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Query: UMLS:C0034065 (pulmonary embolism)
 14,979 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Acute massive pulmonary embolism has a high mortality rate. Fatal haemodynamic deterioration is caused by an acute increase in pulmonary vascular resistance. Traditionally, the degree of mechanical obstruction of the pulmonary vasculature by the embolic thrombus is considered to be the major determinant of this increase in right ventricular afterload. However, there is evidence to suggest that another factor plays an important role, since there is a marked discrepancy between the haemodynamic manifestations of acute pulmonary embolism and the degree of mechanical obstruction. Historic studies indicate that this discrepancy is largely explained by pulmonary vasoconstriction caused by vasoactive mediators, released mainly by activated platelets. Thromboxane-A(2) and serotonin are probably the two most important pulmonary vasoconstrictors in this context. Antagonising their effects dramatically increases tolerance to experimental pulmonary embolism in animals. In humans, this concept should eventually find its way into clinical practice. In the future, acute massive pulmonary embolism could be treated with antagonists to pulmonary vasoconstrictors, or with direct pulmonary vasodilators.
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PMID:Pathophysiology and treatment of haemodynamic instability in acute pulmonary embolism: the pivotal role of pulmonary vasoconstriction. 1103 5

Acute pulmonary embolism with haemodynamic instability has a high mortality rate. Death results from an acute increase in right ventricular afterload, and the commonly held view is that mechanical obstruction of the pulmonary vascular bed is largely responsible for this increase. In accordance, recent treatment guidelines for severe pulmonary embolism focus exclusively on interventions aimed at relieving this mechanical obstruction, either by thrombolysis or (catheter) embolectomy. However, there is evidence to indicate that vasoconstriction is a very important contributor to the initial increase in pulmonary vascular resistance after pulmonary embolism. This is consistent with the observation that the degree of mechanical obstruction correlates at best poorly with haemodynamic manifestations. Thromboxane A(2) and serotonin are probably mainly responsible for pulmonary vasoconstriction. Cyclooxygenase inhibitors and serotonin antagonists have been shown in animal experiments to attenuate the haemodynamic response to acute pulmonary embolism and to reduce mortality. In addition, reports of a favourable response to pulmonary vasodilators in animals and in humans with acute severe pulmonary embolism have been published. In this paper, it is argued that we may need to reconsider our current therapeutic approach to patients with acute severe pulmonary embolism. Antagonising pulmonary vasoconstrictive mediators or administering pulmonary vasodilators may prove to be life-saving interventions in these patients.
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PMID:Contribution of pulmonary vasoconstriction to haemodynamic instability after acute pulmonary embolism. Implications for treatment? 1139 21

Thromboxane A2 (TXA2) is a key mediator of platelet aggregation and smooth muscle contraction. Its action is mediated by its G protein-coupled receptor of which two isoforms, termed TPalpha and TPbeta, occur in humans. TXA2 has been implicated in pathologies such as cardiovascular diseases, pulmonary embolism, atherosclerosis, and asthma. This study describes the pharmacological characterization of BM-613 [N-n-pentyl-N'-[2-(4'-methylphenylamino)-5-nitrobenzenesulfonyl]urea], a new combined TXA2 receptor antagonist and TXA2 synthase inhibitor. It exhibits a strong affinity for human platelet TP receptors (IC50 = 1.4 nM), TPalpha and TPbeta expressed in COS-7 cells (IC(50) = 2.1 and 3.1 nM, respectively), and TPs expressed in human coronary artery smooth muscle cells (IC50 = 29 microM). BM-613 shows a weak ability to prevent contraction of isolated rat aorta (ED50 = 1.52 microM) and guinea pig trachea (ED50 = 2.5 microM) induced by TXA2 agonist U-46619 (9.11-dideoxy-9.11-methanoepoxy-prostaglandin F2). Besides, BM-613 antagonizes TPalpha (IC50 = 0.11 microM) and TPbeta (IC50 = 0.17 microM) calcium mobilization induced by U-46619 and inhibits human platelet aggregation induced by U-46619 (ED50 = 0.278 microM), arachidonic acid (ED50 = 0.375 microM), and the second wave of ADP. BM-613 also dose dependently prevents TXA2 production by human platelets (IC50 = 0.15 microM). In a rat model of ferric chloride-induced thrombosis, BM-613 significantly reduces weight of formed thrombus by 79, 49, and 28% at 5, 2, and 1 mg/kg i.v., respectively. In conclusion, BM-613 is a dual and potent TP receptor antagonist and TXA2 synthase inhibitor characterized by a strong antiplatelet and antithrombotic potency. These results suggest that BM-613 could be a potential therapeutic drug for thrombotic disorders.
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PMID:In vitro and in vivo pharmacological characterization of BM-613 [N-n-pentyl-N'-[2-(4'-methylphenylamino)-5-nitrobenzenesulfonyl]urea], a novel dual thromboxane synthase inhibitor and thromboxane receptor antagonist. 1562 21