Effect of prazosin vs placebo on chronic left ventricular heart failure

Do adrenergic alpha-antagonists increase the risk of poor cardiovascular outcomes? A systematic review and meta-analysis

Due to concerns regarding neurohormonal activation and fluid retention, adrenergic alpha-1 receptor antagonists (A1Bs) are generally avoided in the setting of heart disease, namely, symptomatic heart failure (HF) with reduced ejection fraction (HFrEF). However, this contraindication is mainly supported by ancient studies, having recently been challenged by newer ones. We aim to perform a comprehensive meta-analysis aimed at ascertaining the extent to which A1Bs might influence cardiovascular (CV) outcomes. We systematically searched PubMed, Cochrane Central Register of Controlled Trials and Web of Science for both prospective and retrospective studies, published until 1 December 2020, addressing the impact of A1Bs on both clinical outcomes-namely, acute heart failure (AHF), acute coronary syndrome (ACS), CV and all-cause mortality-and on CV surrogate measures, specifically left ventricular ejection fraction (LVEF) and exercise tolerance, by means of exercise duration. Both randomized controlled trials (RCTs) and studies including only HF patients were further investigated separately. Study-specific odds ratios (ORs) and mean differences (MDs) were pooled using traditional meta-analytic techniques, under a random-effects model. A record was registered in PROSPERO database, with the code number CRD42020181804. Fifteen RCTs, three non-randomized prospective and two retrospective studies, encompassing 32 851, 19 287, and 71 600 patients, respectively, were deemed eligible; 62 256 patients were allocated to A1B, on the basis of multiple clinical indications: chronic HF itself [14 studies, with 72 558 patients, including seven studies with 850 HFrEF or HF with mildly reduced ejection fraction (HFmrEF) patients], arterial hypertension (four studies, with 44 184 patients) and low urinary tract symptoms (two studies, with 6996 patients). There were 25 998 AHF events, 1325 ACS episodes, 955 CV deaths and 33 567 all-cause deaths. When considering only RCTs, A1Bs were, indeed, found to increase AHF risk (OR 1.78, [1.46, 2.16] 95% CI, P < 0.00001, i2 2%), although displaying no significant effect on neither ACS nor CV or all-cause mortality rates (OR 1.02, [0.91, 1.15] 95% CI, i2 0%; OR 0.95, [0.47, 1.91] 95% CI, i2 17%; OR 1.1, [0.84, 1.43] 95% CI, i2 17%, respectively). Besides, when only HF patients were evaluated, A1Bs revealed themselves neutral towards not only ACS, CV, and all-cause mortality events (OR 0.49, [0.1, 2.47] 95% CI, i2 0%; OR 0.7, [0.21, 2.31] 95% CI, i2 21%; OR 1.09, [0.53, 2.23] 95% CI, i2 17%, respectively), but also AHF (OR 1.13, [0.66, 1.92] 95% CI, i2 0%). As for HFrEF and HFmrEF, A1Bs were found to exert a similarly inconsequential effect on AHF rates (OR 1.01, [0.5-2.05] 95% CI, i2 6%). Likewise, LVEF was not significantly influenced by A1Bs (MD 1.66, [-2.18, 5.50] 95% CI, i2 58%). Most strikingly, exercise tolerance was higher in those under this drug class (MD 139.16, [65.52, 212.8] 95% CI, P < 0.001, i2 26%). A1Bs do not seem to exert a negative influence on the prognosis of HF-and even of HFrEF-patients, thus contradicting currently held views. These drugs' impact on other major CV outcomes also appear trivial and they may even increment exercise tolerance.

Direct Vasodilators and Sympatholytic Agents

Direct vasodilators and sympatholytic agents were some of the first antihypertensive medications discovered and utilized in the past century. However, side effect profiles and the advent of newer antihypertensive drug classes have reduced the use of these agents in recent decades. Outcome data and large randomized trials supporting the efficacy of these medications are limited; however, in general the blood pressure-lowering effect of these agents has repeatedly been shown to be comparable to other more contemporary drug classes. Nevertheless, a landmark hypertension trial found a negative outcome with a doxazosin-based regimen compared to a chlorthalidone-based regimen, leading to the removal of α-1 adrenergic receptor blockers as first-line monotherapy from the hypertension guidelines. In contemporary practice, direct vasodilators and sympatholytic agents, particularly hydralazine and clonidine, are often utilized in refractory hypertension. Hydralazine and minoxidil may also be useful alternatives for patients with renal dysfunction, and both hydralazine and methyldopa are considered first line for the treatment of hypertension in pregnancy. Hydralazine has also found widespread use for the treatment of systolic heart failure in combination with isosorbide dinitrate (ISDN). The data to support use of this combination in African Americans with heart failure are particularly robust. Hydralazine with ISDN may also serve as an alternative for patients with an intolerance to angiotensin antagonists. Given these niche indications, vasodilators and sympatholytics are still useful in clinical practice; therefore, it is prudent to understand the existing data regarding efficacy and the safe use of these medications.

Muscle metaboreflex-induced coronary vasoconstriction limits ventricular contractility during dynamic exercise in heart failure

Muscle metaboreflex activation (MMA) during dynamic exercise increases cardiac work and myocardial O2 demand via increases in heart rate, ventricular contractility, and afterload. This increase in cardiac work should lead to metabolic coronary vasodilation; however, no change in coronary vascular conductance occurs. This indicates that the MMA-induced increase in sympathetic activity to the heart, which raises heart rate, ventricular contractility, and cardiac output, also elicits coronary vasoconstriction. In heart failure, cardiac output does not increase with MMA presumably due to impaired ability to improve left ventricular contractility. In this setting actual coronary vasoconstriction is observed. We tested whether this coronary vasoconstriction could explain, in part, the reduced ability to increase cardiac performance during MMA. In conscious, chronically instrumented dogs before and after pacing-induced heart failure, MMA responses during mild exercise were observed before and after α1-adrenergic blockade (prazosin 20-50 μg/kg). During MMA, the increases in coronary vascular conductance, coronary blood flow, maximal rate of left ventricular pressure change, and cardiac output were significantly greater after α1-adrenergic blockade. We conclude that in subjects with heart failure, coronary vasoconstriction during MMA limits the ability to increase left ventricular contractility.

Circulatory response to prenalterol in normal subjects and in patients with primary congestive cardiomyopathy

Experimental pharmacology indicates that prenalterol is a selective beta 1-adrenoceptor activator. In 5 normal individuals, 15 minutes after the drug (infused at a dose of 15 micrograms/kg over 5 min) the following circulatory changes were seen: a) increase of cardiac index (+31%), heart rate, stroke index, systolic aortic pressure, left and right ventricular mean rate of ejection and mean rate of the pressure rise in either ventricle during the pre-ejection phase; b) reduction of systemic vascular resistance (-18%), appearance, built-up and disappearance times in the left ventricular dye dilution curves. Pulmonary systolic, diastolic and wedge pressures and vascular resistance did not vary consistently. The circulatory effects persisted almost unchanged 30 minutes after the infusion. In a group of 5 patients with heart failure due to primary congestive cardiomyopathy, refractory to conventional therapy, the haemodynamic response to prenalterol (infused at a dose of 30 micrograms/kg over 5 min) was qualitatively similar to that of normal subjects in 3 cases. In 2 other patients cardiac performance deteriorated. The reasons for this paradoxical effect were not identified. These preliminary results suggest that prenalterol is a potent selective inotropic agent in man, that may assist in the therapeutic management of refractory heart failure due to congestive cardiomyopathy. However, careful haemodynamic monitoring is advisable for its use in this dysfunction until broader clinical experience can be accumulated.

Effects of red rest and prazosin in congestive heart failure

Twelve patients with congestive heart failure were monitored with invasive and noninvasive techniques to evaluate the effect of vasodilator treatment. During the 18 hours of strict bed rest before administration of prazosin, the hemodynamics improved substantially while only small and transient heModynamic changes were observed after introduction of prazosin. At 6 weeks' control the effect of vasodilator treatment with prazosin, 3 mg x 4, was lost. The beneficial results often credited to vasodilators in studies on congestive heart failure might in part be due to the concomitant bed rest introduced during the monitoring of the patients.

Hemodynamic effects at rest and during exercise in long-term treatment with prazosin in chronic congestive heart failure

The long-term effects of prazosin in chronic congestive heart failure were studied in 10 patients (New York Heart Association class III-IV) in a double-blind cross-over study. Patients with systolic blood pressure greater than 120 mmHg and left ventricular filling pressure greater than 15 mmHg were included. Prazosin lowered the arteriovenous oxygen difference both at rest and during exercise (p less than 0.05), increased cardiac index (p less than 0.01) and reduced right atrial pressure and systemic vascular resistance (p less than 0.05) during exercise. Left ventricular filling pressure was also reduced, but not significantly, during exercise. Our data show that prazosin has beneficial long-term effects during exercise in patients with chronic congestive heart failure.

Prazosin in chronic congestive heart failure due to ischemic heart disease

Oral prazosin hydrochloride (2-20 mg/day) was administered to 38 patients with chronic congestive heart failure due to ischemic heart disease for 6-18 months. Half (19) of the patients were hypertensive and half (19) nonhypertensive. All were receiving furosemide (80 mg/day, orally) and 19 were receiving digoxin (0.25-0.5 mg/day, orally) in addition to prazosin. Clinical radiological, mechanocardiographic, echocardiographic, and biochemical observations were made initially, at peak response, and at the end of 6 months. Prazosin improved left ventricular function indexes at rest, relieved symptoms and signs of congestion, and remained effective for 6-18 months with little or no increase in dose. There was no reflex tachycardia, tension-time indexes fell in all patients, angina was relieved in 8 patients who complained of it, and dyskinesia of left ventricular wall was corrected in 8 of 13 patients. The New York Heart Association functional class improved in all patients, but to a greater extent in hypertensive patients and in those not receiving concomitant digoxin. Mild, transient side effects occurred in 6 patients.

Duration and reproducibility of initial hemodynamic effects of flosequinan in patients with congestive heart failure

The duration and reproducibility of hemodynamic effects of flosequian, a direct-acting, balanced-type vasodilator, were studied in 19 heart failure patients (NYHA class 3.0 +/- 0.7) receiving 100 mg orally (day 1), placebo (day 2), and again 100 mg (day 3). Flosequinan immediately reduced systemic and pulmonary resistance (23% and 35%, respectively, at 60-90 minutes postdrug) and decreased pulmonary wedge, right atrial, mean pulmonary artery, and mean arterial pressure by 38%, 50%, 25%, and 7%, respectively. Concomitantly, cardiac output, and stroke volume and work increased by 26%, 20%, and 22%, respectively. Most hemodynamic effects persisted for 48 hours. In contrast, changes in pulmonary wedge and arterial pressures, stroke volume, and stroke work only lasted for 2-12 hours. Maximum absolute changes on day 3 were generally comparable with first-dose effects with, again, long-lasting effects on systemic resistance and cardiac output. However, changes in pulmonary artery, wedge, and resistance were significantly shorter than after first dose administration. These data indicate sustained and reproducible arterial dilating effects of flosequinan, but less pronounced and shorter lasting pulmonary arterial and venodilator properties.

Haemodynamic dose-response effects of UK-52,046 in ischaemic disease with or without impaired left ventricular function

1. The haemodynamic effects of a new cardioselective postsynaptic alpha 1-adrenoceptor antagonist UK-52,046, were evaluated in 25 patients with stable coronary disease, with or without impaired left ventricular function. At rest the haemodynamic effects to two dose-response regimens were determined. In an initial eight patients 0.125, 0.125 and 0.25 micrograms kg-1 were administered peripherally at 15 min intervals; the haemodynamic measurements were determined between 10 to 15 min after each dose. In a further 17 patients, the dose regimen was doubled yielding a cumulative dose-regimen of 0.25, 0.5 and 1.0 micrograms kg-1. The exercise effects were determined by comparison of measurements during 4 min of supine sub-maximal bicycle exercise at a fixed workload before and after drug treatment. 2. At rest, the lower dose regimen of UK-52,046 significantly reduced systemic mean arterial blood pressure (-5 mm Hg; P less than 0.05) and increased cardiac index (+0.2 l min-1 m-2, P less than 0.01). The higher dose regimen of UK-52,046 reduced systemic mean arterial blood pressure (-7 mm Hg; P less than 0.01), pulmonary artery occluded pressure (PAOP) (-2 mm Hg, P less than 0.01) and vascular resistance index (-314 dyn s cm-5 m2; P less than 0.05) with an increase in heart rate (+7%, P less than 0.05) and cardiac index (+0.2 l min-1 m-2, P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Alpha-adrenergic blockers

alpha-Adrenergic blockers are important drugs in the treatment of hypertension and other cardiovascular and noncardiovascular disorders. The ability to selectively block alpha-receptor subtypes provides a greater margin of safety and efficacy for these drugs.

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.

Vasodilator therapy

Vasodilators are a group of drugs with various degrees of arteriolar or venous dilatation used in the treatment of congestive heart failure when symptoms persist after digoxin and diuretic therapy. Nitrates and captopril provide the most consistent improvement in symptoms. Reduced mortality rates in congestive heart failure with vasodilator therapy has not been demonstrated, and prediction of clinical response to therapy is difficult.

Effects of enalapril in heart failure: a double blind study of effects on exercise performance, renal function, hormones, and metabolic state

Several studies have shown symptomatic and haemodynamic improvement after the introduction of angiotensin converting enzyme inhibitors in patients with heart failure treated with diuretics. The concomitant long term effects of the new orally effective long acting angiotensin converting enzyme inhibitor, enalapril, on symptoms, exercise performance, cardiac function, arrhythmias, hormones, electrolytes, body composition, and renal function have been further assessed in a placebo controlled double blind cross over trial with treatment periods of eight weeks. Twenty patients with New York Heart Association functional class II to IV heart failure who were clinically stable on digoxin and diuretic therapy were studied. Apart from the introduction of enalapril, regular treatment was not changed over the study period; no order or period effects were noted. Enalapril treatment significantly improved functional class, symptom score for breathlessness, and exercise tolerance. Systolic blood pressure was significantly lower on enalapril treatment. Echocardiographic assessment indicated a reduction in left ventricular dimensions and an improvement in systolic time intervals. In response to enalapril, the plasma concentration of angiotensin II was reduced and that of active renin rose; plasma concentrations of aldosterone, vasopressin, and noradrenaline fell. There were significant increases in serum potassium and serum magnesium on enalapril. Glomerular filtration rate measured both by isotopic techniques and by creatinine clearance declined on enalapril while serum urea and creatinine rose and effective renal plasma flow increased. Body weight and total body sodium were unchanged indicating that there was no overall diuresis. There was a statistically insignificant rise in total body potassium, though the increase was related directly to pretreatment plasma renin (r = 0.5). On enalapril the improvement in symptoms, exercise performance, fall in plasma noradrenaline, and rise in serum potassium coincided with a decline in the frequency of ventricular extrasystoles recorded during ambulatory monitoring. Adverse effects were few. In patients with heart failure, enalapril had a beneficial effect on symptoms and functional capacity. The decline in glomerular filtration rate on enalapril may not be beneficial in early heart failure.

Methodologic problems in clinical trials in heart failure

Trials designed to establish the effectiveness of pharmacologic therapy in chronic heart failure illustrate methodologic problems associated with intervention trials in chronic disease. Early improvement in hemodynamic status or exercise capacity does not predict long-term changes, and hemodynamic variables do not correlate with exercise capacity. Mortality may not be a feasible outcome, suggesting that an adequate measure of quality of life is necessary to establish patient benefit. Care must be taken to ensure that subjects recruited are representative of the underlying population with respect to drug response. Need for cointervention can be dealt with by comparing only periods of comparable treatment, treating need for cointervention as a treatment failure, or using changes in non-study drugs as a measure of outcome. While cross-over designs can improve feasibility, the investigator runs the risk of inadequate followup and a time-treatment interaction. These issues must be considered in planning intervention trials in chronic disease.

Acute and chronic effects of sustained action buccal nitroglycerin in severe congestive heart failure

Vasodilators, such as nitroglycerin, have been widely used in the treatment of acute and chronic heart failure for therapeutic manipulation of the venous and arterial circulations to improve left ventricular function. We have tested the efficacy of a new formulation for sustained release buccal delivery of nitroglycerin (biological life 5-6 hr) in 21 patients with severe congestive heart failure due to ischaemic cardiomyopathy using maximal treadmill exercise testing and radionuclide angiography. A single-blind placebo-controlled acute and an open chronic phase (4 weeks) of treatment were employed. The mean dose was 23.4 mg daily, and clinical assessment suggested significant improvement in 15 patients. The mean ejection fraction (placebo) of 14.1% +/- 1.6 SEM increased to 19.1% +/- 1.7 (acute) and to 21.6% +/- 1.7 (chronic treatment) (P less than 0.001; n = 16). The mean exercise time increased from 3.02 +/- 0.4 min (basal) to 5.95 +/- 0.6 min (chronic) (P less than 0.001). Segmental wall motion abnormality was shown to improve after treatment for 4 weeks. There were no major side effects. Nine patients were reassessed after 24 weeks on the same regimen; exercise time and left ventricular ejection fraction were similar to the 4-week period, thus demonstrating a sustained improvement in cardiac function and functional capacity. A worthwhile functional and objective haemodynamic improvement was demonstrated in these patients with severe chronic congestive heart failure. This mode of treatment may have useful therapeutic value in the management of patients with a wide range of ischaemic heart failure.

Vasodilator and inotropic therapy for severe chronic heart failure: passion and skepticism

Although substantial progress has been made in the last 5 years in the development of vasodilator and inotropic drugs for the management of patients with severe chronic heart failure, much of the enthusiasm that surrounded the introduction of many of these agents has subsequently been tempered by reports of drug failure or adverse reactions. In this review and analysis, currently available vasodilator and inotropic agents are critically and comparatively evaluated to assess their respective advantages and limitations. It is apparent that the ability of most of these drugs to produce substantial clinical benefits in patients with severe heart failure has probably been overstated. Therapy fails to achieve the desired clinical results all too frequently, possibly as the result of: the choice of an ineffective drug; the administration of an effective drug in subtherapeutic doses; the administration of an effective drug to improperly selected patients; the failure of initial hemodynamic benefits to be sustained; the occurrence of severe or serious adverse reactions; and the failure to alter concomitant therapy appropriately. The present analysis indicates that there is no uniformly effective or safe vasodilator or inotropic drug for patients with severe heart failure; all agents have important limitations. Of the available therapeutic choices, however, long-term converting enzyme inhibition appears to produce more consistent hemodynamic and clinical benefits with an acceptable degree of adverse reactions than other pharmacologic approaches for the management of these severely ill patients.

Improvement in exercise capacity despite cardiac deteriora tion: nonivasive assessment of long-term therapy with amrinone in severe heart failure

Seven patients with severe congestive heart failure (CHF) were treated with oral amrinone for a mean duration of 39 weeks (range 16 to 72). During the first week of therapy, exercise capacity as assessed on a treadmill using the Naughton protocol, increased substantially from 7.6 +/- 4.2 to 12.1 +/- 4.4 minutes (p less than 0.01). At an early period of follow-up (8 to 12 weeks), a further significant increase in exercise capacity to 14.7 +/- 5.0 minutes (p less than 0.05) was demonstrated, while at a later follow-up exercise capacity had decreased to 11.4 +/- 6.8 minutes (p less than 0.05). This was still significantly greater than prior to amrinone therapy (p less than 0.01). Left ventricular ejection fraction was increased from 14 +/- 4 to 19 +/- 4% (p less than 0.05) during the first week of therapy, but was not significantly different from control at the early and late periods of follow-up. Left ventricular end-diastolic dimension index increased from control value of 43 +/- 5 to 47 +/- 7 mm/m2 (p less than 0.01) at the late period of follow-up. Thus long-term amrinone therapy resulted in a substantial improvement in exercise capacity despite a slow, but progressive decline in cardiac performance.

How much of the placebo 'effect' is really statistical regression?

Statistical regression to the mean predicts that patients selected for abnormalcy will, on the average, tend to improve. We argue that most improvements attributed to the placebo effect are actually instances of statistical regression. First, whereas older clinical trials susceptible to regression resulted in a marked improvement in placebo-treated patients, in a modern series of clinical trials whose design tended to protect against regression, we found no significant improvement (median change 0.3 per cent, p greater than 0.05) in placebo-treated patients. Secondly, regression can yield sizeable improvements, even among biochemical tests. Among a series of 15 biochemical tests, theoretical estimates of the improvement due to regression by selection of patients as high abnormals (i.e. 3 standard deviations above the mean) ranged from 2.5 per cent for serum sodium to 26 per cent for serum lactate dehydrogenase (median 10 per cent); empirical estimates ranged from 3.8 per cent for serum chloride to 37.3 per cent for serum phosphorus (median 9.5 per cent). Thus, we urge caution in interpreting patient improvements as causal effects of our actions and should avoid the conceit of assuming that our personal presence has strong healing powers.

Vasodilator therapy in chronic congestive heart failure

Vasodilator agents are relatively new additions to the armamentarium for the management of patients with congestive heart failure. Myocardial failure, irrespective of the aetiology, tends to create a vicious cycle characterised by reduced cardiac output and elevated systemic vascular resistance, which further decrease cardiac output by increasing left ventricular ejection impedance. The rationale for the use of vasodilators is to interrupt the vicious cycle by decreasing the left ventricular ejection impedance by peripheral vasodilatation. Although most vasodilator agents produce qualitatively similar haemodynamic responses, quantitatively their haemodynamic effects differ considerably. Knowledge of the haemodynamic effects of the various vasodilators helps in the selection of a particular drug for the management of such patients. This article reviews the mechanisms of action, haemodynamic effects, pharmacokinetics, clinical usage and adverse effects of non-parenteral vasodilator agents currently available for the management of patients with chronic heart failure.

Efficacy of prazosin in the management of chronic congestive heart failure: a 6-month randomized, double-blind, placebo-controlled study

The beneficial effects of acute prazosin therapy in patients with congestive heart failure (CHF) have been well documented; however, its chronic efficacy over several months has not previously been evaluated in a placebo-controlled manner. Therefore, an assessment was made by radionuclide ventriculography of the effect of prazosin, 20 mg/day, on left ventricular ejection fraction and end-systolic and end-diastolic volumes at rest and on peak upright bicycle exercise, as well as its effect on right ventricular ejection fraction at rest, exercise time and work load, and standard clinical variables in 23 patients with stable class III symptoms of CHF. The study consisted of a 6-month randomized, double-blind, controlled evaluation of prazosin versus placebo in patients receiving a stable dose of digitalis and diuretics for at least 1 month. At entry, the prazosin and placebo groups did not differ in any respect. Prazosin caused no demonstrable effect on clinical variables such as status of symptoms, heart rate, mean arterial pressure, and cardiothoracic ratio when compared with placebo. Prazosin also caused no demonstrable effect compared with placebo on absolute or percent changes in radionuclide variables at rest or on peak exercise, or on exercise time or exercise work load. In addition, prazosin had no consistent effect compared with placebo on plasma renin activity or plasma catecholamine levels. However, there was a slight but significant increase in weight (p less than 0.0001) and in plasma renin activity in the upright position (p less than 0.002) with time, as well as a tendency for the diuretic dose to increase with time in both groups. Thus, long-term prazosin therapy generally produces no demonstrable subjective or objective improvement in patients with stable, chronic class III CHF receiving digitalis and diuretic therapy.

Unloading effects of prazosin in patients with chronic aortic regurgitation

Seventeen patients with chronic aortic regurgitation (AR) were examined by echocardiography and left and right heart catheterization. Cardiac output and regurgitation volume were measured by the dye dilution method. Administration of single and four repeated doses of prazosin (PZ) led to reductions of left ventricular (LV) end-diastolic, end-systolic, and left atrial end-systolic diameters, and decrease of left ventricular filling pressure. Regurgitation fraction, regurgitation flow, and volume indexes decreased significantly (p less than 0.01). Total left ventricular output decreased (p less than 0.001) as did derived parameters of left ventricular work and performance. Fractional shortening, ejection fraction, and mean circumferential fiber shortening velocity increased as did LV dP/dt and dP/dt/P. Changes in heart rate and cardiac and stroke indexes after PZ were not significant. Preload reduction (dilation of the venous bed and reduction of regurgitation) seems to be the most important effect of PZ in AR. We found PZ to be a suitable and effective drug for oral treatment of chronic AR.

Assessment of vasodilator therapy in patients with severe congestive heart failure: limitations of measurements of left ventricular ejection fraction and volumes

Although noninvasive techniques are often used to assess the effect of vasodilator therapy in patients with congestive heart failure, it is unknown whether changes in noninvasively determined left ventricular ejection fraction, volume, or dimension reliably reflect alterations in intracardiac pressure and flow. Accordingly, we compared the acute effect of sodium nitroprusside on left ventricular volume and ejection fraction (determined scintigraphically) with its effect on intracardiac pressure and forward cardiac index (determined by thermodilution) in 12 patients with severe, chronic congestive heart failure and a markedly dilated left ventricle. Nitroprusside (infused at 1.3 +/- 1.1 [mean +/- standard deviation] microgram/kg/min) caused a decrease in mean systemic arterial, mean pulmonary arterial, and mean pulmonary capillary wedge pressure as well as a concomitant increase in forward cardiac index. Simultaneously, left ventricular end-diastolic and end-systolic volume indexes decreased, but the scintigraphically determined cardiac index did not change significantly. Left ventricular ejection fraction averaged 0.19 +/- 0.05 before nitroprusside administration and increased by less than 0.05 units in response to nitroprusside in 11 of 12 patients. The only significant correlation between scintigraphically and invasively determined variables was that between the percent change in end-diastolic volume index and the percent change in pulmonary capillary wedge pressure (r = 0.68, p = 0.01). Although nitroprusside produced changes in scintigraphically determined left ventricular ejection fraction, end-systolic volume index, and cardiac index, these alterations bore no predictable relation to changes in intracardiac pressure, forward cardiac index, or vascular resistance. Furthermore, nitroprusside produced a considerably greater percent change in the invasively measured variables than in the scintigraphically determined ones.

Hemodynamic effects of captropril in chronic heart failure: efficacy of low-dose treatment and comparison with prazosin

The acute hemodynamic effects and long-term therapeutic actions of low doses of the oral angiotensin-converting enzyme (ACE) inhibitor captopril (CPT) were evaluated in 18 patients with severe chronic congestive heart failure (CHF). Increasing doses of 1, 2.5, 6.25, 12.5, and 25 mg of CPT were given at 2-hour intervals. Increased stroke volume index (SVI) and reduced mean pulmonary capillary wedge (PCW) pressure occurred at 1 hour (p less than 0.05) with an associated decline of blood pressure. Maximal hemodynamic improvement for the group was seen at 6 and 7 hours following the 6.25 and 12.5 mg doses when SVI was elevated 35% and mean PCW pressure decreased 40% from control. CPT in doses of 12.5 to 50 mg every 8 hours was continued long term in these 18 CHF patients. Four patients died, and one was noncompliant; drug therapy was withdrawn in two patients with symptomatic hypertension and in one patient who experienced an alteration in taste. The remaining 10 patients showed significant improvement in symptoms and treadmill exercise duration at 3 months after CPT therapy was started. Moreover, repeat hemodynamic measurements were similar to optimal measurements obtained during the initial study. In a further study, the acute hemodynamic and hormonal effect of sequentially randomized 5 mg prazosin and 25 mg CPT were compared in 10 CHF patients. While both drugs reduced PCW pressure and vascular resistance, CPT effects were greater. Further, CPT alone effected a small rise in cardiac index and minor decline in heart rate, and CPT diminished aldosterone levels and increased plasma renin activity while prazosin did not.

Prazosin and captopril in chronic heart failure: comparison of acute haemodynamic and hormonal effects

Ten patients with severe chronic heart failure were given prazosin 5 mg and captopril 25 mg in random order on consecutive days. Small increases in cardiac index and reductions in heart rate were effected by both drugs, but these alterations and the accompanying increases in stroke volume index were significant only following captopril. Both drugs significantly reduced mean pulmonary capillary wedge pressure and mean right atrial pressure and also systemic vascular resistance and blood pressure, the effect of captopril being greater than that of prazosin. Following captopril, plasma aldosterone levels were significantly reduced and plasma renin activity increased from control values, whereas prazosin did not alter these hormone indices.

Long-term captopril therapy in congestive heart failure: serial hemodynamic and echocardiographic changes

Ten patients with refractory congestive heart failure (CHF) were followed serially for systemic hemodynamic (radionuclide techniques) and M-mode echocardiographic changes during long-term captopril therapy with optimum doses. After 1 week of maintenance captopril therapy, all patients were clinically improved. This was associated with a significant (p less than 0.05) reduction of total blood volume (-6 +/- 2% N), mean blood pressure (-9 +/- 3 mm Hg), and peak systolic left ventricular wall stress (-50 +/- 19 X 10(3) dynes/cm2). At the end of 2 months of maintained therapy, mean blood pressure reduction was -12 +/- 4 mm Hg (p less than 0.05); further hemodynamic improvement was manifested by a significant shortening of pulmonary mean transit time (-3.7 +2- 1.33 seconds, p less than 0.05). Echocardiographic data revealed an increase in end-diastolic septal wall thickness (+0.13 +/- 0.05, p less than 0.05) and left ventricular posterior wall thickness (+0.13 +/- 0.03, p less than 0.05), and further reduction in peak systolic stress (-84 +/- 23 X 10(3) dynes/cm2, p less than 0.05). The present study indicates the importance of measuring peak systolic wall stress in the follow-up of CHF patients. Moreover, we found that for functional circulatory evaluation during vasodilator therapy, the radionuclide first-pass methods were more helpful than both M-mode echocardiography and radionuclide gated blood pool techniques.

Hydralazine in the long-term treatment of chronic heart failure: lack of difference from placebo

Although hydralazine improves cardiac performance in patients with chronic left ventricular failure, its long-term clinical efficacy has not been established in controlled trials. We carried out a double-blind randomized trial of hydralazine (200 mg daily in 16 patients) versus placebo (16 patients) in patients with class III and IV symptoms while they were taking digitalis and diuretics. Maximal treadmill exercise time was determined prior to and at 4, 10, 18, and 26 weeks of hydralazine or placebo treatment; average follow-up was 20 weeks. We found no change in body weight, clinical class, resting heart rate and blood pressure, or heart size (by chest x-ray examination and echocardiogram) during treatment in either group. The total number of complicating clinical events was insignificantly fewer in the hydralazine treated group (8 vs 13). Control exercise duration in the hydralazine group averaged 259 +/- 21 seconds (SEM), and increased to 347 +/- 35 seconds at 4 weeks (p less than 0.01) and 421 +/- 38 seconds at 26 weeks (p less than 0.001). Exercise duration also increased significantly in the placebo group, from 271 +/- 30 seconds at control to 340 +/- 44 seconds at 4 weeks (p less than 0.02) and 339 +/- 46 seconds at 26 weeks (p less than 0.02). No differences between groups were significant. Left ventricular ejection fraction remained depressed and unchanged in both groups. Thus long-term vasodilator treatment with hydralazine alone is not significantly more effective than placebo in chronic heart failure.

Physiologic and pharmacologic determinants of vasodilator response: a conceptual framework for rational drug therapy for chronic heart failure

This article has attempted to summarize the increasing number of pharmacologic and physiologic variables that are being recognized as important determinants in the response to vasodilator therapy in patients with severe chronic heart failure. It is apparent that a careful consideration of many factors is necessary before proper selection of a specific drug can be made for a specific patient, since not all patients with refractory heart failure demonstrate beneficial hemodynamic and clinical responses to all agents. Each patient presents us with a unique set of physiologic variables; each drug has its own advantages and limitations. Identification of those subgroups of patients most likely to benefit from a specific agent or combination of agents is a major goal for future research. Although a number of hemodynamic variables can be made to improve acutely with a wide variety of vasodilator drugs, well tolerated sustained meaningful clinical benefits are probably observed in relatively few patients. Rational and successful vasodilator therapy is possible only through a highly individualized approach.

Long-term amrinone therapy in patients with severe heart failure: drug-dependent hemodynamic benefits despite progression of disease

Six patients with severe congestive heart failure refractory to conventional therapy, including vasodilators, were treated with oral amrinone for a mean duration of 41 weeks (range 20 to 72 weeks). At initiation of therapy, the cardiac index increased from 1.74 +/- 0.31 to 2.62 +/- 0.52 (mean +/- SD) liters/min/m2 (p less than 0.01) and pulmonary capillary wedge pressure decreased from 26.5 +/- 3.5 to 19.5 +/- 5.4 mm Hg (p less than 0.05). Symptoms were alleviated and exercise capacity increased from 5.9 +/- 2.9 to 11.5 +/- 4.5 minutes (p less than 0.05). During long-term therapy, exercise capacity remained constants in three patients whereas it decreased in three others. All patients demonstrated an increase in heart size. Withdrawal of amrinone therapy precipitated severe symptoms at rest and hemodynamic deterioration in all patients. The cardiac index decreased from 1.87 +/- 0.49 to 1.32 +/- 0.30 liter/min/m2 (p less than 0.05) and pulmonary capillary wedge pressure rose from 20.6 +/- 2.9 to 28.8 +/- 5.6 mm Hg (p less than 0.05). These changes were reversed by reinstitution of therapy. Thus, amrinone-dependent hemodynamic benefits were demonstrated during long-term therapy without tachyphylaxis. In addition, progression of the underlying cardiac disease was observed in every patient.

Antihypertensive therapy with prazosin in patients with left ventricular dysfunction. Improvement in cardiac performance and exercise tolerance

Although the relationship between blood pressure and cardiac performance has been widely recognized, there are few published clinical observations concerning the effect of blood pressure control on cardiac function. We evaluated the effect of prazosin, an antihypertensive agent which also improves hemodynamic measurements in normotensive patients with heart failure, in 16 patients with moderate hypertension and reduced ejection fractions. Therapy with digoxin and diuretics was continued throughout the study, but other antihypertensive agents were withdrawn at least one week prior to the initiation of the study. Measurements of ejection fraction, cardiothoracic ratio and the duration of maximal treadmill exercise were made before and after two months of antihypertensive therapy with prazosin. On prazosin, blood pressure fell from a mean of 169/103 to 141/84. Excellent control was achieved in 13/16 patients and significant reductions were noted in the remaining three. Concomitantly, ejection fraction rose from .38 +/- .02 (SEM) to .43 +/- .03 (P less than .02), cardiothoracic ratio decreased from .55 +/- .02 to .53 +/- .02 (P less than .05) and exercise capacity increased from 9.2 +/- 0.9 to 11.9 +/- 1.1 minutes (P less than .005). Prazosin was well tolerated except in one patient who experienced worsening angina. These findings emphasize the importance of rigorous blood pressure control in hypertensive patients with left ventricular dysfunction and indicate that prazosin is effective in this setting.

Immediate and sustained haemodynamic effects of prazosin during upright exercise in man

To ascertain the immediate pharmacodynamic and long-term haemodynamic effects of prazosin in chronic ambulant heart failure, measurements were made during sitting, standing, and walking in 12 patients with severe ischaemic left ventricular failure before and after their first dose of prazosin (2 mg) and in six of these patients after a further 12 weeks of sustained treatment (2 mg tds). When first added to treatment with digoxin and frusemide, prazosin was followed within an hour by substantial reductions in systemic arterial, pulmonary arterial, and pulmonary venous pressures in both postures at rest and also during walking. These changes were significantly attenuated after continued treatment. Cardiac output while sitting and standing at rest was reduced in both instances but the response to exercise was unchanged. The pharmacodynamic effects of prazosin in heart failure are explicable in terms of blockade of alpha1 adrenoceptors in arterial resistance and venous capacitance vessels augmented perhaps by lessening of reflex vasoconstriction secondary to the reduction in pulmonary venous pressure. The cause of the attenuation of the acute haemodynamic effects of the drug during sustained treatment is unknown.

Circulatory improvement after hydralazine or isosorbide dinitrate administration in patients with heart failure. Effect on metabolic responses to submaximal exercise

Hydralazine and isosorbide dinitrate can increase the cardiac output during submaximal exercise in patients with heart failure but whether this increase improves oxygen delivery to underperfused exercising muscle is uncertain. To investigate this question, we measured three systemic markers of skeletal muscle oxygen availability--exercise VO2, mixed venous lactate concentration and oxygen debt--during submaximal exercise in 15 patients with heart failure both before after hydralazine (nine patients) or isosorbide dinitrate (eight patients) administration. Hydralazine increased the cardiac output during exercise from 4.9 +/- 1.2 liter/min to 6.5 +/- 1.8 liter/min (p less than 0.01) but had no effect on exercise VO2 (control, 531 +/- 135 ml/min; hydralazine, 489 +/- 102 ml/min), peak lactate concentration (control, 18.3 +/- 4.2 mg/dl; hydralazine, 17.9 +/- 3.6 mg/dl) or oxygen debt (control, 474 +/- 213 ml; hydralazine, 465 +/- 170 ml) (all p greater than 0.10). Isosorbide dinitrate increased the cardiac output during exercise from 4.6 +/- 0.9 liter/min to 5.3 +/- 0.8 liter/min (p less than 0.01) but also did not change exercise VO2 (control, 488 +/- 62 ml/min; isosorbide, 473 +/- 44 ml/min), peak lactate concentration (control, 19.2 +/- 6.0 mg/dl; isosorbide, 21.4 +/- 8.2 mg/dl) or oxygen debt (control, 522 +/- 154 ml; isosorbide, 445 +/- 147 ml) (all p less than 0.10). We conclude that short-term administration of hydralazine or nitrates to patients with heart failure can substantially improve circulatory function during exercise but that this improvement probably does not enhance skeletal muscle nutritional flow.

Comparative pharmacology and clinical efficacy of newer agents in treatment of heart failure

The animal and human pharmacology of several new drugs (prazosin, trimazosin, pirbuterol, and carbazeran) useful in the treatment of congestive heart failure (CHF) is delineated in relation to the pharmacology of other agents employed for CHF management. Prazosin and trimazosin are selective alpha 1-blockers that cause a balanced increase in cardiac output (CO) and reduction in left ventricular filling pressure (LVFP); the reduction in diastolic blood pressure with these drugs is significantly related to increase in treadmill exercise, fall in LVFP, and increase in CO. Pirbuterol is a relatively selective beta 2-agonist with somewhat greater effects on CO than on LVFP. Early promise in CHF therapy is being shown by a novel series of cyclic adenosine monophosphate (cAMP) phosphodiesterase inhibitors with combined direct inotropic and vasodilator effects. Double-blind long-term studies demonstrate persistent efficacy of prazosin and trimazosin in CHF as measured by improvement in New York Heart Association functional class, treadmill exercise performance, and noninvasive measures of cardiac function; these data are supported by studies in which repeat cardiac catheterization has been performed after several months of therapy. Double-blind studies of other CHF drugs are in progress.

Hemodynamic effects of prazosin in chronic heart failure

Three series of investigations were carried out with prazosin (PZN) hydrochloride. In the first, hemodynamic effects of PZN were compared with those of hydralazine (HDZ) in 11 patients with chronic congestive heart failure (CHF). In doses up to 5 mg, PZN increased cardiac output (CO) 20% accompanied by a 20% decrease in pulmonary capillary wedge pressure (LVFP). HDZ increased CO by 50% with little or no effect on LVFP. An additional 12 patients were given multiple 5 mg doses of PZN at 6-hour intervals with measurements of hemodynamic and plasma blood levels. Results suggested an attenuation of the effects of PZN on increasing CO but not on decreasing LVFP. This attenuation of CO was not due to inadequate plasma levels. Acute exercise studies (supine bicycle) were performed in 10 patients with severe CHF before and after the administration of several doses of PZN. There appeared to be a greater effect of PZN during exercise than at rest, with a beneficial increase in CO and reduction in LVFP. These data suggest that, despite hemodynamic attenuation of its effects on CO at rest, PZN may still be beneficial to active patients with CHF. In vitro studies with various vasodilators were performed to evaluate potential intropic effects. Isometric force (cat papillary muscle) increased 2% with 10-4M and 31% with 10-3M HDZ. PZN increased force 4% at 10-6M and 18% at 10-4M. Captopril did not increase force development at any dose level. The doses of HDZ and PZN that increased force development were higher than usual clinical doses.

Problems in assessment of new pharmacologic agents for the heart failure patient

Modern management of congestive heart failure (CHF) employs inotropic drugs, vasodilators, and diuretics. Although pharmacologic classification of drugs is possible in animals, identification of predominant hemodynamic mechanisms in humans is more complex, because many effects of vasodilators and inotropic drugs are similar. We compared the effects of a vasodilator, prazosin, and two agents with both inotropic and vasodilatory properties, amrinone and pirbuterol, on cardiac index (CI), mean aortic pressure, left ventricular stroke work index (LVSWI), LV filling pressure (LVFP), systemic vascular resistance, LV ejection fraction (LVEF), and myocardial O2 consumption (MVO2) in 34 patients with advanced CHF. We concluded that (1) a rise in CI and LVEF, together with a fall in LVFP, does not necessarily indicate an inotropic effect; (2)both CI and LVEF may be increased by an inotropic mechanism in advanced CHF without a rise in MVO2; and (3) a drug-induced rise in LVSWI with stable or lower LVFP suggests an inotropic mechanism of action.

Clinical, hemodynamic, and neuroendocrine effects of chronic prazosin therapy for congestive heart failure

We report our hemodynamic, clinical, and neuroendocrine observations during long-term (8 weeks) prazosin (PZN) administration to assess the efficacy of this agent in the long-term therapy of congestive heart failure (CHF) and to emphasize the potential role of neuroendocrine mechanisms in the determination of overall drug effect. During long-term PZN therapy there is improvement in functional status, exercise tolerance, and left and right ventricular ejection fractions. However, we also observed an increase in fluid retention and attenuation of the initial hemodynamic and clinical responses to the drug. Plasma renin activity and plasma norepinephrine concentration are increased during long-term PZN therapy despite clinical and hemodynamic improvement and potentially may be involved in the pathogenesis of the increased fluid retention and hemodynamic attenuation. Three pharmacologic considerations appear relevant to the use of an alpha-adrenergic antagonist such as PZN in CHF therapy: (1) the drug response may be related to the baseline level of sympathetic tone. (2) The dose-response pattern exhibits a plateau phase, beyond which higher doses cause little further effect. (3) The overall drug effect is the sum of its direct actions and the secondary actions of the neuroendocrine response it elicits.

Management of refractory congestive heart failure with prazosin

The cardiocirculatory actions of prazosin (PZN) orally were evaluated by cardiac catheterization, forearm plethysmography, echocardiography, treadmill exercise, and symptoms in patients with advanced long-standing congestive heart failure (CHF). PZN orally (2 to 7 mg) reduced forearm venous tone and decreased forearm vascular resistance. Concomitantly mean systemic arterial pressure declined, left ventricular filling pressure (LVFP) decreased, and cardiac index (CI) was raised. These effects of a single dose of PZN on LV function were rapid in onset, maximal at 1 hour, and sustained for the entire 6 hours of observation. After 2 weeks of outpatient therapy with 2 to 7 mg PZN four times daily, echographic LV end-diastolic dimension decreased and the duration of treadmill exercise increased. Symptoms (dyspnea, fatigue, angina) were diminished throughout the course of PZN therapy, and New York Heart Association functional class improved for III to II. Thus PZN possesses sustained nitroprusside-like balanced dilator actions on the systemic arterial and venous beds, which are effectively translated into beneficial hemodynamics of augmenting lowered cardiac output and relieving excessive LVFP. Delayed vasodilator tolerance, occurring in 30% of patients, is prevented by prior use of aldosterone antagonists and is easily treated. Subacute hemodynamic suppression of beneficial PZN vasodilator actions is transient and does not preclude successful sustained PZN therapy of severe chronic CHF.

Prazosin and congestive heart failure: short- and long-term therapy

Reviewed here are the data from 34 patients given prazosin for chronic intractable heart failure. In 13 patients in whom hemodynamics were measured after the fifth 3 mg dose of prazosin was given, no attenuation was found. The cardiac index increased from 1.77 +/- 0.13 to 2.5 +/- 0.13 liters/min/m2 (p less than 0.001), and the pulmonary capillary wedge pressure decreased from 31,46 +/- 1.56 to 23.54 +/- 1.11 mg Hg (p less than 0.001). During long-term follow-up (15.9 +/- 1.5 months) the administration of spironolactone proved to be very useful. Within three months of starting prazosin therapy, none of the 15 patients discharged on a regimen of spironolactone needed readmission for edema, but 11 of the 13 patients discharged without a spironolactone regimen did. The addition of spironolactone or an increase in furosemide to the therapeutic regimen was helpful but a change to hydralazine was not. We concluded that prazosin causes short-term hemodynamic and long-term clinical improvement in patients with intractable heart failure; that spironolactone helps to prevent clinical attenuation but that more detailed studies are required to better characterize the attenuation to vasodilators seen in patients with congestive heart failure.