Prazosin and hydralazine in congestive heart failure. Regional hemodynamic effects in relation to dose

Low-dose hydralazine improves endotoxin-induced coagulopathy and multiple organ dysfunction via its anti-inflammatory and anti-oxidative/nitrosative properties

Coagulopathy is the major cause of organ injury as well as a strong predictor of mortality in septic patients. Systemic inflammatory response and redox imbalance are regarded as the major causes of sepsis-induced coagulopathy. There is growing evidence that a vasodilator hydralazine has beneficial effects on heart failure, hypertension, and ischemia/reperfusion injury via its antioxidant and anti-inflammatory properties. However, the effects of hydralazine on sepsis have not been examined. Therefore, we evaluated the effects of low-dose hydralazine on coagulopathy and multiple organ dysfunction in septic rats induced by endotoxin. Sepsis-induced coagulopathy was established by intravenous injection of rats with lipopolysaccharide (LPS). The changes of blood pressure, heart rate, blood glucose, hemostatic variables, prothrombin time, organ function indices, interleukin-6 (IL-6) concentration, and nitric oxide (NO) level were assessed during the experimental period. In addition, the aortas, lungs, livers, and kidneys were dissected to analyze superoxide levels and protein expressions. LPS induced (i) coagulopathy, multiple organ dysfunction, and circulatory failure successfully, and (ii) excessive superoxide, NO, and IL-6 production, accompanied by the overexpression of iNOS and Wnt5a in animals. Treatment of LPS-induced septic rats with low-dose hydralazine not only improved coagulopathy but also ameliorated multiple organ dysfunction. These could be due to attenuation of the overproduction of superoxide, NO, and IL-6, which were attributed to reduction of the overexpression of iNOS and Wnt5a. Thus, these findings indicate that low-dose hydralazine could be a potential therapy for sepsis-induced coagulopathy and multiple organ dysfunction via its anti-inflammatory and anti-oxidative/nitrosative properties.

Evaluation of two intravenous single-bolus methods for measuring effective renal plasma flow

This open-label, three-way crossover study examined the feasibility of measuring effective renal plasma flow (ERPF) using a single intravenous (IV) bolus method. Eight healthy young adults (four women aged 28 +/- 5 years [mean +/- SD] and four men aged 30 +/- 7 years) received on separate days an IV bolus of p-aminohippurate (PAH) 10 mg/kg, an IV bolus of phenolsulfonphthalein (PSP) 1 mg/kg, and the standard constant-rate IV infusion of PAH. The renal clearance (CLR) and plasma clearance (CLP) of PAH after constant infusion were 623.7 +/- 62.9 and 869.0 +/- 58.8 mL/min/1.73 m2, respectively. After PAH bolus injection, CLR and CLP were 538.9 +/- 110.8 and 677.6 +/- 122.4 mL/min/1.73 m2, respectively. After PSP bolus injection, CLR and CLP were 252.8 +/- 57.9 and 350.0 +/- 41.3 mL/min/1.73 m2, respectively. The ERPF measured by PSP bolus injection was significantly lower (P < 0.05) than by PAH infusion. The CLP of PAH after IV bolus injection was significantly lower than after IV infusion when men and women were analyzed together (P < 0.05). However, there appeared to be a greater magnitude of difference between the CLR after IV bolus and infusion of PAH for women than for men. In summary, PSP administered as an IV bolus injection does not appear to be a reliable marker of ERPF. The difference in ERPF determined by the PAH infusion and bolus methods may require further evaluation.

Regional blood flow in human congestive heart failure

Despite the total-body consequences of congestive heart failure, little information is available on the distribution of cardiac output and regional-organ hemodynamics in this condition in humans. Technical and methodologic limitations probably account for the paucity of data in this area. Available data indicate that blood flow to the regions or organs studied, namely, the kidneys, hepatosplanchnic region, and upper limbs, decreases in proportion to the reduction in cardiac output. However, renal blood flow appears to be protected in human heart failure by a form of "autoregulation" during marked depression of cardiac output (less than 2.0 L/min/m2). Results of preliminary studies suggest that the regulation of regional-organ hemodynamics is disturbed in this human condition. Cardioactive drugs profoundly affect regional-organ hemodynamics independent of changes in central hemodynamics and cardiac output. The determination of regional blood flow responses in human heart failure will become more important as we expand our knowledge base of the pathophysiology of heart failure, learn more about local vascular control mechanisms, and pursue the potential therapeutic objective of selectively augmenting regional-organ hemodynamics and function.

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.

Regional blood flow supply and demand in heart failure

Heart failure results not only in a fall in cardiac output but also in a redistribution of blood flow favoring some regional beds (the brain and the heart) at the expense of others (the kidney and working skeletal muscle). The chronic resting hypoperfusion of striated muscle is further compromised with exercise. Maladaptive vasoconstrictor control mechanisms prevent the redirection of blood flow from nonworking muscle and liver to working muscle. This inappropriate preservation of nonworking organ perfusion further compromises the functional capacity of working muscle and is associated with evidence for metabolic deconditioning with reduced oxygen extraction and impaired oxidative phosphorylation. It is becoming increasingly clear that the clinical response to the inotropic and vasodilator therapy used in heart failure is in part dependent on the differing regional blood flow profiles of the various agents studied. The ability of the angiotensin-converting enzyme inhibitors to redirect blood flow away from nonworking regional beds to exercising muscle, and thereby to reestablish an appropriate physiologic response to changing metabolic needs, may be the overriding reason for their long-term efficacy. Certainly in the future the comprehensive therapy of heart failure will have to take into consideration not only central hemodynamic but also regional blood flow/supply and demand issues.

Acute effects of felodipine and nifedipine on hepatic and forearm blood flow in healthy men

The acute effects of oral administration of felodipine 10 mg and nifedipine 10 mg on heart rate, blood pressure, forearm blood flow and hepatic blood flow were studied in nine healthy men. Both drugs caused an increase in heart rate of 16 and 7 beats.min-1, respectively. Hepatic blood flow was significantly increased by 1.2 and 0.41.min-1 after felodipine and nifedipine. There was also a decrease in diastolic blood pressure, 10 and 5 mm Hg, respectively, after felodipine and nifedipine. The forearm blood flow was increased by about 30 ml.100 ml-1.min-1 after felodipine, but nifedipine had no effect. The haemodynamic effects were most pronounced 50 min after drug administration.

Rest and exercise cardiovascular effects of terazosin in congestive heart failure

This study investigated the acute effects of the alpha 1 antagonist terazosin on myocardial circulatory responses at rest and during exercise. Ten patients with congestive heart failure (class III and IV) underwent hemodynamic evaluation before and after a 5-mg oral dose of terazosin. At rest and during exercise, terazosin significantly decreased pulmonary capillary wedge pressure, systemic vascular resistance and mean arterial pressure while cardiac index increased. Stroke volume index increased (p less than 0.01) during exercise while left ventricular stroke work index remained unchanged in both experimental conditions. Terazosin administration significantly decreased both rest and exercise myocardial oxygen consumption while exercise coronary sinus oxygen content increased and arterial-coronary sinus oxygen difference diminished (p less than 0.05). Parallel with these changes, alpha blockade decreased the ratio of coronary blood flow to total cardiac output. Coronary vascular resistance remained unaltered with alpha blockade both at rest and during exercise. Coronary blood flow tended to diminish with decreased myocardial oxygen demand. Alpha 1 blockade induces systemic vasodilation and improves myocardial circulatory parameters without inducing coronary dilation or altering metabolic autoregulation.

Central and regional hemodynamic effects of flosequinan for congestive heart failure

The central and regional hemodynamic effects of flosequinan, a new orally administered vasodilator, were examined in 10 patients with moderate to severe congestive heart failure. A single-blind design was used to compare a standard dose of flosequinan (100 mg) with placebo. Flosequinan produced a statistically significant increase in cardiac output, primarily through its augmentation of stroke volume. This response was accompanied by significant reductions in systemic vascular resistances and right and left ventricular filling pressures. A reduction in pulmonary artery pressure and total pulmonary vascular resistance also was observed. The vasodilatory actions of flosequinan improved overall left ventricular performance; the inotropic indexes measured were not altered. There were no significant changes in upper limb, renal or hepatic-splanchnic blood flow or in the vascular resistances of these regions after flosequinan administration. The upper limb venous capacitance increased significantly. First-dose flosequinan evokes favorable central hemodynamic changes and improves overall left ventricular performance in patients with congestive heart failure. The acute augmentation in cardiac output, however, is not accompanied by a preferential alteration of flow to any of the major vascular regions studied.

Vasodilator therapy without converting-enzyme inhibition in congestive heart failure--usefulness and limitations

Despite a well-established rationale for pharmacologically induced arterial and venous vasodilatation in congestive heart failure, the clinical usefulness of long-term vasodilator therapy without concomitant converting-enzyme inhibition generally has been disappointing. With the exception of nitrates and, possibly, the combination of nitrates and hydralazine, the use of converting-enzyme inhibitors in many aspects appears preferable in the majority of patients. This article reviews the pathophysiology of inappropriate vasoconstriction in heart failure, the cellular mode of action of the various vasodilators, hemodynamic effects with respect to the peripheral site of action, clinical usefulness and limitations of different vasodilators, and the various determinants of clinical efficacy. Finally, an attempt is made to assess when and how to introduce vasodilator treatment with and without concomitant ACE inhibition.

Clinical pharmacokinetics and therapeutic use of hydralazine in congestive heart failure

Hydralazine (1-hydrazinophthalazine) has been used extensively in the treatment of hypertension and congestive heart failure and produces arteriolar vasodilation, in part, mediated by prostaglandins. Its associated reflex baroreceptor-mediated responses of tachycardia and increased ejection velocity are attenuated in congestive heart failure. A direct inotropic effect has been attributed to the drug. Pharmacokinetic data indicate hydralazine is absorbed well from the gastrointestinal tract, and has an extensive and complex metabolism depending on acetylator status: slow acetylators undergo primary oxidative metabolism, while rapid acetylators are acetylated. Half-lives, clearances and bioavailability of the drug are not significantly altered in congestive heart failure compared with hypertensive patients. A wide range of dosages in heart failure has been noted (150 to 3000 mg/24h), and may related to a saturation of the first-pass effect. Hydralazine improves haemodynamics in the short term in patients with increased peripheral vascular resistance, and has variable effects on pulmonary capillary wedge and left ventricular filling pressures. Prediction of the short term clinical response is difficult and appears to be independent of pharmacokinetics. A meta analysis did not demonstrate long term efficacy of hydralazine alone in heart failure, but combination therapy with nitrates has been shown to improve survival and exercise performance in patients with mild to moderate heart failure. Side effects are common and are dependent on dose, duration and acetylator status.

Regional blood flow responses to vasodilators and inotropes in congestive heart failure

Regional blood flow and the distribution of cardiac output is an important aspect of the pathophysiology and pharmacology of human congestive heart failure. This study presents the cumulative experience and data from our laboratories with specific reference to (1) the regional blood flow responses, some rather unique, to various vasodilators and inotropes in patients with congestive heart failure (CHF), and (2) the pharmacophysiologic conclusions and concepts that have evolved from these data. Certain drugs and drug groups evoke rather consistent changes in the blood flow of certain organ systems in CHF. Renal blood flow is augmented by hydralazine, an effect that persists with chronic administration. The converting enzyme inhibitors, captopril and enalapril, increase renal blood flow; this implies that the renin-angiotensin II-aldosterone axis plays a major role in modifying renal blood flow and regional blood flow distribution in human CHF. Nitrates either reduce or do not change renal blood flow. Augmentation of hepatic-splanchnic blood flow occurs after first-dose alpha 1-adrenoceptor blockade suggesting that alpha-adrenergic agonism plays an important role in modifying hepatic-splanchnic flow and the regional distribution of cardiac output in CHF. A number of drugs and drug groups increase limb blood flow (e.g., dobutamine, dopexamine, intravenous nitrates, nitroprusside, hydralazine and nifedipine). With respect to regional blood flow and the distribution of cardiac output in CHF, major differences have been shown to exist between drug groups, between drugs within a group and between different doses of a drug. Certain agents can cause a redistribution of systemic flow without changing cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)

Vasodilator therapy in chronic congestive heart failure

Benefits from vasodilator therapy in patients with chronic heart failure are partly related to the severity of functional derangements. Agents with an arteriolar-dilating effect are more likely to be effective in patients with higher left ventricular outflow resistance. Vasodilators with primary venodilating properties are more likely to be effective in the presence of an increased ventricular preload. The mechanisms by which preload and left ventricular outflow resistance increase in patients with cardiac insufficiency are not well understood and may not be similar in all patients. Vasodilators also have the capacity to ameliorate myocardial metabolic functional abnormalities by influencing myocardial energetics, but the effects of different agents on coronary hemodynamics may not be uniform. Effects on renal hemodynamics may also vary, as may neurohumoral changes after therapy. Angiotensin-converting enzyme inhibitors have been shown to exert beneficial effects on both coronary and renal hemodynamics in patients with chronic heart failure, while producing favorable neurohumoral changes. These agents provide some advantages over direct-acting vasodilators in that myocardial oxygen consumption is decreased, myocardial metabolic function is improved, and norepinephrine and aldosterone levels are reduced. Further controlled studies are needed to assess the efficacy of angiotensin-converting enzyme inhibitors in relation to other vasodilators for the long-term management of these patients.

Hemodynamic responses to different levels of alpha-adrenergic interruption in congestive heart failure

The effects of prazosin, clonidine, and indoramin on central and regional hemodynamic parameters and left ventricular performance were analyzed in a congestive heart failure population to compare the pharmacodynamic responses to different levels of alpha-adrenergic interruption in this condition. The sympathetic nervous system is blocked at the peripheral alpha1-receptor by prazosin, at central nervous system alpha-receptor sites (via alpha-adrenoceptor agonism) by clonidine, and at peripheral and central sites by indoramin. Prazosin and indoramin produced reductions in total systemic and pulmonary vascular resistances, mean systemic and pulmonary artery pressures, and pulmonary capillary wedge pressure with little change in heart rate. Both agents selectively increased hepatic blood flow. Clonidine also decreased pulmonary artery pressure and vascular resistance, but evoked negative inotropic and chronotropic activity and did not alter regional blood flow. In contrast to prazosin, indoramin and clonidine did not augment cardiac output or stroke volume. In the setting of congestive heart failure, the central and regional hemodynamic effects and the responses in left ventricular performance vary considerably depending on the site of alpha-adrenergic interruption.

A preliminary report of the effects of orally administered enoximone on regional hemodynamics in congestive heart failure

Twelve patients with moderately severe congestive heart failure underwent the simultaneous determination of central and regional hemodynamics after administration of placebo and enoximone. The regions examined hemodynamically included renal, hepatic-splanchnic and upper limb. Enoximone was studied in 2 doses, 1 and 2 mg/kg, and administered in a double-blind, placebo-controlled, crossover design. At these doses enoximone elicited a significantly greater increase in cardiac output and a greater decrease in systemic vascular resistance than placebo. Systemic blood pressure was not significantly altered. Enoximone did not significantly change the flow or resistance of renal or hepatic-splanchnic vascular beds. Limb vascular resistance decreased modestly after enoximone with a significant augmentation (+12% to 17%) of limb blood flow compared with placebo. The initial oral administration of the 1 and 2 mg/kg doses of enoximone improved central hemodynamic parameters with apparent preferential reduction of limb vascular resistance and augmentation of blood flow to the limb region (peripheral musculoskeletal system).

Hemodynamic responses to indoramin at rest and during exercise in congestive heart failure

Twenty patients with congestive heart failure underwent hemodynamic studies before and over 10 hours after the administration of 25, 50, and 75 mg of indoramin, an alpha 1-adrenergic antagonist. Hemodynamic studies were repeated during exercise after the administration of the optimal dose of indoramin. The drug reduced resting and exercise pulmonary capillary wedge pressure, right atrial pressure, systemic blood pressure and vascular resistance, and pulmonary artery pressure and vascular resistance. Resting and exercise stroke volume and cardiac output rose in response to the fall in vascular resistances. Heart rate was not altered at rest or during exercise. The first dose of the alpha 1 blocker indoramin elicits a significant reduction in ventricular preload and afterload and augmentation of ventricular performance in patients with congestive heart failure.

Contribution of the renin-angiotensin-aldosterone system to development of tolerance and fluid retention in chronic congestive heart failure during prazosin treatment

To determine the effects of the renin-angiotensin-aldosterone system on development of tolerance and fluid retention in patients with chronic congestive heart failure during long-term prazosin treatment, plasma renin concentration, aldosterone, norepinephrine and maximal exercise tolerance were measured during chronic therapy with digitalis and diuretics, to which prazosin, captopril or a combination of both drugs was added. Plasma renin concentration and aldosterone level decreased slightly during prazosin therapy and norepinephrine level increased significantly. When captopril was given, plasma renin concentration increased as expected, aldosterone level normalized and norepinephrine level decreased significantly. When prazosin was added to captopril therapy, norepinephrine level increased and plasma renin concentration and aldosterone level did not change. Exercise capacity did not increase during prazosin treatment, but was increased with captopril treatment. Prazosin treatment was associated with an increase in body weight even though the dose of furosemide was increased. Inhibition of the renin-angiotensin system did not prevent fluid retention induced by prazosin during combination therapy. These findings suggest that the renin-angiotensin-aldosterone system is not substantially involved in development of tolerance and fluid retention during prazosin therapy; stimulation of plasma norepinephrine may be of decisive importance.

Angiotensin inhibitors and other vasodilators with special reference to congestive heart failure

ACE inhibitors have emerged as important pharmacologic agents for treatment of hypertension and heart failure. Attenuation or inhibition of angiotensin mediated vasoconstriction appears to be the principal mechanism for the reduction of arterial pressure and systemic vascular resistance.

[Regional blood flow in congestive cardiac failure and inhibition of angiotensin converting enzyme]

In congestive cardiac failure myocardial deficiency is accompanied by neurohormonal dysfunction with reflex stimulation of the sympathetic nervous system and the renin-angiotensin-aldosterone system (RAAS). These two systems act synergistically, resulting in peripheral vasoconstriction with increased vascular resistance and therefore greater demand on left ventricular haemodynamics. The role of the RAAS is better understood when angiotensin-converting enzyme inhibitors (ACEI) are used. The vasodilatation produced by these inhibitors mostly affects those vascular beds that depend on the vasopressor effect of angiotensin II, and primarily the renal vascular system: glomerular filtration is improved, and sodium excretion is increased. The RAAS has little influence on the other regional blood flows, so that the administration of ACEI is not followed by cutaneous, muscular or visceral vasodilatation. However, the cerebral blood flow remains normal or even increases despite the fall in systemic arterial pressure, and the coronary output is preserved. Angiotensin-converting enzyme inhibitors produce a strong, though selective, vasodilatation without reflex tachycardia, benefiting primarily the kidneys. The resulting increase in sodium excretion contributes to the long-term effect of ACEI in the treatment of congestive cardiac failure.

The hemodynamic and clinical responses to terazosin, a new alpha blocking agent, in congestive heart failure

To determine the hemodynamic effects of a new alpha 1 blocker, terazosin, in congestive heart failure, six patients with this condition underwent hemodynamic testing (at rest and during exercise) before and after dosing. Doses of 2, 5, and 10 mg were examined in sequence over 3 days to define dose-response characteristics. Terazosin, in these doses, decreased pulmonary and systemic vascular resistances and right atrial and pulmonary capillary wedge pressures. Terazosin increased stroke volume and cardiac output, presumably through afterload-reduction, without altering heart rate. These aforementioned responses were apparent both at rest and during exercise. While a direct relationship existed between dose and plasma concentration, a similar relationship was not observed for dose (or plasma concentration) and hemodynamic response; no differences were noted between the hemodynamic responses to the three doses. Improvement in hemodynamics persisted and the clinical status and exercise capacity improved in the four patients chronically treated (over 2 months) with terazosin. Treating the heightened tone of the sympathetic nervous system in congestive heart failure with the alpha 1 blocker, terazosin, may be of benefit to some patients afflicted with this disorder.

Congestive heart failure

A review of the epidemiology, pathophysiology, and treatment of congestive heart failure is presented, with particular attention given to newer modalities of therapy.

Neurohumoral consequences of vasodilator therapy with hydralazine and nifedipine in severe congestive heart failure

We evaluated the effects of intravenous hydralazine (5 to 30 mg) and oral nifedipine (20 to 80 mg) on plasma catecholamines, renin, and aldosterone in 18 patients with severe chronic heart failure. Both drugs resulted in a significant decrease in systemic vascular resistance and mean systemic blood pressure, and led to an increase in cardiac output. Baseline plasma norepinephrine concentration was elevated in most patients; however, augmentation of cardiac output with both drugs did not decrease the values of this hormone (from 870 +/- 128 to 946 +/- 161 pg/ml with hydralazine and from 1088 +/- 260 to 1106 +/- 187 pg/ml with nifedipine). Plasma epinephrine level was also elevated at baseline and did not change significantly following nifedipine therapy (164 +/- 44 vs 199 +/- 54 pg/ml), but increased in most patients following the administration of hydralazine (from 105 +/- 45 to 153 +/- 27 pg/ml, p less than 0.01). The renin-aldosterone system was activated in our patients and also demonstrated a different response to both drugs. Hydralazine therapy did not change either the plasma renin concentration (30 +/- 7 vs 28 +/- 7 ng/ml/hr) or the aldosterone level (24 +/- 7 vs 22 +/- 5 ng/dl). In contrast, nifedipine increased the plasma renin concentration (22 +/- 7 to 29 +/- 8 ng/ml/hr, p less than 0.05). This change did not correlate with changes in systemic blood pressure (r = 0.03) and was probably the result of previously shown calcium blockade-mediated stimulation of renin release from the juxtaglomerular cells of the kidney.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of the renin-angiotensin system in the development of hemodynamic and clinical tolerance to long-term prazosin therapy in patients with severe chronic heart failure

Right heart catheterization was performed before and during long-term therapy with prazosin in 27 patients with severe chronic heart failure who underwent serial hemodynamic studies during 3 to 12 weeks of treatment with the drug. Doses of digoxin and furosemide remained constant during the trial; in addition, 11 of the 27 patients were assigned to concomitant therapy with spironolactone, while the remaining 16 patients did not receive the aldosterone antagonist. First doses of prazosin produced marked increases in cardiac index and marked decreases in mean arterial pressure, left ventricular filling pressure and systemic vascular resistance in both groups of patients (all p less than 0.01), but these effects became rapidly attenuated (p less than 0.01) in both groups after 48 hours and remained attenuated during long-term therapy. After 3 to 12 weeks, values for cardiac index returned to pretreatment levels and did not decrease when the drug was withdrawn; values for mean arterial pressure, left ventricular filling pressure and systemic vascular resistance remained significantly decreased (although attenuated) after 3 to 12 weeks (p less than 0.01) and increased to pretreatment values when the drug was withdrawn. The magnitude and time course of these responses were not altered by concomitant therapy with spironolactone. Complete loss of hemodynamic efficacy (prazosin tolerance) was noted in 14 (58%) of the 24 patients who underwent long-term hemodynamic study and was not accompanied by long-term changes in plasma renin activity or body weight. These data indicate that prazosin produces long-term hemodynamic and clinical benefits in only 30 to 40% of patients with severe chronic heart failure and do not support a role for the renin-angiotensin system in the development of tolerance to alpha-adrenergic blockade. This low response rate explains why most randomized double-blind trials of prazosin in heart failure have not been able to demonstrate a significant difference between patients treated with placebo and those receiving active drug.

Differential long-term intrarenal and neurohormonal effects of captopril and prazosin in patients with chronic congestive heart failure: importance of initial plasma renin activity

Fifty patients with congestive heart failure received, by infusion, 15 ml/kg body weight water load, and systemic hemodynamic, renal function, and neurohumoral parameters values were measured before, 2 days, and 1 month after randomly allocating patients to prazosin or captopril therapy. Both prazosin and captopril caused similar and persistent hemodynamic changes, but important differences existed between their renal and neurohumoral effects. After 1 month of continuous therapy, captopril increased creatinine clearance from 71 to 84 ml/min/1.73(2) (p less than .05), increased the water load excreted in 5 hr from 50% to 71% (p less than .005), and increased 5 hr sodium excreted from 6.8 to 14.7 meq (p less than .005), Captopril also caused a decrease in plasma norepinephrine from 568 to 448 pg/ml (p less than .005), in plasma epinephrine from 94 to 73 pg/ml (p less than .05), and in plasma aldosterone from 57 to 28 ng/dl (p less than .005), without changing plasma vasopressin. These beneficial effects were greater after 1 month of therapy than after 2 days. The only beneficial effect of prazosin was to increase water excretion from 49% to 59% (p less than .05). The long-term response to captopril was similar in patients with higher (greater than 2.5 ng/ml/hr) and lower renin levels. However, in patients with lower renin levels, prazosin decreased pulmonary capillary wedge pressure (24.8 to 21.8 mm Hg, p less than .05), decreased plasma arginine vasopressin (1.16 to 0.75 pg/ml, p less than .05), increased water excretion (62% to 85%, p less than .005), and decreased plasma epinephrine (81 to 46 pg/ml, p less than .05), while in patients with higher renin levels none of these beneficial effects were noted. We conclude that captopril produces long-term beneficial renal and neurohumoral effects that prazosin does not despite similar hemodynamic changes with the two drugs, that these effects are at least partially dependent on the initial neurohumoral and hemodynamic status of the patient, and that through hemodynamic improvement vasodilators may chronically interrupt vasopressin overstimulation.

Mixed venous blood temperature response to exercise in heart failure patients treated with short-term vasodilators

Deep-body or core temperature decreases during exercise in patients with heart failure, primarily due to the circulatory inadequacies associated with the pathophysiology of this condition. Vasodilators are commonly used to treat patients suffering from heart failure because these drugs improve total cardiac output and blood-flow to the regional circulations. In heart failure patients, the core temperature response to exercise should also be affected if the circulation is improved by vasodilators. Patients with severe heart failure were studied at rest and during upright bicycle exercise before, and after, short-term treatment with vasodilators (2-minoxidil, 3-hydralazine, 5-captopril). Their heart rate increased significantly (P less than 0.05) from rest to exercise before (87 +/- 15 109 +/- 14 beats/min), and after 89 +/- 13- 112 +/- 15 beats/min) vasodilators, but there was no drug-related affect on these changes. Mean arterial and pulmonary capillary wedge pressures were significantly (P less than 0.05) decreased at rest and after the administration of vasodilators (mean arterial pressure 88 +/- 7 mmHg before; 77 +/- 8 mmHg after; pulmonary capillary wedge pressure 25 +/- 8 mmHg before, 19 +/- 9 mmHg after). During exercise, the increases in mean arterial and pulmonary capillary wedge pressures were not significantly different from the before vasodilator values (mean arterial pressure 92 +/- 14 mmHg before, 87 +/- 14 mmHg after; pulmonary capillary wedge pressure 31 +/- 11 mmHg before, 29 +/- 11 mmHg after). Vasodilators increased cardiac output significantly (P less than 0.05) at rest (3.1 +/- 0.6 litre/min to 4.1 +/- 1.1 litre/m) and during exercise (4.8 +/- .2 litre/min-5.6 +/- 1.7 litre/min). The core temperature (mixed venous blood temperature) decreased significantly (P less than 0.05) during exercise from 37.04 +/- 0.62 degrees C to 36.65 +/- 0.65 degrees C, before treatment with vasodilators. After administration of vasodilators, resting core temperature was not significantly different (36.95 +/- 0.54 degrees C) and still decreased significantly (P less than 0.05) during exercise to 36.73 +/- 0.53 degrees C. This decrease was significantly (P less than 0.05) different from the core temperature response before the administration of vasodilators. We conclude that heart failure patients, treated with short-term vasodilators, have an attenuation of the core temperature response that typically occurs during exercise. This change in the core temperature response is the result of the vasodilator-induced improvement in circulation.

The influence of captopril, the nitrates and propranolol on apparent liver blood flow

Indocyanine green estimated apparent liver blood flow was measured in normal volunteers following glyceryl trinitrate, propranolol, isosorbide mononitrate and captopril. Glyceryl trinitrate and propranolol significantly reduced apparent liver blood flow. Isosorbide mononitrate did not alter apparent liver blood flow or produce an additional reduction in apparent liver blood flow when combined with propranolol. Captopril did not alter apparent liver blood flow despite a significant fall in mean arterial pressure and rise in plasma renin activity. Captopril and isosorbide mononitrate if shown to reduce portal pressure, do so without a fall in apparent liver blood flow.

Role of vasodilators in the treatment of congestive heart failure

Appreciation of the important role played by peripheral vasoconstriction in the pathophysiology of congestive heart failure (CHF) has led to the widespread use of vasodilators as treatment. Short-term studies show that, regardless of the vasodilator used, the arterial and venous dilatation produced invariably results in improvement in the hemodynamic status of patients. This short-term response, however, does not automatically translate to long-term clinical improvement. The reasons for this are not well understood but such factors as differing mechanisms of action, development of tolerance and unique patterns of regional redistribution of blood flow may all play a modifying role in differentiating one vasodilator from another. Nevertheless, a number of controlled trials have demonstrated sustained symptomatic and functional improvement when vasodilators such as the converting enzyme inhibitors or nitrates are given to patients with CHF.

Renal hemodynamic effects of vasodilation with nifedipine and hydralazine in patients with heart failure

The central and renal hemodynamic effects of nifedipine were evaluated in nine patients with severe chronic congestive heart failure. Oral nifedipine (34 +/- 22 mg, mean +/- standard deviation) was associated with a decrease in systemic vascular resistance from 1,748 +/- 436 to 1,321 +/- 302 dynes . s . cm-5 (p less than 0.001) and mean arterial blood pressure from 96 +/- 11 to 87 +/- 6 mm Hg (p less than 0.05) and with an increase in cardiac output from 4.2 +/- 1.1 to 4.9 +/- 1.2 liters/min (p less than 0.001). Although renal vascular resistance decreased from 11,988 +/- 2,256 to 10,286 +/- 3,011 dynes . s . cm-5 (p less than 0.05), no significant change was seen in renal blood flow (599 +/- 120 to 640 +/- 162 ml/min), glomerular filtration rate (62 +/- 18 to 62 +/- 17 ml/min), filtration fraction (18 +/- 5 to 17 +/- 6%), the ratio of renal/systemic vascular resistance (7.0 +/- 1.0 to 7.9 +/- 1.8) and the ratio of renal blood flow/cardiac output (0.15 +/- 0.02 to 0.13 +/- 0.03). Intravenous hydralazine (10 +/- 5 mg), given to eight of the patients in a randomized crossover design, resulted in a larger increase in cardiac output than did nifedipine (38 +/- 7 versus 19 +/- 10%, p less than 0.001) and in an increase in total renal blood flow from 570 +/- 152 to 645 +/- 174 ml/min (p less than 0.001). Renal vascular resistance decreased from 12,080 +/- 2,934 to 10,153 +/- 2,372 dynes . s . cm-5 (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Nifedipine in congestive heart failure: effects on resting and exercise hemodynamics and regional blood flow

Ten patients with moderate to severe congestive heart failure (CHF) underwent central and regional hemodynamic measurements at rest and central hemodynamic measurements during exercise before and after the oral administration of nifedipine (0.2 mg/kg). Nifedipine significantly decreased systemic blood pressure, systemic vascular resistance, pulmonary artery pressure, pulmonary vascular resistance, and pulmonary capillary wedge pressure. Stroke volume and cardiac output increased after nifedipine. The measured parameters of left ventricular inotropy did not change significantly for this calcium channel blocker. While blood flow to renal, hepatic, and limb vascular beds increased (p less than 0.05 for renal and limb) after nifedipine, only limb blood flow increased in proportion to the increase in cardiac output, suggesting preferential dilatation of limb vasculature. Although initial-dose nifedipine did not increase exercise duration, it elicited an improvement in exercise hemodynamics by reducing systemic vascular resistance and pulmonary capillary wedge pressure and increasing stroke volume and cardiac output. The calcium channel blocker, nifedipine, can be administered safely in the setting of ventricular failure and appears to favorably alter resting and exercise hemodynamics. A select number of patients with CHF may benefit from its long-term administration.

Beneficial effects of nifedipine on rest and exercise myocardial energetics in patients with congestive heart failure

Rest and exercise systemic hemodynamic parameters, coronary blood flow, and myocardial energetics were assessed before and 15 min after the sublingual administration of 20 mg of nifedipine in 10 patients with idiopathic congestive cardiomyopathy. When compared with control, nifedipine increased rest and exercise cardiac index by 37% and 28%, respectively (p less than .001). Peripheral vasodilation was demonstrated with a drop in systemic arterial pressure, exercise pulmonary capillary wedge pressure, and systemic vascular resistance (p less than .05). The calcium-channel blocker did not alter myocardial oxygen consumption; however, coronary blood flow increased by 32% at rest (p less than .01) while coronary vascular resistance diminished both at rest and after exercise compared with control (p less than .05). Nifedipine elicited a decrease in the rest and exercise aortocoronary sinus oxygen difference while the coronary sinus oxygen saturation increased (p less than .01). In this group of patients with idiopathic congestive cardiomyopathy, nifedipine enhanced myocardial performance while increasing coronary blood flow and favorably altering the myocardial oxygen supply-demand balance.

Hydralazine therapy in chronic congestive heart failure. Sustained central and regional hemodynamic responses

Central and regional hemodynamic parameters were evaluated at baseline and following three months of placebo or hydralazine therapy (100 mg orally every eight hours) in 20 patients with idiopathic dilated cardiomyopathy. Both control (placebo) and hydralazine groups were comparable with respect to functional classification (New York Heart Association classes III and IV) and baseline hemodynamic variables. In the hydralazine group, cardiac index increased 25 percent (2.4 +/- 0.4 to 3.0 +/- 0.5 liters/minute/m2), renal blood flow increased 26 percent (648 +/- 199 to 815 +/- 229 ml/minute), and limb blood flow was augmented by 35 percent (6.8 +/- 3.0 to 9.2 +/- 4.6 ml/dl/minute) with long-term therapy. These changes were significant (all p less than 0.05) when compared with both baseline values and values in the control group. Both central and regional hemodynamic parameters remained unaltered in the control group. Long-term hydralazine therapy (three months) elicited a favorable circulatory response in this group of patients with chronic congestive heart failure. Central or regional hemodynamic tolerance to oral hydralazine failed to develop in the majority of patients.

Conceptual dilemmas in the classification of vasodilator drugs for severe chronic heart failure. Advocacy of a pragmatic approach to the selection of a therapeutic agent

Two distinct systems of classifying vasodilator drugs have been developed over the past decade in an attempt to guide the choice of a therapeutic agent for the patient with severe heart failure, but the merits and utility of these systems have not been critically evaluated. Vasodilator drugs may be categorized according to their peripheral site of action: an agent may exert its effects preferentially on systemic arteries, systemic veins, or on both circulations. However, changes in the peripheral circulation cannot be directly translated into an improvement in central hemodynamic variables; furthermore, immediate hemodynamic responses may not be predictive of long-term clinical efficacy. Hence, there is no evidence that characterization of patients into hemodynamic subsets determined by the findings of right heart catheterization improves the clinical outcome of vasodilator therapy in chronic heart failure. An alternative classification system groups vasodilator drugs according to their mechanism of action: an agent may possess direct vasodilating effects or may exert its actions via selective neurohumoral inhibition. However, attempts to identify patients who might be most responsive to neurohumoral antagonism by measuring plasma renin activity or circulating levels of catecholamines before treatment have not been successful in predicting the clinical responses to therapy. Because neither system of drug classification provides the clinician with useful therapeutic guidelines, patients with severe heart failure appear to be best managed using a pragmatic approach in which specific drugs that produce predictable therapeutic benefits with a low frequency of side effects are utilized preferentially. Among presently available vasodilator agents, only captopril and oral isosorbide dinitrate have been shown to produce consistent hemodynamic and clinical improvement with an acceptable degree of adverse reactions.

Nifedipine increases and glyceryl trinitrate decreases apparent liver blood flow in normal subjects

The effects of sublingual nifedipine (10 mg) and of glyceryl trinitrate (500 micrograms), which produce arterial and venous vasodilatation respectively, on indocyanine green estimated apparent liver blood flow (LBF) were studied in six healthy volunteers. Nifedipine significantly increased (33 +/- 12%; mean +/- s.e. mean) and glyceryl trinitrate significantly reduced (18 +/- 3%) LBF. There was a positive relationship (r = 0.92, P less than 0.05) between the reduction in mean arterial pressure produced by nifedipine and the percentage increase in LBF. These results show that single doses of nifedipine and glyceryl trinitrate significantly alter LBF.

Chronic heart failure in the elderly: vasodilator therapy

The clinical efficacy of vasodilator therapy in the treatment of chronic congestive heart failure specifically in the elderly population has not been previously reported. Fifteen patients age 71 to 91 years with symptomatic heart failure were given vasodilator in addition to a digitalis and diuretic regimen. Seven received hydralazine 100-400 mgms. per day plus nitrates and 8 were treated with prazosin 6-60 mgms. per day, 6 of whom received additional nitrates. Initial systolic blood pressure was 130-220 mm Hg (166 +/- 25.3). This gradually fell with recurrent failure and increasing doses of medications. Heart rate remained relatively unchanged. Side effects were similar to these reported in younger patients. The only serious incident occurred in the one patient receiving minoxidil when aggressive angina developed culminating in nonfatal myocardial infarction. Implications and possible precautions are discussed. Duration of effectiveness was variable but a program of evaluation by nurses at home often allowed for early recognition of decompensation. Readjustment of medication commonly alleviated symptoms, increased exercise tolerance and decreased the frequency of rehospitalization.

Effect of hydralazine on perfusion and metabolism in the leg during upright bicycle exercise in patients with heart failure

The aerobic exercise capacity of patients with chronic heart failure is frequently impaired because of inadequate O2 transport to working skeletal muscle. To determine whether hydralazine improves O2 transport to working muscle, we examined the effect of intravenous hydralazine on blood flow (measured by thermodilution) and metabolism in the leg during maximal upright bicycle exercise in 10 patients with chronic heart failure. Hydralazine increased maximal exercise cardiac output (5.6 +/- 0.7 to 6.7 +/- 0.6 l/min; p less than .01) and decreased systemic O2 extraction (79 +/- 3% to 65 +/- 2%; p less than .01) but did not alter maximal O2 uptake (787 +/- 105 vs 779 +/- 82 ml/min). Leg blood flow at maximal exercise increased from 1.6 +/- 0.2 to 2.1 +/- 0.4 l/min (p less than .03); the proportion of cardiac output delivered to the leg remained unchanged (59 +/- 3% vs 57 +/- 9%). This increase in flow was associated with a decrease in O2 extraction in the leg (84 +/- 2% to 79 +/- 2%; p less than .01) and no change in peak femoral venous lactate (59.1 +/- 7.4 vs 54.1 +/- 5.3 mg/dl), suggesting that there is functional or anatomic shunting of the augmented limb flow rather than delivery to metabolizing muscle. These data suggest that hydralazine augments flow to the exercising limb in patients with heart failure but that this augmented flow does not increase oxygen availability within working muscle.

Dobutamine and hydralazine: comparative influences of positive inotropy and vasodilation on coronary blood flow and myocardial energetics in nonischemic congestive heart failure

Coronary blood flow and myocardial energetics were assessed after the administration of a parenteral inotrope (dobutamine hydrochloride) and an oral vasodilator agent (hydralazine) in 10 patients with nonischemic congestive heart failure. Dobutamine (5 micrograms/kg per min) and hydralazine (1 mg/kg) when group-matched elicited an identical increase in cardiac index and stroke volume index. Both agents augmented coronary blood flow while reducing coronary vascular resistance. Both forms of therapy elicited a significant increase in myocardial oxygen consumption. Dobutamine, demonstrating a balanced effect on the coronary circulation, induced a proportional increase in coronary blood flow and myocardial oxygen consumption, with the arterial-venous oxygen difference across the coronary vascular bed remaining unchanged. Hydralazine enhanced the myocardial oxygen supply versus demand ratio; despite a significant increase in myocardial oxygen consumption, the arterial-venous oxygen difference and the myocardial extraction ratio diminished. Both forms of therapy enhanced cardiac performance without inducing any electrocardiographic or clinical evidence of ischemia. Dobutamine, a positive inotropic agent, elicited a balanced effect on the coronary circulation while hydralazine, a vasodilator agent, induced a greater increase in coronary flow than in myocardial oxygen demand.

Vasodilator therapy for acute myocardial infarction and chronic congestive heart failure

Vasodilator therapy is useful adjunctive therapy in the management of both acute and chronic heart failure. Arteriolar dilators, such as hydralazine, increase cardiac output by decreasing the elevated peripheral vascular resistance that occurs in heart failure. Venodilators, such as nitrates, decrease ventricular filling pressures by redistributing blood so that more is pooled in peripheral veins. Vasodilators that produce both effects (nitro-prusside, prazosin, captopril, for example) are usually helpful in short-term improvement of hemodynamics. Long-term treatment with nonparenteral vasodilators often reduces symptoms and increases exercise tolerance, although there is inconclusive evidence regarding the effects of these agents on mortality. In acute myocardial infarction, intravenous vasodilators frequently improve cardiac performance. Evidence regarding their beneficial effects on infarct size and immediate mortality is encouraging but inconclusive. There is little evidence that they prolong life in patients who survive cardiogenic shock and leave the hospital. Thus, vasodilators can improve hemodynamics and lessen symptoms, but more evidence is needed regarding their long-term effects on survival.

Regional and systemic metabolic effects of angiotensin-converting enzyme inhibition during exercise in patients with severe heart failure

The acute hemodynamic and metabolic effects of captopril therapy were studied in 12 patients with severe heart failure during maximal exercise performed on an upright bicycle ergometer. During the control period, exhaustion occurred after 4.2 +/- 2.7 minutes of exercise. Cardiac index increased from 1.54 +/- 0.36 l/min/m2 at rest to 3.39 +/- 1.54 l/min/m2 (p less than 0.001) at exhaustion; systemic arteriovenous oxygen difference increased from 8.8 +/- 2.1 to 12.8 +/0 2.4 ml/100 ml (p less than 0.001) and oxygen uptake from 3.4 +/- 0.5 to 10.8 +/- 3.0 ml/kg/min (p less than 0.001). Pulmonary arterial oxygen content decreased from 7.3 +/- 1.3 to 3.7 +/- 1.5 ml/100 ml (p less than 0.001) and femoral vein oxygen content from 5.0 +/- 1.7 to 2.5 +/- 1.2 ml/100 ml (p less than 0.001). During captopril therapy, cardiac index significantly increased both at rest (1.83 +/- 0.54 vs 1.54 +/- 0.36 l/min/m2, p less than 0.01) and during maximal exercise (3.67 +/- 1.51 vs 3.39 +/- 1.54 l/min/m2, p less than 0.01). Systemic arteriovenous oxygen difference decreased significantly at rest, from 8.8 +/- 2.1 to 7.7 +/- 2.1 ml/100 ml (p less than 0.01) and during maximal exercise from 12.8 +/- 2.4 to 12.3 +/- 2.2 ml/100 ml (p less than 0.01). Pulmonary arterial oxygen content at exhaustion was significantly higher during captopril therapy than during the control period (4.1 +/- 1.1 vs 3.7 +/- 1.5 ml/100 ml, p less than 0.05), while femoral venous blood content was unchanged. Captopril therapy did not significantly increase maximal oxygen uptake or exercise duration. Thus, the acute administration of captopril to patients with severe heart failure does not increase exercise capacity despite improved cardiac performance. Moreover, captopril therapy does not acutely result in metabolic benefits to the skeletal muscles during exercise.

Contrasting hemodynamic responses in severe heart failure: comparison of captopril and other vasodilator drugs

Four studies were conducted in 36 patients with severe chronic heart failure to compare the central hemodynamic effects of captopril (CPT) to other vasodilator agents. While CPT produced less marked increases in cardiac output than did hydralazine (n = 14), nitroprusside (n = 15), or prazosin (n = 7), it produced decreases in left ventricular filling pressures similar to nitroprusside and prazosin but more than hydralazine. CPT and isosorbide dinitrate (n = 11) produced similar decreases in systemic vascular resistance and left ventricular filling pressure. However, cardiac output increased less with CPT than with nitrates, because heart rate slowed during CPT therapy. In addition, mean right atrial pressure decreased less with CPT than with nitrates, because CPT had minimal effects on limb venous capacitance and pulmonary arteriolar resistance. Alterations in left ventricular pressure-volume relationships likely contributed to the marked decreases in left ventricular filling pressures seen with CPT. In conclusion, the central hemodynamic effects of CPT differ significantly from other vasodilator drugs used in the treatment of heart failure patients. These effects cannot be characterized simply in terms of "balanced" peripheral arterial and venous vasodilation; CPT exerts highly complex effects on peripheral vessels as well as having actions independent of its peripheral vasodilator effects.

The contributions of sympathetic tone and the renin-angiotensin system to severe chronic congestive heart failure: response to specific inhibitors (prazosin and captopril)

The contribution of sympathetic tone and the renin-angiotensin system to the pathogenesis of chronic heart failure was evaluated. In 20 paired studies of the same 10 patients, the baseline hemodynamic and humoral correlates of congestive heart failure, and the response to alpha adrenergic blockade (prazosin) and angiotensin converting enzyme inhibition (captopril) were assessed. Despite the extent of failure, baseline plasma renin activity ranged from normal to very high. In contrast, baseline plasma catecholamine levels were always elevated. Baseline plasma norepinephrine reflected the severity of heart failure, correlating inversely with baseline cardiac index before administration of both drugs. Comparable improvement in left ventricular function was noted after acute therapy. Baseline renin and norepinephrine did not predict the response to prazosin, but baseline renin did predict the response to captopril: pulmonary wedge pressure (r=-0.776, p less than 0.01), stroke index (r=0.752, p less than 0.02), systemic vascular resistance (r=-0.673, p less than 0.05). In summary, elevated levels of plasma norepinephrine were inversely correlated with baseline cardiac function but norepinephrine levels did not change despite improved hemodynamics with specific prazosin therapy. The renin-angiotensin system exhibited a wide spectrum of activity and hemodynamic improvement with captopril was related to this activity. Absence of a correlation between plasma norepinephrine and plasma renin activity suggested that their contributions to vasoconstriction were not interdependent. Increased sympathetic tone was consistent in severe heart failure, whereas renin-angiotensin activity differed widely. The response to captopril can be used to identify a subset of patients with severe heart failure and adverse angiotensin-mediated vasoconstriction.