Increase In Mean Pulmonary Arterial Pressure Research Articles

Losartan exerts no protective effects against acute pulmonary embolism-induced hemodynamic changes

The acute obstruction of pulmonary vessels by venous thrombi is a critical condition named acute pulmonary embolism (APE). During massive APE, severe pulmonary hypertension may lead to death secondary to right heart failure and circulatory shock. APE-induced pulmonary hypertension is aggravated by active pulmonary vasoconstriction. While blocking the effects of some vasoconstrictors exerts beneficial effects, no previous study has examined whether angiotensin II receptor blockers protect against the hemodynamic changes associated with APE. We examined the effects exerted by losartan on APE-induced hemodynamic changes. Hemodynamic evaluations were performed in non-embolized lambs treated with saline (n = 4) and in lambs that were embolized with silicon microspheres and treated with losartan (30 mg/kg followed by 1 mg/kg/h, n = 5) or saline (n = 7) infusions. The plasma and lung angiotensin-converting enzyme (ACE) activity were assessed using a fluorometric method. APE increased mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance index (PVRI) by 21 ± 2 mmHg and 375 ± 20 dyn s cm⁻⁵ m⁻², respectively (P < 0.05). Losartan decreased MPAP significantly (by approximately 15%), without significant changes in PVRI and tended to decrease cardiac index (P > 0.05). Lung and plasma ACE activity were similar in both embolized and non-embolized animals. Our findings show evidence of lack of activation of the renin-angiotensin system during APE. The lack of significant effects of losartan on the pulmonary vascular resistance suggests that losartan does not protect against the hemodynamic changes found during APE.

Biventricular systolic and diastolic function in a cohort of juvenile-onset systemic lupus erythematosus patients

Results 13 Juvenile-SLE female patients were included, with disease onset between 6 and 16 years of age (mean 11,8 years), and mean disease duration of 6,6 years (2-15 years). One patient had moderate to severe aortic regurgitation (AoR), one had pulmonary hypertension (HTP), 5 patients had systemic hypertension (HTA); none smoked. The majority of patients presented at least one criteria of LV diastolic dysfunction. E/A ratio was normal in 6 patients and showed restrictive pattern in 4. E/E` septal ratio showed increased left atrium pressure in 2 patients. E/Vp ratio was clearly abnormal in 3 cases, predicting high mean pulmonary capillary wedge pressure. Reduced propagation velocity of the mitral valve (Vp) was observed in 4 cases, implying impaired relaxation. LV systolic function was preserved in all cases, with normal Tei index. RV systolic function was normal in all patients except for one, with AoR (TDI S velocity 9,3 cm/s, tricuspid annular plane systolic excursion (TAPSE) 14,8 mm). RV diastolic function markers were altered in some patients: decreased peak velocity of E wave in 4 patients, with increased A’ wave velocity in 1 patient (HTP case). E/E’and E/A ratios were normal in all cases. RV outflow tract acceleration time was decreased (implying increased mean pulmonary artery pressure) in the patient with HTP. Due to the small sample size, no correlations with other clinical or laboratorial markers were statistically significant. BNP was increased only in the AoR patient.

Prolonged overcirculation-induced pulmonary arterial hypertension as a cause of right ventricular failure

Three-month chronic systemic-to-pulmonary shunting in growing piglets has been reported as an early pulmonary arterial hypertension (PAH) model with preserved right ventricular (RV) function. We sought to determine whether prolonged shunting might be associated with more severe PAH and RV failure. Fourteen growing piglets were randomized to a sham operation or the anastomosis of the left innominate artery to the pulmonary arterial trunk. Six months later, the shunt was closed and the animals underwent haemodynamic evaluation followed by tissue sampling for pathobiological assessment. Prolonged shunting had resulted in increased mean pulmonary artery pressure (22 ± 2 versus 17 ± 1 mmHg) and pulmonary arteriolar medial thickness, while cardiac output was decreased. However, RV-arterial coupling was markedly deteriorated, with a ~50% decrease in the ratio of end-systolic to pulmonary arterial elastances (Ees/Ea). Lung tissue expressions of endothelin-1, angiopoietin-1, and bone morphogenetic protein receptor-2 were similarly altered compared with previously observed after 3-month shunting. At the RV tissue level, pro-apoptotic ratio of Bax-to-Bcl-2 expressions and caspase-3 activation were increased, along with an increase in cardiomyocyte size, while expressions in voltage-gated potassium channels (Kv1.5 and Kv2.1) and angiogenic factors (angiopoietin-2 and vascular endothelial growth factor) were decreased. Right ventricular expressions of pro-inflammatory cytokines [interleukin (IL)-1α, IL-1β, tumour necrosis factor-α (TNF-α)] and natriuretic peptide precursors (NPPA and NPPB) were increased. There was an inverse correlation between RV Ees/Ea and pro-apoptotic Bax/Bcl-2 ratios. Prolonged left-to-right shunting in piglets does not further aggravate pulmonary vasculopathy, but is a cause of RV failure, which appears related to an activation of apoptosis and inflammation.

Hémodynamique de repos et d’effort dans l’hypertension artérielle pulmonaire

The normal mean pulmonary artery pressure (PAP) is 14 ± 3 mmHg. Precapillary pulmonary hypertension is defined as a mean PAP ≥ 25 mmHg at rest and a pulmonary capillary wedge pressure ≤ 15 mmHg as assessed by right heart catheterization. When performed in experienced centers, right heart catheter procedures in patients with pulmonary hypertension are associated with low morbidity and mortality rates. Right heart catheterization remains essential for the management of pulmonary arterial hypertension (PAH) as it confirms the diagnosis, determines the type of pulmonary hypertension, its severity, its vasoreactivity as well as response to therapeutic interventions. The hemodynamic severity largely influences patients' management including the choice of initial and subsequent therapies. Hemodynamic evaluation during exercise allows a precise characterization of the true resistive properties of pulmonary vessels through the assessment of the pressure-flow relationship. The significance of isolated pulmonary hypertension during exercise remains unknown. Indeed, roughly 50% of healthy subjects > 50 years old exhibit mean PAP > 30 mmHg during mild exercise. Isolated exercise-induced increases in mean PAP > 30 mmHg during exercise is thus no longer used to define pulmonary hypertension. More complex hemodynamic parameters allow partitioning of arterial and venous vascular resistance, as well as a better characterization of pulmonary artery compliance, right ventricle function and right ventriculo-arterial coupling. The clinical relevance of these subtle markers of pulmonary vascular abnormalities remains unknown.

The role of echocardiography in the diagnosis and management of patients with pulmonary hypertension

Pulmonary hypertension (PH) is defined as an increased mean pulmonary artery pressure (P(pa)) >25 mmHg at rest as assessed by right heart catheterisation (RHC). However, this technique is invasive and noninvasive alternatives are desirable for early diagnosis of PH. Although estimation of systolic pulmonary arterial pressure is easily obtained using Doppler echocardiography, cases of under- and over-estimations are not rare and direct measurement of P(pa) is not possible using this method. Therefore, echocardiography should be considered as a tool for assessment of the likelihood rather than the definite presence or absence of PH. Transthoracic echocardiography may be useful for noninvasive screening of patients at risk of PH. On the basis of an echocardiographic assessment, patients showing signs suggestive of PH can be referred for a confirmatory RHC. A number of variables measured during echocardiography reflect the morphological and functional consequences of PH and have prognostic value. The presence of pericardial effusion, reduced tricuspid annular plane excursion and right atrial enlargement are associated with a poorer prognosis. Echocardiography is also an important procedure for monitoring the response of patients to therapy, and is recommended 3-4 months after initiation of, or a change in, therapy. Echocardiographic assessment as part of a goal-oriented approach to therapy is essential for the effective management of PH patients.

Hemodynamic effects of inducible nitric oxide synthase inhibition combined with sildenafil during acute pulmonary embolism

While endogenous nitric oxide (NO) may be relevant to the beneficial hemodynamic effects produced by sildenafil during acute pulmonary embolism (APE), huge amounts of inducible NO synthase (iNOS)-derived NO may contribute to lung injury. We hypothesized that iNOS inhibition with S-methylisothiourea could attenuate APE-induced increases in oxidative stress and pulmonary hypertension and, therefore, could improve the beneficial hemodynamic and antioxidant effects produced by sildenafil during APE. Hemodynamic evaluations were performed in non-embolized dogs treated with saline ( n = 4), S-methylisothiourea (0.01 mg/kg followed by 0.5 mg/kg/h, n = 4), sildenafil (0.3 mg/kg, n = 4), or S-methylisothiourea followed by sildenafil ( n = 4), and in dogs that received the same drugs and were embolized with silicon microspheres ( n = 8 for each group). Plasma nitrite/nitrate (NOx) and thiobarbituric acid reactive substances (TBARS) concentrations were determined by Griess and a fluorometric assay, respectively. APE increased mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance index (PVRI) by 25 ± 1.7 mm Hg and by 941 ± 34 dyn s cm −5 m −2, respectively. S-methylisothiourea neither attenuated APE-induced pulmonary hypertension, nor enhanced the beneficial hemodynamic effects produced by sildenafil after APE (>50% reduction in pulmonary vascular resistance). While sildenafil produced no change in plasma NOx concentrations, S-methylisothiourea alone or combined with sildenafil blunted APE-induced increases in NOx concentrations. Both drugs, either alone or combined, produced antioxidant effects. In conclusion, although iNOS-derived NO may play a key role in APE-induced oxidative stress, our results suggest that the iNOS inhibitor S-methylisothiourea neither attenuates APE-induced pulmonary hypertension, nor enhances the beneficial hemodynamic effects produced by sildenafil.

Effects of electro-acupuncture on endothelium-derived endothelin-1 and endothelial nitric oxide synthase of rats with hypoxia-induced pulmonary hypertension

Pulmonary hypertension (PH) is characterized by elevated pulmonary artery pressure (PAP), pulmonary vascular remodeling and right ventricular hypertrophy, which are mainly due to endothelial dysfunction. Electro-acupuncture has shown beneficial effects on cardiovascular homeostasis, but little evidence has been obtained on pulmonary effects. The goal of the present study was to investigate whether electro-acupuncture on bladder-13 and -15 points can protect against chronic hypoxia-induced PH by regulating endothelium-derived endothelin (ET)-1 and endothelial nitric oxide synthase (eNOS). Male Wistar rats were exposed to hypoxia to induce PH. Hemodynamic analysis revealed that mean PAP was similar under normoxic conditions. Chronic hypoxia increased mean PAP to 37 +/- 3 mmHg, and electro-acupuncture attenuated it to 29 +/- 3 mmHg. Absolute right ventricular weight was ameliorated by electro-acupuncture from 0.288 +/- 0.048 g to 0.228 +/- 0.029 g under hypoxic conditions. Hypoxia-induced right ventricular hypertrophy index decreased from 0.477 +/- 0.069 to 0.378 +/- 0.053 with electro-acupuncture treatment. Histological examination revealed that hypoxic rats showed increased medial pulmonary artery wall thickness as well as muscularization. However, these alternations by chronic hypoxia were attenuated by electro-acupuncture. There was no difference in eNOS or ET-1 between groups under normoxic conditions. Electro-acupuncture treatment significantly improved the circulating eNOS concentration (365.36 +/- 31.51 pg/mL) compared with only hypoxia exposure (247.60 +/- 30.64 pg/mL). In lung homogenate, levels of eNOS under hypoxia increased from 684.96 +/- 117.90 to 869.86 +/- 197.61 pg/mg by electro-acupuncture treatment. Levels of ET-1 changed oppositely to eNOS in response to electro-acupuncture (ET-1 in plasma, 29.44 +/- 2.09 versus 20.70 +/- 2.37 pg/mL; ET-1 in lung homogenate, 120.51 +/- 3.03 versus 110.60 +/- 4.04 pg/mg). In conclusion, these results indicated that treatment with electro-acupuncture can protect against hypoxia-induced PH, possibly by regulating the balance of endothelium-derived vasoconstrictors and vasodilators.

Inhalational Therapy for Pulmonary Arterial Hypertension: Current Status and Future Prospects

This review summarizes the pathophysiology and current therapeutic and drug delivery strategies for pulmonary arterial hypertension (PAH), a rare but devastating disorder of the pulmonary circulation affecting 50,000 to 100,000 persons in the United States. Chief clinical features of PAH include increased mean pulmonary arterial pressure (>25 mm Hg) and right ventricular and smooth muscle hypertrophy. A wide variety of agents have been studied for use as anti-PAH drugs, including prostacyclin analogues, endothelin receptor antagonists, and phosphodiesterase-5 inhibitors, to name a few. However, a major shortcoming of anti-PAH medications is their short half-lives, requiring them to be administered via parenteral routes, which lead to undesirable side effects, including systemic vasodilation. Inhalational delivery of anti-PAH drugs provides an attractive alternative to conventional routes, with ease of administration and minimal systemic vasodilation. Recently, the U.S. Food and Drug Administration approved inhalable iloprost (Ventavis®), a prostacyclin analogue, for PAH treatment. Other drugs being studied for their potential in inhalable PAH therapy include PGE1, treprostinil, vasoactive intestinal peptide, and fasudil. Controlled-release inhalable delivery systems for anti-PAH medications have also been proposed to facilitate long-term and selective vasodilation of pulmonary arteries. Extensive studies are warranted to develop safe and effective drug delivery systems that will provide a better quality of life to patients.

Near-fatal haemorrhage from pulmonary arteriovenous malformation in HHT with increased cardiac output

To the Editor: We read with interest the report by Montani et al. [1] of fatal rupture of pulmonary arteriovenous malformation (AVM) in a patient with hereditary haemorrhagic telangiectasis (HHT) and severe pulmonary arterial hypertension (PAH) confirmed by right heart catheterisation. The authors hypothesised that bleeding from pulmonary AVM may have been facilitated by increased mean pulmonary artery pressure ( P pa). Here, we report a patient with near-fatal haemorrhage from pulmonary AVM, probably facilitated by increased cardiac output, but without severe PAH. A 35-yr-old female nonsmoker, with a history of obesity and fenfluramide use 10 yrs previously for 2 months, was admitted for exertional dyspnoea during pregnancy. Arterial blood gases showed arterial oxygen tension ( P a,O2) of 8.2 kPa, and arterial carbon dioxide tension of 3.5 kPa, with markedly increased alveolar–arterial oxygen tension difference on 100% oxygen (74 kPa, normally <18.6 kPa). Chest radiograph revealed numerous pulmonary AVMs. Transthoracic contrast echocardiography showed estimated systolic P pa of 47 mmHg with moderate dilatation of the right heart cavities, and extracardiac right-to-left shunting. She had recurrent epistaxis since childhood, numerous characteristic telangiectasiae, and possible familial HHT in her paternal grandmother. HHT was diagnosed according to the Curacao criteria [2]. One deletion was found in exon 9 of the ENG gene, and analysis of the ACVRL1 gene was normal. Long-term oxygen therapy was initiated. Emergency caesarean delivery was performed at 25 weeks of gestation because of …

A porcine model of massive, totally occlusive, pulmonary embolism

Background A reliable, animal model of massive, totally occlusive, pulmonary embolism (PE) is lacking. Objectives To design an animal model of totally occlusive PE and to challenge the model by a plasminogen activator. Methods In eight anaesthetized pigs (~ 90 kg) a massive preformed autologous thrombus was injected into the caval vein. One animal was autopsied to assess the extent of injected clot, whereas in the other animals extracorporeal life support (ECLS) was initiated and continued for three hours. These animals received 100 mg rt-PA. Blood gases, coagulation tests, creatine kinase (CK), lactate dehydrogenase (LDH), end-tidal CO2, systemic and pulmonary artery blood pressures and flow were registered. Results All animals went into circulatory arrest within 2 minutes after injection of the thrombus. In the animal where ECLS was not started, autopsy relieved a totally occlusive embolus of the pulmonary artery. The ECLS maintained a systemic blood flow of 6-8 L/min with adequate oxygenation and CO2-removal. However, lactate increased and base-excess became negative. Ddimer increased, fibrinogen decreased, and CK and LDH increased. All seven animals were weaned from ECLS. Despite the rt-PA treatment, the animals had at that time low end tidal CO2/PaCO2 ratio and increased mean pulmonary arterial pressure, suggesting a significant amount of embolic material remaining in the pulmonary artery. Conclusion This model of massive, totally occlusive, pulmonary embolism mimics well fatal PE seen in the clinic, and has the potential for use in testing of new therapeutic interventions.

Pulmonary arterial hypertension

Pulmonary arterial hypertension is a progressive disease of pulmonary vasculature characterized by increased mean pulmonary arterial pressure and elevated vascular resistance with normal left-sided pressures, differentiating it from left-sided heart disease. The pathogenesis involves thrombosis, vasoconstriction, and remodeling of small pulmonary arteries. It presents with common symptoms such as shortness of breath, chest pain, and decreased exercise tolerance. Left untreated, progressive increase in right ventricular overload leads to right heart failure and death. Over the course of the past decade, better understanding of the pathogenesis and an increasing number of treatment options have resulted in improved prognosis and quality of life.

Nitrite or sildenafil, but not BAY 41-2272, blunt acute pulmonary embolism-induced increases in circulating matrix metalloproteinase-9 and oxidative stress

Introduction Inhibition of matrix metalloproteinases (MMPs) improves the hemodynamics during acute pulmonary embolism (APE) and oxidative stress upregulates MMPs. We compared the effects of different NO-cGMP pathway activators on APE-induced increases in MMPs. Materials and Methods Hemodynamic and biochemical evaluations were performed in non-embolized dogs treated with saline (N = 5), and in microspheres embolized dogs receiving saline (n = 9), or nitrite (6.75 µmol/kg i.v. over 15 min followed by 0.28 µmol/kg/min; n = 5), or sildenafil (0.25 mg/kg; n = 5), or BAY 41-2272 (0.03, 0.1, 0.3, and 1 mg/kg/h; n = 5). Plasma thiobarbituric acid reactive substances (TBARS) concentrations were determined. Zymograms of plasma samples were performed, and in vitro antioxidant effects or inhibition of MMPs by these drugs were examined. Results APE increased mean pulmonary artery pressure by ~ 25 mmHg. Nitrite, BAY 41-2272, or sildenafil reversed this increase by ~ 40% (P < 0.05). Similar effects were seen on the pulmonary vascular resistance. While both nitrite and sildenafil produced no systemic effects, the highest dose of BAY 41-2272 produced systemic hypotension (P < 0.05). While nitrite and sildenafil blunted the increases in plasma pro-MMP-9 levels and TBARS (all P < 0.05), BAY 41-2272 produced no such effects. Nitrite and sildenafil produced in vitro antioxidant effects and inhibited MMPs only at high concentrations. BAY 41-2272 produced no such effects. Conclusions Activation of the NO-cGMP pathway with nitrite or sildenafil, but not with BAY 41-2272, attenuates APE-induced oxidative stress and increased MMP-9 levels. These findings are consistent with the idea that NO-cGMP pathway activators with antioxidant effects prevent the release of MMP-9 during APE.

Hypoxia-induced mitogenic factor (HIMF/FIZZ1/RELMα) induces the vascular and hemodynamic changes of pulmonary hypertension

Pulmonary hypertension (PH) is a serious disease of multiple etiologies mediated by hypoxia, immune stimuli, and elevated pulmonary pressure that leads to vascular thickening and eventual right heart failure. In a chronic hypoxia model of PH, we previously reported the induction of a novel pleiotropic cytokine, hypoxia-induced mitogenic factor (HIMF), that exhibits mitogenic, vasculogenic, contractile, and chemokine properties during PH-associated vascular remodeling. To examine the role of HIMF in hypoxia-induced vascular remodeling, we performed in vivo knockdown of HIMF using short hairpin RNA directed at rat HIMF in the chronic hypoxia model of PH. Knockdown of HIMF partially blocked increases in mean pulmonary artery pressure, pulmonary vascular resistance, right heart hypertrophy, and vascular remodeling caused by chronic hypoxia. To demonstrate a direct role for HIMF in the mechanism of PH development, we performed HIMF-gene transfer into the lungs of rats using a HIMF-expressing adeno-associated virus (AAV). AAV-HIMF alone caused development of PH similar to that of chronic hypoxia with increased mean pulmonary artery pressure and pulmonary vascular resistance, right heart hypertrophy, and neomuscularization and thickening of small pulmonary arterioles. The findings suggest that HIMF represents a critical cytokine-like growth factor in the development of PH.

SIMVASTATIN RESTORES DOWN-REGULATED GATA-6 EXPRESSION IN PULMONARY HYPERTENSIVE RATS

Vascular smooth muscle cell proliferation has been known to be predominant in vascular remodeling of pulmonary hypertensive. The GATA family proteins, a group of zinc finger transcription factors, play an important role during cell proliferation. The aim of present study was to investigate the expression of GATA-6 gene in experimental pulmonary hypertensive rats and explore the effect of regulation of GATA-6 expression by simvastatin on pulmonary vascular remodeling. The male Sprague-Dawley rats model was established with receiving pneumonectomy and monocrotaline (MCT) administration. Right pulmonary artery remodeling in these animals was compared with untreated rats or rats receiving simvastatin. The level of GATA-6 mRNA and protein expression was detected by reverse transcriptase–polymerase chain reaction (RT-PCR) and Western blotting, respectively. Pneumonectomized, MCT-treated rats had significantly increased mean pulmonary arterial pressure (mPAP), RV/(LV + S) ratio (ratio of the right ventricular to left ventricular and septum weights), vascular occlusion scores (VOSs), and percent media wall thickness on day 35, all the indices were significantly decreased after simvastatin administration in these rats. The level of GATA-6 mRNA and protein were markedly decreased in these pneumonectomy and MCT-treated rats, and they were significantly up-regulated in these rats after receiving simvastatin. These results indicate that the development and progression of pulmonary hypertension is prevented by simvastatin by up-regulating GATA-6 expression in the lung tissue.

Decreases in myocardial glucose and increases in pyruvate but not ischaemia are observed during porcine endotoxaemia

Myocardial dysfunction occurs commonly in septic shock. It is not known whether this is due to local ischaemia and metabolic disturbances. Our hypothesis was that endotoxaemic myocardial dysfunction may be associated with interstitial ischaemic and metabolic changes, measured using interstitial microdialysis (MD). Eighteen pigs were randomized to control (n=6) or endotoxin infusion (n=12). MD catheters were inserted into the myocardium for measurement of interstitial glucose, pyruvate and lactate concentrations. Plasma glucose and lactate concentrations and systemic haemodynamic parameters were measured simultaneously. Compared with the control group, the endotoxaemic animals had significantly decreased left ventricular stroke work and venous oxygen saturation (SvO2), and increased mean pulmonary artery pressure and plasma lactate. In the endotoxaemic group, decreases in interstitial glucose were observed, occurring simultaneously with increases in interstitial pruvate. Interstitial lactate: pyruvate ratios decreased with time in all animals. Despite severe systemic and pulmonary haemodynamic changes, interstitial MD measurements revealed no evidence of anaerobic metabolism in the myocardium of endotoxaemic pigs. There were, however, changes in glucose and pyruvate concentrations, suggesting local energy metabolic disturbances.

68: Secondary Pulmonary Hypertension Is a Risk Factor for Primary Graft Dysfunction Following Lung Transplantation for Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and often fatal interstitial lung disease that is often associated with elevation in pulmonary artery pressures. Although pulmonary arterial hypertension has been associated with primary graft dysfunction (PGD), the role of secondary pulmonary hypertension in PGD risk is incompletely understood. The purpose of this study was to evaluate whether increased mean pulmonary artery pressure (mPAP) is a clinical risk factor for the development of severe PGD in patients with IPF.

The reperfusion syndrome: Have we made any progress?

in 1987. They described a syndrome ofsevere cardiovascular dysfunction, bradyarrhythmia,decreased mean arterial pressure, and systemic vascu-lar resistance, along with an increased mean pulmo-nary artery pressure, pulmonary capillary wedge pres-sure, and central venous pressure. The etiology of thissyndrome had been attributed to acute acidosis, hyper-kalemia, and hypothermia, and the authors also con-cluded that vasoactive substances released from theliver graft may be involved.

Inhalation of the ETAreceptor antagonist LU-135252 selectively attenuates hypoxic pulmonary vasoconstriction

Endogenous endothelin (ET)-1 modulates hypoxic pulmonary vasoconstriction (HPV). Accordingly, intravenously applied ET(A) receptor antagonists reduce HPV, but this is accompanied by systemic vasodilation. We hypothesized that inhalation of an ET(A) receptor antagonist might act selectively on the pulmonary vasculature and investigated the effects of aerosolized LU-135252 in an experimental model of HPV. Sixteen piglets (weight: 25 +/- 1 kg) were anesthetized and mechanically ventilated at an inspiratory oxygen fraction (Fi(O(2))) of 0.3. After 1 h of hypoxia at Fi(O(2)) 0.15, animals were randomly assigned either to receive aerosolized LU-135252 as bolus (0.3 mg/kg for 20 min; n = 8, LU group), or to receive aerosolized saline (n = 8, controls). In all animals, hypoxia significantly increased mean pulmonary arterial pressure (32 +/- 1 vs. 23 +/- 1 mmHg; P < 0.01; means +/- SE) and increased arterial plasma ET-1 (0.52 +/- 0.04 vs. 0.37 +/- 0.05 fmol/ml; P < 0.01) compared with mild hyperoxia at Fi(O(2)) 0.3. Inhalation of LU-135252 induced a significant and sustained decrease in mean pulmonary arterial pressure compared with controls (LU group: 27 +/- 1 mmHg; controls: 32 +/- 1 mmHg; values at 4 h of hypoxia; P < 0.01). In parallel, mean systemic arterial pressure and cardiac output remained stable and were not significantly different from control values. Consequently, in our experimental model of HPV, the inhaled ET(A) receptor antagonist LU-135252 induced selective pulmonary vasodilation without adverse systemic hemodynamic effects.

Exogenous adrenomedullin prevents and reverses hypodynamic circulation and pulmonary hypertension in ovine endotoxaemia

Hypodynamic septic shock is associated with a poor prognosis. The present randomized-controlled laboratory experiment was designed to test the hypothesis that the vasodilatory peptide hormone adrenomedullin (ADM) is a useful agent to prevent and reverse the development of hypodynamic circulation in ovine endotoxaemia. Twenty-four healthy ewes were chronically instrumented for haemodynamic monitoring and randomly allocated to either the control, treatment, or prophylaxis group (n = 8 each). After a baseline (BL) measurement in the healthy state, all sheep were subjected to a continuous endotoxin infusion started at 10 ng kg(-1) min(-1) and doubled every hour six times. After 4 h of endotoxin challenge, the treatment group received ADM (50 ng kg(-1) min(-1)) for the remaining 3 h of the experiment. The prophylaxis group received a simultaneous infusion of endotoxin and ADM (50 ng kg(-1) min(-1)) from the beginning to the end of the 7 h intervention period. In the control and treatment groups, the ewes exhibited a hypodynamic circulation at 4 h (>20% reduction in cardiac index, both P < 0.01 vs BL). Endotoxin also increased mean pulmonary arterial pressure (MPAP) and arterial lactate concentrations. Prophylactic infusion of ADM prevented the occurrence of pulmonary hypertension and hypodynamic circulation and thereby blunted the increase in arterial lactate concentrations. In the treatment group, ADM administration increased CI (P < 0.001) and reduced both MPAP (P = 0.023) and arterial lactate concentrations (P < 0.001 each at 7 h) when compared with the control group. This study demonstrates that exogenous ADM prevents and reverses hypodynamic circulation, attenuates pulmonary hypertension, and limits lactic acidosis in ovine endotoxaemia.

Effects of erythropoietin on advanced pulmonary vascular remodelling

Erythropoietin (EPO) mobilises endothelial progenitor cells and promotes neovascularisation in heart failure. The present authors studied the effects of EPO on pulmonary vascular and cardiac remodelling in a model for flow-associated pulmonary arterial hypertension (PAH). PAH was induced in adult male Wistar rats by the injection of monocrotaline combined with an abdominal aortocaval shunt 1 week later (PAH or experimental group). Immediately afterwards, rats were randomised into those who received treatment with EPO (PAH+EPO group) and controls. Pulmonary and systemic haemodynamics, and right ventricular and pulmonary vascular remodelling were evaluated 3 weeks later. Vascular occlusion of the intra-acinar pulmonary vessels (13.4+/-0.7 versus 16.7+/-1.3% in PAH+EPO and PAH, respectively) and medial wall thickness of the pre-acinar arteries (wall-to-lumen ratio 0.13+/-0.01 versus 0.17+/-0.01 in PAH+EPO and PAH, respectively) decreased after treatment with EPO. Moreover, right ventricular capillary density was increased by therapy (2,322+/-61 versus 2,100+/-63 capillaries x mm(-2) in PAH+EPO and PAH, respectively). Increased mean pulmonary arterial pressure and decreased right ventricular contractility in the model were not altered by EPO treatment. In this rat model of flow-associated pulmonary arterial hypertension, erythropoietin treatment beneficially affected pulmonary vascular and cardiac remodelling. These histopathological effects were not accompanied by significantly improved haemodynamics.