A comparison of the acute hemodynamic effects of prostacyclin and hydralazine in primary pulmonary hypertension

In vitro and in silico lipoxygenase inhibition studies and antimicrobial activity of pyrazolyl-phthalazine-diones

The series of pyrazolyl-phthalazine-dione derivatives (PPDs) was subjected to evaluation of their in vitro lipoxygenase (LOX) inhibition and antimicrobial activities. Results obtained for LOX inhibition activities of PPDs showed that all compounds exhibit good to excellent activity, whereby compounds with eudesmic, syringic, vanillic or toluic moiety are the most active. Molecular modelling study was performed to investigate the possible mechanism of action and binding mode of compounds within the LOX active site. Docking results revealed that activity of the examined compounds depends on the functional group ability to create hydrogen bond accepting (HBA) and hydrophobic features (Hy) in the LOX-Ib active site. In addition, all substances were tested for their antibacterial and antifungal activities. The investigated compounds showed better antifungal than antibacterial activity. The highest antifungal activity was on Aspergillus fumigatus ATTC 204305 and Trichoderma viridae ATCC 13233.

Evaluation and Management of Right-Sided Heart Failure: A Scientific Statement From the American Heart Association

Background and Purpose:

The diverse causes of right-sided heart failure (RHF) include, among others, primary cardiomyopathies with right ventricular (RV) involvement, RV ischemia and infarction, volume loading caused by cardiac lesions associated with congenital heart disease and valvular pathologies, and pressure loading resulting from pulmonic stenosis or pulmonary hypertension from a variety of causes, including left-sided heart disease. Progressive RV dysfunction in these disease states is associated with increased morbidity and mortality. The purpose of this scientific statement is to provide guidance on the assessment and management of RHF.

Methods:

The writing group used systematic literature reviews, published translational and clinical studies, clinical practice guidelines, and expert opinion/statements to summarize existing evidence and to identify areas of inadequacy requiring future research. The panel reviewed the most relevant adult medical literature excluding routine laboratory tests using MEDLINE, EMBASE, and Web of Science through September 2017. The document is organized and classified according to the American Heart Association to provide specific suggestions, considerations, or reference to contemporary clinical practice recommendations.

Results:

Chronic RHF is associated with decreased exercise tolerance, poor functional capacity, decreased cardiac output and progressive end-organ damage (caused by a combination of end-organ venous congestion and underperfusion), and cachexia resulting from poor absorption of nutrients, as well as a systemic proinflammatory state. It is the principal cause of death in patients with pulmonary arterial hypertension. Similarly, acute RHF is associated with hemodynamic instability and is the primary cause of death in patients presenting with massive pulmonary embolism, RV myocardial infarction, and postcardiotomy shock associated with cardiac surgery. Functional assessment of the right side of the heart can be hindered by its complex geometry. Multiple hemodynamic and biochemical markers are associated with worsening RHF and can serve to guide clinical assessment and therapeutic decision making. Pharmacological and mechanical interventions targeting isolated acute and chronic RHF have not been well investigated. Specific therapies promoting stabilization and recovery of RV function are lacking.

Conclusions:

RHF is a complex syndrome including diverse causes, pathways, and pathological processes. In this scientific statement, we review the causes and epidemiology of RV dysfunction and the pathophysiology of acute and chronic RHF and provide guidance for the management of the associated conditions leading to and caused by RHF.

Synthesis and Evaluation of New Phthalazine Urea and Thiourea Derivatives as Carbonic Anhydrase Inhibitors

A new series of phthalazine substituted urea and thiourea derivatives were synthesized, and their inhibitory effects on the activity of purified human carbonic anhydrases (hCAs I and II) were evaluated. 2H-Indazolo[2,1-b]phthalazine-trione derivative(1)was prepared with 4-nitrobenzaldehyde, dimedone, and phthalhydrazide in the presence of TFA in DMF, and nitro group was reduced to amine derivative(2)with SnCl2·2H2O. The compound was reacted with isocyanates and isothiocyanates to get the final products(3a–p). The results showed that all the synthesized compounds inhibited the CA isoenzymes activity.3a(IC50= 6.40 µM for hCA I and 6.13 µM for hCA II) has the most inhibitory effect. The synthesized compounds are very bulky to be able to bind near the zinc ion, and they much more probably bind as the coumarin derivatives.

Effects of hydralazine on the pulmonary vasculature and respiratory control in humans

This study sought: (1) to clarify the effects of hydralazine on both the pulmonary vasculature and respiratory control in euoxia and hypoxia in healthy humans; and (2) to determine whether hydralazine alters the expression of genes regulated by hypoxia-inducible factor 1 (HIF-1). Ten volunteers participated in two 2 day protocols. Hydralazine (25 mg) or placebo was administered at 1 pm and 11 pm on the first day, and at 1 pm on the second day. In the mornings and afternoons of both days, we measured plasma vascular endothelial growth factor (VEGF) and erythropoietin (EPO) concentrations (both HIF-1-regulated gene products), systemic arterial blood pressure, and changes in heart rate, cardiac output, maximal systolic pressure difference across the tricuspid valve (delta Pmax) and ventilation in response to 20 min of isocapnic hypoxia. Recent hydralazine: (1) decreased diastolic blood pressure; (2) increased heart rate and cardiac output in euoxia and hypoxia whilst having no effect on delta Pmax; and (3) increased the ventilatory sensitivity to hypoxia. Hydralazine had no effect on plasma EPO or VEGF concentration. We conclude that hydralazine increases the sensitivity of the ventilatory response to hypoxia, but lacks any effect on the pulmonary vasculature at the dose studied. It did not affect the expression of HIF-1-regulated genes.

Pharmacotherapy for idiopathic pulmonary arterial hypertension during the past 25 years

OBJECTIVE

To review the current pharmacotherapy for idiopathic pulmonary arterial hypertension (IPAH).

METHODS

A search of the primary literature was conducted by using MEDLINE, the National Institutes of Health medical research Web site (www.clinicaltrials.gov), and the United States Food and Drug Administration's Center for Drug Evaluation and Research Web site (www.fda.gov/cder).

RESULTS

Until the early 1980s, conventional therapy for IPAH consisted of anticoagulation, diuretics, digitalis extracts, and supplemental oxygen, yet the 5-year mortality rate remained at 66%. Calcium channel blocker therapy was introduced with the hope that it would improve survival in patients with IPAH, but it was found to be effective in only approximately 25% of patients. In 1996, intravenous epoprostenol was the first drug to show long-term benefit on hemodynamics, exercise capacity, and survival. However, administration of epoprostenol requires a permanently indwelling central venous catheter, and tachyphylaxis is common, necessitating continuous dosage escalations. Subsequently, treprostinil, a prostacyclin analog of epoprostenol that can be administered by continuous subcutaneous infusion, was introduced, followed by aerosolized iloprost, a prostacyclin analog for inhalation. An increasing understanding of the multiple pathogeneses of IPAH led to the discovery of another target for drug therapy, and bosentan, an orally administered agent, became the first endothelin-receptor antagonist approved for treatment of IPAH. Most recently, the phosphodiesterase inhibitor, sildenafil, has received approval from the United States Food and Drug Administration for the treatment of IPAH.

CONCLUSION

Recently developed pharmacotherapies offer greater effectiveness and safety than traditional agents for the treatment of IPAH.

Prostacyclin and its analogues in the treatment of pulmonary hypertension

Prostacyclin and its analogues (prostanoids) are potent vasodilators and possess antithrombotic and antiproliferative properties. All of these properties help to antagonize the pathological changes that take place in the small pulmonary arteries of patients with pulmonary hypertension. Indeed, several prostanoids have been shown to be efficacious to treat pulmonary hypertension, while the main mechanism underlying the beneficial effects remains unknown. There are indications of beneficial combination effects of prostaglandins and phosphodiesterase inhibitors and endothelin receptor antagonists. This speaks in favor of combination therapies for pulmonary hypertension in the future. The mode of application of prostanoids used in randomized controlled studies has been quite variable: continuous i.v. infusion of prostacyclin, continuous s.c. infusion of treprostinil, p.o. application of beraprost, and inhaled application of iloprost. In addition, the applied doses were quite different, ranging from 0.25 ng/kg/min for inhaled iloprost to 30-50 ng/kg/min for i.v. prostacyclin. While the principal pharmacological properties of all prostanoids are very similar due to a main action on IP receptors, there are considerable differences in pharmacokinetics and metabolism, with half-lives of 2 min for prostacyclin and about 34 min for treprostinil for i.v. infused drugs and half-lives of about 85 min for s.c. infused treprostinil. In addition, the adverse effects largely depend on the doses used and the mode of application, although there is great variability between subjects. It remains to be determined which patients will profit most from which substance (or combination) and mode of application.

A noninvasive assessment of pulmonary perfusion abnormality in patients with primary pulmonary hypertension

STUDY OBJECTIVES

The ventilatory equivalent for CO(2) (ie, the ratio of minute ventilation [VE] to carbon dioxide output [VCO(2)]) is increased in patients with primary pulmonary hypertension (PPH) consequent to an increase in physiologic dead space and alveolar ventilation. We wished to see whether the VE/V(2) ratio correlated with the abnormality in pulmonary hemodynamics in PPH patients and whether it changed in response to prostacyclin infusion.

METHODS

Following right-sided heart catheterization, 10 patients with severe PPH were studied in the coronary-care unit while hemodynamic and gas exchange measurements were measured simultaneously before and after infusion with epoprostenol (Epo), a prostacyclin analog. Studies were performed at baseline and during IV infusion of two to three increasing dosages of Epo in 10 PPH patients (NYHA class III-IV). Four patients had radial artery catheters for simultaneous blood gas measurements. Nine healthy subjects who were matched by sex, height, and weight underwent gas exchange analyses only.

RESULTS

The mean (+/- SD) VE/VCO(2) ratio was higher in PPH patients than in control subjects (50.7 +/- 9.7 vs 30.6 +/- 3.8; p < 0.001). Thirteen measurements made in four patients showed that the VE/VCO(2) ratio correlated with the physiologic dead space/tidal volume ratio (r = 0.78; p = 0.002). The VE/VCO(2) ratio measurement at baseline correlated significantly with total pulmonary vascular resistance (TPVR) (r = 0.70; p = 0.02) but not with mean pulmonary artery pressure (mPAP) or cardiac index. During Epo infusion, the VE/VCO(2) ratio decreased with increasing dosage in 6 of 10 patients, with no change or slight increases in the 4 remaining patients. Considering all doses, the VE/VCO(2) ratio decreased significantly in response to the short-term administration of Epo. The decrease tended to parallel the pattern of decrease in TPVR, but the changes in both variables were too small to provide a statistically significant correlation. The mPAP did not change significantly in response to Epo infusion, although TPVR did change at the highest dosage.

CONCLUSIONS

In patients with severe PPH, the VE/VCO(2) ratio correlated significantly with TPVR but not with mPAP or cardiac index. The VE/VCO(2) ratio decreased systematically from baseline with the dose of Epo in some but not all patients. The VE/VCO(2) ratio and TPVR decreased significantly in response to Epo when all doses were considered. Further studies are needed to elucidate whether noninvasive gas exchange measurements may be clinically useful in the evaluation of the severity of pulmonary vascular disease and the effectiveness of pulmonary vasodilator therapy.

Improvement in pulmonary hemodynamics during intravenous epoprostenol (prostacyclin): A study of 15 patients with moderate to severe portopulmonary hypertension

Pulmonary hypertension associated with increased pulmonary vascular resistance (PVR) and occurring in the setting of portal hypertension is referred to as "portopulmonary hypertension." Intravenous epoprostenol (prostacyclin) is a potent pulmonary and systemic vasodilator with antithrombotic properties. It can decrease PVR and pulmonary artery pressure in patients with primary (idiopathic) pulmonary hypertension. Using right-heart catheterization, we evaluated the acute pulmonary hemodynamic effects of intravenous epoprostenol in patients with moderate to severe pulmonary hypertension (mean pulmonary artery pressure [MPAP] >/=35 mm Hg) associated with clinical manifestations of portal hypertension. Effects of long-term infusion of epoprostenol were also evaluated. We studied 15 consecutive patients with portopulmonary hypertension; 14 underwent acute administration of epoprostenol, and no significant side effects were noted. Ten patients received continuous epoprostenol (range, 8 days-30 months). Acute changes in PVR (-34% +/- 18%), MPAP (-16% +/- 10%), and cardiac output (CO) (+21 +/- 18%), were statistically significant (P <.01). Long-term use of epoprostenol further lowered PVR (-47% +/- 12% from baseline and -31% +/- 22% from the acute change; P <.05) in the 6 patients restudied by right-heart catheterization. Death occurred in 6 of 10 (60%) of those receiving long-term epoprostenol. In moderate to severe portopulmonary hypertension, intravenous epoprostenol resulted in a significant improvement (both acute and long-term) in PVR, MPAP, and CO. Potential adverse effects on portal hypertension and implications for orthotopic liver transplantation (OLT), however, require further study.

Effects of prostacyclin on the pulmonary vascular tone and cardiac contractility of patients with pulmonary hypertension secondary to end-stage heart failure

Long-term administration of prostacyclin (PGI2) improves the hemodynamic state, symptoms, and survival in patients with primary pulmonary hypertension, but it increases mortality in patients with heart failure despite obvious hemodynamic benefits when it is given acutely. We evaluated the mechanisms of action of PGI2 in patients with heart failure and secondary pulmonary hypertension. Nineteen patients with end-stage heart failure and pulmonary hypertension, all candidates for heart transplantation, underwent right- and left sided cardiac catheterization with micromanometer-tipped catheters and were tested for PGI2 at incremental doses. PGI2 infusion significantly improved pulmonary hemodynamics with a 47% reduction in pulmonary vascular resistance (p=0.0003) and a doubling of pulmonary artery compliance (p <0.0001), reflecting improvement in pulmonary vascular tone. The dose of PGI2 necessary to reach this hemodynamic effect correlated significantly to the baseline severity of pulmonary artery compliance (r=0.54, p=0.01). Furthermore, PGI2 produced a significant positive inotropic effect (contractile element maximum velocity increased from 1.10+/-0.09 to 1.33+/-0.13 circ/s, p <0.009). The hemodynamic effects of PGI2 infusion were independent of the plasma and urinary levels of endogen prostaglandins. Thus, PGI2 at therapeutic doses exerts a positive inotropic effect in patients with heart failure, which may explain the increased mortality rate observed with the long-term use of PGI2 in this type of patient. The spectacular acute benefits on right ventricular afterload, however, may be useful in unstable patients with heart failure and secondary pulmonary hypertension or in transplanted patients with acute right ventricular failure of the donor heart.

Pulmonary hypertension and selective pulmonary vasodilators in acute lung injury

The pulmonary circulation and the mechanisms which generate pulmonary hypertension are reviewed. The role of these mechanisms in the common pulmonary hypertensive states are analysed, particularly those in acute lung injury. Management options are discussed, with particular emphasis on the use of selective pulmonary vasodilators.

A placebo-controlled trial of prostacyclin in acute respiratory failure in COPD

Although patients with COPD often have elevated pulmonary artery pressures (PAP) and pulmonary vascular resistance (PVR), it is uncertain whether treatment of this pulmonary hypertension is beneficial. We evaluated the extent of pulmonary hypertension in 16 patients with severe COPD complicated by acute respiratory failure and pulmonary hypertension. We assessed the hypothesis that the vasodilator prostacyclin (PGI2) would reduce PVR and improve systemic O2 transport. Patients with a COPD exacerbation requiring mechanical ventilation, and mean PAP greater than 30 mm Hg, were randomized to receive PGI2 or placebo, in addition to conventional therapy. Randomization to PGI2 or placebo therapy occurred 1 to 12 h after intubation, while the patient was mechanically ventilated. An optimal PGI2 dose (2 to 12 ng/kg/min, IV) was established in an initial dose-ranging study and then this dose was infused continuously for 48 h. PGI2 initially reduced PVR, but this effect dissipated within 24 h, indicating the development of tachyphylaxis. Tolerance to the adverse effects of PGI2 (tachycardia, hypotension, flushing, and headache) also developed over time. PGI2 treatment was associated with a significant fall in PaO2 but no increase in systemic oxygen transport. PGI2 proved to be a nonselective vasodilator that caused mild hypoxemia. Despite acute respiratory failure, pulmonary hypertension is mild in patients with severe COPD receiving mechanical ventilation and IV PGI2 is not beneficial in such patients.

Role of prostacyclin in the treatment of primary pulmonary hypertension

Over the last decade, new medical and surgical treatments have become available for primary pulmonary hypertension that have influenced the natural history of the disease. Vasodilator therapy is aimed at overcoming pulmonary vasoconstriction with consequent decrease in afterload and improved right ventricular output. The endpoint of vasodilator therapy is therefore to reduce pulmonary vascular resistance, without causing significant systemic hypotension. Prostacyclin, a potent vasodilator and antiaggregating agent, has been successfully used by continuous infusion in the treatment of severe pulmonary hypertension. The marked improvement in quality of life observed with the use of prostacyclin in these patients, as well as the increased survival time on the waiting list for transplantation, has influenced us to adopt prostacyclin infusion as a fundamental element of our therapeutic strategy for the management of this rare but fatal condition.

Comparison between prostaglandin E1 and epoprostenol (prostacyclin) in infants after heart surgery

OBJECTIVE

To study the dose response characteristics of prostaglandin E1 and epoprostenol (prostacyclin) and directly to compare their effectiveness as pulmonary vasodilators in infants with pulmonary hypertension.

DESIGN

A crossover design with each patient receiving both drugs in random order.

SETTING

Infants were studied in the intensive care unit while they were sedated, paralysed, and ventilated.

PATIENTS

Twenty infants who had undergone corrective cardiac surgery and who were in sinus rhythm, had stable haemodynamic function, and had a pulmonary artery catheter in place. All infants were receiving dopamine and phenoxybenzamine.

INTERVENTIONS

Baseline haemodynamic measurements were taken and an infusion of the first drug was started at the lowest dose: after 20 minutes the measurements were repeated and the dose increased. This protocol was repeated for all doses of both drugs: 10, 30, and 100 ng/kg/min of prostaglandin E1 and 5, 10, and 25 ng/kg/min of epoprostenol. Cardiac output was measured by the pulsed Doppler ultrasound method.

MAIN OUTCOME MEASURES

Pulmonary and systemic vascular resistances were calculated from the cardiac output and compared by the Wilcoxon signed ranks test.

RESULTS

Both prostaglandin E1 and epoprostenol were effective vasodilators: 5 ng/kg/min of epoprostenol was equivalent to 30 ng/kg/min of prostaglandin E1.

CONCLUSIONS

Neither drug showed pulmonary specificity.

Influence of adenosine and prostacyclin on hypoxia-induced pulmonary hypertension in the anaesthetized pig

The effects of adenosine and prostacyclin (PGI2) infusions on hypoxia-induced pulmonary hypertension in the pulmonary and systemic circulatory systems of nine pigs were compared. The animals received the drugs in random order, and they were allowed to recover between each experimental sequence. Hypoxia was induced by reducing FiO2 to 0.12-0.13 so as to result in an arterial PO2 of approximately 6 kPa. Dose rates of adenosine or PGI2 during hypoxia were individualized in order to achieve a maximal reduction of 15% in the mean arterial blood pressure. Adenosine and PGI2 produced a fall in pulmonary vascular resistance of 36 +/- 4% (s.e.mean P less than 0.01) and 37 +/- 6% (P less than 0.01), respectively. The mean pulmonary artery pressure was reduced by 19 +/- 3% (P less than 0.01) during adenosine infusion and by 36 +/- 4% (P less than 0.01) during PGI2 infusion. The systemic haemodynamic responses to the two drugs were similar but adenosine produced a 7 +/- 2% (P less than 0.01) increase in cardiac output. Arterial PO2 during hypoxia and vasodilator treatment did not differ from the hypoxic situation without drug infusion. It is concluded that adenosine and PGI2 counteract hypoxia-induced increases in pulmonary vascular resistance similarly, but the reduction in pulmonary artery pressure was greater with PGI2 at infusion rates, causing minor systemic haemodynamic changes.

Prostacyclin and acetylcholine as screening agents for acute pulmonary vasodilator responsiveness in primary pulmonary hypertension

Epoprostenol sodium (prostacyclin) administered intravenously is considered the standard for assessing the ability of the pulmonary circulation to vasodilate. At present, epoprostenol sodium is an investigational drug that has limited availability. In contrast, acetylcholine, also a pulmonary vasodilator, is readily available. Therefore, we assessed the feasibility of using acetylcholine as an alternative to prostacyclin in testing for the capacity of the pulmonary vasculature to vasodilate. Twenty-three patients with primary pulmonary hypertension (mean pulmonary arterial pressure, 58.5 +/- 13.4 mm Hg) received incremental infusions of prostacyclin and acetylcholine to predetermined maximal infusion rates as part of a battery of vasodilator agents administered according to standard protocols (mean, 5.4 +/- 1.2 agents/patient; range, 3-8 agents/patient); the administration of the different agents was timed to avoid synergistic effects. Of all the agents tested, prostacyclin and acetylcholine were most consistently effective in evoking acute pulmonary vasodilation, and both seemed to distinguish patients capable of manifesting acute pulmonary vasodilation from those who were not. However, at maximal doses set by protocol, prostacyclin generally elicited a greater vasodilator response than acetylcholine. The difference in magnitude of response may have been due to use of prescribed dosages of acetylcholine that were submaximal. In other respects, the two agents were similar; both were equally well-tolerated, and side effects were mild and resolved rapidly when the vasodilator infusions were stopped. We conclude that in the majority of patients with primary pulmonary hypertension, acetylcholine appears to be an effective and available substitute for prostacyclin in screening for pulmonary vasodilator responsiveness.

Prostacyclin and vascular function: implications for hypertension and atherosclerosis

Prostacyclin and endothelium-derived relaxing factor (or nitric oxide) are unstable mediators produced by the vascular endothelium, that are important for local regulation of platelet behavior and blood flow. This review focuses on the basic biochemistry and pharmacology of prostacyclin, its interactions with nitric oxide and nitrovasodilator drugs, and the implications of disturbances in this system for vascular disease, particularly hypertension and atherosclerosis. Prostacyclin and its stable analogs are also finding limited therapeutic applications in preservation of platelet function, pulmonary hypertension, and investigation into the cytoprotective and antiatherosclerotic properties is continuing.

Chronic cor pulmonale

Chronic cor pulmonale is defined as right heart hypertrophy and/or chronic right heart failure. There are many etiologies, but the common cause is increased right heart work from pulmonary hypertension. Etiology can be conveniently discussed by assuming two prototypes, the asphyxial or hypoxic type and the vascular obliterative type. A common cause of the asphyxial type is chronic obstructive pulmonary disease, and the obliterative type is represented by chronic pulmonary thromboembolic disease or primary pulmonary hypertension. Pathology is discussed, emphasizing the cardiac manifestations of chronic cor pulmonale including data of specific cardiac chamber size. An overview of hemodynamics is given, and the use and limitation of electrocardiography and chest x-rays are discussed. The exciting potential use of echocardiography for the serial non-invasive measurement of anatomical and pathophysiological features is outlined, along with the value of a careful physical examination and the proper utilization of laboratory tests in the diagnosis of chronic cor pulmonale. In the patient with the asphyxial type, the treatment of pulmonary infectious exacerbations, the role of corticosteroids, digoxin, diuretics, phlebotomy, bronchodilators (theophylline, beta adrenergic agonists, and anticholinergics), and long-term oxygen therapy is noted. The controversy surrounding the use of vasodilators and calcium blockers in these patients is discussed. Treatment aspects of the vascular obliterative type, including the role of vasodilators, calcium blockers, prostacyclin, anticoagulants, and overall strategy are discussed. A brief note is mentioned of the promising role of surgical therapy in chronic thromboembolic disease causing chronic cor pulmonale.

Prostacyclin I2 (PGI2) increases left ventricular ejection fraction (LVEF)

In order to evaluate the effect of PGI2 on left ventricular ejection fraction (LVEF) an intravenous infusion in 10 patients (3 males, 7 females; 36 to 63 years) with an impaired LVEF (34.7 +/- 14.8%) was performed. LVEF was determined by means of 99mTc-pertechnetate radionuclide ventriculography. An increase of LVEF to 36.2 +/- 13.5% during administration of PGI2 at a rate of 1 ng/kg/min for 15 min and to 43.8 +/- 15.8% during a rate of 5 ng/kg/min (p less than 0.01) for an additional 15 min was observed. Analyzing the data in more detail in 6 patients, an improvement in LVEF became obvious during the administration of 1 ng/kg/min (108, 109, 116, 118, 121, and 123% of pre-infusion value, respectively). In 5 out of these 6 patients a dose-increment to 5 ng/kg/min further increased LVEF (139, 179, 187, 148, and 128% of pre-infusion value, respectively). In contrast, in the other 4 patients no response of LVEF to PGI2 at a rate of 1 ng/kg/min could be observed. However, in 2 out of these 4 patients LVEF increased during the administration of 5 ng/kg/min (111 and 117% of pre-infusion value). Individual changes in hemodynamic parameters showed no correlation to the improvement seen in LVEF in response to PGI2. It is concluded that PGI2 may exert beneficial effects on LVEF, and might be used in certain clinical conditions, such as before heart transplantation, to achieve a temporary improvement in LVEF.

Prediction of favourable responses to long term vasodilator treatment of pulmonary hypertension by short term administration of epoprostenol (prostacyclin) or nifedipine

Eighteen patients with moderate to severe pulmonary hypertension were studied, nine with intracardiac shunts and nine without. The effects of an incremental infusion of epoprostenol (prostacyclin) (0.5-8 ng/kg per minute) or sublingual nifedipine (20-30 mg) were compared with the response to three months' treatment with oral nifedipine. Both epoprostenol and sublingual nifedipine caused a fall in pulmonary vascular resistance and pressure and a rise in cardiac output. Patients with intracardiac shunts had higher systemic blood flows than those without shunts. Exercise in the shunt group was accompanied by systemic desaturation and hyperventilation. Analysis of individual results showed that the size of the response was inversely related to the severity of the pulmonary vascular disease. A good long term response to nifedipine seemed to be as readily predicted by the resting control values for haemodynamic variables as by values after short term treatment. A favourable response was likely if the pretreatment mean pulmonary artery pressure was less than 50 mm Hg, the ratio of total pulmonary to systemic resistance was less than 0.7, or the ratio of mean pulmonary artery pressure to systemic artery pressure was less than 0.6. Short term vasodilator protocols may do harm. If such studies are carried out, an adequate dose range must be tried before the long term efficacy of an individual drug can be forecast.

Current approach to treatment of primary pulmonary hypertension

Based upon our experience with a cohort of 46 patients referred to the UCHSC from April, 1980 to April, 1987 for evaluation and treatment of PPH, we currently assess acute pulmonary vasoreactivity as defined by the patient's response to intravenous PGI2 during the initial diagnostic catheterization. A 3 to 5 day trial of high dose oral diltiazem treatment (720 mg/day maximum) is given while monitoring the patient in the clinical research center to detect significant side effects including arrhythmias, orthostatic systemic hypotension, arterial desaturation, and worsened right ventricular dysfunction. We believe it is necessary to recatheterize each patient to establish the efficacy of calcium antagonist treatment prior to discharge. Those patients who are responsive to diltiazem are discharged and followed in our pulmonary hypertension clinic. Since an occasional patient will deteriorate after several weeks of therapy, repeat right heart catheterization after 8 weeks of treatment is used to determine which patients should be continued on diltiazem for chronic therapy. Approximately 30 percent of our patients with PPH have been improved on diltiazem treatment. Most patients who have a good response to treatment after eight weeks continue to benefit from long-term treatment. It appears that the response to an acute infusion of PGI2 is useful in safely identifying those PPH patients who are likely to benefit from vasodilator therapy. Debilitated patients who are unresponsive to PGI2 and vasodilator therapy are considered potential candidates for cardiopulmonary transplantation.

Early partial systolic closure of the pulmonic valve relates to severity of pulmonary hypertension

Ultrasound studies in pulmonary hypertension often show systolic partial closure of the pulmonic valve and early peaking of Doppler pulmonary flow velocity, but these findings are poorly understood. Our initial observations of earlier systolic partial closure with higher pulmonary pressures suggested that this phenomenon might relate to pressure. In 30 patients with documented pulmonary hypertension, the timing of systolic partial closure and the corresponding decrease in Doppler flow velocity related inversely to pulmonary artery pressure at catheterization. Peak flow preceded the systolic velocity decrease and also related inversely to pressure. Since changing flow velocity might reflect a changing driving force across the valve, we examined simultaneous high-fidelity catheter pressure tracings from the right ventricle and pulmonary artery from 24 patients with and without pulmonary hypertension. In 30 studies, a positive right ventricular to pulmonary artery pressure gradient was present early in systole, but the gradient decreased to a minimum value in mid-to-late systole. The timing of this minimum also related inversely to pressure. We conjectured that forces opposing ejection occur earlier in pulmonary hypertension, thereby decreasing the forward driving force and allowing earlier partial systolic closure.

Prostaglandin E1 as a screening vasodilator in primary pulmonary hypertension

Pulmonary vasodilators are variably efficacious in primary pulmonary hypertension (PPH). None has consistently improved hemodynamics enough to obviate the need for complex and potentially hazardous testing of several vasodilators. Prostaglandin E1 (PGE1), a potent, short-acting pulmonary vasodilator, was administered to seven patients with PPH in order to determine whether PGE1 could accurately predict the hemodynamic and gas exchange effects of other commonly used vasodilators. Prostaglandin E1, nifedipine and hydralazine were administered to the patients while measuring pulmonary and systemic hemodynamics and arterial blood gases. Prostaglandin E1 was easily titrated but was inconsistent as a predictor of the effects of the other vasodilators with respect to pulmonary artery pressure, cardiac output and adverse effects on arterial oxygenation. This study suggests that patients with PPH must still receive carefully monitored trials of several vasodilators to determine whether there is a beneficial response and to select the appropriate treatment.

Prostaglandins in the pathogenesis and prevention of vascular disease

Metabolism of arachidonic acid gives rise to a number of products with potent, and sometimes opposing, biological actions. Prostacyclin, the main product of arachidonic acid in vascular tissue, is a vasodilator and inhibitor of platelet aggregation whereas thromboxane A2, produced by the platelet, is a vasoconstrictor and inducer of platelet aggregation. Generation of these products may be modified in certain diseases, such as atherosclerosis and diabetes, so that prostacyclin production is reduced and thromboxane A2 production increased, resulting in a pro-thrombotic condition. Synthesis of arachidonic acid metabolites may be manipulated using drugs such as aspirin or imidazole analogues which selectively inhibit different enzymes in the metabolic pathway. Such drugs have proved beneficial in the treatment of some vascular disorders. Clinical use of prostacyclin has shown it to be effective in the treatment of peripheral vascular disease, Raynaud's Syndrome and pulmonary hypertension. Stable analogues of prostacyclin are being developed which may lead to a separation of the vasodilator and anti-platelet actions of prostacyclin.