Influence of inhaled iloprost on transpulmonary gradient of big endothelin in patients with pulmonary hypertension

The association of eicosanoids and eicosanoid-related metabolites with pulmonary hypertension

BACKGROUND

Eicosanoids are bioactive lipids that regulate systemic inflammation and exert vasoactive effects. Specific eicosanoid metabolites have previously been associated with pulmonary hypertension (PH), yet their role remains incompletely understood.

METHODS

We studied 482 participants with chronic dyspnoea who underwent clinically indicated cardiopulmonary exercise testing (CPET) with invasive haemodynamic monitoring. We performed comprehensive profiling of 888 eicosanoids and eicosanoid-related metabolites using directed non-targeted mass spectrometry, and examined associations with PH (mean pulmonary arterial pressure (mPAP) >20 mmHg), PH subtypes and physiological correlates, including transpulmonary metabolite gradients.

RESULTS

Among 482 participants (mean±sd age 56±16 years, 62% women), 200 had rest PH. We found 48 eicosanoids and eicosanoid-related metabolites that were associated with PH. Specifically, prostaglandin (11β-dhk-PGF2α), linoleic acid (12,13-EpOME) and arachidonic acid derivatives (11,12-DiHETrE) were associated with higher odds of PH (false discovery rate q<0.05 for all). By contrast, epoxide (8(9)-EpETE), α-linolenic acid (13(S)-HOTrE(γ)) and lipokine derivatives (12,13-DiHOME) were associated with lower odds. Among PH-related eicosanoids, 14 showed differential transpulmonary metabolite gradients, with directionality suggesting that metabolites associated with lower odds of PH also displayed pulmonary artery uptake. In individuals with exercise PH, eicosanoid profiles were intermediate between no PH and rest PH, with six metabolites that differed between rest and exercise PH.

CONCLUSIONS

Our findings highlight the role of specific eicosanoids, including linoleic acid and epoxide derivatives, as potential regulators of inflammation in PH. Of note, physiological correlates, including transpulmonary metabolite gradients, may prioritise future studies focused on eicosanoid-related pathways as important contributors to PH pathogenesis.

A retrospective comparison of inhaled milrinone and iloprost in post-bypass pulmonary hypertension

During cardiac operations, weaning from cardiopulmonary bypass (CPB) may prove challenging as a result of superimposed acute right ventricular dysfunction in the setting of elevated pulmonary vascular resistance (PVR). The aim of this study was to retrospectively evaluate the effect of inhaled milrinone versus inhaled iloprost in patients with persistent pulmonary hypertension following discontinuation of CPB. Eighteen patients with elevated PVR post-bypass were administered inhaled milrinone at a cumulative dose of 50 μg kg^-1. These patients were retrospectively matched with 18 patients who were administered 20 μg of inhaled iloprost. Both drugs were administered through a disposable aerosol-generating jet nebulizer device and inhaled for a 15-min period. Hemodynamic measurements were performed before and after cessation of the inhalation period. Both inhaled milrinone and inhaled iloprost induced significant reductions in mean pulmonary artery pressure and PVR and significant increases in cardiac index in patients with post-CPB pulmonary hypertension. The favorable effect of both agents on the pulmonary vasculature was confirmed by echocardiographic measurements. Both agents were devoid of systemic side effects, since mean arterial pressure and systemic vascular resistance were not affected. A decrease in intrapulmonary shunt by inhalation of both agents was also demonstrated. Pulmonary vasodilatation attributed to iloprost seems to be of greater magnitude and of longer duration as compared to that of inhaled milrinone. Both substances proved to be selective pulmonary vasodilators. The greater magnitude and of longer duration vasodilatation attributed to iloprost may be due to its longer duration of action.

Clinical and prognostic value of endothelin-1 and big endothelin-1 expression in children with pulmonary hypertension

OBJECTIVE

Pulmonary arterial hypertension is known to be associated with increased expression of endothelin (ET)-1 and its precursor big ET-1. Therefore, we hypothesised that in children with pulmonary hypertension (PH) altered levels of ET-1 and big ET-1 may have clinical and prognostic impact.

METHODS

Sixty-six children with different forms of PH (mean age 10.4±9.7 years) were included. Blood samples were taken from the pulmonary artery and a systemic artery. Levels of ET-1/big ET-1 were measured via ELISA method and compared with clinical and haemodynamic data. To assess prognostic relevance, Kaplan-Meier survival analysis was conducted with definition of end point as the composite of mortality, lung transplantation, use of intravenous prostanoids and Potts shunt creation.

RESULTS

ET-1 levels ranged between 0.09 and 11.64 (mean 1.48±2.34) fmol/mL, and big ET-1 levels between 0.05 and 2.92 (mean 0.84±0.58) fmol/mL. No significant relationships were found between ET-1/big ET-1 levels and functional class as well as haemodynamic indices of PH severity. Mean follow-up after catheterisation was 63.2±44.1 months. While 31 of the 66 (47%) patients with PH reached a predefined end point, there was no significant relation between levels of ET-1/big ET-1 and patient outcome.

CONCLUSIONS

Although children with PH had alterations in ET-1/big ET-1 expression, which may reflect changes in net release or lung clearance, levels of ET-1/big ET-1 showed no correlation with clinical and haemodynamic parameters, and were not able to predict outcome.

Elevated pulmonary arterial and systemic plasma aldosterone levels associate with impaired cardiac reserve capacity during exercise in left ventricular systolic heart failure patients: A pilot study

BACKGROUND

Elevated levels of aldosterone are a modifiable contributor to clinical worsening in heart failure with reduced ejection fraction (HFrEF). Endothelin-1 (ET-1), which is increased in HFrEF, induces pulmonary endothelial aldosterone synthesis in vitro. However, whether transpulmonary aldosterone release occurs in humans or aldosterone relates to functional capacity in HFrEF is not known. Therefore, we aimed to characterize ET-1 and transpulmonary aldosterone levels in HFrEF and determine if aldosterone levels relate to peak volume of oxygen uptake (pVO2).

METHODS

Data from 42 consecutive HFrEF patients and 18 controls referred for invasive cardiopulmonary exercise testing were analyzed retrospectively.

RESULTS

Radial ET-1 levels (median [interquartile range]) were higher in HFrEF patients compared with controls (17.5 [11.5-31.4] vs 11.5 [4.4-19.0] pg/ml, p = 0.04). A significant ET-1 transpulmonary gradient (pulmonary arterial [PA] - radial arterial levels) was present in HFrEF (p < 0.001) but not in controls (p = 0.24). Compared with controls, aldosterone levels (median [interquartile range]) were increased in HFrEF patients in the PA (364 [250-489] vs 581 [400-914] ng/dl, p < 0.01) and radial compartments (366 [273-466] vs 702 [443-1223] ng/dl, p < 0.001). Akin to ET-1, a transpulmonary increase (median [interquartile range]) in aldosterone concentration was also observed between controls and HFrEF patients at rest (7.5 [-54 to 40] vs 61.6 [-13.6 to 165] ng/dl, p = 0.01) and peak exercise (-20.7 [-39.6 to 79.1] vs 25.8 [-29.2 to 109.3] ng/dl, p = 0.02). The adjusted pVO2 correlated inversely with aldosterone levels at peak activity in the PA (r = -0.31, p = 0.01) and radial artery (r = -0.32, p = 0.01).

CONCLUSIONS

These data provide preliminary evidence in support of increased transpulmonary aldosterone levels in HFrEF and suggest an inverse relationship between circulating aldosterone and pVO2. Future prospective studies are needed to characterize the functional effects of transpulmonary and circulating aldosterone on cardiac reserve capacity in HFrEF.

Efficacy of inhaled iloprost in cor pulmonale and severe pulmonary hypertension associated with tuberculous destroyed lung

Chronic obstructive pulmonary disease (COPD) is one of the causes of cor pulmonale. Cor pulmonale patients with pulmonary hypertension have a significant lower survival rate than patients without. However, there is no conclusive treatment options in cor pulmonale and pulmonary hypertension associated with COPD until now. We report a patient with cor pulmonale and pulmonary hypertension associated with severe form of COPD and tuberculous destroyed lung who achieved marked clinical, functional and echocardiographic hemodynamic improvements with inhaled iloprost for six months.

Inhaled iloprost to control pulmonary artery hypertension in patients undergoing mitral valve surgery: a prospective, randomized-controlled trial

BACKGROUND

Pulmonary hypertension (PHT) is common in patients undergoing mitral valve surgery and is an independent risk factor for the development of acute right ventricular (RV) failure. Inhaled iloprost was shown to improve RV function and decrease RV afterload in patients with primary PHT. However, no randomized-controlled trials on the intraoperative use of iloprost in cardiac surgical patients are available. We therefore compared the effects of inhaled iloprost vs. intravenous standard therapy in cardiac surgical patients with chronic PHT.

METHODS

Twenty patients with chronic PHT undergoing mitral valve repair were randomized to receive inhaled iloprost (25 microg) or intravenous nitroglycerine. Iloprost was administered during weaning from cardiopulmonary bypass (CPB). Systemic and pulmonary haemodynamics were assessed with pulmonary artery catheterization and transoesophageal echocardiography. Milrinone and/or inhaled nitric oxide were available as rescue medication in case of failure to wean from CPB.

RESULTS

Inhaled iloprost selectively decreased the pulmonary vascular resistance index after weaning from CPB (208 +/- 108 vs. 422 +/- 62 dyn.s/cm(5)/m(2), P<0.05), increased the RV-ejection fraction (29 +/- 3% vs. 22 +/- 5%, P<0.05), improved the stroke volume index (27 +/- 7 vs. 18 +/- 6 ml/m(2), P<0.05) and reduced the transpulmonary gradient (10 +/- 4 vs. 16 +/- 3 mmHg, P<0.05). In all patients receiving inhaled iloprost, weaning from CPB was successful during the first attempt. In contrast, three patients in the control group required re-institution of CPB and had to be weaned from CPB using rescue medication.

CONCLUSIONS

In patients with pre-existing PHT undergoing mitral valve surgery, inhaled iloprost is superior to intravenous nitrogylycerine by acting as a selective pulmonary vasodilator, reducing RV afterload and moderately improving RV-pump performance.

Intravenous tezosentan improves gas exchange and hemodynamics in acute lung injury secondary to meconium aspiration

OBJECTIVE

Meconium aspiration induces acute lung injury (ALI) and subsequent pulmonary arterial hypertension (PAH) which may lead to right ventricular failure. Increase of endothelin-1, thromboxane-A, and phosphodiesterases are discussed molecular mechanisms. We investigated the intrapulmonary and hemodynamic effects of the intravenous dual endothelin A and B receptor blocker tezosentan and inhalational iloprost in a model of ALI due to meconium aspiration.

DESIGN

Animal study.

SETTING

University-affiliated research laboratory.

SUBJECTS

White farm pigs.

INTERVENTIONS

Acute lung injury was induced in 24 pigs by instillation of meconium. Animals were randomly assigned to four groups to receive either intravenous tezosentan, inhalational iloprost, or combined tezosentan and iloprost, or to serve as controls.

MEASUREMENTS AND RESULTS

After meconium aspiration-induced lung injury each treatment increased oxyhemoglobin saturations (TEZO: 88 +/- 6% (p = 0.02), ILO: 85 +/- 13% (p = 0.05), TEZO-ILO: 89 +/- 6% (p = 0.02), control: 70 +/- 18%). TEZO but not ILO significantly decreased pulmonary arterial pressure and pulmonary vascular resistance (both p < 0.01). ILO alone decreased intrapulmonary shunt blood flow (p < 0.01). Compared with control, TEZO-ILO yielded the highest arterial partial pressure of oxygen (70 +/- 6 torr vs.49 +/- 9 torr, p = 0.04), although it decreased arterial blood pressure (change from 71 +/- 13 mmHg to 62 +/- 12 mmHg vs.85 +/- 14 mmHg to 80 +/- 11 mmHg (p = 0.01).

CONCLUSIONS

Intravenous TEZO improves pulmonary gas exchange and hemodynamics in experimental acute lung injury secondary to meconium aspiration. Inhaled ILO improves gas exchange only, thereby reducing intrapulmonary shunt blood flow. Combination of TEZO and ILO marginally improves pulmonary gas exchange at the disadvantage of pulmonary selectivity.

Effects of endothelin receptor antagonism on acute lung injury induced by chlorine gas

OBJECTIVE

To test the hypothesis that the endothelin system is involved in chlorine gas-induced lung injury.

DESIGN

Experimental study.

SETTING

Academic research laboratory.

SUBJECTS

Twenty-four domestic juvenile pigs.

INTERVENTIONS

Anesthetized, ventilated pigs were exposed to chlorine gas (400 parts per million in air) for 20 mins and then randomly allocated to four groups (n=6 in each group). The tezosentan pretreatment group received the dual endothelin receptor antagonist tezosentan 20 mins before and hyperoxic gas (Fio2 0.6) after chlorine gas exposure. The tezosentan postinjury treatment group received hyperoxic gas after chlorine gas exposure and tezosentan 60 mins later. Animals in the oxygen group received hyperoxic gas after chlorine gas exposure. Pigs in the fourth group (air) were ventilated with room air (Fio2 0.21) throughout the experiment.

MEASUREMENTS AND MAIN RESULTS

Hemodynamics, gas exchange, lung mechanics, and plasma endothelin-1 were evaluated for 6 hrs. Chlorine gas exposure induced an increase in circulating endothelin-1 by 90% (p<.05). The acute chlorine gas-induced rise in pulmonary vascular resistance was partly blocked by tezosentan pretreatment (p<.001). Tezosentan postinjury treatment also decreased pulmonary vascular resistance to levels significantly lower than in the air and oxygen groups (p<.001). Recovery of peak airway pressure was better in the tezosentan-treated groups than in the air group. There were significant linear relationships between circulating endothelin-1 and pulmonary vascular resistance (r=.47, p<.001) and endothelin-1 and peak airway pressure (r=.41, p<.001). These relationships were modified by tezosentan.

CONCLUSIONS

Tezosentan modified chlorine gas-induced pulmonary dysfunction, indicating that the endothelin system is involved in this mode of acute lung injury.

Inhalative Pre-Treatment of Donor Lungs Using the Aerosolized Prostacyclin Analog Iloprost Ameliorates Reperfusion Injury

BACKGROUND

Lung transplantation is effective for end-stage pulmonary disease, but its successful application is still limited by organ shortage and sub-optimal preservation techniques. Therefore, optimal allograft protection is essential to reduce organ dysfunction, especially in the early post-operative period. Intravenous prostanoids are routinely used to ameliorate reperfusion injury. However, the latest evidence suggests similar efficacy using inhaled prostacyclin. Thus, we evaluated the impact of donor pre-treatment using the prostacyclin analog, iloprost, on post-ischemic function of Perfadex-protected allografts.

METHODS

In Group 1, 5 pig lungs were preserved with Perfadex (PER group) solution and stored for 27 hours. In Group 2, 100 microg of iloprost was aerosolized over 30 minutes using a novel mobile ultrasonic nebulizer (Optineb) before identical organ harvest (PER-ILO group). After left lung transplantation and contralateral lung exclusion, hemodynamic variables, Po2/Fio2 and dynamic compliance were monitored for 6 hours and compared with sham-operated controls. Pulmonary edema was determined stereologically and by wet-to-dry (W/D) weight ratio. Statistical assessment included analysis of variance (ANOVA) with repeated measures.

RESULTS

Dynamic compliance and pulmonary vascular resistance (PVR) were superior in iloprost-treated compared with untreated organs (p < 0.05), whereas oxygenation was comparable between groups. W/D ratio revealed a significantly smaller amount of lung water in PER-ILO organs (p = 0.048), whereas stereologic data showed a trend toward less intra-alveolar edema.

CONCLUSIONS

Endobronchial application of iloprost in donor lungs before Perfadex preservation decreases post-ischemic edema and significantly improves lung compliance and vascular resistance. This innovative approach is easily applicable in the clinical setting and offers a new strategy for improvement of pulmonary allograft preservation.

Inhaled Iloprost in Pulmonary Arterial Hypertension

OBJECTIVE

To review the pharmacology, pharmacodynamics, and clinical trials evaluating inhaled iloprost in pulmonary arterial hypertension (PAH).

DATA SOURCES

A MEDLINE search (1996–February 2005) was performed using the key words pulmonary hypertension, iloprost, and epoprostenol. Information regarding Food and Drug Administration approval was obtained via the Internet.

STUDY SELECTION AND DATA EXTRACTION

All clinical trials using inhaled iloprost in PAH published in English were identified. Additionally, references from the identified articles were reviewed.

DATA SYNTHESIS

A stable analog of prostacyclin, inhaled iloprost is thought to promote benefit in PAH through vasodilation, antiproliferative effects, and inhibition of platelet aggregation. In a placebo-controlled trial of 203 patients, inhaled iloprost significantly improved the combined endpoint of change in New York Heart Association functional class and 10% improvement in 6-minute walk distance (p = 0.007). Small, short-term clinical trials demonstrated hemodynamic benefits for inhaled iloprost alone and in combination with other pulmonary vasodilating agents. The aerosolized delivery route and low incidence of adverse events are positive attributes for inhaled iloprost, while the frequency of administration and lack of comparative data limit its role in PAH.

CONCLUSIONS

Currently, inhaled iloprost offers potential benefit for patients with contraindications to bosentan, preference for non-parenteral products, ineligibility for parenteral therapy, or as adjunctive therapy with other pulmonary vasodilators. Larger, long-term clinical trials are needed to solidify the role for inhaled iloprost in the management of PAH.

Endothelin and pulmonary arterial hypertension

BACKGROUND AND OBJECTIVES

Pulmonary arterial hypertension (PHT) is a potentially fatal disease. The purpose of this article is to review the current knowledge of the role played by endothelin (ET) in PHT and the relevant drug regimens used in the treatment of this condition.

METHODS

A detailed search via MEDLINE (PubMed) was performed by using PHT and ET as the key terms.

RESULTS

PHT could be a primary or a secondary diagnosis associated with various heart and lung diseases. PHT appears during the late stage of systemic sclerosis and may complicate other systemic diseases such as systemic lupus erythematosus. The vascular endothelium and activation of various mediators and growth factors such as the ET system are thought to play a crucial role in the development of this condition. The pathologic process progresses very rapidly from vasoconstriction to widespread pulmonary vascular obstruction. The use of high doses of calcium channel blockers is of limited value. Life-long anticoagulant therapy is recommended for the treatment of PHT. Currently, the drug being used in PHT therapy is continuous central-venous prostacyclin infusion. Prostacyclin is a strong vasodilator with antiaggregate and antifibrotic properties and has the potential to reduce endothelial injury and to induce vasculature remodeling. This treatment results in improved functional status and increased life span. Unfortunately, its use is accompanied by various side effects, technical difficulties, and high cost. The role of other therapeutic modalities (inhaled prostacyclin, subcutaneous treprostinil, oral beraprost, sildenafil) in vascular remodeling, and the improvement in functional capacity and survival of patients with PHT, are currently under investigation. Bosentan, administered orally, is a recently developed active ET receptor antagonist. It is a promising new therapeutic tool in the treatment of PHT because of its potent vasodilator, antiproliferative, and vascular remodeling activity.

CONCLUSIONS

The revolutionary conceptual shift in understanding the pathogenesis of PHT from a vasoconstrictive process to a vasoproliferative one, has led to a modification in the treatment of this disease from the use of vasodilators to the use of drugs with antiproliferative and vascular remodeling activity. Until now, prostacyclin was the only drug of this type available for the treatment of PHT. ET blockade seems to be a reasonable and potential therapeutic option.

Inhaled iloprost: in primary pulmonary hypertension

Iloprost is a stable prostacyclin analogue with a pharmacokinetic profile allowing nebulised administration in patients with primary pulmonary hypertension (PPH). Inhaled iloprost is a potent acute pulmonary vasodilator with a duration of action of about 60 minutes. It may exert additional long-term benefit through antiproliferative and antithrombotic effects. Inhaled iloprost 2.5 or 5 microg six or nine times daily for 12 weeks (n = 101) significantly (p < 0.01) improved a combined clinical endpoint of a > or =10% increase in distance walked in 6 minutes and an improvement of > or =1 class in New York Heart Association functional class without clinical deterioration or death (16.8 versus 4.9% of placebo recipients, n = 102) in patients with severe PPH or selected forms of nonprimary pulmonary hypertension. Statistical analysis of the response for the PPH subgroup (20.8 versus 5.5% with placebo; n = 51 and 51) was not reported. Improvements from baseline in exercise capacity and haemodynamic/gas exchange variables have been reported in patients with PPH with continued use of inhaled iloprost. In addition, improvement in preinhalation vascular resistance occurred after 12 weeks of inhaled iloprost (p < 0.01 versus placebo) in a large randomised trial. Increased cough, headache, flushing and an influenza-like syndrome were the most common adverse events in the largest trial of patients receiving inhaled iloprost. Headache, flushing and jaw pain occurred significantly more frequently with inhaled iloprost than with placebo.

[Endothelin system and inhalation of iloprost in pulmonary hypertension]

The haemodynamics and vascular proliferation (remodelling) in pulmonary hypertension are unfavourably affected by a malfunction of the endothelial cells of the pulmonary vessels. A characteristic result is reduced formation of endothelial dilators and increased formation of vasoconstrictors. The favourable effects of a blockade of the endothelin (ET) system with receptor antagonists suggest that the increased formation and limited clearance of ET-1 reaches pathogenetic significance. The therapeutic effects of inhaled iloprost on right cardiac haemodynamics and clinical course, could in addition to the direct vasodilatory effect, also be considered to have a favourable influence on the ET system as a pathophysiologically effective mediator system.