Hemodynamic assessment of oral peripheral vasodilator therapy in chronic congestive heart failure: prolonged effectiveness of isosorbide dinitrate

Development and Evolution of a Hierarchical Clinical Composite End Point for the Evaluation of Drugs and Devices for Acute and Chronic Heart Failure: A 20-Year Perspective

Traditional approaches to the assessment of new treatments for heart failure have generally evaluated individual components of the syndrome at fixed points in time or have relied on surrogate physiological measures that are poorly correlated with the clinical status of patients. Conventional time-to-event trials that focus on morbidity and mortality represent an important methodological advance, but they generally assign undue weight to clinical events of less importance and are insensitive to difference in functional capacity among individuals who do not experience a clinical event during follow-up. Twenty years ago, a hierarchical clinical composite was developed to address these limitations; it aims to assess the clinical course of patients as a physician would in practice by combining a symptomatic assessment of the patient at each visit with an evaluation of the clinical stability of the patient between visits. The composite does not generate a numeric score by summing arbitrarily assigned weights to certain symptoms or events; instead, the composite ranks relevant measures and outcomes according to clinical priority. In doing so, the clinical composite minimizes the biases created by noncompleting patients in the assessment of symptoms or exercise tolerance while expanding the range of patients who contribute to the treatment difference in a typical morbidity and mortality trial. When applied appropriately, the hierarchical clinical composite end point has reliably distinguished effective from ineffective treatments. The composite may have particular advantages in the evaluation of new devices and transcatheter interventions in chronic heart failure and of new drugs for acute heart failure. Recent modifications enhance its discriminant characteristics and its ability to accurately assess the efficacy of novel interventions for heart failure.

The effect of intermittent administration of sustained release isosorbide dinitrate (sr-ISDN) in rats with volume overload heart

Recently, it has been reported that intermittent administration of nitrate, with a nitrate-free interval of 10 to 12 hr eliminated expression of tolerance, and maintained its hypotensive effect. In the present study, we evaluated whether nitrate tolerance developed or not with an intermittent administration of sr-ISDN (5 mg/kg/ once a day) in Wistar rats. The effect of this administration protocol for sr-ISDN on the volume overload heart model, aortovenous fistula, was also examined. Furthermore, blood pressure was monitored by radio telemetry during sr-ISDN (5 mg/kg/once a day) administration. Nitrate tolerance did not develop, and eccentric hypertrophy due to volume overload was moderated by sr-ISDN administration. Sr-ISDN administration maintained blood pressure lower level than the placebo group. In conclusion, prolonged intermittent administration of sr-ISDN maintained its hypotensive effect during the entire experiment period, without developing tolerance, and moderated efferent hypertrophy with attenuated volume overload.

Nitrates in congestive heart failure

Nitrates are commonly used in the therapy of congestive heart failure (CHF). They exert beneficial hemodynamic effects by decreasing left ventricular filling pressure and systemic vascular resistance while modestly improving cardiac output. The improvement in left ventricular function caused by nitrates is the result of combined reduction in outflow resistance and mitral regurgitation, while decreased pericardial constraint and subendocardial ischemia may also contribute to the process. With continuous nitrate administration, complete arterial tolerance develops, while venous tolerance appears to be only partial. The major mechanism of tolerance is loss of vascular smooth muscle sensitivity to nitrates. An increase in total blood volume occurring during the first few hours of an acute administration may partly contribute to tolerance. The importance of reflex neurohumoral activation is controversial; although it may contribute to tolerance in CHF, its role does not appear to be major. Chronic continuous nitrate therapy in CHF improves submaximal and maximal exercise tolerance. In combination therapy with hydralazine, isosorbide dinitrate reduces mortality, although to a lesser extent than the angiotensin converting enzyme inhibitor enalapril. Intravenous or sublingual nitrates are first-line agents in the therapy of acute pulmonary edema. In severe CHF, refractory to standard medical therapy, a short course of intravenous nitroglycerin, with or without inotropic agents, can help break the vicious spiral of CHF. Because tolerance occurs without nitrate-free intervals and until an optimal schedule of administration is determined, it makes good sense to include a nightly nitrate-free interval when prescribing nitrates for CHF in order to maintain maximal benefit during the hours of activity.

Sublingual administration of captopril versus nitroglycerin in patients with severe congestive heart failure

Angiotensin-converting enzyme inhibition has proven to be a successful approach for the long-term treatment of patients with congestive heart failure. This investigation compared the acute hemodynamic changes after sublingual administration of the angiotensin-converting enzyme inhibitor captopril with those after nitroglycerin. A total of 24 patients with severe left heart failure (New York Heart Association classes III and IV) were given 25 mg captopril and 0.8 mg nitroglycerin sublingually in this randomized, cross-over study. Hemodynamic monitoring revealed a clear improvement in pre- and afterload parameters for both drugs (P less than 0.01 and P less than 0.001), while captopril induced a higher increase in cardiac index (+49.2% vs. +25%), stroke volume index (+53.5% vs. +25.7%), and stroke work index (+55% vs. +28%) than nitroglycerin (P less than 0.001). Although not statistically significant, the onset of change for most hemodynamic parameters was measured earlier after nitroglycerin (after 12-19 vs. 16-22 minutes). Captopril revealed later peak effects (after 47-84 vs. 25-55 minutes, P less than 0.001) and a longer sustained improvement in hemodynamic values (return to baseline values after 117-162 vs. 68-120 minutes, P less than 0.001). No side effects occurred after either captopril or nitroglycerin in this study. Thus, these results indicate there is an early improvement in hemodynamic parameters after the sublingual administration of both drugs in patients with severe congestive heart failure, and that captopril induces a more pronounced and prolonged improvement than nitroglycerin.

Effect of isosorbide dinitrate on cardiac output in severe cardiac failure: relation to initial hemodynamics, ventricular volume, and the preload reserve mechanism

Isosorbide dinitrate (ISDN) improves the clinical and hemodynamic state of patients with heart failure, but may cause dizziness and syncope. To characterize patients in whom cardiac output falls with high-dose nitrate therapy and to examine further the pathophysiology of the fall in cardiac output in these patients, we studies the effect of sublingual ISDN on forward cardiac output in 14 patients with severe cardiac failure (New York Heart Association grades 3-4). We examined systolic and diastolic left ventricular (LV) function from pressure and volume analyses of LV function. After administration of 15 mg ISDN, cardiac output was either unaltered or increased in 7 patients (Group 1) (11 +/- 12%, mean +/- SD), and decreased in 7 (Group 2) (-13 +/- 10%) (Group 1 vs. 2, p less than 0.002). Initial systemic arterial pressure, LV ejection fraction, wedge and LV transmural filling pressures were similar in both groups, but Group 2 patients had a lower systemic vascular resistance (p = 0.07) and tended to have a larger initial LV end-diastolic volume and increased end-diastolic compliance; following ISDN the decrease in LV filling pressure and end-diastolic volume was larger and the product of the changes greater (p less than 0.02). Thus ISDN decreases filling pressure and improves forward cardiac output in some patients with congestive heart failure, but large doses may decrease cardiac output in a subset of patients who have a lower systemic vascular resistance and a larger more compliant ventricle, maintaining forward blood flow predominantly by a preload reserve mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Beneficial hemodynamic effects of milrinone and enalapril in conscious rats with healed myocardial infarction

Milrinone and enalapril, which inhibit PDE-III and ACE, respectively, are able to prolong survival of myocardially infarcted (MI) rats. This study sought to identify oral hemodynamic effects of these agents which could underlie such efficacy in this heart failure model. Four weeks after ligation of the left main coronary artery, basal left ventricular (LV) systolic pressure and dP/dtmax, heart rate and mean blood pressure of the MI rats were significantly less than that of sham-operated controls, and LV end-diastolic pressure (LVEDP) was markedly elevated. Milrinone, at 2.0 mg/kg, reduced LVEDP and renal blood flow of these 4-week MI rats by an average of 39 and 18%, respectively (P less than 0.05) within 1 h. At 4.0 mg/kg, it reduced LVEDP by 46% and raised heart rate by 16% (P less than 0.05). Enalapril (1.0 mg/kg) increased small intestine blood flow of these compromised rats by 16% (P less than 0.05), and tended to reduce LVEDP (-28%) within 1.5 h. Treatment with milrinone (2.0 mg/kg) plus enalapril (1.0 mg/kg) promoted LV dP/dtmax, coronary blood flow, and heart rate by 48, 40 and 13%, and reduced LVEDP by 40% (P less than 0.05 for all effects). Thus these agents can reduce LVEDP and redistribute cardiac output of MI rats. Furthermore, the combination of enalapril and milrinone can restore LVEDP and LV dP/dtmax of MI rats to near normal and promote coronary blood flow without compromising cardiac output or renal blood flow. Such effects, it timely or sustained, may prolong survival.

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.

Nitrates in congestive heart failure

An important role for nitrates in the treatment of patients with congestive heart failure has been demonstrated. By dilating the venous and arterial vasculature, they improve hemodynamics as well as exercise tolerance. Attenuation of nitrate action that occurs with chronic therapy can be minimized by following certain treatment strategies.

Resistance to isosorbide dinitrate in patients with severe chronic heart failure: incidence and attempt at hemodynamic prediction

Oral isosorbide dinitrate has been widely used to lower elevated left ventricular filling pressure in patients with chronic heart failure. Although the recommended dose of this drug is 40 mg every 6 h, failure to respond to this dose has been observed in many patients with heart failure. In the present study the incidence of resistance to isosorbide dinitrate was evaluated and an attempt was made to identify baseline hemodynamic predictors for this phenomenon in 50 patients with severe chronic heart failure due to left ventricular systolic dysfunction (mean left ventricular ejection fraction 0.23 +/- 0.08). Twenty-seven (54%) of the 50 patients responded to 40 mg of isosorbide dinitrate (greater than 20% decrease in mean pulmonary artery wedge pressure sustained greater than or equal to 1 h) and 23 patients (46%) failed to respond. Nonresponders to 40 mg of isosorbide dinitrate had a significantly higher baseline right atrial pressure than did responders (14 +/- 5 versus 10 +/- 6 mm Hg, p less than 0.02). In addition, all 7 patients with a baseline right atrial pressure of less than 7 mm Hg and 12 of 14 patients with a baseline right atrial pressure less than 10 mm Hg responded to 40 mg. No significant differences were noted between responders and nonresponders in any other baseline hemodynamic or clinical variables, or in peak isosorbide dinitrate serum levels (32 +/- 19 ng/ml in nonresponders versus 44 +/- 36 ng/ml in responders). Of the 23 nonresponders to 40 mg, 22 received a higher dose (80 to 120 mg).(ABSTRACT TRUNCATED AT 250 WORDS)

Combination of positive inotropic and vasodilating substances in congestive heart failure

Therapy combining vasodilators and inotropic agents is considered to be one of the most powerful means of improving cardiac function in patients with congestive heart failure (CHF). The vasodilators enhance the effectiveness of inotropic agents by providing a reduction in preload and/or afterload. Inotropic drugs with different mechanisms of action, such as digitalis glycosides, ephedrine, dopamine, dobutamine, ibopamine, terbutaline, salbutamol, pirbuterol, prenalterol, amrinone, and milrinone, have been tested in combination with vasodilators with a predominant effect on preload (nitrates, molsidomine), with a predominant effect on afterload (hydralazine, nifedipine), or with a balanced action on both arterial and venous beds (nitroprusside, prazosin, captopril), showing positive results. The problem of the combination of digitalis glycosides and vasodilators with different sites of action has been considered by our group. In 42 patients with CHF, digoxin (DIG, 0.01 mg/kg intravenously) was tested in combination with molsidomine (MLS, 4 mg sublingually) (12 patients), a nitrate-like agent with a predominant vasodilating action on the capacitance vessels, nifedipine (NFP, 10 mg sublingually) (22 patients), a Ca2+ antagonist drug with a predominant action on the resistance vessels, and captopril (CPT, 25 mg orally) (8 patients), an ACE inhibitor with a balanced effect on both preload and afterload. The combination DIG plus MLS caused a reduction in left ventricular filling pressure (LVFP) greater than that achieved with either agent alone. The hemodynamic improvement was obtained without side effects, in spite of the striking fall in preload. We stress that this investigation was performed on patients with CHF following acute myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparative evaluation of isosorbide-5-mononitrate and nitroglycerin in chronic congestive heart failure

The hemodynamic effects of isosorbide-5-mononitrate (IS-5-MN) and nitroglycerin were compared in 10 patients with chronic congestive heart failure (CHF). Both drugs were given intravenously, at an infusion rate individually titrated to achieve a maximal increase in cardiac output and a maximal decrease in pulmonary capillary wedge pressure. Both drugs produced the typical hemodynamic responses to nitrates, the most prominent of which were decreases in pulmonary capillary wedge, pulmonary arterial and right atrial pressures, and an increase in cardiac output. Several differences in the response to these 2 drugs were observed. Pulmonary capillary wedge pressure was reduced from 31.5 +/- 3.0 to 19.6 +/- 5.0 mm Hg with nitroglycerin and to 15.0 +/- 3.12 mm Hg with IS-5-MN. Both the absolute and the percent decrease with IS-5-MN were significantly greater (p less than 0.05) than those observed with nitroglycerin. Mean systemic arterial pressure was reduced from 89.2 +/- 11.3 to 79.8 +/- 10.8 with IS-5-MN (difference not significant) and to 67.5 +/- 7.7 mm Hg with nitroglycerin (p less than 0.01). The difference, both in absolute and percent reductions, was statistically significant. Thus, in patients with chronic CHF, IS-5-MN produced a greater decrease in pulmonary capillary wedge pressure (the major beneficial effect of nitrates in this condition) and a smaller decrease in systemic arterial pressure (the potentially deleterious effects of nitrates). These findings indicate a potential advantage of IS-5-MN over nitroglycerin in patients with CHF, particularly in those with CHF of ischemic etiology.

The effect of isosorbide dinitrate on the arterial vascular bed: a dose response study in dogs

Isosorbide dinitrate (ISDN) was infused stepwise intraarterially into the left hindlimb (5.7-364.8 micrograms/kg/min.) into six dogs. The mean local vascular resistance was decreased by 32% in the left hindlimb after a dose of up to 91.2 micrograms/kg/min. corresponding to a 1.6-fold increase in the left femoral artery blood flow, without significant changes in the control limb or central haemodynamics. The muscular blood flow in the adductor magnus muscle obtained by the Xenon washout technique remained unchanged in 6 of 7 other dogs at ISDN infusion rates of 91.2 micrograms/kg/min., indicating that the increase in femoral artery blood flow was not a consequence of increased muscular blood flow. The arterio-venous extraction fraction of radioactive microspheres was lower in the experimental leg during ISDN infusion when compared with the control leg, suggesting that AV-shunts are opened during ISDN infusion. In addition to the well-known effect on preload, the present results confirm that ISDN also acts on afterload. Thus, ISDN may be classified as a mixed agent acting on both pre- and afterload which is in agreement with some previous studies.

Use of nitrates in acute and chronic congestive heart failure

The literature available on the use of nitrates (glyceryl trinitrate, isosorbide dinitrate and isosorbide 5-mononitrate) as various formulations (oral, buccal, sublingual, transdermal and intravenous) in the treatment of acute and chronic congestive heart failure is reviewed. There are adequate data on the acute haemodynamic effects of these preparations, but little information is available on the long term use of nitrates in chronic congestive heart failure. The exception is isosorbide dinitrate, which, in combination with hydralazine, has been shown to reduce mortality.

Prolonged hemodynamic effect of a slow-release nitroglycerin ointment

Nitroglycerin (NTG) ointment has been shown to be effective in the treatment of angina pectoris and congestive heart failure. Its duration of action is usually 4 to 6 hours. This study presents data that show that a new slow-release NTG ointment produces hemodynamic improvement over at least 24 hours. Twenty patients with coronary artery disease were tested with serial gated equilibrium radionuclide ventriculography before and at various stages of continuous, once-a-day use of slow-release NTG ointment and 4 days after cessation of therapy. NTG ointment significantly (p less than 0.005) decreased left ventricular end-diastolic and end-systolic volumes both at rest (23% and 33%) and during handgrip exercise (22% and 32%) when examined after continuous usage of at least 24 hours. Ejection fraction increased 21% at rest, from 0.42 +/- 0.15 to 0.51 +/- -0.18, p less than 0.0005). The ratio of peak systolic pressure to end-systolic volume increased 85% at rest (p less than 0.05) and 54% during exercise (p less than 0.01). All values had returned to baseline 4 days after cessation of treatment. Thus, slow-release NTG ointment may be useful in the treatment of angina pectoris and congestive heart failure on a once-a-day basis.

Alterations in myocardial perfusion during exercise after isosorbide dinitrate infusion in patients with coronary disease: assessment by thallium-201 scintigraphy

We studied the effect of intravenous isosorbide dinitrate (ISDN) on myocardial perfusion of patients with coronary artery disease, by using exercise thallium-201 (TI-201) myocardial scintigraphy. A control study was conducted initially to assess regional myocardial perfusion rate. Left ventricular myocardium was divided into six parts: anterior, lateral, apical, inferior, posterior, and septal segments. The segmental myocardial perfusion was characterized according to TI-201 initial uptake index (IUI) of relative distribution and redistribution index (RDI) of TI-201 washout. The normal limit of IUI and RDI was established from the data of 17 persons with normal coronary arteries, and then the IUI less than or equal to 84% and the RDI greater than or equal to 1.12 was defined as abnormal. Based on IUI and RDI, each segment was characterized into three types: A type = IUI less than or equal to 84%, RDI greater than or equal to 1.12; B type = IUI less than or equal to 84%, RDI less than 1.12; and C type = IUI greater than 84%, RDI less than 1.12. ISDN was given as a dose of 0.1 mg/kg/hr, and then treadmill testing was repeated for the same duration of exercise time using the same protocol as in the control period. The segments of A type showed a significant improvement in IUI and RDI after receiving ISDN infusion, while the B and C type segments showed no change. It was also shown that the improvement of IUI and RDI of the A type segments was not as marked in multivessel disease as in cases of single-vessel disease.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Abnormalities of the peripheral circulation and respiratory function in patients with severe heart failure

To investigate the peripheral circulatory and respiratory abnormalities which occur in patients with heart failure, forearm and calf blood flow were measured before and after upright exercise, and respiratory gas exchange was measured during exercise in 26 patients with severe heart failure. Compared with a group of normal subjects the patients had reduced limb blood flow at rest and the response of limb blood flow to upright exercise was also abnormal. The increase in calf blood flow after exercise and the reduction in blood flow in the non-exercising forearm were both smaller in patients than in controls. There was a significant correlation between the maximum exercise duration of the patients and calf blood flow both after exercise and at rest. Compared with another group of control subjects the patients had a higher minute ventilation during exercise and a reduced oxygen consumption. The respiratory exchange ratio during exercise was also higher in patients than in controls. This suggests that there is early onset of anaerobic metabolism during exercise in patients with severe heart failure.

The acute haemodynamic effects of quinapril, a new non-sulfhydryl angiotensin converting enzyme inhibitor, in patients with severe congestive cardiac failure

This study investigates the acute haemodynamic effects of Quinapril (CI-906) a new non-sulphydryl angiotensin converting enzyme inhibitor in 15 patients with refractory congestive cardiac failure. There were 14 males and 1 female mean age 59.5 years. After administration of Quinapril there was a significant reduction in mean arterial pressure (MAP) from 93.1 to 79 mmHg, systemic vascular resistance (SVR) from 1887 to 1349 dyn s cm-5 and PCW from 27.3 to 15.3 mmHg. This was accompanied by an increase in CO from 3.7 to 4.71/min, cardiac index (CI) from 1.97 to 2.51/min/m2 and Stroke volume index from 21.1 to 28.7 ml/m2. There was no significant change in heart rate (HR), right atrial pressure (RAP), or pulmonary vascular resistance. The peak effect on pulmonary capillary wedge pressure (PCW) and cardiac output (CO) occurred at 75-120 min after Quinapril administration. The maximum effect on mean arterial pressure (MAP) occurred slightly later at 120-150 min. SVR and CI exhibited 2 periods of peak effects, at 90 and 180 min. This time course is very similar to that observed in studies on the acute effects of Captopril. The significant improvement in haemodynamic measurements acutely, following administration of Quinapril 5 mg orally, suggests that this drug is worthy of further study in the management of patients with refractory congestive cardiac failure, in particular its long term effects.

Role of isosorbide dinitrate in management of chronic congestive heart failure

Congestive heart failure is accompanied by a number of compensatory mechanisms that may overshoot the mark. Among these are excessive arteriolar and venous constriction. Nitrates are effective in producing venodilation, redistributing blood from the chest to the periphery, and lowering right and left atrial pressures. Although oral isosorbide dinitrate is effective in producing acute beneficial hemodynamic effects, it usually does not increase exercise tolerance in the short term. Prolonged administration, however, does increase exercise tolerance and improve clinical class. Isosorbide dinitrate can be effectively combined with an arteriolar dilator such as hydralazine, which increases cardiac output. Such vasodilator therapy is symptomatically effective in patients with heart failure, although there is no evidence to date to suggest a prolongation of life.

Specialized delivery systems for intravenous nitroglycerin. Are they necessary?

Nitroglycerin is absorbed in vitro into polyvinyl chloride tubing, and it has been recommended that nitroglycerin be administered intravenously through specialized polyethylene infusion sets. To determine if tubing type is essential to achieve physiologic effectiveness, we studied dose responses to intravenous nitroglycerin in 15 patients with heart failure using standard polyvinyl chloride tubing in seven (group 2) and special polyethylene infusion sets in seven (group 1) (one patient was excluded from analysis because of technical difficulties). We monitored heart rate, blood pressure, right atrial pressure, pulmonary artery pressure, pulmonary capillary wedge pressure, and cardiac output. Cardiac index, systemic and pulmonary vascular resistance, triple index, rate pressure product, stroke volume, stroke volume index, and stroke work index were calculated. Baseline and treatment measurements were obtained from five to 15 minutes after the infusion of 10, 20, 40, and 80 micrograms of nitroglycerin per minute. Over-all, systolic blood pressure decreased (p less than 0.05) about 8 percent and mean blood pressure approximately 12 percent, mean pulmonary artery pressure and mean pulmonary capillary wedge pressure decreased 30 to 40 percent, and the decline in mean right atrial pressure was 35 percent of baseline (all p less than 0.05). Heart rate and cardiac index did not change (p greater than 0.05). Pulmonary vascular resistance decreased slightly (p = 0.07) and systemic vascular resistance significantly (p less than 0.05). When the two groups were compared physiologic changes were virtually identical (p less than 0.05). Two-way analysis of variance for baseline corrected data proved no differences between tubing sets (p less than 0.05), but the infusion concentration rate was highly related to response (p = 0.0001). A significant (p less than 0.05) decrease in mean blood pressure and mean right atrial pressure was noted at lower dose rates (20 micrograms per minute and 40 micrograms per minute, respectively) in group 1. Beneficial hemodynamic effects in heart failure patients can, then, be predicted to occur at 80 micrograms per minute infusion rates; these responses seem independent of the type of infusion tubing system employed. Additionally, when patients given intravenous nitroglycerin for various reasons were followed for 48 hours, the majority receiving infusions via polyvinyl chloride tubing (group 2) did not require dosage adjustments. Also, at lower flow rates, more solution than calculated may be delivered when polyethylene tubing infusion sets are employed with volumetric infusion pumps.

Nitrate delivery systems in perspective. A decade of progress

In recent years the use of nitroglycerin and long-acting nitrate compounds in clinical practice has been increasing. Only 10 to 15 years ago these drugs, at least in oral formulation, were felt to have no clinical utility because of concern that potent hepatic enzyme activity would degrade sufficient amounts of the nitrate compounds from reaching the systemic circulation. However, it is now recognized that oral nitrate administration when given in sufficient amounts achieves therapeutic plasma concentrations and desired clinical effects. Nitrates are routinely used for the treatment of stable and unstable angina and also play a role in therapy for complications of myocardial infarction. Nitrates are very effective agents for preload reduction in vasodilator therapy of congestive heart failure. A wide variety of nitrate delivery systems, including the standard oral and sublingual formulations, and as well as the new transdermal nitroglycerin discs and buccal nitroglycerin, are now available. Sublingual nitroglycerin, isosorbide dinitrate, and buccal nitroglycerin are used for acute treatment of attacks of ischemic chest pain. For ambulatory patients, long-acting therapy can be administered by oral, topical ointment, transdermal disc, and buccal nitroglycerin formulations. Each compound has a slightly different onset and duration of action, which is in part dose-dependent. The relative merits and problems with each of the formulations are reviewed. Intravenous nitroglycerin is now commercially available and plays an increasing role in the intensive care units. It is an ideal drug for acute chest pain syndromes, including acute myocardial infarction. Specialized tubing does not need to be employed. The wide variety of nitrate delivery systems available to physicians makes use of this tried and true therapy practical and easy to carry out for clinicians.

Haemodynamics and plasma concentrations following sublingual GTN and intravenous, or inhaled, isosorbide dinitrate

We measured plasma nitrate levels and haemodynamics following sublingual glyceryl trinitrate (GTN) (0.5 mg), or isosorbide dinitrate (ISDN) administered intravenously (0.5 mg) or by inhalation (1.25 mg) in 23 patients undergoing cardiac catheterisation for investigation of chest pain. Peak levels were detected at 90 s and 5 min following intravenous and inhaled ISDN respectively and at 3 min following sublingual GTN. Intravenous and inhaled ISDN produced similar plasma levels at 30 s and both were significantly greater than following sublingual GTN. Plasma levels were maintained for longer following inhaled ISDN than intravenous ISDN or sublingual GTN. Haemodynamic responses were qualitatively similar following each treatment; reduction in pulmonary vascular resistance and pressure and left ventricular end diastolic pressure occurred in each group. Heart rate, cardiac output and LV dP/dt.P-1 remained unchanged. Maximal haemodynamic responses were greater following ISDN than GTN, with little difference between the two preparations of ISDN. Haemodynamic responses were more sustained following inhaled ISDN than following sublingual GTN or intravenous ISDN, the latter two being similar in this respect. These findings suggest that inhaled ISDN may provide more rapid and sustained relief from angina than sublingual GTN.

Controlled, eight-hour haemodynamic study of a sustained-release formulation of isosorbide dinitrate in moderate left ventricular failure

The aim of the study was to assess the duration of the haemodynamic effects of a new sustained-release oral formulation of isosorbide dinitrate (ISDN). Twenty patients (17 men and 3 women; mean age 60 years) with acute myocardial infarction (10 anterior, 10 inferior) complicated by moderate left ventricular failure took part in a randomized controlled trial. Ten patients were randomly assigned to the placebo group and 10 to the ISDN group, who received 40 mg sustained release isosorbide dinitrate. Haemodynamic variables were measured before treatment, after 0.5 and 1 h and then every 2 hours up to the 8th hour after treatment. There was no significant change in any haemodynamic parameter in the placebo group, during the study period. In the ISDN group there was a significant fall in pulmonary artery diastolic pressure at 4 and 8 h, from 19.0 +/- 1.0 mm Hg to 16.5 +/- 1.2 mm Hg and 15.5 +/- 0.8 mmHg, respectively. The mean pulmonary capillary wedge pressure fell progressively from 17.9 +/- 1.0 to 12.5 +/- 1.2 mmHg at 2 h (p less than 0.001 in comparison with the placebo group. The fall remained significant up to 8 h. There was no statistically significant change in heart rate, cardiac index, systemic blood pressure or systemic and pulmonary vascular resistances. On the whole the cardiac index remained unchanged. There were numerous individual variations of cardiac index in relation to the initial mean pulmonary capillary wedge pressure and the magnitude of its fall following administration of ISDN. The change in cardiac index was inversely correlated with the control cardiac index (r = -0.69, p less than 0.02).

A new oral slow release form of isosorbide dinitrate. Effect on the hemodynamics and exercise capacity of patients with angina

To assess the bioavailability of a new oral and slow release form of isosorbide dinitrate (ISDN-SR), we evaluated 12 patients with confirmed coronary artery disease, chronic stable angina pectoris and abnormal maximal exercise tests (angina-limited and associated with greater than or equal to 0.1 mV ST displacement). Each patient was known to have an increased exercise time after 0.4 mg of sublingual nitroglycerin. Patient responses to exercise on the treadmill at two, four, six, and eight hours after the double-blind administration of 40 mg of ISDN-SR were compared to an identical placebo. It is concluded that 40 mg of this slow release form of isosorbide dinitrate is bioavailable for at least eight hours as demonstrated by significantly improved exercise capacity of the majority (64 percent) of angina patients in this study, each of whom demonstrated anginal limitation to exercise and favorable responses to 0.4 mg of sublingual nitroglycerin.

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.

Tolerance to isosorbide dinitrate: rate of development and reversal

The circulatory response and plasma concentrations of isosorbide dinitrate (ISDN) were determined in 10 patients with chronic, stable angina after administration of 5 mg of sublingual ISDN during the control stage, after 48 hr of therapy with 15 mg of ISDN orally every 6 hr, and subsequently after a 48 hr period when ISDN was substituted by placebo four times daily. Initially, sublingual ISDN induced major reductions in both supine and standing systolic and diastolic blood pressure, but after 45 hr of therapy with oral ISDN, there was a significantly diminished vasodepressor response in both positions. Subsequently, when placebo was substituted for ISDN, the circulatory response initially seen was restored within 21 hr. Plasma ISDN concentrations after the test sublingual dose were slightly higher after 48 hr of oral ISDN dosing (i.e., the tolerant state) than at the start of the study. This suggests that tolerance is unlikely to be caused by reduced bioavailability or accelerated elimination of ISDN. It is possible that tolerance is related to accumulation of ISDN metabolites. The attenuation of the circulatory response to ISDN may be related to the altered antianginal efficacy commonly seen during sustained therapy with ISDN.

Symptoms, haemodynamics, and exercise capacity during long term treatment of chronic heart failure. Experience with pirbuterol

An open study of long term treatment with an oral beta 2 agonist (pirbuterol 20 mg three times daily) was undertaken in 63 patients with severe chronic heart failure. During three months of treatment 20 (32%) patients died, of whom 16 were taking the drug at the time of death. Mortality was related to initial functional class (New York Heart Association classification: 23% in grade III and 75% in grade IV). Concomitant treatment with digoxin did not affect mortality. The drug was well tolerated by most patients but unwanted side effects necessitated withdrawal of the drug in six (10%). Thirty-five patients were continuing to take the drug after three months, of whom 22 reported symptomatic improvement and only four deterioration. There was a relation between symptomatic improvement and increase in exercise capacity. At initial haemodynamic assessment a single dose of pirbuterol increased the cardiac index by 34% and the stroke index by 21%. Left ventricular filling pressure fell by 23% and systemic vascular resistance by 22%. Haemodynamic reassessment after three months of continuous treatment in 29 patients showed maintained improvement in the group as a whole, although individual variation was considerable. There was no apparent relation between haemodynamic improvement and improvement in exercise duration and symptoms. Severe heart failure has a poor prognosis. Identification of those patients who may derive benefit from treatment with a particular drug is not yet possible.

Nitroglycerin and long-acting nitrates in clinical practice

Nitrates are potent relaxers of vascular smooth muscle and act by dilating veins, arteries, and arterioles (especially at high doses). Their clinical effects have been considered to be dominantly related to peripheral actions: systemic venodilatation and a decrease in systemic vascular resistance, reducing the preload and afterload of the heart. Considerable experimental work confirms potent salutary effects on the coronary circulation. These drugs are readily absorbed across mucosal surfaces; they are available in multiple formulations, including sublingual, buccal, oral, and topical delivery systems. Nitrate administration should begin with low doses and increased to doses that are often higher than previously recommended until a specific clinical end point or limiting side effects occur. Organic nitrate esters are effective in the treatment of stable angina pectoris, unstable angina, coronary vasospastic syndromes, and in vasodilator therapy in severe congestive heart failure. The pathophysiology of these syndromes is reviewed with respect to the clinical actions of nitrates on the central and peripheral circulations. The side effects of nitrates include headache, dizziness, and nausea. Nitrate tolerance, a controversial subject, does not appear to be an important clinical problem. Using the guidelines presented in this review, nitrate therapy provides effective, inexpensive, well-tolerated therapy for many patients with cardiovascular disease.

New perspectives on therapeutic application of nitrates as vasodilator agents for severe chronic heart failure

Although nitrates produce marked decreases in ventricular filling pressures in patients with severe heart failure, their therapeutic value has long been believed to be limited because they were thought to exert minimal arterial dilating effects. Recently, however, new conceptual approaches to vasodilator drugs have been developed that have challenged this traditional view. These new perspectives indicate that nitrates exert dilator actions on both the arterial and venous circulations, and reduce both preload and afterload; such balanced circulatory responses are particularly evident when large doses of these drugs are used. Cardiac output increases markedly with nitrates in patients with a greatly increased systemic vascular resistance before treatment or with significant mitral regurgitation. The major reason for the limited increases in cardiac output noted in previous studies is the inclusion of patients with heart failure whose pretreatment values for cardiac output were within normal limits; in these persons nitrates markedly activate neurohumoral vasoconstrictor mechanisms that counteract the arterial dilating actions of these drugs. Long-term nitrate therapy attenuates exercise-induced increases in pulmonary venous pressures, which permit patients to undergo repeated submaximal exercise with fewer symptoms; this improves physical conditioning and exercise capacity, even in the absence of drug-related changes in cardiac output. The long-term hemodynamic and clinical benefits of nitrates in heart failure have been confirmed by two independent randomized double-blind placebo-controlled clinical trials.

Improved exercise capacity and differing arterial and venous tolerance during chronic isosorbide dinitrate therapy for congestive heart failure

We studied 30 patients with moderate-to-severe congestive heart failure in a double-blind, randomized, placebo-controlled trial to determine the acute and long-term effects of isosorbide dinitrate on clinical status and on resting and exercise hemodynamics. Seventeen patients received placebo and 13 isosorbide dinitrate. First-dose isosorbide dinitrate (40 mg orally) decreased resting and exercise pulmonary capillary wedge pressure, pulmonic and systemic arterial pressures and pulmonic and systemic vascular resistances without augmenting exercise capacity. Compared with placebo, chronic therapy with isosorbide dinitrate (40 mg orally every 6 hours for 12 weeks) significantly improved clinical status and exercise capacity. Resting and exercise systemic blood pressure and systemic vascular resistance returned to baseline values during chronic isosorbide dinitrate therapy, but pulmonary capillary wedge pressure, pulmonary artery pressure and pulmonary vascular resistance remained improved. In patients with congestive heart failure, 12 weeks of oral isosorbide dinitrate therapy improves resting and exercise hemodynamics, exercise capacity, and clinical status; tolerance develops to the systemic arterial vascular effects without attenuation of the venous and pulmonary vascular effects.

Haemodynamic and clinical effects of isosorbide-dinitrate in patients with severe effort angina on beta-blocking treatment

The effect of isosorbide-dinitrate (ISDN) 20 mg 4 times daily against placebo has been tested in 12 patients with stable effort induced angina pectoris receiving prophylactic treatment with metoprolol. ISDN did not decrease the attack rate or nitroglycerine consumption, nor was exercise tolerance increased after it. Left ventricular function, assessed by radionuclide ventriculography, increased in 6 out of 8 patients (p less than 0.1). It is concluded that ISDN has no place in the treatment of haemodynamically intact patients with severe angina pectoris in spite of beta-blocking treatment, but that it may be of value in the treatment of patients with left ventricular failure, including those whose left ventricular failure has been brought about by beta-blocking treatment necessitated by angina pectoris.

Pharmacokinetics of intravenous isosorbide-dinitrate

The kinetics of isosorbide dinitrate (ISDN) after i.v. administration and the absolute availability of an oral slow release preparation (SR) were studied in young healthy volunteers. ISDN and the 2- and 5-mononitrates of isosorbide (2-MN, 5-MN) were determined by GLC. After i.v. administration plasma levels of ISDN declined biexponentially and could be adequately described by an open two compartment body model. Distribution half-life was extremely rapid (2-5 min). Terminal disappearance had a half-life of 67 (62-75) min (mean, range). Total plasma clearance was 1.6 (1.2-2.2) litres X min-1, thus approaching liver blood flow. Nevertheless, absolute systemic availability (F) or oral ISDN amounted to 22% (16-29%). Assuming that oral ISDN is completely absorbed and blood levels do not exceed serum levels, an upper limit of hepatic clearance (liver blood flow 1.5 litres X min-1 X (1-F/100)) can be estimated, which is significantly smaller (p less than 0.05) than the measured clearance. This finding is best interpreted by assuming that ISDN is partly eliminated by extrahepatic routes, which is further substantiated by a different pattern of metabolites after i.v. and oral dosing. Whereas after i.v. administration more 2-MN is produced, 5-MN is the main metabolite after oral ISDN. Since the glutathione-S-transferases are found in the cytosol of most cells, it seems likely that other organs than the liver contribute to the metabolism of ISDN.

Hemodynamic effects of vasodilator therapy in severe left heart failure combined with large atrial septal defects

Two patients presented with severe left heart failure and large secundum atrial septal defects without severe pulmonary hypertension. The acute hemodynamic effects of two commonly used vasodilator agents, isosorbide dinitrate and hydralazine, are described. Although isosorbide dinitrate improved systemic forward cardiac output, it also increased left-to-right intracardiac shunting in both patients. On the other hand, hydralazine dramatically improved systemic toward output and concomitantly diminished left-to-right shunt flow in each patient (43 and 21 percent). The complexities of combined severe left ventricular failure and a large atrial septal defect with left-to-right shunting, and the importance of extensive hemodynamic monitoring at the time of pharmacologic intervention, are discussed.

Oral theophylline in chronic heart failure

Theophylline choline 600 mg was given as a single oral dose to nine patients in chronic left ventricular failure due to myocardial dysfunction. Cardiac output, left ventricular filling pressure (LVFP) and right atrial pressure (RAP) were measured with a pulmonary artery thermodilution catheter for the following 3 hr. Continuous recordings of cardiac rhythm were made throughout the study. Mean cardiac index increased from 1·75 (±0·14 s.e. mean) to 2·04 (±0·11) 1/min/m² (P<0·02), mean LVFP fell from 27 (±2·4) to 22 (±1·5) mmHg (P<0·01), mean RAP fell from 5 (±1·3) to 3 (±2·0) mmHg (P<0·05) and mean systemic arterial pressure rose from 80 (±3) to 86 (±3·5) mmHg (P<0·05). There were no significant changes in heart rate or systemic vascular resistance; thus the increase in cardiac output was probably due to a positive inotropic effect. Side effects were seen in two patients, both of whom proved to have toxic plasma theophylline concentrations.

This study demonstrated a beneficial acute haemodynamic effect of oral theophylline in chronic cardiac failure.

Intravenous isosorbide dinitrate in patients with refractory pump failure and acute myocardial infarction

We studied the hemodynamic effects of isosorbide dinitrate administered by continuous i.v. infusion to 22 patients with chronic refractory pump failure and 18 with pump failure due to acute myocardial infarction. In patients with severe pump failure, i.v. ISDN markedly decreased pulmonary capillary wedge pressure (p less than 0.001), moderately increased cardiac output (p less than 0.01), and decreased systemic vascular resistance (SVR) (p less than 0.001). There were no deleterious effects on arterial pressure and heart rate. The effects obtained in acute and chronic left ventricular failure were similar. Patients with initial SVR levels lower than 1500 dyn-sec-cm-5 did not significantly increase their cardiac output (p less than 0.005). Cardiac output increased more than 25% only in patients with initial high SVR levels (greater than 2000 dyn-sec-cm(-)5). Positive correlations were found between high SVR and elevated plasma catecholamines (r = 0.53, p less than 0.05) and between the initial SVR and initial heart rate (r = 0.70, p less than 0.01). The i.v. administration of isosorbide dinitrate appears to be an efficient therapy, particularly in selected patients with ischemic pump failure.

Oral isosorbide dinitrate in angina pectoris: comparison of duration of action an dose-response relation during acute and sustained therapy

The effects of different oral doses of isosorbide dinitrate administered acutely and four times daily during sustained therapy were studied in 12 patients with angina pectoris. After administration of 30, 60 and 120 mg of isosorbide dinitrate, the average plasma concentrations were higher and the area under the plasma concentration time curve was greater during sustained than during acute therapy (p less than 0.01). Reduction in standing systolic blood pressure was greater during acute than during sustained therapy (p less than 0.001). This reduction in systolic blood pressure was dose-related and persisted for 8 hours during acute therapy, but was not dose-related and was demonstrable for only 4 hours during sustained therapy. Compared with placebo therapy, exercise duration to the onset of angina and to the development of moderate angina increased significantly after each dose of isosorbide dinitrate for 8 hours during acute therapy but for only 2 hours during sustained therapy. During acute therapy, administration of a single dose of 15 or 30 mg of isosorbide dinitrate produced similar improvement in exercise tolerance as did a dose of 60 or 120 mg. During sustained therapy (15 mg four times daily), exercise tolerance increased to the same magnitude as with doses of 30, 60 or 120 mg four times daily. In most patients, near maximal improvement in exercise tolerance occurred after a dose of 15 or 30 mg four times daily. It is concluded that during sustained therapy with isosorbide dinitrate, partial tolerance to the antianginal and circulatory effects develops rapidly.

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.

Acute and long-term effects of vasodilator therapy on resting and exercise hemodynamics and exercise tolerance

The acute hemodynamic response to vasodilators in patients with chronic heart failure has been well characterized, but less is known about the long-term hemodynamic effects of vasodilator therapy. We measured hemodynamic variables at rest and during upright exercise in 11 patients during the initiation of therapy with oral hydralazine and sublingual isosorbide dinitrate and, in eight of these, after 3 months of continuous treatment. Marked initial increases in resting cardiac output and stroke volume and reductions in wedge pressure were sustained during chronic therapy. Similarly, the early improvement in exercise hemodynamic measurements persisted in most subjects. Exercise tolerance, quantified as the maximum duration of treadmill exercise, increased modestly (7.7 +/- 2.6 to 8.9 +/- 3.3 minutes, 0.05 less than p less than 0.10) after several days on vasodilators and further (10.2 +/- 3.7 minutes, p less than 0.01) during long-term treatment. The acute hemodynamic effects of vasodilator therapy at rest or during exercise did not correlate well with the changes in exercise tolerance. Our findings suggest that the combination of hydralazine and isosorbide dinitrate improves cardiac performance at rest and during exercise in patients with chronic heart failure and that this improvement persists during chronic therapy. In most patients, this hemodynamic improvement is accompanied by greater exercise tolerance.

Determinants of drug response in severe chronic heart failure. 1. Activation of vasoconstrictor forces during vasodilator therapy

Vasodilator drugs activate neurohumoral forces that produce peripheral vasoconstriction and tachycardia and probably cause the rebound events observed upon abrupt withdrawal of therapy. To determine their role in limiting therapeutic vasodilator responses, these reactive forces were measured in 40 patients with severe chronic heart failure by quantifying the magnitude of rebound change (MRC) after nitroprusside withdrawal. Group 1 patients (n = 22), who had minimal reactive vasoconstriction (MRC less than or equal to 27%), showed marked hemodynamic effects with nitroprusside (4.5 microgram/kg/min) and isosorbide dinitrate (40 mg orally), associated with significant decreases in heart rate with both drugs (p less than 0.001). Despite administration of the same doses of both drugs, group 2 patients (n = 18), who had marked rebound changes (MRC greater than 27%), showed significantly smaller changes in cardiac index, systemic vascular resistance and mean arterial pressure (p less than 0.001), associated with no change or increases in heart rate. Rebound events were attenuated and the responses to nitroprusside and nitrates were enhanced in four patients in whom these drugs were readministered after pretreatment with i.v. phentolamine (0.3mg/min). We conclude that activation of neurohumoral forces can limit the hemodynamic responses to vasodilator administration; this supports the use of combination therapy of direct-acting vasodilators and neurohumoral antagonists in selected patients with severe chronic heart failure.

The prolonged effect of pentaerythritol tetranitrate on exercise capacity in stable effort angina pectoris

We studied the effect of a single oral dose of 40 mg of pentaerythritol tetranitrate (PETN) on the exercise capacity of ten patients with angina pectoris. The study design was a randomized double-blind crossover comparing the effects of 40 mg of oral PETN with placebo on exercise tolerance. Patients were exercised to moderate angina pectoris before and 2 1/2 and 4 1/2 hours after receiving the placebo or PETN at seven-day intervals during the double-blind crossover period. Exercise tolerance time was measured using a multistage, progressive treadmill test. Exercise times were greater 2 1/2 hours and 4 1/2 hours following PETN compared with placebo (P less than 0.05). Heart rate, systolic and diastolic blood pressure, and double product at rest (supine and standing) and at point of angina pectoris did not change significantly.

[Treatment of severe congestive heart failure with the beta-agonist fenoterol (author's transl)]

The acute hemodynamic effects of the semiselective beta 2-stimulating compound Fenoterol were studied in 7 patients with severe congestive heart failure (IV NYHA) as a result of a low-output-syndrome of varying aetiology (coronary heart disease/cardiomyopathy). The continuous infusion of Fenoterol (2.5 micrograms/min for 60 min) induced the following changes in parameters of pump function: a slight but not yet significant fall of PCPm which we considered as a reference value of LVEDP from 24 +/- 9 to 20 +/- 6 mm Hg (13%); a highly significant increase in CI from 1.96 +/- 04 to 2.71 +/- 0.53 l/min . m2 (39%; p less than 0.001) and in SVI from 18.7 +/- 4.9 to 24.8 +/- 8.1 ml/m2 (32%; p less than 0.01); a clear reduction of TPR from 1374 +/- 427 to 977 +/- 282 dyn . s . cm-5 (28%; p less than 0.001). PVR was reduced from 245 +/- 158 to 192 +/- 85 dyn . s . cm-5 (n.s.). There were no significant changes in right ventricular filling pressure (15 +/- 8 to 15 +/- 9 mm Hg), mean arterial pressure (76 +/- 17 to 75 +/- 16 mm Hg) and heart rate (107 +/- 13 to 117 +/- 23 beats/min). The study indicates that the "selective" beta 2-agonist Fenoterol in severe congestive heart failure produces a significant improvement in pump function. We assume the increase in SV to be due to a positive inotropic effect -- caused by beta 1-stimulation -- and a reduction of impedance to left ventricular ejection by decrease in TPR -- caused by beta 2-stimulation. Thus Fenoterol seems to be useful in treatment of severe congestive heart failure with elevated TPR.

Treatment of chronic heart failure with pirbuterol: acute haemodynamic responses

Fifty-nine patients with severe chronic heart failure were given pirbuterol, a beta agonist with vasodilator and positive inotropic properties. The acute haemodynamic responses to both single (20 patients) and incremental doses (39 patients) were measured. Pirbuterol increased cardiac index and reduced left ventricular filling pressure and systemic vascular resistance with only small changes in heart rate and blood pressure. Maximal effects were observed at an average of 170 minutes after a single oral dose of pirbuterol. In the incremental dose studies the plasma pirbuterol concentration was found to increase with increasing doses and was related to the magnitude of the haemodynamic response. Pirbuterol was well tolerated, and no drug-related side effects were recorded. Oral pirbuterol clearly improved pump performance in these patients, the haemodynamic changes being consistent with vasodilatation as the dominant mechanism rather than a direct inotropic effect.

Sustained effectiveness of chronic prazosin therapy in severe chronic congestive heart failure

Twelve patients with severe chronic congestive heart failure (CHF) (NYHA class III and IV) resistant to digitalis and diuretics were treated with the postsynaptic alpha-blocking agent prazosin (PZ) (3 to 20 mg/day). In 11 patients oral PZ treatment was well tolerated; the agent was discontinued in the remaining patient because of orthostatic dizziness. After 4 weeks of PZ, total systemic vascular resistance decreased from 2245 +/- 792 to 1603 +/- 355 dyn sec cm-5, mean blood pressure declined from 100 +/- 15 to 90 +/- 14 mm Hg, and pulmonary capillary wedge pressure decreased from 29 +/- 8 to 25 +/- 9 mm Hg. Cardiac index increased from 1.92 +/- 0.63 to 2.30 +/- 0.41 l/min/m2. The increase of stroke volume index correlated with the fall in peripheral vascular resistance (r = --0.79, p less than 0.01) and the decline in pulmonary capillary wedge pressure (r = --0.75, p less than 0.05). In parallel, exercise tolerance increased significantly. Four patients improved from functional class IV to II, four from class IV to III, and one from class III to II, while two patients were unchanged. In the eight patients followed for 6 months, the beneficial effects of ambulatory PZ were maintained throughout the expansive observation period. Three patients died as their disease process progressed during the study (sudden death, pneumonia, and post-PZ withdrawal pump failure). Prazosin is a valuable vasodilator for long-term treatment of otherwise refractory congestive heart failure with the agent given in sufficient individualized dosage.

Ambulatory prazosin treatment of chronic congestive heart failure: development of late tolerance reversible by higher dosage and interrupted substitution therapy

To evaluate whether long-term administration of the oral vasodilator, prazosin, in the ambulatory therapy of chronic refractory congestive heart failure (CHF) results in gradual attentuation of its marked salutary peripheral circulatory relaxing actions, 16 coronary heart failure patients receiving chronic prazosin, 16 mg daily, were assessed for the development of vasodilator tolerance for 12 months. In six of these patients such tolerance was documented after 7 months which was readily surmountable, thereby allowing continuation of effective chronic prazosin therapy. Each of the six tolerance patients underwent four forearm plethysmography studies: prior to chronic prazosin (study I; 4.0 mg study dose), after 7 months prazosin (study II; 4.0 mg), repeated following 1 additional week on higher effective prazosin dose of 32 mg daily (study III; 8.4 mg), and following 2 weeks of prazosin withdrawal (study IV; 4.0 mg). The prazosin study dose increased forearm blood flow, decreased forearm vascular resistance and venous tone in studies I, III, and IV; these variables were unchanged by prazosin in study II. Despite vasodilator tolerance to the initial daily dosage at 7 months (study II), symptomatic effectiveness and improved cardiac performance were sustained throughout the entire 12 months of chronic prazosin therapy by increasing dosage (study III) and brief interruption of the vasodilator (study IV) (NYHA class IV pre-prazosin symptoms improved to class 2.7 at 3 months, class 2.4 at 6 months, and class 2.5 at 12 months chronic prazosin). This study showed that prazosin vasodilator tolerance occurred in approximately one third of CHF patients after several months of chronic prazosin therapy. More importantly, however, the present investigation demonstrated that chronic prazosin symptomatic efficacy can be maintained in such CHF patients by overcoming tolerance with higher effective prazosin dosage or brief prazosin discontinuation.