Comparison of B-Type Natriuretic Peptides for Assessment of Cardiac Function and Prognosis in Stable Ischemic Heart Disease

In 1,049 patients with stable ischemic heart disease (IHD), brain natriuretic peptide (BNP) and amino terminal pro-brain natriuretic peptide (NTproBNP) correlated closely (r = 0.09, p < 0.001) and were similarly related to left ventricular ejection fraction (LVEF) (r = -0.50 and -0.46, respectively), age (0.44 and 0.47), and creatinine clearance (-0.51 and -0.51). Receiver-operating characteristic curves for detection of LVEF <30% were similar (area under the curves = 0.83 and 0.80, both p < 0.001), and both peptides had strong negative predictive value (95% and 94%). Both independently predicted all-cause mortality and/or heart failure with closely overlapping event-free survival curves; BNP and NTproBNP display strong, near-identical test performance in ruling about severely reduced LVEF and in prediction of all-cause mortality or heart failure in stable IHD.

OBJECTIVES

The aim of this work was to test B-type natriuretic peptides for assessment of function and prognosis in stable ischemic heart disease (IHD) and to compare brain natriuretic peptide (BNP) with amino terminal pro-brain natriuretic peptide (NTproBNP), including the relative effects of age and renal function on test performance.

BACKGROUND

Brain natriuretic peptide and NTproBNP are emerging diagnostic and prognostic markers in heart failure and acute coronary syndromes. Their performance in assessing function and prognosis in stable IHD is unknown. Whether one marker is superior and the relative effects of age and renal function on test performance are uncertain.

METHODS

In 1,049 patients with stable IHD, left ventricular ejection fraction (LVEF) was measured by radionuclide scanning and creatinine clearance estimated by the Cockroft-Gault equation. Age, gender, and body mass index were recorded. Twelve-month all-cause mortality or admission with heart failure was prospectively recorded; BNP and NTproBNP were measured by radioimmunoassay.

RESULTS

Brain natriuretic peptide and NTproBNP correlated closely (r = 0.90, p < 0.001) and had similar relationships to LVEF (r = -0.50 and -0.46, respectively, both p < 0.001), age (0.44 and 0.47, both p < 0.001), and creatinine clearance (-0.51 and -0.51, both p < 0.001). Areas under receiver-operating characteristic curves for detection of LVEF <30% were similar (0.83 and 0.80, both p < 0.001) with strong negative predictive values for both (95% and 94%). Both markers independently predicted the clinical end point with closely overlapping event-free survival curves.

CONCLUSIONS

In stable IHD, BNP and NTproBNP display strong and near-identical test performance in ruling out severely reduced LVEF and in prediction of all-cause mortality or heart failure despite significant effects of age, gender, and renal function on levels of both markers.

Radiofrequency ablation for common atrial flutter using an 8-mm tip catheter and up to 150 W

The formation of bi-directional block in atrial flutter can be adversely affected by problems with the delivery of effective energy related to isthmus anatomy and contact. Higher energies can produce larger and more effective lesions. The optimum setting for power delivery using temperature controlled ablation has not been established, with the maximum reported being 100 W. This is a retrospective review of the first 50 new cases assessing the efficacy and safety of using temperature controlled (60-65 degrees C) flutter ablation with an 8mm tip electrode catheter and up to 150 W. All cases had either typical flutter alone (34%) or predominant flutter as the indication, no combined procedures were included. Acute procedural success was 94% and long-term success of 88%. Median number of ablations required was 11 (interquartile range 10-19), median procedure time 120 min (IQR 102-164), fluoroscopy time 22 min (IQR 17-36), radiation dose 17 Gy cm(2) (IQR 10-27), median number of lines 1 (IQR 1-2). Six patients achieved 150 W, but 42 achieved >100 W (median watts 142 W, IQR 104-147). Patients (12%) experienced an uncomplicated pop during the procedure. None experienced a significant complication. There were three late relapses. The setting of 150 W maximum delivered energy in temperature regulated ablation allowed higher energies (>100 W) to be delivered in most patients. This resulted in acute and long-term success rates that compare well with the literature but is associated with a 12% rate of pop. Subsequent to this series our 54th patient sustained a pop due to high energy ablation that resulted in perforation and tamponade, from which there was survival.

B-type natriuretic peptides and ejection fraction for prognosis after myocardial infarction

BACKGROUND

A recent landmark report has demonstrated that plasma B-type natriuretic peptide (BNP) measured in acute coronary syndromes independently predicts mortality, heart failure, and new myocardial infarction. After acute cardiac injury, left ventricular ejection fraction (LVEF) is also of prognostic significance and plays a major role in determining the therapeutic response.

METHODS AND RESULTS

The present report is the first from a substantial (n=666) cohort of patients with acute myocardial infarction to test the prognostic utility of concurrent measurements of BNP, amino-terminal BNP (N-BNP), norepinephrine, and radionuclide LVEF. The B-type peptides and LVEF were predictors of death, heart failure, and new myocardial infarction (all P<0.001) independent of patient age, gender, previous myocardial infarction, antecedent hypertension or diabetes, previous heart failure, plasma norepinephrine, creatinine, cholesterol, drug therapy, and coronary revascularization procedures. The combination of N-BNP (or BNP) with LVEF substantially improved risk stratification beyond that provided by either alone. Elevated N-BNP (or BNP) predicted new myocardial infarction only in patients with LVEF <40%. LVEF <40% coupled to N-BNP over the group median conferred substantial 3-year risks of death, heart failure, and new myocardial infarction of 37%, 18%, and 26%, respectively. N-BNP and BNP were equivalent prognostic markers for these clinical outcomes.

CONCLUSIONS

Plasma N-BNP (or BNP) and LVEF are complementary independent predictors of major adverse events on follow-up after myocardial infarction. Combined measurement provides risk stratification substantially better than that provided by either alone.

Decrease in cardiac output and muscle sympathetic activity during vasovagal syncope

The importance of cardiac output (CO) to blood pressure level during vasovagal syncope is unknown. We measured thermodilution CO, mean blood pressure (MBP), and leg muscle mean sympathetic nerve activity (MSNA) each minute during 60 degrees head-up tilt in 26 patients with recurrent syncope. Eight patients tolerated tilt (TT) for 45 min (mean age 60 +/- 5 yr) and 15 patients developed syncope during tilt (TS) (mean age 58 +/- 4 yr, mean tilt time 15.4 +/- 2 min). In TT patients, CO decreased during the first minute of tilt (from 3.2 +/- 0.2 to 2.5 +/- 0.3 l x min(-1) x m(-2), P = 0.001) and thereafter remained stable between 2.5 +/- 0.3 (P = 0.001) and 2.4 +/- 0.2 l x min(-1) x m(-2) (P = 0.004) at 5 and 45 min, respectively. In TS patients, CO decreased during the first minute (from 3.3 +/- 0.2 to 2.7 +/- 0.1 l x min(-1) x m(-2), P = 0.02) and was stable until 7 min before syncope, falling to 2.0 +/- 0.2 at syncope (P = 0.001). Regression slopes for CO versus time during tilt were -0.01 min(-1) in TT versus -0.1 l x min(-1) x m(-2) x min(-1) in TS (P = 0.001). However, MBP was more closely correlated to total peripheral resistance (R = 0.56, P = 0.001) and MSNA (R = 0.58, P = 0.001) than CO (R = 0.32, P = 0.001). In vasovagal reactions, a progressive decline in CO may contribute to hypotension some minutes before syncope occurs.

Antecedent hypertension and heart failure after myocardial infarction

OBJECTIVES

We sought to assess the relationship of antecedent hypertension to neurohormones, ventricular remodeling and clinical heart failure (HF) after myocardial infarction (MI).

BACKGROUND

Heart failure is a probable contributor to the increased mortality observed after MI in those with antecedent hypertension. Hence, neurohormonal activation, adverse ventricular remodeling and a higher incidence of clinical HF may be expected in this group. However, no previous report has documented serial postinfarction neurohumoral status, serial left ventricular imaging and clinical outcomes over prolonged follow-up in a broad spectrum of patients with and without antecedent hypertension.

METHODS

Inpatient events were documented in 1,093 consecutive patients (436 hypertensive and 657 normotensive) with acute MI. In 68% (282 hypertensive, 465 normotensive) serial neurohormonal sampling and radionuclide ventriculography were performed one to four days and three to five months after infarction. Clinical outcomes were recorded over a mean follow-up of two years.

RESULTS

Plasma neurohormones were significantly higher in hypertensives than in normotensives one to four days and three to five months after infarction. From similar initial values, left ventricular volumes increased significantly in hypertensives, compared with normotensives. Left ventricular ejection fraction rose significantly in normotensive but not hypertensive patients. Together with higher inpatient (8.1% vs. 4.4%, p < 0.002) and post-discharge mortality (9.5% vs. 5.5%, p = 0.043), hypertensive patients incurred more inpatient HF (33% vs. 24%, p < 0.001) and more late HF requiring readmission to hospital (12.4% vs. 5.5%, p < 0.001). Antecedent hypertension predicted late HF in patients >64 years of age with neurohormonal activation and early left ventricular dilation.

CONCLUSIONS

Antecedent hypertension interacts with age, neurohumoral activation and early ventricular remodeling to confer greater risk of HF after MI.

Effects of omapatrilat on systemic arterial function in patients with chronic heart failure

The mechanisms of action of omapatrilat, an agent that inhibits both neutral endopeptidase 24.11 and angiotensin-converting enzyme, on arterial function in patients with heart failure have not been previously reported. Forty-eight patients in New York Heart Association functional class II to III, left ventricular ejection fraction < or = 40%, and in sinus rhythm were randomized to a dose-ranging (2.5, 5, 10, 20, or 40 mg) study of omapatrilat for 12 weeks. Measurements were obtained at baseline and 12 weeks. Decreases in systolic (25.0 +/- 4.5 vs 2.8 +/- 5.0 mm Hg, p < 0.05) and mean arterial (13.9 +/- 3.0 vs 0.3 +/- 3.3 mm Hg, p < 0.05) pressure were seen after 12 weeks of therapy with higher doses. Ventricular-arterial coupling was improved with a dose-related decrease in augmentation index (-13.8 +/- 1.7% vs +6.1 +/- 2.1%, p < 0.01). There was no change in resting forearm blood flow between groups; however, maximum forearm vasodilator response during reactive hyperemia increased in the high-dose groups compared with the control group (+266 +/- 43% vs - 14 +/- 92%, p < 0.05). Omapatrilat induced an increase in postdose plasma atrial natriuretic peptide levels (30 +/- 11 vs -2 +/- 7 pmol/L, p < 0.01) in high-dose groups consistent with endopeptidase 24.11 inhibition. Omapatrilat shows beneficial changes in ventricular-vascular coupling and arterial function in heart failure.

The clinical, cardiac, renal, arterial and neurohormonal effects of omapatrilat, a vasopeptidase inhibitor, in patients with chronic heart failure

OBJECTIVES

We sought to examine the effects of long-term vasopeptidase inhibition in patients with heart failure.

BACKGROUND

The long-term effects of omapatrilat, an agent that inhibits both neutral endopeptidase and angiotensin-converting enzyme, on clinical status, neurohormonal indexes and left ventricular function in patients with chronic heart failure (CHF) have not been previously documented.

METHODS

Forty-eight patients in New York Heart Association functional class II or III, with left ventricular ejection fraction (LVEF)< or =40% and in sinus rhythm were randomized to a dose-ranging pilot study of omapatrilat for 12 weeks. Measurements were performed at baseline and 12 weeks.

RESULTS

There was an improvement in functional status, as reported by the patient (p<0.001) and physician (p<0.001) at 12 weeks. Dose-dependent improvements in LVEF (p<0.001) and LV end-systolic wall stress (sigma) (p<0.05) were seen, together with a reduction in systolic blood pressure (p<0.05). There was evidence of a natriuretic effect (p<0.001), and total blood volume decreased (p<0.05). Omapatrilat induced an increase in postdose plasma atrial natriuretic peptide levels (p<0.01) in the high dose groups, with a reduction in predose plasma brain natriuretic peptide (p<0.001) and epinephrine (p<0.01) levels after 12 weeks of therapy. Omapatrilat was well tolerated.

CONCLUSIONS

The sustained hemodynamic, neurohumoral and renal effects of omapatrilat, together with improved functional status, suggest that vasopeptidase inhibition has potential as a new therapeutic modality for the treatment of CHF.

Baroreceptor denervation presenting as part of a vagal mononeuropathy

A 48-year-old woman presented with a history of progressive cough, dysphonia, dysphagia, and postural symptoms. Subsequent neurological investigations were consistent with a bilateral vagal mononeuropathy, and neurosarcoidosis was diagnosed after scalene node biopsy. Autonomic investigations including microneurography, neurohormones, and heart rate variability demonstrated arterial and cardiopulmonary baroreflex failure. In addition, parasympathetic control of heart rate was absent and consistent with a bilateral, nonselective lesion in the proximal vagus.

Neuroendocrine prediction of left ventricular function and heart failure after acute myocardial infarction. The Christchurch Cardioendocrine Research Group

OBJECTIVE

To determine the relations of plasma levels of brain natriuretic peptide (BNP), atrial natriuretic factor (ANF), N-terminal ANF (N-ANF), cyclic guanosine monophosphate (cGMP; the cardiac peptide second messenger), and plasma catecholamines to left ventricular function and to prognosis in patients admitted with acute myocardial infarction.

DESIGN

Plasma hormones and ventricular function (radionuclide ventriculography) were measured 1-4 days after myocardial infarction in 220 patients admitted to a single coronary care unit. Radionuclide scanning was repeated 3-5 months after infarction. Clinical events were recorded over a mean period of 14 months.

RESULTS

Both early and late left ventricular ejection fraction (LVEF) were most closely related to plasma BNP (r = -0.60, n = 220, p < 0.001; and r = -0.53, n = 192, p < 0.001, respectively), followed by ANF, N-ANF, cGMP, and the plasma catecholamines. Early plasma BNP concentrations less than twofold the upper limit of normal (20 pmol/l) had 100% negative predictive value for LVEF < 40% at 3-5 months after infarction. In multivariate analysis incorporating all the neurohormonal factors, only BNP remained independently predictive of LVEF < 40% (p < 0.005). Survival analysis by median levels of candidate predictors identified BNP as the most powerful discriminator for death (p < 0.0001). No early deaths (within 4 months) occurred in patients with plasma BNP concentrations below the group median (27 pmol/l), and over follow up only three of 26 deaths occurred in this subgroup. Of all episodes of left ventricular failure, 85% occurred in patients with plasma BNP above the median (p < 0.001). In multivariate analyses, BNP alone gave additional predictive information beyond sex, age, clinical history, LVEF, and plasma noradrenaline for both subsequent onset of LVF and death.

CONCLUSIONS

Plasma BNP measured within 1-4 days of acute myocardial infarction is a powerful independent predictor of left ventricular function, heart failure, or death over the subsequent 14 months, and superior to ANF, N-ANF, cGMP, and plasma catecholamines.

Autonomic control of vasovagal syncope

In the pathophysiological study of vasovagal syncope, the nature of the interaction between baroreceptor sensitivity (BS), sympathetic withdrawal, and parasympathetic activity has yet to be ascertained. Altered BS may predispose toward abnormal sympathetic and parasympathetic responses to orthostasis, causing hypotension that may progress to syncope if there is sympathetic withdrawal. To examine this hypothesis, we monitored blood pressure (BP), heart rate (HR), BS, forearm blood flow, and muscle nerve sympathetic activity (MNSA) continuously in 18 vasovagal patients during 60 degrees head-up tilt, syncope, and recovery. Results were compared with those of 17 patients who were able to tolerate tilt for 45 min. During early tilt, BP was maintained in both groups by an increase in HR and MNSA from baseline (P < 0.01), but BS decreased more in the syncopal group (P < 0.05). At the start of presyncope (mean 2.7 +/- 0.2 min before syncope and 15.2 +/- 12 min after tilt), when BP fell, HR and sympathetic activity remained increased from baseline (P < 0.01). Thereafter, BP and HR correlated directly with sympathetic activity and regressed in linear fashion until syncope (P < 0.001), whereas BS increased to baseline. At syncope, BP, HR, and sympathetic activity fell below baseline (P < 0.01, P < 0.05, and P < 0.01, respectively), but BS did not increase. During recovery, sympathetic activity increased to baseline and BS increased (P < 0.05), whereas HR and BP remained low (P < 0.01 and P < 0.05, respectively). The mechanism for the initiation of hypotension during presyncope remains unknown, but BS may contribute. Vasodilatation and bradycardia during presyncope appear to be more closely related to withdrawal of sympathetic activity than to increased parasympathetic cardiac activity.

Plasma N-terminal pro-brain natriuretic peptide and adrenomedullin: new neurohormonal predictors of left ventricular function and prognosis after myocardial infarction

BACKGROUND

Newly discovered circulating peptides, N-terminal pro-brain natriuretic peptide (N-BNP) and adrenomedullin (ADM), were examined for prediction of cardiac function and prognosis and compared with previously reported markers in 121 patients with myocardial infarction.

METHODS AND RESULTS

The association between radionuclide left ventricular ejection fraction (LVEF) and N-BNP at 2 to 4 days (r=-.63, P<.0001) and 3 to 5 months (r=-.58, P<.0001) after infarction was comparable to that for C-terminal BNP and far stronger than for ADM (r=-.26, P<.01), N-terminal atrial natriuretic peptide (N-ANP), C-terminal ANP, cGMP, or plasma catecholamine concentrations. For prediction of death over 24 months of follow-up, an early postinfarction N-BNP level > or = 160 pmol/L had sensitivity, specificity, positive predictive value, and negative predictive values of 91%, 72%, 39%, and 97%, respectively, and was superior to any other neurohormone measured and to LVEF. Only 1 of 21 deaths occurred in a patient with an N-BNP level below the group median (Kaplan-Meier survival analysis, P<.00001). For prediction of heart failure (left ventricular failure), plasma N-BNP > or = 145 pmol/L had sensitivity (85%) and negative predictive value (91%) comparable to the other cardiac peptides and was superior to ADM, plasma catecholamines, and LVEF. By multivariate analysis, N-BNP but not ADM provided predictive information for death and left ventricular failure independent of patient age, sex, LVEF, levels of other hormones, and previous history of heart failure, myocardial infarction, hypertension, or diabetes.

CONCLUSIONS

Plasma N-BNP measured 2 to 4 days after myocardial infarction independently predicted left ventricular function and 2-year survival. Stratification of patients into low- and high-risk groups can be facilitated by plasma N-BNP or BNP measurements, and one of these could reasonably be included in the routine clinical workup of patients after myocardial infarction.

Neurohormonal response to head-up tilt and its role in vasovagal syncope

In a controlled study, 26 patients with a history of recurrent syncope were found to have increased arginine vasopressin, corticotrophin, and atrial natriuretic factor levels after 5 minutes of 60 degrees head-up tilt, long before they became hypotensive. The exaggerated neurohormonal response in these patients may indicate a greater sensitivity to central hypovolemia which may predispose to vasovagal syncope, mediated by the vasodilatory effects of atrial natriuretic factor or the sensitization of mechanoreceptors by arginine vasopressin.

Autonomic control of asystolic vasovagal syncope

A 30 year old woman with a lifelong history of severe, recurrent, vasovagal syncope became asystolic for 30 seconds after 37 minutes of 60 degrees head-up tilt. During early tilt, sympathetic activity, heart rate, left ventricular contractility, and cardiac output increased. Mean blood pressure was initially maintained. Presyncope was associated with maximal contractility and bradycardia despite sustained sympathetic activity. Subsequently, asystole occurred associated with complete withdrawal of muscle nerve sympathetic activity. In asystolic vasovagal reactions, presyncope may be triggered by increased left ventricular contractility and is associated with increased levels of parasympathetic and sympathetic activity. Asystole and peripheral vasodilatation may be caused by sudden and complete withdrawal of the increased sympathetic activity.

Plasma cortisol, PRL, ACTH, AVP and corticotrophin releasing hormone responses to direct current cardioversion and electroconvulsive therapy

OBJECTIVE

We aimed to evaluate and contrast the hypothalamo-pituitary-adrenal (HPA) response to direct current (DC) cardioversion and electroconvulsive therapy (ECT).

SUBJECTS

Six male subjects (mean age 61.2 years, range 46-74) with chronic atrial fibrillation were selected for cardioversion. Six subjects with depression (one male, five female; mean age 43.2 years, range 31-59) were selected for ECT. Those taking glucocorticoid drugs, opiates or beta-adrenoceptor antagonists were excluded.

MEASUREMENTS

Patients attended for serial blood sampling on the day of cardioversion or ECT, and for an equivalent time period on a control day at least one week before. Intravenous propofol was given to each subject for anaesthesia on the day of cardioversion or ECT. On both study and control days, blood samples were taken at -30, -15, 0 (just prior to cardioversion or ECT), +5, +10, +15, +30, +60, +90 and +120 minutes for assay of cortisol, PRL, ACTH, AVP and CRH.

RESULTS

For cardioversion: plasma cortisol increased from 252.5 +/- 39.8 to a maximum of 721.3 +/- 50 nmol/l at 30 minutes (P < 0.0001 compared with control day). ACTH increased from 12.8 +/- 2.8 to a maximum of 64 +/- 14 pmol/l at 5 minutes (P < 0.0001 compared with control day). AVP increased from 6.6 +/- 3.3 to a maximum of 42.9 +/- 16 pmol/l at 5 minutes post-cardioversion (P < 0.005 compared with control day). PRL increased from 141 +/- 28 mlU/l to a maximum of 873 +/- 219 mlU/l at 10 minutes (P < 0.001 compared with control day). There was no significant difference in CRH responses between cardioversion and control days. There was no significant correlation between total electrical energy delivered and maximum ACTH and AVP responses (R = 0.54 and -0.13, respectively). For ECT: on the day of ECT plasma cortisol increased from 419.5 +/- 25.9 to a maximum of 614.7 +/- 26.9 nmol/l (P < 0.002 compared with control day). ACTH increased from 22.7 +/- 6.2 to a maximum of 77.8 +/- 19.1 pmol/l (P < 0.0003 compared with control day). PRL increased from 771 +/- 317 to a maximum of 3152 +/- 703 mlU/l (P < 0.001 compared with control day, and significantly greater than the peak response to cardioversion, P < 0.03). AVP increased from 13.0 +/- 10.8 to a maximum of 35.1 +/- 5.6 pmol/l (P < 0.02 compared with control day). There was no significant difference in CRH responses between ECT and control days. Peak cortisol and ACTH responses did not differ significantly between ECT and cardioversion. Baseline cortisol levels, however, were significantly higher in the depressed group compared with the cardioversion group, P < 0.02, but not ACTH or AVP.

CONCLUSION

Significant hypothalamic-pituitary-adrenal activation and PRL release occur in response to both cardioversion and ECT. AVP may have an important role in mediating the acute ACTH response to electrical stimulation.

Hemodynamic comparison of dopexamine and nitroprusside at high and low doses in patients with coronary artery disease and impaired left ventricular function

Pure vasodilator drugs are currently the preferred agents for treatment of acute and chronic heart failure of all grades of severity. In contrast, the role of drugs that combine vasodilation with inotropic action remains highly controversial despite their several advantageous physiological actions and long therapeutic history in heart failure. We hypothesize that this uncertainty might be due first to subtle unfavorable hemodynamic effects not detectable by the relatively crude hemodynamic methods by which these agents are usually analyzed, particularly with regard to the quantification of afterload, and secondly to the narrow therapeutic range of these drugs, such that the dose administered is critical. We tested this hypothesis by comparing several refined hemodynamic measurements of dopexamine, an inotropic vasodilator, with a pure arteriovenous dilator (sodium nitroprusside, SNP) on left ventricular (LV) systolic and diastolic function, large arterial behavior, and coupling of the left ventricle to the arterial system at two dose levels in 35 patients with ischemic heart disease. The study protocol was a fixed order of 15-min infusions of saline, dopexamine 1 microg/kg/min, and dopexamine 3 + ++microg/kg/min, or saline, SNP 1 microg/kg/min, and SNP 3 microg/kg/min. Detailed hemodynamic observations were made at the end of each 15-min infusion period. Both drugs produced equivalent arterial vasodilation, as measured by the decrease in systemic vascular resistance index (SVRI), but dopexamine resulted in a significantly greater increase in cardiac index (CI). Myocardial contractility, assessed by several load-independent indexes, increased with dopexamine, as anticipated with an inotropic drug, but did not alter with SNP. Arterial compliance, a measure of the distensibility of large conduit arteries, was increased by SNP but not by dopexamine. Arterial wave reflection was increased by dopexamine, especially at high doses, but reduced by SNP. Increased arterial compliance and reduced wave reflection reduce LV afterload. SNP reduced preload, whereas dopexamine had no effect on this aspect of ventricular function. Vasodilator drugs and those which combine vasodilator and inotropy increase cardiac output (CO) and reduce SVR. Therapy with inotropic vasodilators has no effect on preload and does not reduce the dynamic components of ventricular afterload, although it does reduce its static components. These effects are dose dependent; there is less perturbation of afterload at lower doses. In contrast, vasodilator therapy reduces preload and both static and dynamic parts of afterload.

Neurohormonal changes after acute myocardial infarction. Relationships with haemodynamic indices and effects of ACE inhibition

To determine the neurohormonal response to angiotensin-converting enzyme (ACE) inhibition after acute myocardial infarction, 36 patients presenting within 6 h of the onset of chest pain were studied in a single regional cardiology service. In this double-blind study, 13 patients were randomized to receive captopril, 12 patients received enalapril, and 11 patients received placebo, for 12 months. In patients receiving placebo, acute myocardial infarction was associated with activation of the renin-angiotensin-aldosterone and sympathetic nervous systems, and stimulation of plasma brain natriuretic peptide and atrial natriuretic peptide levels. ACE inhibition did not significantly alter circulating levels of norepinephrine, brain natriuretic peptide or atrial natriuretic peptide. Compared with placebo, enalapril induced a steep decline in plasma ACE activity, and plasma angiotensin II levels were reduced by both ACE inhibitors. Using grouped data, circulating levels of brain natriuretic peptide at the zero sampling time were significantly higher than atrial natriuretic peptide values. Brain natriuretic peptide levels at 72 h were significantly correlated with the radionuclide left ventricular ejection fraction measured 5 days and 3 months after infarction. Similar associations were observed for atrial natriuretic peptide and norepinephrine. We confirm activation of the renin-angiotensin-aldosterone and sympathetic nervous systems after acute myocardial infarction. The atrial natriuretic peptide and brain natriuretic peptide and sympathetic nervous system responses to acute myocardial infarction were not significantly modified by ACE inhibition. Brain natriuretic peptide and atrial natriuretic peptide levels were significantly correlated with the left ventricular ejection fraction measured 5 days and again 3 months after myocardial infarction, and may prove a useful prognostic index.

Blockade of the renin-angiotensin system

HISTORICAL OVERVIEW

Milestones in understanding the renin-angiotensin system (RAS) until the development of angiotensin II antagonists are described briefly. Sites at which the RAS might be blocked are outlined.

PEPTIDE ANALOGUE ANTAGONISTS OF ANGIOTENSIN II RECEPTORS

Saralasin-like compounds were used in numerous experimental and clinical situations and clarified the role of the RAS. Some of these situations are described (e.g. hypertension and cardiac failure) particularly in regard to the control of arterial pressure and aldosterone secretion by the RAS. Saralasin and its analogues allowed visualization, for the first time, of complete angiotensin II/effector (especially blood pressure) dose-response curves.

ANGIOTENSIN CONVERTING ENZYME (ACE) INHIBITORS

The clinical usefulness of ACE inhibitors in hypertension, cardiac failure, diabetes mellitus and after acute myocardial infarction is emphasized. In particular, ACE inhibitors have actions beyond blockade of angiotensin II formation, necessitating cautious interpretation of data from their use.

RENIN INHIBITORS

Experience with renin inhibitors in documenting and confirming the role of the RAS is outlined. NON-PEPTIDE ANGIOTENSIN II RECEPTOR ANTAGONISTS: Characteristics of losartan-like compounds are discussed in brief, and the results of their limited use in clinical medicine are outlined.

CONCLUSION

Blocking agents have led to great advances in knowledge of the RAS and its physiological and pathophysiological functions. ACE inhibitors are used regularly in a number of clinical disorders and, in theory, have therapeutic potential beyond alternative antihypertensive drugs in the prevention of cardiovascular complications in essential hypertension. The place of renin inhibitors and angiotensin II receptor antagonists in clinical practice, however, remains to be determined.

Comparison of enalapril versus captopril on left ventricular function and survival three months after acute myocardial infarction (the "PRACTICAL" study)

Left ventricular (LV) function and survival can be improved with captopril when initiated later than 24 hours after acute myocardial infarction. Animal studies suggest additional benefits may be obtained with earlier initiation of angiotensin-converting enzyme (ACE) inhibitors. The effects on LV function of captopril and enalapril initiated within 24 hours of myocardial infarction were studied. Two hundred twenty-five patients with acute myocardial infarction were enrolled within 24 hours of the onset of chest pain. They were randomized to receive either captopril 25 mg three times daily, enalapril 5 mg three times daily, or placebo. LV ejection fraction (EF) and volumes were measured by radionuclide ventriculography at baseline during treatment and at 3 months after a 3-day withdrawal from therapy. The ACE inhibitor group had a significant increase in EF (45 +/- 1 to 47 +/- 1%; p = 0.005) and significantly attenuated LV dilatation compared with results in the placebo group (175 +/- 6 to 189 +/- 7 ml in the placebo group vs 168 +/- 4 to 172 +/- 4 ml in the ACE inhibitor group; p = 0.051 for LV end-diastolic volume; and 99 +/- 6 to 108 +/- 7 ml in the placebo group vs 94 +/- 3 to 94 +/- 4 ml; p = 0.026 for LV end-systolic volume). The beneficial effects of ACE inhibitor therapy on LV function were observed irrespective of the degree of initial LV dysfunction and were comparable in both the captopril and enalapril groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma corticotrophin releasing hormone, vasopressin, ACTH and cortisol responses to acute myocardial infarction

OBJECTIVES

We assessed the magnitude and duration of the response of hypothalamic-pituitary-adrenal hormones to the stress of myocardial infarction, in the presence and absence of angiotensin converting enzyme inhibitors. In particular, we wished to analyse the interrelationships between peripheral plasma levels of corticotrophin releasing hormone (CRH), vasopressin (AVP) and adrenocorticotrophin (ACTH), and also between ACTH and cortisol, during a prolonged medical stress.

DESIGN

All hormones were measured within 6 hours of the onset of an acute myocardial infarction. Patients were randomly allocated to three different study groups according to a double blind procedure.

PATIENTS

Group 1 (10 patients) received placebo treatment, Group 2 (13 patients) received a maintenance dose of captopril 25 mg three times daily, Group 3 (11 patients) received enalapril 5 mg three times daily.

MEASUREMENTS

Peptide hormones were measured by radioimmunoassay, and cortisol by ELISA. Reference ranges for all hormones were obtained from 40 or more volunteers from the electoral roll.

RESULTS

At the start of the study, mean +/- SEM plasma AVP (27.9 +/- 4.6 pmol/l) was significantly (P < 0.001) raised above the mean for the reference range (1.82 +/- 0.09 pmol/l), and 12 patients had values > 50 pmol/l. Mean plasma cortisol (960 +/- 89.6 nmol/l) was also raised above the reference range mean (554 +/- 28 nmol/l, P < 0.001), as was mean plasma CRH (4.97 +/- 0.5 pmol/l, reference mean 1.52 +/- 0.09 pmol/l, P < 0.001). By contrast, mean ACTH (3.88 +/- 0.66 pmol/l) was significantly less than the reference mean (10.7 +/- 0.7 pmol/l, P < 0.001). During the 72-hour observation period there was a highly significant fall (P < 0.001) in plasma CRH, AVP and cortisol. By contrast, plasma ACTH rose, and the change with time of ACTH was significantly different from the fall in plasma CRH, AVP or cortisol (P < 0.001 for each comparison). No significant differences in plasma CRH, AVP, ACTH or cortisol responses to placebo, captopril or enalapril were observed.

CONCLUSIONS

Within 6 hours of a myocardial infarction, mean plasma CRH, AVP and cortisol values were very significantly raised above mean control values, while ACTH was very significantly reduced. During the 3 days following an acute myocardial infarction, plasma CRH, AVP and cortisol fell substantially, and this pattern was not influenced by angiotensin converting enzyme inhibitors. By contrast, plasma ACTH showed a significant increase with time. This suggests that the usual relationships between CRH, AVP and ACTH, and between ACTH and cortisol are disturbed in patients admitted to hospital with myocardial infarction. Maximum levels of AVP observed in 12 patients exceeded 50 pmol/l, which may be sufficiently high to interfere with tissue perfusion. It is postulated that V1 AVP receptor antagonists may have a therapeutic application in limiting infarct size.

Angiotensin converting enzyme inhibition in chronic stable angina: effects on myocardial ischaemia and comparison with nifedipine

OBJECTIVES

To determine the anti-ischaemic effects of a new angiotensin converting enzyme inhibitor, benazepril, compared with nifedipine, alone and in combination, in chronic stable angina caused by coronary artery disease.

DESIGN

Placebo controlled, double blind, latin square design.

SETTING

Regional cardiology service for a mixed urban and rural population.

SUBJECTS

40 patients with stable exertional angina producing at least 1 mm ST segment depression on exercise test with the Bruce protocol. 34 patients completed all four phases of the trial.

INTERVENTIONS

Each patient was treated with placebo, benazepril (10 mg twice daily), nifedipine retard (20 mg twice daily), and a combination of benazepril and nifedipine in the same doses, in random order for periods of two weeks.

MAIN OUTCOME MEASURES AND RESULTS

Total duration of exercise was not increased by any treatment. Exercise time to the development of 1 mm ST segment depression was not significantly changed with benazepril alone or in combination with nifedipine but was increased with nifedipine from 4.18 (1.8) min to 4.99 (1.6) min (95% confidence interval (95% CI) 0.28 to 1.34; p < 0.05). There was a significant relation between increase in duration of exercise and resting renin concentration (r = 0.498; p < 0.01). Myocardial ischaemia during daily activity, as assessed by ambulatory electrocardiographic monitoring, was reduced by benazepril and by the benazepril and nifedipine combination. This was significant for total ischaemic burden (451(628) min v 231(408) min; 95% CI -398 to -41 min; p < 0.05) and maximal depth of ST segment depression (-2.47(1.2) mm v -2.16 mm; 95% CI 0.04 to 0.57; p < 0.05) for the combination and for maximal ST segment depth for benazepril monotherapy (-2.47 (1.2) mm v -1.96(1.2) mm; 95% CI 0.18 to 0.91; p < 0.05). Benazepril significantly altered the circadian rhythm of cardiac ischaemia, abolishing the peak ischaemic periods at 0700 to 1200 and 1700 to 2300 (p < 0.05).

CONCLUSIONS

Benazepril, an angiotensin converting enzyme inhibitor, had a modest anti-ischaemic effect in effort angina, but this effect was not as pronounced as with nifedipine. The anti-ischaemic action was more noticeable in asymptomatic ischaemia during daily activity, whereas nifedipine had little effect on this aspect of myocardial ischaemia. The combination of benazepril and nifedipine reduced ischaemia of daily activity.