Peripheral hemodynamic effects of captopril in patients with congestive heart failure

Acute administration of diclofenac, but possibly not long term low dose aspirin, causes detrimental renal effects in heart failure patients treated with ACE-inhibitors

BACKGROUND

Non-steroidal anti-inflammatory drugs (NSAID) or high doses of aspirin (acetylsalicylic acid) can exert detrimental effects on renal function and counteract the beneficial effects of angiotensin-converting enzyme (ACE) inhibitors in patients with congestive heart failure.

AIMS

The objective of our study was to evaluate the renal effects of low dose aspirin and the NSAID diclofenac in patients with congestive heart failure treated with ACE-inhibitors.

METHODS

Ten patients on their individually titrated dose of ACE-inhibitors and low dose aspirin (< or =125 mg daily) with stable congestive heart failure from coronary artery disease, entered an open investigation while on low dose aspirin, which was then discontinued. After one week wash-out they received an oral dose of 50 mg diclofenac potassium or placebo in a double-blind cross-over fashion with a one week wash-out period between treatments.

RESULTS

Diclofenac caused significant (P<0.05) decreases in GFR, urine flow, osmolality clearance, and excretion rates of sodium and potassium compared to placebo and aspirin. At t(max) for diclofenac or corresponding time for placebo diclofenac caused 40 (11-59)% (geometric mean and 95% confidence limits) reduction in GFR compared to placebo and 36 (5.4-56)% reduction to low-dose aspirin. No significant changes between low dose aspirin and placebo were found.

CONCLUSION

Acute administration of diclofenac, but not long term low dose aspirin, has profound impact on renal function in patients with heart failure treated with ACE-inhibitors and may cause worsened heart failure.

Cyclooxygenase inhibition causes marked impairment of renal function in elderly subjects treated with diuretics and ACE-inhibitors

BACKGROUND

Treatment with angiotensin-converting enzyme (ACE)-inhibitors is known to cause an initial reduction in glomerular filtration rate (GFR) in patients with congestive heart failure. The long-term beneficial effects of ACE-inhibitors in these patients can be counteracted by cyclooxygenase-inhibitors.

AIMS

To quantify the negative renal effects of the cyclooxygenase-inhibitor diclofenac in elderly healthy subjects and to assess how treatment with an ACE-inhibitor, after activation of the renin-angiotensin system, influences these renal effects.

METHODS

Fourteen elderly, healthy subjects received oral diclofenac and placebo in a double-blind cross-over fashion. The study was divided in two parts; in part one, subjects received no pre-treatment and in part two, the subjects were given pre-treatment with bendroflumethiazide and enalapril in order to activate the renin-angiotensin system.

RESULTS

Diclofenac induced significant (p<0.05) decreases in GFR, urine flow, excretion rates of sodium and potassium, electrolyte clearance, osmolality clearance and free water clearance both with and without renin-angiotensin system activation. Least square means (95% CI) of all observations during the first 6 h after dosing showed that diclofenac caused a reduction in GFR from 71 (64-78) to 59 (52-66) ml/min. After pre-treatment, diclofenac further reduced GFR from 60 (52-67) to 48 (40-55) ml/min. After diclofenac administration, urine flow fell from 7.4 (6.4-8.3) to 5.1 (4.2-6.1) ml/min, after pre-treatment, diclofenac gave a further reduction from 4.1 (3.1-5.1) to 2.2 (1.3-3.2) ml/min. More than half of the reductions were caused by the pre-treatment.

CONCLUSION

Renal function in elderly, healthy subjects is impaired after acute intake of diclofenac. This impairment is observed both with and without activation of the renin-angiotensin system and ACE-inhibitor treatment but is more pronounced after pre-treatment.

Aspirin Inhibits the Acute Arterial and Venous Vasodilator Response to Captopril in Patients with Chronic Heart Failure

PURPOSE

The potentially beneficial hemodynamic effects of angiotensin-converting enzyme (ACE) inhibitors in heart failure may relate, in part, to their ability to increase the production of vasodilator prostanoids. Low dose aspirin is commonly prescribed in CHF and may attenuate the vasodilator effects of ACE inhibitors. We sought to determine the effects of low dose aspirin on the peripheral hemodynamic effects of captopril in patients with chronic heart failure (CHF).

METHODS

Nine patients with chronic heart failure were randomized in a placebo controlled, cross over study, to 75 mg of aspirin daily or placebo. After 7 days treatment the response to 25 mg of captopril was evaluated over 180 min using venous occlusion plethysmography. Forearm blood flow (FBF) and forearm venous capacitance (FVC) were measured.

RESULTS

Mean arterial pressure and heart rate did not change. After placebo, FBF increased in response to captopril (+18%, 95%CI 24.2, 11.8), a response inhibited by aspirin (-1.4%, 2.9, -5.7), p < 0.005. After placebo, FVC increased in response to captopril (+7.6%, 9.8, 5.4), which was also inhibited by aspirin (+2.0%, 4.6, -0.6), aspirin vs. placebo, p = 0.02).

CONCLUSION

In patients with chronic heart failure even low dose aspirin inhibits both the acute arterial and venous dilator responses to captopril. This action of aspirin may reduce the long-term clinical benefits of ACE inhibitors.

Forearm hyperemia is a better marker than carotid intima-media thickness or ankle-brachial index for coronary artery disease in Japanese males under 65

Forearm hyperemia, carotid intima-media thickness (IMT), and ankle-brachial pressure index (ABI) are subclinical markers associated with coronary artery disease (CAD). However, it is not known which marker is most highly correlated with CAD. We therefore compared these three parameters in the same patients under 65 years of age. In 40 males with documented CAD (mean age, 53 years), we measured forearm hyperemia by plethysmography, carotid IMT by B-mode ultrasound, and ABI by Doppler ultrasonography. Microalbuminuria, serum lipids, glucose and C-reactive protein (CRP) were also measured. Thirteen normal males served as controls (mean age, 49 years). Compared with normal subjects, CAD patients had lower hyperemia (42 vs. 92%; p < 0.001) and greater carotid IMT (0.81 vs. 0.67 mm; p < 0.01), but ABI was similar. The sensitivity of forearm hyperemia (72%) was higher than that of carotid IMT (22%) or ABI (3%) (abnormal criteria: forearm hyperemia < 60%, carotid IMT 21.0 mm, and ABI < 0.9). The patients had higher serum low-density lipoprotein (LDL) cholesterol, glucose and CRP, and lower high-density lipoprotein (HDL) cholesterol than the controls. Albuminuria was present in 49% of patients. Subclinical markers were further analyzed by age (35-54 vs. 55-64 years). The sensitivity of carotid IMT was lower in the younger patients (4% vs. 33%), while that of forearm hyperemia (69% vs. 75%) and albuminuria (47% vs. 52%) did not change with age. While carotid ultrasound was useful in older patients ( > or = 55 years), forearm hyperemia and microalbuminuria were sensitive markers irrespective of age. ABI was not useful in the Japanese men with CAD under age 65.

Bradykinin infusion in chronic cardiac failure and the effects of captopril

BACKGROUND

Patients with chronic cardiac failure (CCF) have abnormal vascular responses. Bradykinin (BK) is thought to contribute to the vasodilator effects of ACE inhibitors, but the effect of BK itself in patients with CCF has not been examined.

METHODS

We studied the responses to infused BK at 10, 30 and 100 pmol min(-1) in patients with CCF (n=10) and controls (n=10). The slope of the dose-response curve was used for comparisons between the groups. Forearm blood flow (FBF) was measured by venous occlusion plethysmography.

RESULTS

Following BK, vasodilatation was observed in both groups as the slopes were positive in all, but the difference between the groups was not significant (P=0.77). The study was repeated with the co-administration of 4 micromol min(-1) of N(G)-monomethyl L-arginine (L-NMMA). The vasodilator response to BK was reduced in both groups, and the effect was somewhat greater in the patient group (P=0.23). The vasodilator response to the endothelium-independent vasodilator sodium nitroprusside was slightly less in the patient group (P=0.08). The patients only then underwent repeat infusion of BK before and after a single oral dose of captopril 12.5 mg or placebo. Following captopril, the vasodilator response to BK was unchanged when compared to placebo (difference between slopes, P=0.53).

CONCLUSIONS

BK produces dose-dependent vasodilatation in both patients with CCF and controls; there was no difference in the responses, which were antagonised by L-NMMA and therefore in part NO (endothelium)-dependent. The responses were also unchanged after administration of an ACE inhibitor (captopril).

Neuroendocrine and renal effects of intravascular volume expansion in compensated heart failure

To examine if the neuroendocrine link between volume sensing and renal function is preserved in compensated chronic heart failure [HF, ejection fraction 0.29 +/- 0.03 (mean +/- SE)] we tested the hypothesis that intravascular and central blood volume expansion by 3 h of water immersion (WI) elicits a natriuresis. In HF, WI suppressed ANG II and aldosterone (Aldo) concentrations, increased the release of atrial natriuretic peptide (ANP), and elicited a natriuresis (P < 0.05 for all) compared with seated control. Compared with control subjects (n = 9), ANG II, Aldo, and ANP concentrations were increased (P < 0.05) in HF, whereas absolute and fractional sodium excretion rates were attenuated [47 +/- 16 vs. 88 +/- 15 micromol/min and 0.42 +/- 0.18 vs. 0.68 +/- 0.12% (mean +/- SE), respectively, both P < 0.05]. When ANG II and Aldo concentrations were further suppressed (P < 0.05) during WI in HF (by sustained angiotensin-converting enzyme inhibitor therapy, n = 9) absolute and fractional sodium excretion increased (P < 0.05) to the level of control subjects (108 +/- 34 micromol/min and 0.70 +/- 0.23%, respectively). Renal free water clearance increased during WI in control subjects but not in HF, albeit plasma vasopressin concentrations were similar in the two groups. In conclusion, the neuroendocrine link between volume sensing and renal sodium excretion is preserved in compensated HF. The natriuresis of WI is, however, modulated by the prevailing ANG II and Aldo concentrations. In contrast, renal free water clearance is attenuated in response to volume expansion in compensated HF despite normalized plasma AVP concentrations.

The angiotensin-converting enzyme inhibitor and aspirin interaction in congestive heart failure: fear or reality?

Angiotensin-converting enzyme (ACE) inhibitors have become the cornerstone of therapy for congestive heart failure (CHF). Because ischemic heart disease is the most common cause of CHF, aspirin is frequently given concomitantly with ACE inhibitors in patients with CHF. Increased bradykinin levels, with the consequent enhanced synthesis of vasodilatory prostaglandins, appear to mediate a significant benefit of ACE inhibitor therapy in these patients. In contrast, aspirin inhibits cyclooxygenase, and thereby suppresses prostaglandin production. Thus, these counteracting effects on prostaglandins may result in antagonism between ACE inhibitor and aspirin therapy in heart failure patients. Several early reports questioned the safety of aspirin in CHF, and the potential antagonistic interaction between ACE inhibitors and aspirin in patients with heart failure has become the focus of both increasing research and intense debate. This article briefly highlights the theoretic considerations underlying this interaction, and reviews the available evidence for such an interaction from clinical trials.

Aspirin does not influence the effect of angiotensin-converting enzyme inhibition on left ventricular ejection fraction 3 months after acute myocardial infarction

The aim of the present study was to evaluate the possible interaction between chronic aspirin therapy and angiotensin-converting enzyme inhibitor (ACE-I) on left ventricular ejection fraction (LVEF) in patients surviving an acute myocardial infarction (AMI). Forty-two patients with reduced LVEF were recruited from the warfarin aspirin reinfarction study (WARIS-II), a randomized, open study comparing enteric coated aspirin (160 mg/d), warfarin (INR 2.8--4.2) and the combination of aspirin (75 mg/d) and warfarin (INR 2.0--2.5) on mortality, reinfarction and stroke after AMI. LVEF and relevant biochemical measurements were performed before discharge and after 3 months. The overall LVEF increased during the study period from median 35 to 39% (P<0.001). There was no difference between patients on aspirin and warfarin regarding the main end point, LVEF. Furthermore, neither endothelin-1 nor ANP showed significant differences between the treatment groups. A possible interaction between ACE-I and aspirin might theoretically lead to reduced levels of renin activity in patients on aspirin, but we did not find any such inter-group difference. In conclusion, we did not find evidence of interaction between ACE-I and low-dose aspirin.

Interaction between Aspirin and ACE Inhibitors in Patients with Heart Failure

Both aspirin (acetylsalicylic acid) and ACE inhibitors are often used concomitantly, especially in patients with both heart failure and ischaemic heart disease, which is the most common underlying cause of heart failure. The safety of the association has been questioned because both drugs affect a related prostaglandin-mediated pathway. Thanks to their vasodilating properties, prostaglandins play an important role in heart failure where peripheral vasoconstriction occurs. Some of the beneficial effects of ACE inhibitors might be related to reduced degradation of bradykinin that enhances the synthesis of prostaglandins, while aspirin, through inhibiting the enzyme cyclo-oxygenase, inhibits the production of prostaglandins. To date no prospective study has been conducted to investigate the effect of long term aspirin treatment in the postinfarction period allowing the possible impact of the interaction between aspirin and ACE inhibitors upon survival to be confirmed or negated. However, the practitioner needs to know how to optimise the treatment of his or her patients. In order to stimulate arguments for and against the use of aspirin in patients with heart failure receiving ACE inhibitors, we searched MEDLINE from 1960 to 2000 using the key words heart failure, aspirin, and ACE inhibitors for English language articles and conducted a review of the available data. We report on the potential mechanisms of the interaction and the results of experimental studies on haemodynamic parameters. Results of retrospective clinical studies, subgroup analysis that were undertaken to evaluate the overall action upon haemodynamic parameters and survival of the association are summarised. Conflicting conclusions have been reported in the literature. Many explanations can be advanced to try to understand these conflicting conclusions: differences in study design (results of retrospective trials have to be interpreted with caution); differences in the choice of the evaluation parameter (problem of the clinical relevance of haemodynamic parameters); differences in the characteristics of the patient (different underlying cardiopathy, e.g. heart failure, hypertension or ischaemic cardiopathy); and differences in the type and the dosage of each treatment (especially ACE inhibitors and aspirin since an interaction might occur more often with dosage of aspirin greater than 250mg).

Possible interaction between aspirin and ACE inhibitors: update on unresolved controversy

The widespread use of aspirin and angiotensin converting enzyme (ACE) inhibitors in patients with coronary artery disease contributes significantly to the reduction in morbidity and mortality from this common health problem. These agents are widely and concomitantly used, and they share mechanisms that may interact in negative or positive pathways. Data derived from in vitro preparations, animal studies, human studies, and case-control studies are inconsistent. No study has established firm evidence regarding the safety or adverse effect of aspirin on patients who are on ACE inhibitors. The efficacy and safety of aspirin in combination with ACE inhibitors has been questioned and debated. If a negative interaction does exist, it will affect daily practice in treating patients with coronary artery disease and heart failure. This article reviews the available data regarding the safety of combined aspirin and ACE-inhibitor treatment among patients with ischemic heart disease, to assess the possible interaction between the two drugs and to discuss the significance and implications of the data. (c)2000 by CHF, Inc.

Chronic exercise reduces sympathetic nerve activity in rabbits with pacing-induced heart failure: A role for angiotensin II

BACKGROUND

Chronic exercise (EX) improves the quality of life and increases the survival of patients with chronic heart failure (CHF). Because sympathetic nerve activity is elevated in the CHF state, it is possible that EX is beneficial in this disease due to a decrease in sympathetic outflow.

METHODS AND RESULTS

We evaluated arterial baroreflex function and resting renal sympathetic nerve activity (RSNA) in EX normal and CHF rabbits before and after angiotensin II type 1 (AT(1)) receptor blockade. Four groups of rabbits were studied: a normal non-EX group, a normal EX group, a CHF non-EX group, and a CHF EX group. EX lowered resting RSNA in rabbits with CHF but not in normal rabbits. In addition, EX increased arterial baroreflex sensitivity in the CHF group (heart rate slope: CHF 1. 7+/-0.3 bpm/mm Hg, EX CHF 4.9+/-0.3 bpm/mm Hg; P:<0.01; RSNA slope: CHF 2.2+/-0.2%max/mm Hg, EX CHF 5.7+/-0.4%max/mm Hg; P:<0.01. AT(1) receptor blockade enhanced baroreflex sensitivity in the non-EX CHF rabbits but had no effect in EX CHF rabbits. Concomitant with this effect, EX lowered the elevated plasma angiotensin II concentration in the CHF group. A significant positive correlation was observed between sympathetic nerve activity and plasma angiotensin II.

CONCLUSIONS

These data strongly suggest that EX reduces the sympathoexcitatory state in the setting of CHF. Enhanced arterial baroreflex sensitivity may contribute to this reduction. In addition, EX lowers plasma angiotensin II concentration in CHF. These data further suggest that the lowering of angiotensin II may contribute to the decrease in sympathetic nerve activity after EX in the CHF state.

Effect of indomethacin on blood pressure lowering by captopril and losartan in hypertensive patients

NSAIDs are known to attenuate the effects of some antihypertensive medications. It is not known whether the new class of angiotensin II receptor antagonists is similarly affected. We conducted a multicenter study assessing the effect of indomethacin on the antihypertensive effects of losartan and captopril. After 4 weeks of placebo washout, hypertensive patients received 6 weeks of active antihypertensive therapy with either 50 mg losartan once daily (n=111) or 25 mg captopril twice daily for 1 week, which was increased to 50 mg twice daily for 5 weeks (n=105). This was followed by 1 week of concomitant therapy with indomethacin (75 mg daily). The primary outcome measure was the change in mean 24-hour ambulatory diastolic blood pressure after the addition of indomethacin. Both captopril and losartan significantly lowered ambulatory diastolic blood pressure (losartan -5.3 mm Hg, P:<0.001; captopril -5.6 mm Hg, P:<0.001) after 6 weeks of therapy. Indomethacin significantly attenuated the 24-hour ambulatory diastolic blood pressure for both losartan (2.2 mm Hg, P:<0.05) and captopril (2.7 mm Hg, P:<0.001) and also attenuated the effect of captopril on trough sitting diastolic blood pressure. Changes in daytime diastolic blood pressure (7:00 AM to 11:00 PM) were similar to the 24-hour response in both groups. Nighttime diastolic blood pressure (11:01 PM to 6:59 AM) was significantly attenuated in captopril-treated patients (2.0 mm Hg, P:<0.05), but losartan was unaffected (0.4 mm Hg). Thus, concurrent treatment with indomethacin similarly attenuates the 24-hour antihypertensive response to losartan and captopril.

Bradykinin B(2) receptor antagonism attenuates blood pressure response to acute angiotensin-converting enzyme inhibition in normal men

The physiological effects of angiotensin-converting enzyme (ACE) inhibition may be in part mediated by bradykinin. We investigated the effect of coadministration of the specific bradykinin B(2) receptor antagonist icatibant on hemodynamic and neurohormonal responses to acute intravenous ACE inhibition in normal men on a normal sodium diet. We performed a 4-phase, double-blind, double-dummy, placebo-controlled study in 12 male volunteers. The bradykinin antagonist icatibant (10 mg IV) was coadministered over the first 15 minutes of a 2-hour infusion of the ACE inhibitor perindoprilat (1.5 mg IV). Perindoprilat inhibited ACE activity and elicited the expected changes in active renin concentration and angiotensin peptides. Over the 3 hours after the start of drug infusion, perindoprilat lowered and icatibant increased mean arterial blood pressure (each P<0.0005 versus placebo). Coadministration of icatibant attenuated the mean arterial blood pressure response to perindoprilat (P<0.0005) but had no effect on neurohormonal responses to perindoprilat. Our study indicates that the bradykinin B(2) receptor antagonist icatibant attenuates the short-term blood pressure-lowering effect of acute ACE inhibition in normal men on a normal sodium diet. Bradykinin B(2) receptor antagonism alone increases resting blood pressure. Bradykinin may be involved in the control of blood pressure in the resting state in humans.

Inverse relation between aldosterone and venous capacitance in chronically treated congestive heart failure

The purpose of this study was to examine if there is a relation between the aldosterone escape phenomenon and venous capacitance of the upper and lower limbs in patients with long-term congestive heart failure (CHF) receiving chronic treatment with angiotensin-converting enzyme (ACE) inhibitors. The study group consisted of 16 subjects with ischemic CHF in New York Heart Association functional class II (age 59 +/-2 years, ejection fraction 24+/-4%), stabilized under a constant drug regimen comprising furosemide, captopril 50 mg 3 times daily, and digoxin for at least 3 months. Thirteen apparently healthy volunteers, aged 50+/-4 years acted as controls. Forearm and calf venous capacitances were measured simultaneously by venous occlusion plethysmography using mercury-in-silastic strain gauges. The equilibration technique was used to derive venous capacitance from the recorded pressure-volume curves. Active renin, angiotensin II, and aldosterone levels were determined on venous blood samples obtained in the supine position. Angiotensin II (p<0.05) and aldosterone (p<0.01) were statistically significantly higher in patients with CHF under long-term ACE inhibition than in controls (aldosterone escape phenomenon). In CHF, forearm venous capacitance was 2.19+/-0.18 ml/100 ml; calf venous capacitance was 2.83+/-0.27 ml/100 ml. Aldosterone significantly and inversely correlated with venous capacitance in both upper (r = -0.586; p = 0.017) and lower (r = -0.625; p = 0.01) limbs. No correlations were found between forearm or calf venous capacitance and renin or angiotensin II. In patients with heart failure chronically treated with diuretics and full ACE inhibition, venous capacitance is inversely correlated with aldosterone through the mechanism of aldosterone escape, creating the potential for further deterioration of the CHF process.

Effects of selective angiotensin II type 1 receptor blockade with losartan on arterial compliance in patients with mild essential hypertension

It has been suggested that antihypertensive drugs should not only decrease blood pressure, but also improve large artery compliance. The aim of the present study was to examine the effect of losartan, a selective angiotensin II type 1 receptor antagonist, on parameters reflecting arterial compliance. In a randomized, double-blind cross-over study, 16 patients with mild essential hypertension were examined after 4 weeks of treatment with placebo/losartan. The effect on finger plethysmographic arterial pulse curves were quantified by computing the relative height of the dicrotic notch, and pulse wave velocity was estimated by measurements of the time delay from the start of the QRS-complex (electrocardiogram) to the foot of the plethysmographic pulse wave. Compared with placebo, losartan reduced the relative height of the dicrotic notch from 55% (SD 12) to 47% [14] (p < 0.01), and pulse wave velocity from 9.3 m/sec to 8.7 m/sec (p < 0.05). The supine blood pressure decreased from 146/89 mmHg to 134/82 mmHg (p < 0.01). There was no correlation between the effects on blood pressure and the effects on the arterial compliance parameters, suggesting that losartan exerted an effect on arterial compliance beyond its effect on blood pressure.

Effect of aspirin and ifetroban on skeletal muscle blood flow in patients with congestive heart failure treated with Enalapril. Ifetroban Study Group

OBJECTIVES

The purpose of this study was to determine the acute and chronic effects of cyclooxygenase inhibition with aspirin and thromboxane A2 receptor blockade with ifetroban on the chronic vasodilating effects of enalapril in the skeletal muscle circulation of patients with heart failure.

BACKGROUND

Angiotensin-converting enzyme inhibition and antiplatelet therapy with aspirin independently reduce the risk for subsequent nonfatal coronary events in survivors of myocardial infarction. The safety of the combined administration of angiotensin-converting enzyme inhibitors and aspirin has been questioned due to their divergent effects on the vascular synthesis of vasodilating prostaglandins.

METHODS

Forearm blood flow (ml/min/100 ml) at rest and during rhythmic handgrip exercise and after transient arterial occlusion was determined by strain gauge plethysmography before and 4 h and six weeks after combined administration of enalapril with either aspirin, ifetroban or placebo in a multicenter, double-blind, randomized trial of 62 patients with mild to moderate heart failure.

RESULTS

Before randomization, forearm hemodynamics were similar in the three treatment groups except for increased resting forearm blood flow and decreased resting forearm vascular resistance in the aspirin group when compared with the placebo group. After combined administration of enalapril and study drug for 4 h and six weeks, changes from prerandomization values of mean arterial pressure, forearm blood flow and forearm vascular resistance at rest, during handgrip exercise and after transient arterial occlusion did not differ among the three treatment groups.

CONCLUSIONS

These findings demonstrate that the vasodilating effects of enalapril in the skeletal muscle circulation of patients with heart failure are not critically dependent on prostaglandin pathways.

Pharmacology and cardiovascular implications of the kinin-kallikrein system

Kinins are peptide hormones that can exert a significant influence on the regulation of blood pressure and vascular tone due to their vasodilatatory, natriuretic and growth modulating activity. Their cardiovascular involvement in physiological and pathophysiological situations has been studied intensively since inhibitors for angiotensin I-converting enzyme and selective receptor antagonists have become available for pharmacologically potentiating or inhibiting kinin-mediated reactions. Molecular biological analysis and the establishment of genetically modified animal models have also allowed newer information to be acquired on this subject. In this review, the components and cardiovascularly relevant mechanisms of the kinin-kallikrein system shall be described. Organ-specific effects concerning the kidneys, the vascular system, the heart and nervous tissue shall also be illustrated. On this issue, the physiological functions and pathophysiological implications of the kinin-kallikrein system should be clearly distinguished from the many, mostly endothelium-mediated protective effects which occur during ACE inhibition due to the potentiation of kinin effects. Finally, a view shall also be cast upon newly discovered targets of action, which could be exploited for therapeutically altering the kinin-kallikrein system.

Acute hemodynamic interaction of aspirin and ticlopidine with enalapril: results of a double-blind, randomized comparative trial

BACKGROUND

Coprescription of aspirin and ACE inhibitors is frequent in heart failure caused by coronary artery disease. Negative interaction between aspirin and enalapril has been reported, presumably through inhibition by aspirin of ACE inhibitor-induced prostaglandin synthesis. Ticlopidine is a potent antiplatelet agent without interaction with prostaglandin synthesis.

METHODS AND RESULTS

The objective of this study was to compare the influence of a coadministration of ticlopidine or aspirin on the hemodynamic effects of an ACE inhibitor (enalapril) in patients with chronic heart failure. Twenty patients with severe heart failure were enrolled in a double-blind comparative trial and allocated to ticlopidine (500 mg daily, 12 patients) or aspirin (325 mg daily, 8 patients). Hemodynamic evaluation was performed after 7 days of treatment, every hour for 4 hours after an oral administration of 10 mg of enalapril. Significant reductions in systemic vascular resistance were observed in the ticlopidine group, in contrast to no significant decrease in the aspirin group. A significant (P=0.03) time-by-treatment interaction indicated significant aspirin-enalapril drug interaction. Total pulmonary resistance decreased significantly in both groups, with no difference between patients assigned to aspirin or ticlopidine.

CONCLUSIONS

Enalapril reduced systemic vascular resistance more effectively when given in combination with ticlopidine than with aspirin. In contrast, the reduction in total pulmonary resistance is similar when enalapril is administered in combination with aspirin or ticlopidine. Negative aspirin-enalapril interaction on prostaglandin synthesis presumably alters vasodilatation in systemic vessels, whereas prostaglandin-independent actions of ACE inhibition such as pulmonary arterial vasodilatation are maintained.

Effects of aspirin on angiotensin-converting enzyme inhibition and left ventricular dilation one year after acute myocardial infarction

There are conflicting reports on the interaction of aspirin with angiotensin-converting enzyme inhibitors in heart failure and systemic hypertension. A post hoc analysis of the Captopril and Thrombolysis Study (CATS) study was conducted. At randomization, 94 patients (31.5%) took aspirin. In patients who took aspirin, the cumulative alpha-hydroxy butyrate dehydrogenase release was 1,151 +/- 132 IU/L in patients randomized to captopril compared with 1,401 +/- 136 IU/L in patients randomized to placebo (difference -250 +/- 189 [95% confidence interval (CI) -620 to 120]). This difference was comparable to the difference in patients who did not use aspirin (-199 +/- 147 [95% CI -488 to 897]). One year after acute myocardial infarction, an increase in left ventricular end-diastolic volume index of 2.2 +/- 3.0 ml/m2 in captopril-treated and 1.9 +/- 2.9 ml/m2 in placebo-treated patients was observed in patients who took aspirin (difference 0.4 +/- 4.2 [95% CI -8.2 to 8.9]). This difference was also comparable to the difference in patients who did not take aspirin (2.2 +/- 3.8 [95% CI -5.2 to 9.7]). One year after acute myocardial infarction, patients who did take aspirin had a mean change in LV end-diastolic volume index of 2.1 +/- 2.1 ml/m2 compared with 8.4 +/- 1.9 ml/m2 in patients who did not use aspirin (p = 0.02). Thus, aspirin does not attenuate the acute and long-term effects of angiotensin-converting enzyme inhibition after acute myocardial infarction, but independently reduces LV dilation after myocardial infarction.

Effect of endothelin-1 on exercise-induced vasodilation in normal subjects and in patients with heart failure

Forearm blood flow (ml/min/100 ml) was determined with strain-gauge venous occlusion plethysmography at rest and in response to handgrip exercise in 7 patients with congestive heart failure and in 9 normal subjects before and after regional administration of endothelin-1 in the brachial artery. Administration of endothelin-1 significantly decreased forearm blood flow at rest and during exercise in normal subjects but did not change it at rest or during exercise in patients with congestive heart failure.

Improvement of alveolar-capillary membrane diffusing capacity with enalapril in chronic heart failure and counteracting effect of aspirin

BACKGROUND

KII ACE, the enzyme that converts angiotensin I and inactivates bradykinin, is highly concentrated in the lungs; its blockade reduces exposure to angiotensin II and enhances exposure to prostaglandins generated by local kinin hyperconcentration. Our hypothesis is that ACE inhibitors improve pulmonary function in chronic heart failure (CHF) by readjusting lung vessel tone and permeability or alveolar-capillary membrane diffusion.

METHODS AND RESULTS

In 16 CHF patients and 16 normal volunteers or mild untreated hypertensives, pulmonary function and exercise tests with respiratory gas analysis were assessed on placebo, enalapril (10 mg BID), enalapril plus aspirin (325 mg/d), or aspirin, in random order and double blind, for 15 days each. In CHF, enalapril increased pulmonary carbon monoxide diffusion (DLCO), oxygen consumption (VO2), and exercise tolerance and reduced the ratio of dead space to tidal volume (VD/VT) and the ventilatory equivalent for carbon dioxide production (VE/VCO2). On enalapril, VO2 (r = .80, P < .0001) and VD/VT (r = -.69, P = .003) changes from placebo correlated with those in DLCO. These effects were inhibited by aspirin and were absent in control subjects. In 8 additional patients, hydralazine-isosorbide dinitrate, as an alternative treatment for reducing pulmonary capillary wedge pressure (PCWP) and increasing exercise capacity, were more effective than enalapril for the PCWP but did not affect DLCO and VE/VCO2; amelioration in VO2 and VD/VT was unrelated to DLCO and was not modified by aspirin.

CONCLUSIONS

ACE inhibition improved pulmonary diffusion in CHF. Hydralazine-isosorbide dinitrate failed to provide this result. Counteraction by aspirin, a prostaglandin inhibitor, bespeaks prostaglandin participation while on enalapril that might readjust capillary permeability or alveolar-capillary membrane diffusion.

PGE2 production after angiotensin-converting enzyme inhibition

Using OKT3 monoclonal antibody driven T-lymphocyte proliferation, we investigated the effects of plasma 10, 20 and 30% in cell cultures on the proliferation ex vivo after exposure to captopril or enalapril taken orally by healthy volunteers. We also studied the effects of captopril, angiotensin II and bradykinin in vitro. We observed a plasma dependent dual effect of ACE inhibition both ex vivo and in vitro and of bradykinin in vitro being a stimulated proliferation at low (10% plasma) and a suppression of proliferation at high (30% plasma). The suppression was shown to be PGE2 mediated but the nature of the stimulatory signal is unknown. Proliferation was also suppressed by angiotensin II mediated by PGE2, but angiotensin II had no stimulatory effect. The results indicate that the effects of ACE inhibition on OKT3 mAb driven T-lymphocyte proliferation is plasma dependent, class specific for ACE inhibitors and mediated by both the ACE inhibitor itself and by bradykinin. Furthermore, it was shown that indomethacin in combination with an ACE inhibitor or bradykinin converted a suppressive response into proliferation indicating an immunostimulatory activity by indomethacin.

Exercise-induced vasodilation in forearm circulation of normal subjects and patients with congestive heart failure: role of endothelium-derived nitric oxide

OBJECTIVES

This study was undertaken to investigate the role of endothelium-derived nitric oxide in the regulation of forearm blood flow during exercise in normal subjects and patients with congestive heart failure.

BACKGROUND

Nitric oxide-mediated vasodilation in response to muscarinic stimulation is impaired in the peripheral circulation of patients with congestive heart failure. Whether nitric oxide-mediated vasodilation during exercise is also impaired in patients with congestive heart failure is unknown.

METHODS

Forearm blood flows (ml/min per 100 ml) were determined during rhythmic hand grip exercise at 15%, 30% and 45% of maximal voluntary contraction by venous occlusion plethysmography before and after regional inhibition of nitric oxide synthesis with administration of L-NG-monomethylarginine (L-NMMA) in the brachial artery of 17 patients with congestive heart failure (mean age 49 years, mean left ventricular ejection fraction 0.22) and 10 age-matched normal subjects.

RESULTS

Before administration of L-NMMA in the brachial artery, forearm blood flows in patients with congestive heart failure during rhythmic hand grip exercise at 15%, 30% and 45% of maximal voluntary contraction were slightly but not significantly lower than that of normal subjects ([mean +/- SE] 6.8 +/- 1.0, 8.5 +/- 1.0 and 12.9 +/- 1.7 ml/min per 100 ml, respectively, in patients with congestive heart failure vs. 6.6 +/- 1.2, 11.6 +/- 1.9 and 16.2 +/- 1.9 ml/min per 100 ml, respectively, in normal subjects, p = NS). After administration of L-NMMA in the brachial artery, forearm blood flows in normal subjects significantly decreased by 10% to 21% during hand grip exercise but did not change during exercise in patients with congestive heart failure.

CONCLUSIONS

Regional inhibition of nitric oxide synthase with administration of L-NMMA in the brachial artery significantly decreased forearm blood flows during rhythmic hand grip exercise in normal subjects but not in patients with congestive heart failure. These findings suggest that nitric oxide-mediated vasodilation during submaximal exercise is impaired in the forearm circulation of patients with congestive heart failure.

The renin-angiotensin system in left ventricular remodeling

Left ventricular remodeling is a dynamic process that occurs in reaction to an insult to the myocardium. The response to either loss of cells, as may occur following myocardial infarction, or to hemodynamic overload, as may occur in aortic stenosis, is an attempt to maintain cardiac output and normalize wall tension. This is accomplished through the activation of the renin-angiotensin system and hypertrophy of noninfarcted segments of the myocardium. in the case of moderate or large infarctions these mechanisms fail to normalize wall stress. The stimulus to further remodeling remains, viable myocytes hypertrophy (with greater increases in cell length than width), the mass-to-volume ratio increases, and an exponential increase in wall stress results. This increase in myocyte tension has been associated with premature myocyte cell death. Thus, a vicious cycle is established wherein overstretch of the myocardium while sustaining cardiac output leads to progressive myocyte loss and left ventricular dilation. The renin-angiotensin system plays an integral role in this process. Its inhibition by angiotensin-converting enzyme (ACE) inhibitors both chronically and immediately after myocardial infarction has been shown to decrease left ventricular volumes and reduce mortality. Controversy exists regarding the mechanism through which ACE inhibitors exert their effects. ACE inhibitors reduce afterload/preload, circulating angiotensin II levels, and raise circulating levels of bradykinin. It is not yet clear which mechanism is responsible for the greatest impact on left ventricular dilation and mortality. inhibition of the renin-angiotensin system is clearly beneficial to cardiac performance as well as morbidity and mortality when myocardium is lost and heart failure ensues. Specific modes of action require further definition, including local and systemic effects. Possible benefits of angiotensin receptor blockade versus augmentation of bradykinin requires definition, setting the stage for further study, while the beneficial therapeutic use of these agents continues.

Comparative assessment of the effects of vasodilators on peripheral vascular reactivity in patients with systemic scleroderma and Raynaud's phenomenon: color Doppler flow imaging study

The aim of the present study was assessment of peripheral vascular reactivity during cold test effects of different types of vasodilators on vascular resistance in patients with progressive systemic sclerosis and Raynaud's phenomenon with use of color Doppler flow imaging of upper extremity.

Changes in peripheral hemodynamics and vasodilating prostaglandins after high-dose short-term ibuprofen in chronically treated hypertensive patients

The use of cyclooxygenase inhibitors has been seen to reduce the efficacy of many antihypertensive drugs. However, cyclooxygenase inhibitors are normally non-selective because they affect both vascular tissue, where the endothelial prostanoids exert principally a vasodilatory action, and the kidneys, where they also play an important role in regulating hydroelectrolytic metabolism by redistribution of intraparenchymal flow. To evaluate the relative importance of vascular district in the hypertensive patient, we administered ibuprofen - a drug acting with only a minimal antagonist activity. A group of 20 male hypertensives were randomly allocated, according to a single-blind protocol, to treatment with amlodipine (A, 10 mg/day) or lisinopril (L, 20 mg/day). Blood pressure was significantly reduced after 30 days, with a mean difference of -21.75 mmHg for systolic blood pressure (SBP) (95% confidence interval (Cl): -27.46 to -16.04; P< 0.0001) and -14.15 mmHg for diastolic blood pressure (DBP) (95% Cl: -17.13 to -11.17; P< 0.0001). Brachial artery compliance showed a mean increase of 1.657 x 10(-7) dyn-1 cm(4) (95% Cl: 1.188 to 2.126; P<0.001), and forearm resistances showed a mean decrease of -41.973 mmHg ml(-1)s (95% Cl: -75.479 to -8.467; P = 0.017). Changes in compliance were significantly related to those in SBP (r= -0.546; P= 0.013). The administration of ibuprofen (400 mg, three times a day for 3 days) was accompanied by a slight but significant increase in SBP, but not in brachial artery compliance or forearm resistances. Only SBP was affected, showing a mean increase of 4.25 mmHg (95% Cl: 1.26 to 7.24; P = 0.008). There was also reduced urinary excretion of PGI(2) and TXA(2) metabolites. The mean change in 6-keto-PGF(1 alpha) and 2,3-dinor-6-keto-PGF(1 alpha) was 45.71 ng per g urinary creatinine (uCr) (95% Cl: -0.16 to-91.25; P= 0.049) and -73.17 ng (g uCr)(-1) (95% Cl: -38.81 to -107.53; P<0.001), respectively. The mean decrease in TXA(2) catabolites was highly significant: -39.2 ng (g uCr)(-1) (95% Cl: -18.17 to-60.22; P< 0.001) and -102.87 ng (g uCr)(-1) (95% Cl: -61.86 to -143.88; P< 0.001) for TXB(2) and 2,3-dinor-TXB(2), respectively. Our study highlighted an inverse correlation between changes in blood pressure and those in urinary 2,3-dinor-6-keto-PGF(1alpha) excretion, irrespective of antihypertensive regimen. This suggests that, in the hypertensive patient treated with NSAIDs, inhibition of vascular prostanoid synthesis may play an important role in countering the efficacy of an important vascular tone regulatory mechanism.

Peripheral haemodynamic effects of inhibition of prostaglandin synthesis in congestive heart failure and interactions with captopril

OBJECTIVES

To investigate the role of prostaglandins in maintaining circulatory homoeostasis in chronic heart failure and the hypothesis that an increase in vasodilatory prostaglandin synthesis may contribute to the actions of angiotensin converting enzyme inhibitors in heart failure.

DESIGN

Randomised, double blind, placebo controlled studies. Cardiac output and renal and limb blood flow were measured after oral indomethacin 50 mg or placebo followed by "open" intravenous infusion of prostaglandin E2 (study A). In a second study the same measurements were made after oral indomethacin 50 mg or placebo was given 30 min before "open" captopril (study B).

METHODS

Blood pressure was measured using a mercury sphygmomanometer. Cardiac output was determined by Doppler interrogation of blood flow in the ascending aorta and echocardiographic measurement of aortic root diameter. Renal blood flow was calculated from the effective renal plasma flow measured by p-aminohippurate clearance and the haematocrit, and glomerular filtration rate by endogenous creatinine clearance. Limb blood flow was measured by venous occlusion plethysmography using mercury in silastic strain gauges. The concentration of plasma prostaglandin E2 was measured by radioimmunoassay.

SETTING

University department of cardiovascular medicine.

PATIENTS

12 patients with chronic stable heart failure before starting treatment with angiotensin converting enzyme inhibitors.

RESULTS

Indomethacin resulted in adverse effects on cardiac output, systemic vascular resistance, renal blood flow, glomerular filtration, urinary sodium excretion, and calf vascular resistance. Changes were reversed with infusion of prostaglandin E2. Pretreatment with indomethacin resulted in the attenuation of the acute increase in cardiac output and decrease in systemic vascular resistance that occurred with captopril. Similarly, an increase in renal blood flow with captopril was attenuated by indomethacin.

CONCLUSIONS

The acute adverse effects of indomethacin on central and peripheral haemodynamic and renal function suggest that prostaglandins have a significant role in the regulation of peripheral blood flow and renal function in patients with stable chronic heart failure. The attenuation by indomethacin of captopril induced improvements in haemodynamic function and renal blood flow is consistent with the hypothesis that captopril may act in part via an increase in prostaglandin synthesis.

Combining salicylate and enalapril in patients with coronary artery disease and heart failure

OBJECTIVE

To study the effects of adding a salicylate to the angiotensin converting enzyme inhibitor enalapril in patients with heart failure due to coronary artery disease.

DESIGN

Double blind, crossover study for three days in hospital followed by an extended similar study outside hospital over two months of once daily enalapril plus salicylate and enalapril plus placebo.

SETTING

Tertiary referral centre.

PATIENTS

20 patients with heart failure due to myocardial infarction (New York Heart Association class II or III) and an ejection fraction less than 0.40. Twelve patients completed the two parts of the study.

MAIN OUTCOME MEASURES

Blood pressure, plasma converting enzyme activity; plasma angiotensin II and noradrenaline concentrations; excretion of metabolites of renal and systemic prostanoids.

RESULTS

The unloading effect of first and second dose of enalapril in the morning lasted only during the day; in the extended study it lasted 24 hours because of the drug's accumulation. Converting enzyme inhibitors attenuate the breakdown of bradykinin and therefore enhance prostaglandin E2 synthesis mediated by bradykinin. Evidence was found of such a prostaglandin E2 mediated contribution to ventricular unloading by enalapril, which was blocked by salicylate. The contribution, however, was small and variable, and salicylate addition had on average no significant de-unloading effect during the day. Unloading was abolished in only three of the 20 patients in the short term study and in one of the 12 in the extended study. At night, when other effects of enalapril on blood pressure had waned and the bradykinin induced effect persisted, salicylate significantly reduced the remaining small unloading effect. No effect was seen of salicylate addition on reversal of remodelling. Enalapril reduced angiotensin II induced synthesis of systemic and renal prostaglandin I2 and thromboxane A2, initially only during the day, but later also at night. It thereby masked suppression of thromboxane A2 synthesis by salicylate, which is the effect to which reinfarct prevention by salicylate is attributed.

CONCLUSION

The risk is low that salicylate will substantially reduce the benefit of enalapril in patients with heart failure by de-unloading the ventricle. Like other effects induced by bradykinin significant de-unloading occurs in only a minority of the patients. In the presence of enalapril, however, salicylate will probably not be as effective as expected in reducing reinfarction risk, because enalapril already reduces thromboxane A2 synthesis effectively in patients with heart failure and no further reduction by salicylate was found.

Losartan in heart failure. Hemodynamic effects and tolerability. Losartan Hemodynamic Study Group

BACKGROUND

The aim of the present study was to assess the short- and long-term effects of multiple doses of the angiotensin II receptor antagonist losartan in heart failure.

METHODS AND RESULTS

A multicenter, placebo-controlled, oral, multidose (2.5, 10, 25, and 50 mg losartan once daily) double-blind comparison in patients with symptomatic heart failure and impaired left ventricular function (ejection fraction < 40%). Invasive 24-hour hemodynamic assessment was performed after the first dose and after 12 weeks of treatment. Clinical status and tolerability of treatment with losartan over the 12-week period were also evaluated. One hundred fifty-four patients were enrolled, of which 134 met the protocol criterion of baseline pulmonary capillary wedge pressure > or = 13 mm Hg. During short-term administration, systemic vascular resistance (SVR) (largest reduction against placebo of 197 dyne.s-1.cm-5 at 4 hours) and blood pressure fell significantly with 50 mg, lesser decreases were seen with 25 mg, and no discernible effects were seen with 2.5 and 10 mg. After 12 weeks of treatment, similar effects were seen on SVR and blood pressure (maximal fall in SVR against placebo, 318 dyne.s-1.cm-5 at 5 hours with 50 mg). In addition, pulmonary capillary wedge pressure fell with 2.5, 25, and 50 mg (largest reduction against placebo of 6.3 mm Hg at 6 hours with 50 mg), cardiac index rose with 25 and 50 mg, and heart rate was lower with all active treatment groups. Active treatment was well tolerated, and excess cough was not reported.

CONCLUSIONS

This study showed that oral losartan administered to patients with symptomatic heart failure resulted in beneficial hemodynamic effects with short-term administration, with additional beneficial hemodynamic effects seen after 12 weeks of therapy. Clear effects were seen with both 25 and 50 mg, with the greatest effect seen with 50 mg.

Angiotensinergic versus nonangiotensinergic hemodynamic effects of converting enzyme inhibition in patients with chronic heart failure. Assessment by acute renin and converting enzyme inhibition

BACKGROUND

The contribution of nonangiotensinergic effects of converting enzyme inhibitors to their hemodynamic effects in patients with chronic heart failure is not clear. A comparison of the effects of renin and converting enzyme inhibition should help to clarify this issue.

METHODS AND RESULTS

Thirty-six patients with chronic heart failure (New York Heart Association class II or III) were randomly assigned to receive double-blind either intravenous placebo, the renin inhibitor remikiren, or the converting enzyme inhibitor enalaprilat followed by coinfusion of a second placebo infusion, the addition of remikiren to enalaprilat, or the addition of enalaprilat to remikiren, respectively. Systemic hemodynamics (Swan-Ganz and radial artery catheters) were measured before (rest and submaximal recumbent bicycle ergometry), during (rest), and at the end (rest and exercise) of each 45-minute single- or combination-infusion period. Placebo did not change hemodynamics or renin activity. Effective inhibition of the renin-angiotensin system by remikiren and enalaprilat was indicated by increases of plasma immunoreactive renin together with rapid and complete inhibition of renin activity after remikiren and an increase after enalaprilat (all P < or = .05). Remikiren and enalaprilat rapidly and to a similar extent reduced resting blood pressure through a reduction of systemic vascular resistance, and these changes were significantly correlated to baseline plasma renin activity. Both compounds also decreased pulmonary artery, pulmonary capillary wedge, and right atrial pressures to a similar extent (P < .05). During exercise, pulmonary capillary wedge and right atrial pressures were equally reduced and stroke volume index was increased with remikiren and enalaprilat (P < .05) for both). The combination of converting enzyme with renin inhibition or vice versa did not cause additional hemodynamic changes.

CONCLUSIONS

Specific renin inhibition in patients with chronic heart failure produces short-term hemodynamic effects that are almost indistinguishable from those of converting enzyme inhibition. This finding and the lack of additional effects of converting enzyme inhibition added to renin inhibition suggest that nonangiotensinergic effects of converting enzyme inhibitors do not play a significant role in their short-term hemodynamic effects in patients with chronic heart failure.

Angiotensin-converting enzyme inhibitors in patients with coronary atherosclerosis

Activation of the renin-angiotensin-aldosterone system has been shown to be an independent risk factor for myocardial infarction (MI). The importance of this risk factor has been confirmed by the finding that patients with a DD genotype for the angiotensin-converting enzyme (ACE) gene, which is associated with increased serum ACE levels, have a higher incidence of MI than do patients without this genotype. ACE inhibitors have been shown to significantly reduce the incidence of recurrent MI in patients with left ventricular dysfunction. The mechanism by which activation of the renin-angiotensin-aldosterone system leads to MI has not been ascertained, but it may be related to the effect of angiotensin II or aldosterone on the development of atherosclerosis, endothelial dysfunction, plaque rupture, or thrombosis after plaque rupture. Experimental data suggest that each of these mechanisms may be of importance. Several prospective randomized studies are under way to determine the effect of ACE inhibitors on recurrent ischemic events and the progression of atherosclerosis in patients without left ventricular dysfunction. If these studies yield positive results, ACE inhibitors might assume an important role in the secondary and possibly primary prevention of ischemic heart disease.

Effect of angiotensin-converting enzyme inhibitors on endothelium-dependent peripheral vasodilation in patients with chronic heart failure

OBJECTIVES

This study was performed to determine whether acute inhibition of angiotensin-converting enzyme restores impaired endothelium-dependent vasorelaxation in patients with chronic heart failure.

BACKGROUND

Recent reports have demonstrated that endothelium-dependent vasodilation induced by cholinergic stimuli is attenuated in the peripheral vascular bed of patients with chronic heart failure.

METHODS

We examined the effects of local intraarterial infusion of enalaprilat (0.6 micrograms/min per 100 ml tissue volume) on responses initiated by acetylcholine or sodium nitroprusside in the forearm vascular bed in 8 normal subjects, 12 patients with mild heart failure (New York Heart Association functional classes I and II) and 10 patients with more advanced heart failure (functional classes III and IV). Forearm blood flow was measured by means of venous occlusion plethysmography.

RESULTS

Although enalaprilat alone did not affect basal forearm blood flow, it significantly augmented the increase in forearm blood flow induced by acetylcholine in normal subjects (p < 0.01) and in those with mild heart failure (p < 0.05). However, the effect was not found in patients with more advanced heart failure. Coinfusion of enalaprilat did not enhance sodium nitroprusside-induced vasodilation in any of the groups. To explore the mechanism of the inhibitor's effect, an additional 20 patients with mild heart failure (functional class II) were pretreated with a cyclooxygenase inhibitor, acetylsalicylic acid (n = 10) or an inhibitor of nitric oxide synthesis, NG-monomethyl-L-arginine (n = 10), followed by administration of acetylcholine with or without enalaprilat. Acetylsalicylic acid reduced the converting enzyme inhibitor's effect, whereas NG-monomethyl-L-arginine failed to block the augmentation of blood flow.

CONCLUSIONS

These results suggest that inhibition of angiotensin-converting enzyme potentiates endothelium-dependent vasodilation induced by cholinergic stimuli, presumably through modulation of prostaglandin metabolism, in the peripheral vasculature of patients with mild chronic heart failure.

Effects of converting enzyme inhibitors on angiotensin and bradykinin peptides

We examined the dose-related effects of angiotensin-converting enzyme inhibitors on circulating and tissue levels of angiotensin and bradykinin peptides by administering perindopril or lisinopril to rats in drinking water for 7 days. A reduction in the ratio of plasma angiotensin II (Ang II) to Ang I was seen for 0.006 mg/kg per day perindopril, with an increase in plasma renin and Ang I at 0.017 mg/kg per day. Plasma Ang II levels did not decrease until 1.4 mg/kg per day perindopril, at which dose plasma Ang I levels reached a plateau of an approximate 25-fold increase. The effects of perindopril on Ang II and Ang I levels in heart, lung, aorta, and brown adipose tissue were parallel to those observed for plasma. By contrast, renal Ang I levels did not increase, and renal Ang II levels decreased by 40% at 0.017 mg/kg per day, the same threshold seen for the increase in plasma renin. Perindopril increased circulating bradykinin-(1-9) levels approximately eightfold, with a threshold dose of 0.052 mg/kg per day, and increased bradykinin-(1-9) levels in kidney, heart, and lung in parallel with the changes observed for plasma. By contrast, aortic and brown adipose tissue bradykinin-(1-9) and bradykinin-(1-7) levels increased severalfold for perindopril doses as low as 0.006 mg/kg per day. Lisinopril also increased aortic bradykinin-(1-9) and bradykinin-(1-7) levels at doses below the threshold for the decrease in the ratio of Ang II to Ang I. These data indicate that renal Ang II levels and vascular bradykinin-(1-9) levels respond to low doses of converting enzyme inhibitor and may be important mediators of the effects of these compounds. The parallel increases in bradykinin-(1-9) and bradykinin-(1-7) levels in aorta and brown adipose tissue, at inhibitor doses below the threshold for inhibition of Ang I conversion, may result from a mechanism different from inhibition of "classic" angiotensin-converting enzyme.

Systemic and regional hemodynamic effects of perindopril in experimental heart failure

The effects of converting-enzyme inhibition by perindoprilat (0.5 mg/kg, intravenously, short-term administration) or perindopril (2 mg/kg, orally, long-term administration once a day for 21 days) on systemic and regional hemodynamics were studied on a new rat model of heart failure, which was induced by microembolization of coronary vessels by 15 microns plastic microspheres. Cardiac output and regional blood flows were measured by microsphere technique; the tone of the venous vessels was determined as mean circulatory filling pressure in conscious, freely moving rats. Perindoprilat evoked a much more prominent increase in kidneys, adrenal glands, intestine, and skin blood flows in embolized rats than in sham-operated rats. The differences between the effects of long-term treatment with perindopril in sham-operated and embolized rats were highly significant. Mean circulatory filling pressure was decreased by short-term and long-term administration of an angiotensin-converting enzyme inhibitor. It is concluded that venous vessels could be one of the target sites for the effects of perindopril-like drugs.

Impaired acetylcholine-mediated vasodilation in patients with congestive heart failure. Role of endothelium-derived vasodilating and vasoconstricting factors

BACKGROUND

The vasodilatory response to intra-arterial administration of acetylcholine is reduced in patients with congestive heart failure compared with that of normal subjects. The reduced response to acetylcholine may be related to decreased endothelial release of nitric oxide, interaction with peripheral alpha-adrenergic transmission, or production of cyclooxygenase-dependent vasoconstricting substances. The extent to which each of these mechanisms contributes to the reduced vasodilatory response to acetylcholine in patients with congestive heart failure is not known.

METHODS AND RESULTS

Thirty-one patients with congestive heart failure (New York Heart Association functional class II-III) and five age-matched normal subjects were studied. Regional vascular responses in the forearm to infusions of acetylcholine, an endothelium-dependent vasodilator (10(-7) to 10(-5) mol/L) and nitroglycerin, an endothelium-independent vasodilator (10(-6) mol/L) in the brachial artery were determined with venous occlusion plethysmography before and after regional alpha-adrenergic blockade with intra-arterial phentolamine (25 micrograms/min) and systemic cyclooxygenase with oral indomethacin (50 mg). Administration of phentolamine significantly increased resting baseline forearm blood flow in 11 patients with congestive heart failure (2.9 +/- 0.4 to 5.4 +/- 0.8 mL.min-1.100 mL-1) and normal subjects (4.6 +/- 0.3 to 11.3 +/- 2.1 mL.min-1.100 mL-1). Before administration of phentolamine, intra-arterial infusions of acetylcholine 10(-7), 10(-6), and 10(-5) mol/L increased forearm blood flow to 4.0 +/- 1.0, 6.0 +/- 1.7, and 16.1 +/- 4.0 mL.min-1.100 mL-1, respectively, in patients with congestive heart failure and to 14.7 +/- 6.2, 20.2 +/- 4.7, and 38.7 +/- 7.9 mL.min-1.100 mL-1, respectively, in normal subjects. After administration of phentolamine, the vasodilatory responses to intra-arterial infusions of acetylcholine and nitroglycerin did not change in either patients or normal subjects. Administration of indomethacin did not alter resting forearm blood flow in 15 patients with congestive heart failure (2.7 +/- 0.4 to 2.7 +/- 0.4 mL.min-1.100 mL-1) or normal subjects (4.6 +/- 0.3 to 5.4 +/- 0.8 mL.min-1.100 mL-1). Administration of indomethacin significantly increased the vasodilatory response to infusion of acetylcholine by an average of 39% in patients with congestive heart failure but did not change the vasodilatory response to acetylcholine in normal subjects. In patients with congestive heart failure, baseline forearm blood flow and the vasodilatory responses to intra-arterial infusions of acetylcholine and nitroglycerin were significantly less than those of normal subjects both before and after administration of phentolamine and indomethacin.

CONCLUSIONS

The reduced vasodilatory response to intra-arterial infusion of acetylcholine in patients with congestive heart failure probably results from several coexistent abnormalities in peripheral vascular function, including abnormal production of cyclooxygenase-dependent vasoconstricting factor, impaired endothelial release of nitric oxide, and decreased vascular smooth muscle responsiveness to cyclic GMP-mediated vasodilation.

Lisinopril reduces cardiac hypertrophy and mortality in rats with aortocaval fistula

We evaluated the effects of lisinopril (1 mg/kg per day) on hemodynamics, cardiac hypertrophy, and neurohumoral factors in Wistar rats with an abdominal aortocaval fistula. After 4 weeks of treatment, the results were compared with values obtained for untreated rats with a fistula and for sham-operated rats. Volume loading induced biventricular hypertrophy, hemodynamic signs of high-output heart failure (increased cardiac output, left ventricular end-diastolic pressure, and pulse pressure), and impaired renal function (decreased renal blood flow and kidney weight; increased blood urea nitrogen). Lisinopril did not affect these cardiorenal hemodynamics, but decreased left ventricular mass and mortality rate (both P < 0.05). Lisinopril attenuated the increase in plasma norepinephrine, and increased plasma renin activity (both P < 0.05). Thus, lisinopril reduced left ventricular mass and mortality in rats with high-output heart failure without changing the cardiorenal hemodynamics. Neurohumoral inhibition may play a role in the beneficial effects of lisinopril.

Review of randomized trials of digoxin therapy in patients with chronic heart failure

Although digitalis glycosides were introduced in the treatment of cardiac maladies greater than 200 years ago, controversy persists regarding the precise role of digoxin in any multidrug approach to the treatment of congestive heart failure (CHF). Despite its widespread use for more than 2 centuries, only recently have double-blind, randomized, placebo-controlled trials of digoxin therapy been conducted in patients with moderate CHF and sinus rhythm. These trials demonstrate that digoxin is superior to placebo in improving left ventricular (LV) ejection fraction, increasing exercise capacity, and preventing CHF worsening. Digoxin produces benefits similar to those seen with angiotensin converting enzyme (ACE) inhibitors with regard to clinical compensation and improvement in LV function. However, improved survival is demonstrated only in response to ACE inhibitors. The recently completed RADIANCE study addresses the value of combining digoxin with ACE inhibitor therapy in patients with mild-to-moderate CHF. Because increased mortality has been reported with the newer oral inotropic agents, it currently appears that digoxin is the only oral inotropic agent useful in clinical practice in the treatment of CHF. However, the effects of digoxin on mortality in patients with CHF remain unknown. In the large, double-blind, randomized trial conducted by the National Heart, Lung, and Blood Institute, the effects of digoxin on mortality in patients with CHF and already being treated with ACE inhibitors are currently being evaluated. Presently, based on the results of placebo-controlled studies, it appears that digoxin, alone or in combination with ACE inhibitors, is beneficial in patients with any signs or symptoms of CHF due to systolic LV dysfunction.

Evaluation of quinapril on regional blood flow and cardiac function in patients with congestive heart failure

Quinapril, a nonsulfhydryl ACE inhibitor, was evaluated in ten New York Heart Association (NYHA) functional class (FC) II-III CHF patients to determine its effects on regional blood flow [effective renal plasma flow (ERPF), renal blood flow (RBF), renal vascular resistance (RVR), hepatic blood flow (HBF), hepatic vascular resistance (HVR), segmental limb pressure (SLP), creatinine clearance (CRCL)] and cardiac function [left ventricular ejection fraction (LVEF)]. Previous vasodilator therapy was withdrawn 2 weeks before baseline measurements. Stable regimens of digoxin and diuretics were continued throughout the study. ERPF was assessed using p-aminohippurate (PAH), HBF by indocyanine green (ICG) clearance, and LVEF by radionuclide scintography. Segmental limb pressures were measured by Doppler flow detection. Measurements were performed at baseline (B) and after 4 weeks of quinapril therapy (10 mg BID). Quinapril increased renal (P less than 0.05) and hepatic blood flow (P = 0.06) and significantly reduced renal and hepatic vascular resistance. Glomerular filtration rate and left ventricular ejection fraction were unchanged. Mean arterial pressure and brachial segmental pressures decreased without change in heart rate. Noninvasive cardiovascular assessments indicate that quinapril improves regional blood flow while exhibiting no change in left ventricular ejection fraction, in patients with NYHA FC II-III CHF.

Blood pressure control by the renin-angiotensin system in normotensive subjects. Assessment by angiotensin converting enzyme and renin inhibition

BACKGROUND

The participation of the renin-angiotensin system in the control of blood pressure in normal, sodium-replete subjects is not clear. The use of a specific inhibitor of human renin should allow a better delineation of the importance of this system.

METHODS AND RESULTS

Blood pressure responses were measured 1 hour after randomized, double-blind administration of the renin inhibitor Ro 42-5892 (600 mg p.o.) or the angiotensin converting enzyme inhibitor captopril (50 mg p.o.) in 20 healthy men on an ad libitum sodium diet. Effective inhibition of the renin-angiotensin system by either compound was indicated by increases of immunoreactive renin associated with an increase of angiotensin I production rate of 67.8 +/- 33.6% after captopril and a decrease of 79.5 +/- 16.4% after Ro 42-5892. Furthermore, Ro 42-5892 decreased plasma renin activity by 64%. Whereas intra-arterial diastolic (60 +/- 5.1 to 51.4 +/- 7.2 mm Hg, p less than 0.01) and mean arterial (77.7 +/- 6.0 to 71.4 +/- 8.5 mm Hg, p less than 0.001) pressures decreased after captopril, they remained unchanged after Ro 42-5892. Captopril, but not Ro 42-5892, increased forearm blood flow (2.4 +/- 0.8 versus 1.9 +/- 0.8 ml/min/100 ml, p less than 0.01) and significantly enhanced the increase of forearm blood flow to brachial artery infusions of bradykinin (0.15, 1.5, 5, 15, and 50 ng/min/100 ml; 5 minutes each) from 744 +/- 632% to 1,383 +/- 514% (p less than 0.01). Furthermore, repeat bradykinin infusions resulted in further decreases of blood pressure (from mean pressure of 71.4 +/- 8.5 to 63.2 +/- 7.6 mm Hg, p less than 0.01) only after captopril. Changes of blood pressure after captopril were unrelated to baseline plasma renin activity but correlated with captopril-induced enhancement of vasodilation to bradykinin (r = 0.68, p less than 0.05).

CONCLUSIONS

The lack of blood pressure effects of renin inhibition in contrast to angiotensin converting enzyme inhibition suggests that the renin-angiotensin system does not contribute significantly to blood pressure control in normotensive, sodium-replete subjects. The hypotensive activity of angiotensin converting enzyme inhibitors may result from additional hormonal effects, for example, inhibition of bradykinin degradation and/or subsequent increases of vasodilating prostaglandins or endothelium-derived relaxing factor(s).

Coronary vasodilatation and improved myocardial lactate metabolism after angiotensin converting enzyme inhibition with cilazapril in patients with congestive heart failure

The effects of angiotensin converting enzyme inhibition on systemic and coronary hemodynamics and on myocardial lactate metabolism were investigated before and 2 and 6 hours after cilazapril at rest and during supine submaximal exercise in 10 patients with New York Heart Association class II or III chronic congestive heart failure. Angiotensin converting enzyme inhibition, indicated by a significant increase in plasma renin activity, resulted in significant reductions in blood pressure and systemic vascular resistance. Myocardial oxygen demand decreased (resting double product 10.9 +/- 3.7 vs 12.2 +/- 3.8 mm Hg beats/min 10(-3); p less than 0.05), but coronary sinus blood flow remained unchanged and calculated coronary resistance decreased (0.45 vs 0.5 units, rest 6 hours; p less than 0.05) suggesting coronary vasodilatation. Changes in coronary vascular resistance were directly related to changes in systemic vascular resistance (r = 0.75, p less than 0.5). Myocardial lactate extraction increased at rest (47 +/- 60 vs 134 +/- 132 mumol/min; p less than 0.5) and during exercise (27 +/- 54 vs 491 +/- 317 mumol/min; p less than 0.05) both in patients with coronary artery disease (n = 5) and idiopathic dilated cardiomyopathy (n = 5). Resting lactate production was converted to lactate extraction in two patients with coronary artery disease. Neither plasma catecholamine nor atrial natriuretic peptide concentrations changed significantly. The results suggest coronary vasodilation and improved aerobic myocardial metabolism by angiotensin converting enzyme inhibition in patients with congestive heart failure.

Effects of bucindolol on neurohormonal activation in congestive heart failure

To examine the effects of beta-adrenergic blockade on neurohormonal activation in patients with congestive heart failure, 15 men had assessments of hemodynamics and supine peripheral renin and norepinephrine levels before and after 3 months of oral therapy with bucindolol, a nonselective beta antagonist. At baseline, plasma renin activity did not correlate with any hemodynamic parameter. However, norepinephrine levels had a weak correlation with left ventricular end-diastolic pressure (r = 0.74, p less than 0.01), stroke volume index (r = 0.61, p less than 0.02) and pulmonary vascular resistance (r = 0.54, p less than 0.05). Plasma renin decreased with bucindolol therapy, from 11.6 +/- 13.4 to 4.3 +/- 4.1 ng/ml/hour (mean +/- standard deviation; p less than 0.05), whereas plasma norepinephrine was unchanged, from 403 +/- 231 to 408 +/- 217 pg/ml. A wide diversity of the norepinephrine response to bucindolol was observed with reduction of levels in some patients and elevation in others. Although plasma norepinephrine did not decrease, heart rate tended to decrease (from 82 +/- 20 vs 73 +/- 11 min-1, p = 0.059) with beta-adrenergic blockade, suggesting neurohormonal antagonism at the receptor level. No changes in I-123 metaiodobenzylguanidine uptake occurred after bucindolol therapy, suggesting unchanged adrenergic uptake of norepinephrine with beta-blocker therapy. Despite reductions in plasma renin activity and the presence of beta blockade, the response of renin or norepinephrine levels to long-term bucindolol therapy did not predict which patients had improved in hemodynamic status (chi-square = 0.37 for renin, 0.82 for norepinephrine).(ABSTRACT TRUNCATED AT 250 WORDS)

Peripheral hemodynamic and humoral effects of oral zofenopril calcium (SQ. 26,991) in patients with congestive heart failure

In 14 patients with congestive heart failure (CHF) of various grade (NYHA class 2-4) the effects of zofenopril calcium (SQ 26,991) on blood pressure and forearm circulation were studied by venous occlusion plethysmography. Changes in plasma renin activity (PRA), aldosterone, Atrial natriuretic factor (ANF) and arginine-vasopressin (AVP) were also measured. Two hours after oral administration of 7.5 mg of zofenopril we observed a decrease in blood pressure, heart rate, and forearm vascular resistance along with an increase in venous distensibility. Zofenopril also decreased ANP levels in a manner directly related to peripheral venodilatation (r = .64; P less than .05) and modified arginine-vasopressin (AVP) proportionally to the fall in blood pressure observed in response to drug administration (%SBP/%AVP: r = .64, P less than .05; %DBP/%AVP: r = .67, P less than .05). Hemodynamic and humoral responses to zofenopril occurred without any significant unwanted adverse reaction, even in patients with greater pressor reduction. We conclude that oral acute zofenopril administration, in patients with congestive heart failure, causes an arterial and venous forearm vasodilatation which is probably involved in the acute changes in plasma levels of ANF and AVP observed after drug administration.