Enalaprilat in acute myocardial infarction: tolerability and effects on the renin-angiotensin system

Effects of losartan and its combination with quinapril on the cardiac sympathetic nervous system and neurohormonal status in essential hypertension

OBJECTIVE

Sympathetic nervous and renin-angiotensin systems play important roles in essential hypertension. This study was aimed at assessing the effects of losartan or its combination with quinapril on the cardiac nervous system and neurohormonal status in essential hypertension.

DESIGN AND METHODS

Randomized, comparative study of 105 patients with mild essential hypertension, carried out at Shizuoka General Hospital. In phase 1, 40 hypertensives were allocated randomly into the losartan (50 mg) group or the quinapril (10 mg) group. In phase 2, 65 hypertensives, after 3 months 10 mg quinapril monotherapy, were allocated randomly into groups with 50 mg losartan (n = 32) or 5 mg amlodipine (n = 33) added to quinapril, and were treated for a further 3 months. All patients underwent [(123)I]metaiodobenzylguanidine (MIBG) imaging and neurohormonal measurements before and 3 months after treatment.

RESULTS

Both monotherapies significantly increased renin activity, while losartan monotherapy also increased angiotensin II (AII) concentration. In both the losartan and quinapril groups, the washout rate was significantly decreased (18.1 +/- 11.4 versus 13.9 +/- 11.0%, P < 0.0002 and 13.3 +/- 9.3 versus 12.3 +/- 9.1%, P < 00001, respectively) without changes in the heart to mediastinum ratio (H/M ratio). Both combined therapies lowered blood pressure to similar levels. A combination therapy with losartan and quinapril significantly increased the H/M ratio (1.93 +/- 0.29 and 2.02 +/- 0.29, P < 0.01) and decreased the washout rate (17.6 +/- 11.0 and 15.3 +/- 9.2%, P < 0.02) without affecting AII concentration, whereas a combination therapy with amlodipine and quinapril therapy did not affect the scintigraphic parameters with an increase in the AII concentration.

CONCLUSIONS

With a usual antihypertensive dose, both losartan and quinapril had a little suppressive effect on the cardiac sympathetic activity in essential hypertension. In contrast, the combination therapy with losartan and quinapril, which results in a higher degree of inhibition of the renin-angiotensin system, could suppress the cardiac sympathetic activity effectively.

Early neurohormonal effects of trandolapril in patients with left ventricular dysfunction and a recent acute myocardial infarction: a double-blind, randomized, placebo-controlled multicentre study

Angiotensin-converting enzyme inhibitors improve long-term survival in patients with left ventricular dysfunction after a myocardial infarction, but their mechanism of action is not entirely clear. The neurohormonal effects may be important in this respect, as well as an early hemodynamic unloading induced by these drugs. The primary objective was to assess the effect of trandolapril on plasma levels of atrial natriuretic peptide. A secondary objective was to assess the effects of trandolapril on selected neurohormones, vasoactive peptides and enzymes, which may be important in the development of left ventricular remodeling and heart failure following an acute myocardial infarction. A total of 119 patients with an acute myocardial infarction and a wall motion index < or =1.2 (16-segment echocardiographic model) were randomized to double blind treatment with trandolapril or placebo within 3-7 days after the onset of infarction. Blind treatment was discontinued 21 days after the index infarction. Venous blood samples were collected at rest, before randomization and on the day after treatment was discontinued. At the end of the study, there were no differences in plasma levels of atrial natriuretic peptide between the two treatment groups. Angiotensin-converting enzyme activity was suppressed and plasma renin activity was higher in the trandolapril group. No differences in plasma levels of N-terminal pro-atrial natriuretic peptide, brain natriuretic peptide, aldosterone, noradrenaline, adrenaline, vasopressin, big endothelin-1 and neuropeptide Y were found between the two treatment groups. There were positive correlations between several markers of neurohormonal activation at baseline and variables expressing left ventricular dysfunction and clinical heart failure. Neurohormonal activation is related to left ventricular dysfunction. The effects of 2-3 weeks of angiotensin-converting enzyme inhibition on neurohormonal activation does not predict the already established beneficial long-term effects after myocardial infarction. Thus, early modulation of circulatory neurohormone levels may not be a major mechanism for the efficacy of angiotensin-converting enzyme inhibitors in these patients. Selected plasma hormone markers may still be used to identify patients who might get the greatest benefit from treatment.

How often are angiotensin II and aldosterone concentrations raised during chronic ACE inhibitor treatment in cardiac failure?

OBJECTIVE

Angiotensin II (AII) and aldosterone are not always fully suppressed during chronic angiotensin converting enzyme (ACE) inhibitor treatment. In congestive heart failure (CHF) such failure of hormonal suppression is associated with increased mortality. This study examined how common AII and aldosterone increases are observed during routine clinical practice.

PATIENTS AND METHODS

91 patients with symptomatic (mean New York Heart Association class 2.7) CHF (mean (SD) left ventricular ejection fraction 29.9 (8)%, range 9-46%) were studied 4-6 hours after ACE inhibitor dosing. A representative range of ACE inhibitors (enalapril, lisinopril, captopril, perindopril, and fosinopril) was examined.

RESULTS

Supine measurements showed a wide range of AII (10.5 (25.5) pg/ml), aldosterone (130.8 (136) pg/ml), and serum ACE (12.1 (13.3) EU/l; excludes captopril data) concentrations on diuretics. AII concentrations > 10 pg/ml were seen in 15% of patients, and aldosterone concentrations > 144 pg/ml were seen in 38% of patients. AII concentrations were significantly correlated (p < 0.001) with ACE but not with aldosterone concentrations. Aldosterone concentrations were not significantly correlated with ACE concentrations.

CONCLUSIONS

AII "reactivation" occurred in 15% and failure of aldosterone suppression in 38% of routine CHF patients taking ACE inhibitor treatment. AII "reactivation" was associated with both low and high levels of ACE activity, which suggests that multiple different mechanisms are at play. In patients with high plasma ACE concentrations, non-compliance should be considered along with inadequate dose titration. In patients with low plasma ACE and high AII concentrations, non-ACE mediated production of AII may be operative. Raised aldosterone concentrations appear to be more common than AII "reactivation". It is important to establish the cause of detectable or increased AII concentrations in a heart failure patient treated with an ACE inhibitor. The measurement of serum ACE may help to identify the likely cause as poor compliance or inadequate dose.

Effect of angiotensin converting enzyme inhibition on sudden cardiac death in patients following acute myocardial infarction. A meta-analysis of randomized clinical trials

Estimate the effect of angiotensin converting enzyme (ACE) inhibitors on the risk of sudden cardiac death (SCD) following myocardial infarction (MI).

BACKGROUND

Trials in post-MI patients have shown that ACE inhibitor therapy reduces mortality. However, the effect on SCD as a mechanism has not been clarified.

METHODS

Trials of ACE inhibitor therapy following MI reported between January, 1978 and August, 1997 were identified. Studies were included if they met the following criteria: 1) randomized comparison of ACE inhibitor to placebo within 14 days of MI; 2) study duration/blinded follow-up of > or =6 weeks; 3) the number of deaths and modes of death were reported or could be obtained from the investigators.

RESULTS

We identified 374 candidate articles, of which 15 met the inclusion criteria. The 15 trials included 15,104 patients, 2,356 of whom died. Most (87%) fatalities were cardiovascular and 900 were SCDs. A significant reduction in SCD risk or a trend towards this was observed in all of the larger (N > 500) trials. Overall, ACE inhibitor therapy resulted in significant reductions in risk of death (random effects odds ratio [OR] = 0.83; 95% confidence interval [CI] 0.71-0.97), cardiovascular death (OR = 0.82; 95% CI 0.69-0.97) and SCD (OR = 0.80; 95% CI 0.70-0.92).

CONCLUSIONS

This analysis is consistent with prior reports showing that ACE inhibitors decrease the risk of death following a recent MI by reducing cardiovascular mortality. Moreover, this analysis suggests that a reduction in SCD risk with ACE inhibitors is an important component of this survival benefit.

Can clonidine, enoximone, and enalaprilat help to protect the myocardium against ischaemia in cardiac surgery?

OBJECTIVE

To evaluate whether clonidine, enoximone, and enalaprilat reduce ischaemia-related myocardial cell damage in cardiac surgery.

DESIGN

Prospective randomised controlled trial.

SETTING

Clinical investigation in a cardiac anaesthesia department of a university hospital.

PATIENTS

88 consecutive patients undergoing coronary artery bypass surgery.

INTERVENTIONS

After induction of anaesthesia patients continuously received the alpha 2 agonist clonidine (group 1, n = 22), the phosphodiesterase (PDE) III inhibitor enoximone (group 2, n = 22), the angiotensin converting enzyme (ACE) inhibitor enalaprilat (group 3, n = 22), or saline solution as placebo (control group, n = 22). The infusion was stopped immediately before the start of cardiopulmonary bypass.

MAIN OUTCOME MEASURES

The ST segment was analysed and the activity of creatine kinase isoenzyme MB (CKMB), cardiac troponin T (TnT), and the BB isoenzyme of glycogen phosphorylase (GPBB) were measured before the start of infusion (baseline), after weaning from cardiopulmonary bypass (CPB), at the end of surgery, 5 h after CPB, and on the morning of the first and third postoperative days.

RESULTS

Biometric data and time of cross-clamping were not significantly different in the four groups. Changes in the ST segment indicating ischaemia were least common in the enalaprilat group (P < 0.05). Postoperatively, CKMB activity was significantly higher in the clonidine and the control groups. Both new markers of myocardial cell damage increased more after CPB and postoperatively in the control patients (TnT peak: (mean (SD)) 3.99 (0.35) microgram/1; GPBB peak: 82 (15) ng/ml) and the clonidine-treated group (TnT peak: 3.80 (0.3) microgram/1; GPBB peak: 85 (14) ng/ml). Enalaprilat-treated patients showed the smallest overall changes in standard (CKMB) and new serological markers of myocardial ischaemia (TnT peak: 0.71 (0.1) microgram/1; GPBB peak: 44 (14) ng/ml).

CONCLUSIONS

In patients treated with enalaprilat before CPB, both new, more sensitive markers of ischaemic myocardial tissue damage increased significantly less than in an untreated control group. Those treated with enoximone also had lower plasma concentration of TnT and GPBB than the control group, whereas clonidine did not reduce the concentration of these markers of myocardial ischaemia. Pharmacological interventions, such as the continuous infusion of the ACE inhibitor enalaprilat, before start of CPB may help to protect the heart against ischaemia/reperfusion injury.

Influence of intravenous administration of angiotensin-converting enzyme inhibitor enalaprilat on cardiovascular mediators in cardiac surgery patients

The renin-angiotensin system (RAS) is important in controlling and maintaining cardiovascular homeostasis. In a randomized, prospective study, the response to intravenous (i.v.) administration of the angiotensin-converting enzyme (ACE) inhibitor enalaprilat (0.06 mg/kg) on important controllers of the circulation was investigated in 14 patients undergoing aortocoronary bypass grafting with a mean arterial blood pressure (MAP) > 85 mm Hg after induction of anesthesia. Fourteen patients received saline solution as placebo (control group). Endothelin (ET), atrial natriuretic peptide (ANP), catecholamine (epinephrine, norepinephrine) plasma levels, and ACE activity were measured from arterial blood sampled before injection of enalaprilat or NaCl solution (baseline values), 10 min and 30 min thereafter, immediately before the start of cardiopulmonary bypass (CPB), immediately after CPB, and at the end of surgery. MAP, heart rate (HR), cardiac index (CI), and systemic vascular resistance (SVR) were also monitored. ACE activity was similar at baseline in both groups; after i.v. injection of enalaprilat, it significantly decreased (from 35.1 +/- 11 to 4.4 +/- 1.0 U.min-1.L-1 30 min after injection) and remained reduced until the end of the operation (295 +/- 31 min after injection). ANP plasma levels were increased beyond normal (> 100 pg/mL) at baseline in both groups. They increased significantly in the control patients, but remained almost unchanged in the enalaprilat-treated patients within the entire study period. Plasma concentration of ET also increased only in the control group and was increased after CPB (8.6 +/- 1.2 pg/mL at the end of the operation).(ABSTRACT TRUNCATED AT 250 WORDS)

Short- and long-term neurohormonal activation following acute myocardial infarction

Plasma levels of atrial natriuretic peptide (ANP), angiotensin II, aldosterone, and catecholamines were followed for 1 month and then for 4 to 6 months in 55 patients with acute myocardial infarction. Plasma hormones were highest within the first 24 hours after the onset of infarction but normalized during the first few days in patients without heart failure. In patients with symptoms of heart failure, angiotensin II and norepinephrine remained elevated for 1 month and ANP remained elevated for 4 to 6 months. During head-up tilt, angiotensin II and norepinephrine increased most in patients with overt heart failure. Among patients with a first myocardial infarction, a positive correlation was found between infarct size and ANP, angiotensin II, and norepinephrine on day 5 to 7 and between infarct size and angiotensin II during head-up tilt at 1 month, and between infarct size and ANP at 1 month. A similar relationship was found when only patients without heart failure were studied. It is concluded that sustained neurohormonal activation after myocardial infarction mainly occurs in patients with clinical heart failure but is related to the magnitude of myocardial damage, even in patients without heart failure. Measurement of neurohormones during head-up tilt may be an additive assessment for the detection of neurohormonal activation.

The effect of early converting enzyme inhibition on neurohumoral activation in acute myocardial infarction

The effect of early converting enzyme inhibition with enalapril on the extent of neurohumoral activation in acute myocardial infarction was evaluated in a randomized, placebo-controlled double blind fashion. Plasma levels of atrial natriuretic factor and noradrenaline on day 1, i.e. prior to randomization (n = 99), and on days 3 (n = 145) and 30 (n = 69) following myocardial infarction were determined. Enalapril did not significantly affect neurohumoral activation on day 3 (enalapril vs. placebo (mean (S.E.M.); atrial natriuretic factor: 35.3 (3.0) vs. 37.2 (2.9) pmol/l; noradrenaline: 2.82 (0.20) vs. 3.70 (1.02) nmol/l) or at 1 month (atrial natriuretic factor: 33.1 (3.0) vs. 32.4 (3.9) pmol/l; noradrenaline: 2.77 (0.25) vs. 2.82 (0.28) nmol/l). However, in myocardial infarction patients developing heart failure, a significant attenuation of the day 3 atrial natriuretic factor, but not of the noradrenaline response, was seen (atrial natriuretic factor: 47.0 (7.7) vs. 59.0 (6.4) pmol/l, P < 0.05; noradrenaline: 3.37 (0.42) vs. 6.59 (3.26) nmol/l, P = ns). In conclusion, enalapril did not significantly reduce neurohumoral activation in acute myocardial infarction, possibly because the activation in most patients is modest and confined to the early convalescent phase. However, in patients with myocardial infarction and heart failure enalapril therapy was associated with a reduction in early plasma atrial natriuretic factor levels, compatible with decreased cardiac filling pressures.

"Cardioprotection" by ACE-inhibitors in acute myocardial ischemia and infarction?

Coronary artery occlusion results in the acute activation of the renin-angiotensin system and production of angiotensin II, a potent vasoconstrictor and positive inotropic agent. This has raised the possibility that angiotensin converting enzyme (ACE) inhibitors might be "cardioprotective" (that is, might attenuate myocardial injury, dysfunction and necrosis) in the setting of acute ischemia and infarction. Captopril, enalapril and ramipril have, in fact, been reported to acutely limit myocardial injury and necrosis in models of permanent coronary artery occlusion. The mechanisms responsible for this cardioprotection are complex, but include favorable alterations in myocardial oxygen supply/demand, and, in some instances, inhibition of bradykinin metabolism and/or increased prostaglandin synthesis. Other studies, however, have failed to document a reduction in infarct size with ACE inhibitor treatment. Results obtained in models of coronary occlusion/reperfusion have also been mixed. In models of brief transient ischemia not associated with necrosis, captopril and zofenopril have consistently been found to attenuate postischemic contractile dysfunction of the viable but "stunned" myocardium during the early hours following relief of ischemia. In contrast, there is no consensus on the effects of enalapril on the stunned myocardium: both positive and negative results have been obtained. Similar disparity has been reported in models of more prolonged ischemia/reperfusion resulting in subendocardial necrosis: some studies have reported myocardial salvage, while others have provided disturbing evidence of apparent exacerbation of myocardial necrosis with captopril and enalapril therapy. Thus, after a decade of investigative effort, the question of whether ACE inhibitors are "cardioprotective" in the setting of acute myocardial ischemia and infarction remains unresolved. Nonetheless, clinical protocols are in progress to assess the effects of early ACE inhibitor treatment in patients with acute myocardial infarction.

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.