)