Regulation of peripheral vascular tone in patients with heart failure: contribution of angiotensin II

OBJECTIVE

To determine directly the contribution of angiotensin II to basal and sympathetically stimulated peripheral arteriolar tone in patients with heart failure.

DESIGN

Parallel group comparison.

SUBJECTS

Nine patients with New York Heart Association grade II-IV chronic heart failure, and age and sex matched controls.

INTERVENTIONS

Forearm plethysmography, lower body negative pressure, local intra-arterial administration of losartan, angiotensin II, and noradrenaline, and estimation of plasma hormone concentrations.

MAIN OUTCOME MEASURES

Forearm blood flow responses, plasma hormone concentrations.

RESULTS

Baseline blood pressure, heart rate, and forearm blood flow did not differ between patients and controls. In comparison with the non-infused forearm, losartan did not affect basal forearm blood flow (95% confidence interval -5.5% to +7.3%) or sympathetically stimulated vasoconstriction in controls. However, the mean (SEM) blood flow in patients increased by 13(5)% and 26(7)% in response to 30 and 90 micrograms/min of losartan respectively (p < 0.001). Lower body negative pressure caused a reduction in forearm blood flow of 20(5)% in controls (p = 0.008) and 13(5)% (p = 0.08) in patients (p = 0.007, controls v patients). Blood flow at 90 micrograms/min of losartan correlated with plasma angiotensin II concentration (r = 0.77; p = 0.03). Responses to angiotensin II and noradrenaline did not differ between patients and controls.

CONCLUSIONS

Losartan causes acute local peripheral arteriolar vasodilation in patients with heart failure but not in healthy control subjects. Endogenous angiotensin II directly contributes to basal peripheral arteriolar tone in patients with heart failure but does not augment sympathetically stimulated peripheral vascular tone.

A prospective controlled study of the association of Streptococcus bovis with colorectal carcinoma

AIM

To investigate the ability of Streptococcus bovis to colonise colorectal cancers.

PATIENTS

19 patients with colorectal cancer and 23 controls without malignancy.

SETTING

University teaching hospital.

METHODS

Prospective study comparing unselected patients with known colorectal cancer with age and sex matched controls. Carcinoma tissue from patients with colorectal cancer and normal colonic mucosa, stool, and blood from both patients and control subjects were cultured.

RESULTS

In contrast to published data, the faecal carriage rate was similar in cancer (11%) and control groups (13%).

CONCLUSIONS

Faecal colonisation by Str bovis in colorectal cancer patients is lower than previously reported and does not differ significantly from controls.

Cell adhesion molecules in cardiovascular disease: a clinical perspective

In summary, there is increasing evidence that cell adhesion molecules play an important role in cardiovascular pathology. They are involved in the main processes that underlie cardiac disease including thrombosis, leucocyte infiltration, smooth muscle proliferation, and cell migration. Anti-integrin treatment is already widely used to treat thrombotic complications, and it seems likely that manipulation of other cell adhesion molecules will be used clinically in the near future.

Effect of DC shock on serum levels of total creatine kinase, MB-creatine kinase mass and troponin T

After successful resuscitation from cardiac arrest, it is important to identify whether the event has been triggered by a myocardial infarction, since this determines subsequent investigations and management. Previous studies have shown that biochemical indices of infarction become elevated after resuscitation in patients without myocardial infarction. This can lead to overdiagnosis of myocardial infarction in the post-arrest setting. The cause of the elevated enzyme levels is not known, but may involve electrical or mechanical injury to the heart during resuscitation. In this study we aimed to identify the effects of isolated direct current shock on serum levels of creatine kinase (CK), MB creatine kinase mass (MB-CK), and troponin T, and examined the relationships between enzyme levels and the dose of electrical energy used. Thirteen patients were studied who underwent DC cardioversion for atrial fibrillation. Serum was obtained for CK, MB-CK and troponin T estimation before and 10 min after cardioversion, at hourly intervals for 8 h, and 18 h after cardioversion. Total serum CK became significantly elevated after only 3 h and rose to a peak of 1294.4 IU l(-1) (P < 0.02) at 18 h. Post-shock CK levels were strongly correlated with total shock energy (r = 0.8, P < 0.01). Serum MB-CK was significantly elevated at 18 h among patients receiving total shock energies greater than 1000 J than in those receiving lower doses, reflecting a positive correlation (r = 0.64, P < 0.05) between shock energy and peak MB-CK level. Troponin T levels were not significantly elevated after cardioversion. In conclusion, total serum CK levels become significantly elevated early after cardioversion, suggesting rapid wash-out from injured skeletal muscle. MB-CK levels become significantly elevated in individuals receiving high energy shocks, probably due to release of small quantities of the CK-MB isoform from skeletal muscle. The negligible troponin T levels seen after high energy cardioversion indicate that significant myocardial injury does not occur. Electrical injury is not likely to account for the elevated troponin T levels seen after out-of-hospital resuscitation in patients without myocardial infarction.

Effects of digoxin on time domain measures of heart rate variability in patients with stable chronic cardiac failure: withdrawal and comparison group studies

The effect on heart rate variability of adding digoxin to a diuretic and ACE inhibitor was studied in patients with chronic stable cardiac failure. Digoxin was found to increase heart rate variability, especially those measures of heart rate variability thought to represent parasympathetic activity. The withdrawal of digoxin led to a decrease in heart rate variability to pre-treatment levels. Whilst digoxin in standard doses does not alter prognosis in chronic cardiac failure, it does have potentially beneficial neurohumoral effects. If the increase in heart rate variability, which represents beneficial neurohumoral modulation, can be divorced from the potentially detrimental effects, perhaps by using smaller doses, then there may be a role for digoxin in the treatment of chronic cardiac failure.

Management after a first myocardial infarction

Treadmill exercise testing is the most important risk-stratifying technique, because of its ability to assess residual ischemia, left ventricular dysfunction, and a tendency toward arrhythmias. Cessation of smoking is the most important lifestyle change. Among prophylactic medications, aspirin can be considered for most patients, beta-blockers for many, and ACE inhibitors for some.

Measurement of parasympathetic activity from 24-hour ambulatory electrocardiograms and its reproducibility and sensitivity in normal subjects, patients with symptomatic myocardial ischemia, and patients with diabetes mellitus

The parasympathetic nervous system plays a major role in the pathophysiology of many cardiovascular disease, particularly in modulating myocardial electrical stability. Measurements of heart rate variability have been widely used to assess parasympathetic activity. The reproducibility of measurements obtained from 24-hour ambulatory electrocardiograms has not been well documented. We have developed a technique for measuring parasympathetic activity from clinical quality 24-hour ambulatory electrocardiograms by counting beat-to-beat increases in RR interval that are > 50 ms. To determine the reproducibility and sensitivity of our technique, we analyzed repeated 24-hour electrocardiograms of 173 subjects (19 normal subjects, 67 patients with ischemic heart disease, and 87 diabetics) followed up over periods of 2 to 16 weeks. In all subject groups, mean values for repeated measurements were virtually identical. Measurements were stable in all 3 groups throughout the course of the study, as assessed by intraclass correlation coefficients. This technique is sensitive enough to detect relatively small changes in parasympathetic activity in subjects, as demonstrated by the calculated Bland and Altman coefficients of repeatability. Reproducibility and sensitivity of our technique are particularly good in normal subjects and in patients with ischemic heart disease. The results obtained with this technique imply that other related measurements of parasympathetic activity will show similar excellent short- and long-term reproducibility and sensitivity.

A comparison of cylindrical and Inoue balloon techniques for mitral valvotomy in patients in the United Kingdom

OBJECTIVES

To compare the use of cylindrical balloons and the Inoue balloon for percutaneous mitral valvotomy in patients in the United Kingdom.

DESIGN

Comparison of the haemodynamic results, complications, and symptomatic outcome of balloon dilatation for mitral stenosis in consecutive patients treated by cylindrical balloons and a second consecutive series of patients treated by the Inoue balloon.

SETTING

A tertiary cardiac referral centre in Scotland.

PATIENTS

70 patients (mean age 60.6 years) treated by the single or double cylindrical balloon technique and 70 patients (mean age 58.9 years) treated with the Inoue balloon method.

MAIN OUTCOME MEASURES

Success in obtaining dilatation at the mitral orifice, procedure and screening times, increase in valve area, complications, and early symptomatic outcome.

RESULTS

Dilatation of the mitral valve was obtained in 91% of patients when cylindrical balloons were used and in 99% of patients treated with the Inoue balloon. Use of the Inoue balloon gave significantly shorter procedure and screening times. Technical problems in obtaining and maintaining the position at the mitral orifice were more common with cylindrical balloons. Improvements in valve area and symptoms were not significantly different with use of the two types of balloon. The Inoue balloon avoided cardiac tamponade and the creation of larger atrial septal defects, but had a higher incidence of increase in mitral reflux.

CONCLUSIONS

In these elderly patients, the Inoue balloon method was safer and faster for percutaneous mitral valvotomy, with a higher success rate for dilatation within the valve orifice. Haemodynamic and symptomatic improvement was similar with the two techniques.

Management of patients after their first myocardial infarction

In the past 20 years there has been a steady improvement in the short term prognosis of patients with myocardial infarction, following the introduction of beta blockers, thrombolysis, and aspirin. Patients treated with thrombolytic drugs have a lower overall mortality after myocardial infarction but remain at risk of non-fatal reinfarction or death, and in one study almost half of all survivors of acute myocardial infarction died or suffered a further ischaemic event within three years. It is therefore important to have a strategy to identify patients at high risk, to reduce the subsequent development of cardiac failure and mortality, and to have effective measures for secondary prevention to reduce the incidence of reinfarction as well as to promote rehabilitation.

Effects of captopril therapy on endogenous fibrinolysis in men with recent, uncomplicated myocardial infarction

OBJECTIVES

This study investigated the effects of captopril therapy on endogenous fibrinolysis in men with recent, uncomplicated myocardial infarction.

BACKGROUND

Angiotensin-converting enzyme inhibitors reduce the incidence of acute coronary syndromes in patients with mild left ventricular dysfunction after myocardial infarction. Abnormal endogenous fibrinolysis, reflected in increased levels of endogenous tissue-type plasminogen activator (t-PA) antigen and plasminogen activator inhibitor type 1 activity, is associated with an increased risk of myocardial infarction in patients with ischemic heart disease.

METHODS

In a randomized, double-blind crossover study beginning 8 weeks after uncomplicated myocardial infarction, patients received 4 weeks of placebo and 4 weeks of captopril (75 mg daily) therapy. At the end of each treatment period, we measured t-PA antigen and plasminogen activator inhibitor type 1 antigen and activity.

RESULTS

Median values in the 15 patients after placebo and in 12 normal men matched for age and body mass index were, respectively, t-PA antigen 16.0 versus 9.5 ng/ml (p = 0.001), plasminogen activator inhibitor type 1 antigen 17.3 versus 8.6 ng/ml (p = 0.29) and plasminogen activator inhibitor type 1 activity 13.2 versus 6.3 AU/ml (p = 0.04). After 4 weeks of treatment with captopril in the 15 patients, the estimated (95% confidence interval) median reduction in t-PA antigen was 7.3 ng/ml (-4.6 to -10.3 ng/ml, p = 0.001), in plasminogen activator inhibitor type 1 antigen 3.1 ng/ml (+1.5 to -8.4 ng/ml, p = 0.17) and in plasminogen activator inhibitor type 1 activity -2.2 AU/ml (-1.0 to -4.3 AU/ml, p = 0.02).

CONCLUSIONS

Treatment with captopril after uncomplicated myocardial infarction is associated with a significant decrease in elevated levels of t-PA antigen and plasminogen activator inhibitor type 1 activity. This may help to explain the reduction in risk of coronary thrombosis associated with the use of angiotensin-converting enzyme inhibitors.

Cardiac parasympathetic activity in severe uncomplicated coronary artery disease

BACKGROUND

Previous studies have suggested that coronary artery disease is independently associated with reduced cardiac parasympathetic activity, and that this is important in its pathophysiology. These studies included many patients with complications that might be responsible for the reported autonomic abnormalities.

OBJECTIVE

To measure cardiac parasympathetic activity in patients with uncomplicated coronary artery disease.

PATIENTS AND METHODS

44 patients of mean (SD) age 56 (8) with severe uncomplicated coronary artery disease (symptoms uncontrolled on maximal medical treatment; > 70% coronary stenosis at angiography; normal ejection fraction; no evidence of previous infarction, diabetes, or hypertension). Heart rate variability was measured from 24 hour ambulatory electrocardiograms by counting the number of times successive RR intervals exceeded the preceding RR interval by > 50 ms, a previously validated sensitive and specific index of cardiac parasympathetic activity.

RESULTS

Mean (range) of counts were: waking 112 (range 6-501)/h, sleeping 198 (0-812)/h, and total 3912 (151-14 454)/24 h. These mean results were unremarkable, and < 10% of patients fell below the lower 95% confidence interval for waking, sleeping, or total 24 hour counts in normal people. There was no relation between the severity of coronary artery disease or the use of concurrent antianginal drug treatment and cardiac parasympathetic activity.

CONCLUSION

In contrast with previous reports no evidence of a specific independent association between coronary artery disease and reduced cardiac parasympathetic activity was found. The results of previous studies may reflect the inclusion of patients with complications and not the direct effect of coronary artery disease itself.

Hyperinsulinaemia in ischaemic heart disease: the importance of myocardial infarction and left ventricular function

Elevated circulating insulin levels have been reported in ischaemic heart disease, and may be of aetiological importance. Previous studies have not considered the potential influence of heart failure or of previous myocardial infarction, as opposed to stable angina. We therefore measured the insulin response to a 75 g oral glucose tolerance test in five groups with normal glucose tolerance, comparing normal male controls to men with chronic stable angina, men with recent myocardial infarction (two groups, 3 weeks and 3 months post infarction), and men with chronic severe heart failure. Only patients with chronic heart failure had fasting hyperinsulinaemia, probably reflecting associated neuroendocrine abnormalities. Stimulated hyperinsulinaemia was present in all patient groups, but was less pronounced and of shorter duration in patients with angina. At 120 min, only patients with heart failure or previous myocardial infarction were hyperinsulinaemic. The degree of stimulated hyperinsulinaemia was not influenced by the presence of heart failure or by the length of time from infarction. Hyperinsulinaemia is associated with impaired peripheral muscle glucose uptake and metabolism, and might contribute to muscular fatigue on exertion in patients with previous myocardial infarction or heart failure.

Differing patterns of cardiac parasympathetic activity and their evolution in selected patients with a first myocardial infarction

OBJECTIVES

The purpose of the study was to compare cardiac parasympathetic activity during the early and convalescent phases of acute anterior and inferior myocardial infarction.

BACKGROUND

Previous studies have shown that cardiac parasympathetic activity may vary with the site of infarction and that recovery may occur after infarction.

METHODS

Cardiac parasympathetic activity was measured from 24-h electrocardiograms by counting the number of times that successive RR intervals (counts) differed by > 50 ms. Recordings began within 12 h of admission and at 7, 42 and 140 days after acute myocardial infarction in 20 patients (mean age 57 +/- 7.9 years). All patients were treated with streptokinase, aspirin and oral beta-adrenergic blocking agents.

RESULTS

For the entire group, mean total 24-h RR counts increased from 592 (range 78 to 3,812) at 48 h to 648 (range 109 to 5,473) at 7 days, 1,145 (range 162 to 6,268) at 42 days and 1,958 (range 344 to 9,632) at 140 days. Patients with anterior infarction had significantly lower counts (mean 277, range 78 to 2,708; n = 11) compared with those with inferior infarction (mean 2,172, range 897 to 3,812; n = 9) at 48 h (p < 0.05). There was no significant difference in counts between patients with anterior (mean 1,051, range 212 to 6,268) and inferior (mean 1,321, range 162 to 3,265) infarction after 42 or after 140 days (anterior: mean 1,655, range 344 to 9,632; inferior: mean 2,588, range 1,700 to 5,767).

CONCLUSIONS

These data suggest that after anterior myocardial infarction there is impaired cardiac parasympathetic function that improves within 6 weeks, whereas in inferior infarction there is relative preservation of cardiac parasympathetic function.

Contrasting patterns of arterial and venous dilatation after intravenous captopril in patients with chronic cardiac failure and their relationship to plasma angiotensin II concentrations

A 25 mg intravenous bolus injection of captopril caused an abrupt and rapid decrease in systemic vascular resistance (time to maximum effect 15 minutes), but a more gradual decrease in right atrial pressure (time to maximum effect 75 minutes) in 12 patients with chronic cardiac failure. Plasma angiotensin II concentrations fell significantly, reaching their lowest concentrations at 75 minutes after the injection of captopril, at which time systemic vascular resistance had begun to return toward control values. There was no correlation between the acute arteriodilator response and pretreatment plasma renin activity or plasma angiotensin II concentrations, or the decrease in plasma angiotensin II concentrations. There was a significant correlation between the decrease in plasma angiotensin II concentrations and the decrease in right atrial pressure (r = 0.67, p < 0.05). These findings suggest that in contrast to the venous response to intravenous captopril, the arterial response is not entirely dependent on a decrease in the circulating plasma angiotensin II concentration.

The relationship between diuretic dose, and the haemodynamic response to captopril in patients with cardiac failure

The effect of diuretic dose on the haemodynamic response to captopril was assessed in nine patients with chronic cardiac failure. Each patient was given an intravenous dose of captopril while maintained on (a) a low dose diuretic regime, and (b) a high dose diuretic regime. Activity of the renin angiotensin aldosterone system, as assessed by plasma concentrations of these hormones, was greater when patients were receiving the higher dose diuretic regime. The magnitude of haemodynamic response produced by intravenous captopril was greater when the patients were maintained on the high dose diuretic regime, although no significant correlation was found between resting plasma renin activity and resting plasma angiotensin II concentration and the change produced by captopril in any haemodynamic response on either diuretic regime. An increased dosage of loop diuretic potentiates the haemodynamic effects of captopril in patients with cardiac failure. Reduction of diuretic dose prior to introduction of captopril may protect against severe first dose hypotension.

Lack of correlation between the acute haemodynamic response to intravenous captopril and plasma concentrations of angiotensin II in patients with chronic cardiac failure

We have given a series of incremental intravenous injections of captopril to ten patients with chronic cardiac failure. Small doses of captopril produced significant changes in pulmonary artery end-diastolic pressure and right atrial pressure, up to a total cumulative dose of captopril of 2.5 mg, after which further injections had no significant effect. There were large changes in systemic vascular resistance and blood pressure up to a cumulative dose of captopril of 5.0 mg, after which the injection of larger doses caused no further significant changes. Small doses of intravenous captopril produced large increases in plasma renin activity and plasma angiotensin I concentrations up to a total cumulative dose of captopril of 1.25 mg, after which there were no significant further changes in either plasma renin activity or plasma angiotensin I concentration. However the plasma concentration of angiotensin II fell more slowly, no further change being recorded after a total cumulative dose of captopril of 10 mg. These results suggest that plasma renin activity is not the only determinant of plasma angiotensin II concentrations.

Percutaneous balloon dilatation of the mitral valve in patients who were unsuitable for surgical treatment

OBJECTIVE

To assess the effects on haemodynamic function and symptoms of percutaneous balloon dilatation of mitral stenosis in patients unable to undergo surgical treatment because of associated medical/cardiac problems.

DESIGN

A review of clinical outcome in 28 patients (of 108 undergoing balloon dilatation of the mitral valve) who were unsuitable for surgery.

SETTING

A tertiary cardiac referral centre: some patients referred were from other cardiac centres in Scotland.

PATIENTS

28 patients judged by cardiac surgeons to be unsuitable for valve replacement or valvotomy because of respiratory disease (15 patients), nonmitral cardiac disease (6), multi-organ impairment (5), psychiatric problems (1) or dense intrathoracic adhesions (1).

INTERVENTIONS

Percutaneous anterograde balloon dilatation of the mitral valve with polyethylene/polyvinyl balloons in 20 patients and the Inoue balloon in eight patients.

MAIN OUTCOME MEASURES

Haemodynamic variables were measured before and immediately after mitral valve dilatation. Patient survival and symptom class (New York Heart Association) were followed for a year after the procedure.

RESULTS

Dilatation at the mitral orifice was achieved in all cases. The mean (SD) pressure drop across the valve fell from 13.9 (5.3) to 5.6 (2.5) mm Hg, cardiac output rose from 3.18 (1.02) to 3.96 (2.5) l/min, and valve area increased from 0.78 (0.32) to 1.58 (0.56) cm2. The procedure was well tolerated by most patients, even those with metabolic/electrolyte disturbance, severe obstructive airways disease, myocardial impairment, and coronary disease. In three patients a small shunt developed at the atrial level: none developed severe mitral reflux. The two patients who required assisted ventilation died soon after the procedure and in one patient with severe coronary artery disease myocardial infarction developed and she died in cardiogenic shock. Early symptomatic improvement was reported by 23 of the 25 survivors, though the increase in exercise capacity was often limited by their non-mitral disease. At one year follow up a further 6 patients had died because of their additional disease: 15 continued to show symptomatic improvement.

CONCLUSIONS

Percutaneous balloon dilatation of the mitral valve is a useful new option in patients who are too ill to undergo cardiac surgery; but longer term benefit can be limited by the associated disease.

The influence of posture on the response to loop diuretics in patients with chronic cardiac failure is reduced by angiotensin converting enzyme inhibition

The diuretic and natriuretic response to an intravenous dose of frusemide 40 mg was assessed in the erect and supine positions in 10 patients with cardiac failure who were being treated with enalapril 10 mg twice daily in addition to diuretics (Enalapril group) and in 10 patients with cardiac failure taking diuretics alone (Control group). Total 4 h diuresis in the erect position was 728 ml and in the supine position was 824 ml in the patients taking enalapril compared to 655 ml in the erect position and 1166 ml in the supine position in those patients taking diuretics alone. Total 4 h natriuresis in the erect positions was 78 mmol and in the supine position was 85 mmol in patients taking enalapril 10 mg twice daily but in those patients taking diuretics alone total 4 h natriuresis in the erect position was 67 mmol increasing to 120 mmol in the supine position. Measurements of plasma renin activity and plasma angiotensin II concentration confirmed effective converting enzyme inhibition, in the group of patients taking enalapril, but in those patients taking diuretics alone the erect position was associated with an increase in plasma renin activity, and plasma concentrations of angiotensin II and aldosterone. We conclude that the renin angiotensin system is a major factor in mediating the effect of posture on loop diuretic drugs.

Decreased cardiac parasympathetic activity in chronic heart failure and its relation to left ventricular function

BACKGROUND

Activation of the sympathetic nervous system has been extensively studied in patients with chronic heart failure, but the parasympathetic nervous system has received relatively little attention. The objective in this study was to investigate cardiac parasympathetic activity in chronic heart failure and to explore its relation to left ventricular function.

METHODS

Heart rate variability was measured from 24 hour ambulatory electrocardiograms by counting the number of times each RR interval exceeded the preceding RR interval by more than 50 ms (counts). This method provided a sensitive index of cardiac parasympathetic activity.

RESULTS

Mean (range) of counts were: waking 48 (1-275)/h, sleeping 62 (0-360)/h, and total 1310 (31-7278)/24 h. These were lower than expected, and in 26 (60%) of the 43 patients counts fell below the lower 95% confidence intervals (95% CI) for RR counts in normal subjects. A significant correlation between total 24 hour RR counts and left ventricular ejection fraction was present (r = 0.49, p less than 0.05).

CONCLUSIONS

These results indicate that most patients with chronic heart failure have reduced heart rate variability and therefore reduced cardiac parasympathetic activity. The degree of parasympathetic dysfunction is related to the severity of left ventricular dysfunction. This may be relevant to the high incidence of ventricular arrhythmias and poor prognosis of patients with chronic heart failure.

Effect of captopril on cardiac parasympathetic activity in chronic cardiac failure secondary to coronary artery disease

Thirty-two patients with chronic cardiac failure underwent 24-hour ambulatory electrocardiographic monitoring on 2 separate occasions: 20 patients before and during treatment with captopril, and 12 acting as controls. Heart rate variability was calculated by counting the number of times successive RR interval differences were greater than 50 ms (this measurement being a reliable index of cardiac parasympathetic activity). During treatment with captopril, group mean total counts increased to 1,032 (range 48 to 7,437) from 482 (range 23 to 6,120) (p = 0.002). There was no change in mean hourly waking or sleeping heart rates. In the control group, no changes were seen: group mean total counts on the first occasion were 340 (range 120 to 3,255) and on the second occasion 400 (range 154 to 3,300) (p = not significant). These results show that treatment with angiotensin-converting enzyme inhibitors increases cardiac parasympathetic activity in patients with chronic cardiac failure. This may be relevant to the improved prognosis of this group of patients when treated with angiotensin-converting enzyme inhibitors.

Posture determines the nature of the interaction between angiotensin converting enzyme inhibitors and loop diuretics in patients with chronic cardiac failure

The effects of inhibition of the renin angiotensin aldosterone system on the natriuretic and diuretic actions of an intravenous dose of frusemide 40 mg in patients with chronic cardiac failure maintained on oral diuretics were studied in the supine and erect positions. In the patients studied in the supine position the total 4 hour diuresis was decreased from 995 (92) ml to 668 (66) ml and the total 4 hour natriuresis fell from 105 (14) mmol to 67 (14) mmol following the administration of captopril. Creatinine clearance fell from 87 (8) ml/minute to 52 (15) ml/minute. In the patients studied in the erect position the total 4 hour diuresis was 596 (87) ml without captopril and 562 (83) ml with captopril. Total 4 hour natriuresis was 71 (13) mmol without captopril and 65 (9) mmol with captopril. Creatinine clearance was reduced by captopril from 82 (7) ml/minute to 47 (12) ml/minute. The reduction in the diuretic and natriuretic response to frusemide caused by captopril in the supine position is mediated through a fall in glomerular filtration rate. However, in the erect position, which is associated with even further increases in activity of the renin angiotensin aldosterone system, the reduction in diuresis and natriuresis that a fall in glomerular filtration rate would cause is offset by abolition of the rise in sodium retaining hormones, angiotensin II and aldosterone that mediate the antinatriuretic effect of the erect position.

Acute administration of captopril lowers the natriuretic and diuretic response to a loop diuretic in patients with chronic cardiac failure

Angiotensin-converting enzyme inhibitors suppress plasma concentrations of the sodium retaining hormones angiotensin II and aldosterone. This action should potentiate the natriuretic and diuretic effects of loop diuretics. Some studies indicate, however, that the introduction of angiotensin-converting enzyme inhibitors for the treatment of cardiac failure is associated with transient weight gain and the development of oedema. We have compared the natriuretic and diuretic response to intravenous frusemide 40 mg alone with the natriuretic and diuretic response to intravenous frusemide 40 mg following the administration of a single dose of captopril in 12 supine male patients with stable chronic cardiac failure. Captopril lowered the 4 h diuretic response to frusemide from 1160 (60) to 685 (77) ml (P less than 0.05) and the natriuretic response from 120 (9.6) to 68 (11.7) mmol (P less than 0.05). Creatinine clearance fell after captopril from 91 (7.2) to 57 (7.7) ml min-1 (P less than 0.05). Systolic and diastolic blood pressures were lower after the administration of captopril but these changes were not significant. Plasma renin activity rose from 3.8 (1.04) to 12.34 (2.94) ng ml h-1 (P less than 0.05) and plasma angiotensin II was reduced from 24.9 (5.05) to 8.14 (1.8) pg ml-1 (P less than 0.05). Plasma aldosterone concentrations were not significantly lower following captopril. Angiotensin-converting enzyme inhibitors cause an acute fall in creatinine clearance which may reduce the effects of loop diuretics and attention must be paid to diuretic dosage when initiating angiotensin-converting enzyme inhibitors for the treatment of cardiac failure.