波生坦对实验性高原性肺动脉高压的逆转作用

目的 研究波生坦对实验性高原性肺动脉高压大鼠的逆转作用。方法 雄性SD大鼠随机分为5组:正常组，低压低氧3周组，，低压低氧6周组，安慰剂组和波生坦组。除正常组外，其它组置于模拟海拔5 000 m高原的减压舱中，8 h/d，分别持续3周，6周。自4周起，安慰剂组和波生坦组大鼠在低压低氧前分别给予生理盐水或波生坦灌胃。测定各组大鼠的肺血流动力学变化、右心室肥厚指数、肺系数；光镜观察直径小于100 μm肺动脉管壁厚度百分比和40~60 μm肺动脉的肌化度；分别测定血浆和肺组织中内皮素-1（ET-1）、一氧化氮（NO）的含量，肺组织中一氧化氮合酶（NOS）活性。结果 波生坦显著降低了高原性PH大鼠的肺动脉压和右心室收缩压，逆转了肺动脉的重构。波生坦减少了肺组织中的ET-1的含量，增加肺组织中结构性NOS(cNOS)和总NOS的活力，升高了血浆和肺组织中NO的水平。结论 波生坦可逆转已形成的高原性肺动脉高压，其机制可能与降低肺组织中ET-1的含量、增加机体内cNOS和总NOS的活性、升高体内NO的水平有关。波生坦对高原性肺动脉高压有积极的治疗意义。     

Melatonin attenuates hypoxic pulmonary hypertension by inhibiting the inflammation and the proliferation of pulmonary arterial smooth muscle cells

Hypoxia‐induced inflammation and excessive proliferation of pulmonary artery smooth muscle cells (PASMCs) play important roles in the pathological process of hypoxic pulmonary hypertension (HPH). Melatonin possesses anti‐inflammatory and antiproliferative properties. However, the effect of melatonin on HPH remains unclear. In this study, adult Sprague–Dawley rats were exposed to intermittent chronic hypoxia for 4 wk to mimic a severe HPH condition. Hemodynamic and pulmonary pathomorphology data showed that chronic hypoxia significantly increased right ventricular systolic pressures (RVSP), weight of the right ventricle/left ventricle plus septum (RV/LV+S) ratio, and median width of pulmonary arterioles. Melatonin attenuated the elevation of RVSP, RV/LV+S, and mitigated the pulmonary vascular structure remodeling. Melatonin also suppressed the hypoxia‐induced high expression of proliferating cell nuclear antigen (PCNA), hypoxia‐inducible factor‐1α (HIF‐1α), and nuclear factor‐κB (NF‐κB). In vitro, melatonin concentration‐dependently inhibited the proliferation of PASMCs and the levels of phosphorylation of Akt and extracellular signal‐regulated kinases1/2 (ERK1/2) caused by hypoxia. These results suggested that melatonin might potentially prevent HPH via anti‐inflammatory and antiproliferative mechanisms.     

Intermedin modulates hypoxic pulmonary vascular remodeling by inhibiting pulmonary artery smooth muscle cell proliferation

BackgroundHypoxic pulmonary arterial hypertension (PAH) is a disabling disease with limited treatment options. Hypoxic pulmonary vascular remodeling is a major cause of hypoxic PAH. Pharmacological agents that can inhibit the remodeling process may have great therapeutic value.ObjectiveTo examine the effect of intermedin (IMD), a new calcitonin gene-related peptide family of peptide, on hypoxic pulmonary vascular remodeling.MethodsRats were exposed to normoxia or hypoxia (∼10% O₂), or exposed to hypoxia and treated with IMD, administered by an implanted mini-osmotic pump (6.5 μg/rat/day), for 4 weeks. The effects of IMD infusion on the development of hypoxic PAH and right ventricle (RV) hypertrophy, on pulmonary vascular remodeling, on pulmonary artery smooth muscle cell (PASMC) proliferation and apoptosis, and on the activations of l-arginine nitric oxide (NO) pathway and endoplasmic reticulum stress apoptotic pathway were examined.ResultsRats exposed to hypoxia developed PAH and RV hypertrophy. IMD treatment alleviated PAH and prevented RV hypertrophy. IMD inhibited hypoxic pulmonary vascular remodeling as indicated by reduced wall thickness and increased lumen diameter of pulmonary arterioles, and decreased muscularization of distal pulmonary vasculature in hypoxia-exposed rats. IMD treatment inhibited PASMC proliferation and promoted PASMC apoptosis. IMD treatment increased tissue level of constitutive NO synthase activity and tissue NO content in lungs, and enhanced l-arginine uptake into pulmonary vascular tissues. IMD treatment increased cellular levels of glucose-regulated protein (GRP) 78 and GRP94, two major markers of endoplasmic reticulum (ER) stress, and increased caspase-12 expression, the ER stress-specific caspase, in lungs and cultured PASMCs.ConclusionsThese results demonstrate that IMD treatment attenuates hypoxic pulmonary vascular remodeling, and thereby hypoxic PAH mainly by inhibiting PASMC proliferation. Promotion of PASMC apoptosis may also contribute to the inhibitory effect of IMD. Activations l-arginine–NO pathway and of ER stress-specific apoptosis pathway could be the mechanisms mediating the anti-proliferative and pro-apoptotic effects of IMD.     

吡那地尔防治大鼠低氧性肺动脉高压肺血管重建的实验研究

目的研究钾通道开放剂吡那地尔对低氧性肺动脉高压（ＨＰＨ）及其肺血管重建的影响。方法Ｗｉｓｔｅｒ大鼠４６只,随机分为３组：对照组１５只;低氧组１６只;治疗组（低氧＋吡那地尔）１５只。低氧组及治疗组建立低氧性肺动脉高压动物模型,治疗组于每天缺氧前腹腔注射吡那地尔３ｍｇ／ｋｇ。 ４周后测定各组平均肺动脉压（ｍＰＡＰ）、右心室（ＲＶ）／左心室＋室间隔（ＬＶ＋ Ｓ）比值和肺小动脉病理及其形态计量学。结果（１）低氧组ｍＰＡＰ、ＲＶ／（ＬＶ＋Ｓ）分别为（２８．４ ± ２．８）ｍｍＨｇ和（０．３０±０．０３）,明显高于对照组（１６．２±１．８）ｍｍ Ｈｇ和（０．２２±０．０３）（Ｐ＜０．０１）,管壁厚度与血管外径比值（ＭＴ％）、管壁面积与血管总面积比值（ＭＡ％）分别为（２５．７±２．６）％和（７５．３±５．６）％,亦明显高于对照组（１８．５±２．９）％和（５９．９±６．６）％（Ｐ＜０．０１）,管腔面积与血管总面积比值（ＶＡ％）为（２４．３±５．６）％,明显低于对照组（４０．７±８．１）％（Ｐ＜０．０１）。提示慢性缺氧导致大鼠发生明显肺动脉高压及右心室肥厚和肺小动脉管壁增厚、管腔狭窄等肺血管重建等改变。（２）治疗组ｍＰＡＰ、ＲＶ／     

慢性低氧对肺动脉高压大鼠肺血管ERK 1/2、p38MAPK表达的影响

目的：通过建立慢性低氧性肺动脉高压大鼠模型,研究慢性低氧对大鼠肺血管细胞外信号调节蛋白激酶(ERK1/2)、p38MAPK蛋白表达的影响。方法建立慢性常压低氧肺动脉高压大鼠模型,将雄性SD大鼠随机分为正常对照组、低氧1d、3d、7d、14d和21d组,应用免疫组织化学技术检测肺动脉高压形成过程中大鼠肺血管 ERK1/2、p38MAPK 蛋白表达水平。结果①RVSP 和 RV/(LV+S)比值较正常对照组明显增加(P<0.05),低氧后3 d、7 d、14 d和21 d后大鼠肺血管明显增厚;②ERK1/2、p38MAPK蛋白广泛分布于肺血管内皮细胞、平滑肌细胞和成纤维细胞中,且随着低氧时间的延长,ERK1/2、p38MAPK蛋白表达量增加。结论 ERK1/2、p38MAPK 蛋白表达量的上调可能参与了慢性低氧诱导的大鼠肺动脉高压肺血管重塑的发生、发展过程。     

Blocking inhibition of prothrombinase by tissue factor pathway inhibitor alpha: a procoagulant property of heparins

Unfractionated heparin (UFH) has procoagulant activity in antithrombin/heparin cofactor II (HCII)‐depleted plasma. UFH prevents tissue factor pathway inhibitor alpha (TFPIα) from inhibiting the procoagulant enzyme complex, prothrombinase, providing a possible mechanism for its procoagulant activity. The procoagulant potential of UFH and various low molecular weight heparins (LMWHs) were characterized for TFPIα dependence, using thrombin generation assays performed with antithrombin/HCII‐depleted plasma. UFH, the LMWHs enoxaparin and dalteparin, and the low anticoagulant LMWH 2‐O, 3‐O desulphated heparin (ODSH) all promoted thrombin generation, but fondaparinux did not, and this activity was blocked by a TFPIα antibody. UFH, enoxaparin, and dalteparin were anticoagulant in reactions containing 1–2% normal plasma. In prothrombinase activity assays, UFH, enoxaparin, dalteparin and ODSH blocked prothrombinase inhibition by TFPIα, while again fondaparinux did not. In both the plasma and purified assays, LMWHs displayed greater procoagulant potential than UFH, even when normalized to saccharide concentration. These biochemical data reveal that UFH and LMWHs, but not fondaparinux, block prothrombinase inhibition by TFPIα, thereby producing their paradoxical procoagulant activity observed in the absence of antithrombin/HCII. The findings may help to understand the complex pathophysiology and treatment of patients that are simultaneously bleeding and clotting, such as those with disseminated intravascular coagulation.     

Effects of the oral endothelin-receptor antagonist bosentan on echocardiographic and doppler measures in patients with pulmonary arterial hypertension

OBJECTIVES: The purpose of this study was to investigate the effects of bosentan (125 or 250 mg twice daily) on echocardiographic and Doppler variables in 85 patients with World Health Organization class III or IV pulmonary arterial hypertension (PAH). BACKGROUND: Bosentan, an orally active dual endothelin-receptor antagonist, improves symptoms, exercise capacity, and hemodynamics in patients with PAH. METHODS: Patients had primary pulmonary hypertension (84%) or PAH associated with connective tissue disease. Of these, 29 patients received placebo and 56 received bosentan (1:2 randomization). Six-minute walk tests and echocardiograms were performed at baseline and after 16 weeks of treatment. RESULTS: Baseline characteristics were similar in the placebo and bosentan groups, and echocardiographic and Doppler findings were consistent with marked abnormalities of right ventricular (RV) and left ventricular (LV) structure and function that were due to PAH. The treatment effect on 6-min walking distance was 37 m in favor of bosentan (p = 0.036). Treatment effects of bosentan compared with placebo on other parameters were as follows: Doppler-derived cardiac index = +0.4 l/min/m(2) (p = 0.007), LV early diastolic filling velocity = +10.5 cm/s (p = 0.003), LV end-diastolic area = +4.2 cm(2) (p = 0.003), LV systolic eccentricity index = -0.12 (p = 0.047), RV end-systolic area = -2.3 cm(2) (p = 0.057), RV:LV diastolic areas ratio = -0.64 (p = 0.007), Doppler RV index = -0.06 (p = 0.03), and percentage of patients with an improvement in pericardial effusion score = 17% (p = 0.05). CONCLUSIONS: Bosentan improves RV systolic function and LV early diastolic filling and leads to a decrease in RV dilation and an increase in LV size in patients with PAH.     

Comparison of effects on markers of blood cell activation of enoxaparin,dalteparin, and unfractionated heparin in patients with unstable angina pectoris or non-ST-segment elevation acute myocardial infarction (the ARMADA study)

The low-molecular-weight heparins (LMWHs) enoxaparin and dalteparin have shown superior and equivalent efficacy, respectively, over unfractionated heparin (UFH) in patients with unstable angina pectoris (UAP) or non-ST-segment elevation myocardial infarction (NSTEMI). This study aimed to identify markers of blood cell activation that are independent predictors of outcomes at 1 month and to compare the effects of enoxaparin, dalteparin, and UFH on any such markers. In this multicenter, prospective, open-label study, 141 patients with UAP or NSTEMI were randomized to treatment for 48 to 120 hours with enoxaparin (n = 46), dalteparin (n = 48), or UFH (n = 47). Blood samples were taken at the time of randomization and after > or =48 hours of treatment but before catheterization. Multivariate analysis identified increased plasma levels of von Willebrand factor (vWF) and decreased platelet levels of glycoprotein Ib/IX complexes as independent predictors of 1-month adverse outcome (a composite of death, myocardial infarction, and recurrent ischemia). vWF release was strongly related to and may have been released by inflammation as measured by C-reactive protein. Both LMWHs reduced the release of vWF in plasma (as well as C-reactive protein) compared with UFH. Enoxaparin had a more favorable effect on glycoprotein Ib/IX complexes than either dalteparin or UFH. The incidence of the composite clinical efficacy end point was: 13% (enoxaparin), 19% (dalteparin), and 28% (UFH). vWF and its receptor glycoprotein Ib/IX play a key role in acute coronary syndromes. vWF is linked to inflammation and, like glycoprotein Ib/IX, is affected more favorably by the LWMHs than by UFH.     

Differential regulation of thrombin activatable fibrinolytic inhibitor by low molecular weight heparins. Pharmacologic implications.

AIM: Thrombin activatable fibrinolytic inhibitor (TAFI) is activated via cleavage by thrombin thrombomodulin in complex, and can be regulated by anticoagulant drugs such as the heparins. Low molecular weight heparins (LMWHs) have different antithrombin/anti-Xa profiles and therefore vary in the degree to which they inhibit TAFI. The purpose of this study was to determine the differential regulation of TAFI by LMWHs. METHODS: Dalteparin, enoxaparin, tinzaparin, parnaparin and heparin were supplemented to normal human pooled plasma at different concentrations (0-2.5 U). A chromogenic based assay (Pentapharm Inc., Basil, Switzerland) was used to measure activatable TAFI in each set of samples. RESULTS: Heparin clearly had the highest degree of TAFI inhibition with an IC50 of 0.10 U, which correlates with its coagulation profile. Dalteparin, Tinzaparin, Parnaparin had similar IC50s, 0.6-0.8 U/ml respectively, while enoxaparin had a higher IC50 (>1.0 U/ml). These results strongly correlate with the anti-IIa inhibition of each agent but not with the anti-Xa. However, it is interesting to note that these drugs are administered according to anti-Xa units not anti-IIa. CONCLUSIONS: These results suggest that each LMWH may inhibit TAFI to a different extent that is not dependent on the anti-Xa potency. Indiscriminate inhibition of TAFI may cause bleeding, while suboptimal inhibition may result in thrombosis. Because of the compositional difference, heparin and LMWHs may produce differential inhibition of TAFI and therefore result in product dependent modulation of hemostatic process which may or may not be related to their antithrombin effects.     

Effect of penicillamine and tetramethyl pyrazine on the hypoxic pulmonary hypertension in rats

Penicillamine (P) and tetramethyl-pyrazine (T) were administered to treat experimentally hypoxic pulmonary hypertension in rats exposed to hypoxia of 380 torr for up to 21-days. The results of this study showed: Hypoxia increased RVP, the RV/LV + S ratio, the MT% and the MA%. P and T all prevented the hypoxia-induced increases in RVP, the RV/LV + S ratio, but the effect of T on the pulmonary artery remodeling induced by hypoxia was weaker than that of P. The MT% and the MA% were significantly lower in H/P group than in H group (P less than 0.01, P less than 0.05; respectively). Although the MT% was lower in H/T group than in hypoxia group (P less than 0.05), there was no statistical difference in the MA% between H/T group and H group (P greater than 0.05). The MT% and the MA% were significantly lower in H/PT group than in H group (P less than 0.01, P less than 0.01, respectively), and there was no statistical difference in MA% between H/PT group and N group (P greater than 0.05). It was concluded that P prevented primarily pulmonary artery remodeling induced by hypoxia and T inhibited mainly hypoxic pulmonary vasoconstriction response, so prevented partially hypoxic pulmonary hypertension and right ventricular hypertrophy.     

Dose-dependent release of endogenous tissue factor pathway inhibitor by different low molecular weight heparins.

Tissue factor pathway inhibitor (TFPI) is released to circulating blood after intravenous and subcutaneous injections of heparins, and may thus contribute to the antithrombotic effect of heparins. A previous study suggested different abilities of various low molecular weight heparins (LMWH) to release endogenous TFPI, but the dose-response relationship was not determined. In the present study, the dose-response relationship for escalating doses of two LMWHs, dalteparin and enoxaparin, on the release of endogenous TFPI was investigated. Six healthy male participants were given 50, 100 and 200 U/kg dalteparin and 0.5, 1.0 and 2.0 mg/kg enoxaparin as a single subcutaneous injection. The study was a randomized, cross-over design with a 1-week wash-out period between each injection. Peak free TFPI antigen and TFPI activity were detected after only 1 h, whereas anti-activated factor X (anti-FXa) and anti-activated factor II (anti-FIIa) activities were detected after 2-6 h. Putative therapeutic equivalent doses of dalteparin and enoxaparin gave similar release of endogenous TFPI, but dissimilar effects on anti-FXa and anti-FIIa activities.     

Function and interaction of the right and left ventricle in patients with mitral valve stenosis

In 17 patients with mitral stenosis functional class III (NYHA) and chronic pulmonary hypertension, volumes and function of the right (RV) and left ventricle (LV) were analysed. Biplane cineventriculography of the right and left ventricle was performed subsequently and repeated 3 min after application of 1.6 mg nitroglycerin (NTG), which was given sublingually to decrease pre- and afterload. Pulmonary artery (PAP) and wedge pressures (PCW) were measured continuously. RV ejection fraction (EF) was 62.8 +/- 7.2% before and did not change significantly after NTG. RV enddiastolic volume index (EDVI) and endsystolic volume index (ESVI) was 80.7 +/- 27.2 ml/m2 and 31.7 +/- 11.9 ml/m2, respectively, and did not change significantly after NTG. Volumes and function of the LV were normal (LVEDVI: 66.5 +/- 13.5 ml/m2, LVESVI: 23.0 +/- 7.1 ml/m2, LVEF: 62.4 +/- 9.5%). Systolic PAP decreased significantly from 43.4 +/- 11.1 mm Hg before to 37.8 +/- 9.1 mm Hg after NTG (p less than 0.025) as well as total pulmonary resistance from 243 +/- 51 to 209 +/- 50.8 dynes . sec . cm-5 (p less than 0.05). No significant correlation was found between function and volumes of both ventricles. In 4 patients, however, the decrease in LV ejection fraction was associated with a considerable increase of right ventricular enddiastolic volume. Thus, the right ventricle compensates moderate pulmonary hypertension completely maintaining normal right ventricular function. If, however, septal dysfunction occurs, right ventricular insufficiency will develop in a shorter period of time.     

Antithrombotics and anticoagulants in coronary syndromes and stroke

The low-molecular-weight heparins (LMWHs) have been proven superior to placebo in reducing the incidence of acute coronary ischemic syndromes. Comparative studies vs. unfractionated heparin have not demonstrated superiority in favor of the LMWH dalteparin. In the Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q-wave Coronary Events (ESSENCE) trial, enoxaparin was demonstrated to have a benefit over heparin. The results have contributed to a better understanding of the relative efficacy of LMWHs in acute coronary syndromes. A second trial with enoxaparin supported the conclusions of the ESSENCE trial. The antithrombotic effects of LMWHs have also been evaluated for the management of ischemic stroke with varied results. A trial assessing tinzaparin in acute ischemic stroke has completed enrollment, and its results may shed new light on the use of an LMWH for the management of stroke.     

Exercise physiology and pulmonary arterial hypertension

The lungs are the only organ that receives the entire cardiac output with every stroke. The pulmonary circulation is normally a high-flow, low-resistance, low-pressure system that carries blood into the pulmonary microcirculation. In pulmonary artery hypertension (PAH)vascular remodeling contributes to a sustained elevation of pulmonary vascular resistance (PVR) and pulmonary artery pressure (PAP) as a result of vascular remodeling characterized largely by vascular smooth muscle cell proliferation and medial hypertrophy, and endothelial cell proliferation resulting in lumen obliteration. The loss of pulmonary arterial compliance and development of elevated PVR puts an excessive burden on the right ventricle due to the increased workload necessary to overcome the downstream pressure, ultimately leading to right-sided heart failure. The functional status of the pulmonary circulation and the levels of PVR and PAP ultimately determine the outcome of patients with PAH. Study of the pressure–flow relationships in the pulmonary vascular bed will provide an improved appreciation of the pathophysiology of pulmonary hypertension.     

Can we differentiate the low-molecular-weight heparins?

The low-molecular-weight heparins (LMWHs) have a number of therapeutic advantages, relative to standard unfractionated heparin (UFH). They are readily bioavailable when injected subcutaneously and can be given in fixed doses, allowing for far simpler administration. Several LMWHs are now commercially available, each demonstrating different physical and chemical properties and different activities in animal models of anticoagulation or hemorrhage. In clinical comparisons with placebo in the treatment of unstable coronary artery disease (UCAD), the LMWHs dalteparin sodium and nadroparin calcium have demonstrated good anticoagulant efficacy. In comparisons with UFH, on the other hand, only enoxaparin has shown superior anticoagulant activity, as reported in the results of the Efficacy and Safety of Subcutaneous Enoxaparin in Non-Q-wave Coronary Events (ESSENCE) and Thrombolysis In Myocardial Infarction (TIMI) 11B trials. However, close scrutiny of the methodology of the clinical trials in UCAD reveals considerable differences in study designs, dosage regimens, duration of administration of active treatments, and the timing and definition of endpoints. Therefore, it would not be scientifically sound to compare results with the different LMWHs based on the current available studies. It is also not possible to draw any conclusions with regard to the relative efficacy of the different LMWHs, since there are no properly-sized comparative data between dalteparin sodium, enoxaparin sodium, and nadroparin calcium.     

Simvastatin attenuates smooth muscle neointimal proliferation and pulmonary hypertension in rats

Hypertensive pulmonary vascular disease is characterized by abnormal proliferation of vascular endothelial and smooth muscle cells, leading to occlusion of pulmonary arterioles, pulmonary hypertension, right ventricular failure, and death. Compounds with antiproliferative effects on vascular endothelial and smooth muscle cells, such as 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, may prevent the development of experimental hypertensive pulmonary vascular disease. Pneumonectomized rats injected with monocrotaline at 7 days develop severe hypertensive pulmonary vascular disease with neointimal formation. Rats were randomized to receive either vehicle or treatment with the HMG-CoA reductase inhibitor simvastatin (2 mg/kg per day). By Day 35, rats that received vehicle had higher mean pulmonary arterial pressures (53 +/- 2 mm Hg) and right ventricular hypertrophy (right ventricle/[left ventricle plus septum] [RV/LV+S] = 0.78 +/- 0.09) than rats in Group PMS5-35 that received simvastatin from Day 5 to 35 (mean pulmonary arterial pressure = 27 +/- 3 mm Hg, RV/LV+S = 0.34 +/- 0.08; p < or = 0.001). Pulmonary vascular remodeling with neointimal formation consisting of vascular smooth muscle cells was more severe in vehicle-treated rats (vascular occlusion score, 1.98 +/- 0.02) than in Group PMS5-35 (vascular occlusion score, 0.59 +/- 0.46; p < 0.001). In addition, lung endothelial nitric oxide synthase gene expression was decreased in vehicle-treated animals but was restored toward normal levels in simvastatin-treated animals. Simvastatin attenuates monocrotaline-induced pulmonary vascular remodeling with neointimal formation, pulmonary arterial hypertension, and right ventricular hypertrophy in rats.     

血管内皮生长因子和内皮素在低氧性肺血管重建中的作用

目的探讨血管内皮生长因子(VEGF)和内皮素(ET)-1在低氧性肺动脉高压(HPH)及其肺血管重建中的作用,并观察钾通道开放剂(pinacidil)对HPH的防治作用及对VEGF和ET-1的影响.方法Wister大鼠46只,随机分为3组,对照组15只,低氧组16只,治疗组15只.缺氧组和治疗组大鼠缺氧[氧浓度为(10.0±0.5)%]4周,每天缺氧8h,其中治疗组大鼠于每天缺氧前腹腔注射pinacidil3mg/kg.缺氧4周后测定各组大鼠血清VEGF和血浆ET-1水平、平均肺动脉压(mPAP)、右心室(RV)/[左心室(LV)+室间隔(S)]比值及肺小动脉病理及其形态计量学.结果(1)缺氧组大鼠血清VEGF[(118.73±55.40)ng/L]和血浆ET-1[(221.2±56.2)ng/L]水平明显高于对照组(P＜0.01);缺氧组较对照组mPAP升高,RV/(LV+S)比值增高,肺小动脉血管壁显著增厚,管腔明显狭窄.(2)治疗组大鼠血清VEGF[(78.20±16.45)ng/L]和血浆ET-1[(181.6±30.5)ng/L]水平明显低于缺氧组(P＜0.01);治疗组较缺氧组mPAP下降(P＜0.01),肺小动脉血管壁增厚、管腔狭窄等明显减轻,但治疗组上述各指标仍未完全恢复到对照组水平.结论VEGF和ET-1在HPH及其肺血管重建中发挥重要作用,钾通道开放剂对HPH及其肺血管重建具有一定的逆转作用.     

Prognostic value of the shock index along with transthoracic echocardiography in risk stratification of patients with acute pulmonary embolism

The initial clinical presentation and echocardiography have key roles in risk stratification of patients with acute pulmonary embolism (PE). To assess the value of shock index and echocardiographic abnormalities as predictors of in-hospital complications and mortality, echocardiographic features of 159 patients diagnosed with acute PE were reviewed. A shock index > or =1, independent of echocardiographic findings, was associated with increased in-hospital mortality. Regardless of shock index, moderate to severe right ventricular (RV) hypokinesis and a ratio of RV to left ventricular (LV) end-diastolic diameter >1 was significantly associated with in-hospital mortality and demonstrated the best predictive values for short-term outcomes. The sensitivity and negative predictive value of diastolic LV impairment (E/A wave <1), RV hypokinesis, RV/LV >1, and end-diastolic RV diameter >3 cm for in-hospital mortality were 100%. Systolic pulmonary artery pressure (PAP) was higher in patients who died before discharge. A cut-off point >50 mm Hg for systolic PAP was significantly associated with increased in-hospital death. In conclusion, among conventional echocardiographic abnormalities attributed to RV dysfunction (E/A wave <1, RV hypokinesis, RV/LV >1, RV end-diastolic diameter >3 cm, and interventricular septal flattening), moderate to severe RV hypokinesis and RV/LV >1 have better predictive values for short-term outcomes of patients with acute PE. In addition, a shock index > or =1 and systolic PAP >50 mm Hg could also be helpful in the triage of these patients.     

Comparative pharmacokinetics of LMWHs

A variety of pharmaceutical preparations of low-molecular-weight heparins (LMWHs) are available. They belong to the same family of compounds-ie, heparin derivatives with a narrow distribution of mean molecular weights (MWs). LMWHs have different methods of preparation, which result in variations in mean MW, distribution of MW, and pharmacokinetic (PK) and pharmacodynamic (PD) profiles. The mean MW of these compounds ranges from 3,600 to 6,500 daltons. The ratio of anti-Xa (aXa) and anti-IIa (aIIa) activities of the different LMWHs ranges from 1.5 to >10. After subcutaneous (SC) injection of a prophylactic or therapeutic dose, the peak values for plasma aXa or aIIa activity may vary twofold to threefold because of differences in bioavailability, plasma clearance (Clplasma), and half-life (t1/2). The injection of equivalent amounts of product, based on aXa and aIIa international units (IU), may result in different areas under the curve for the respective activities. Although tinzaparin has a high aIIa specific activity per milligram (and consequently, a low aXa/aIIa ratio), SC injection of 40 mg of enoxaparin (4,000 aXa IU) results in a higher aXa peak value in patients with total hip replacement than 4,500 aXa IU of tinzaparin. Differences in aIIa and aXa peak activities are more striking when high doses of LMWHs are used. The activated partial thromboplastin time (aPTT) can be significantly prolonged, an effect that is related to aIIa and aXa activity. The volume of distribution of LMWHs is of the same order of magnitude as that of the plasma volume. The mean retention time of aXa activity varies from 5.2 (dalteparin) to approximately 7 h (enoxaparin, nadroparin). Bioavailability of prophylactic doses of LMWHs ranges from 86% (dalteparin) to 98% (enoxaparin, nadroparin). PK parameters appear to be minimally affected by a patient's age. The Clplasma is different for each LMWH: 16 mL/min enoxaparin, 21 mL/min nadroparin, 33 mL/min dalteparin, 19 mL/min reviparin, and 22 mL/min tinzaparin. Accumulation of product has been observed for almost all LMWHs in patients with renal insufficiency. LMWHs are effective and safe for treatment or prophylaxis of venous thromboembolism during pregnancy, because they do not cross the placenta. No data are available regarding the passage of LMWHs into the milk in lactating women. Although LMWHs are also effective in prevention and treatment of thromboembolic disease in children, optimal use of these agents in pediatric patients has not been determined. In summary, the PD and PK of LMWHs have been well documented and have demonstrated that LMWHs have a more predictable response, a greater bioavailability, and a longer aXa t1/2 than unfractionated heparin. However, their distribution of MW affects their physicochemical and biological properties, as well as PK characteristics. The concept of aXa/aIIa ratio (determined in vitro) does not account for the differing PK of aXa and aIIIa activity in circulating blood.