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Query: UMLS:C0020538 (hypertension)
 170,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In this study we examined whether the reduced fibrinolysis and increased platelet activity that are known to occur in hypertension are already present in borderline hypertension. Twelve patients with 'borderline' hypertension (diastolic blood pressure 90-95 mmHg) were found to have substantially reduced fibrinolytic activity, both at rest and during exercise, compared with 12 normotensive controls. Euglobulin clot lysis time (ECLT) was significantly higher in hypertensive subjects (218 min vs. 145 min; P < 0.05), and this difference persisted during exercise. Resting tissue plasminogen activator activity (t-PA) did not differ in the two groups, but the brisk increase in t-PA in controls during exercise (0.64 rising to 1.44 IU mL-1; P < 0.01) did not occur to the same extent in the borderline hypertensive subjects. Levels of the fast-acting t-PA inhibitor, normally referred to as PAI-1, were considerably higher in hypertensives (9.22 vs. 4.41 IU mL-1; P < 0.02), and this difference persisted in the upright posture, indicating a decrease in fibrinolytic activity. Platelet aggregability induced by ADP in vitro was not significantly higher in the hypertensive subjects, but indices of platelet activity in vivo (B-TG and PF-4 levels) revealed enhanced platelet function in the hypertensives. These results indicate that the indicators of altered haemostatic function known to occur in hypertension, namely diminished fibrinolytic activity and increased platelet function, are already detectable during the very earliest stage of the disease.
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PMID:Platelet function and fibrinolytic activity during rest and exercise in borderline hypertensive patients. 760 Dec 2

Platelet function and fibrinolytic activity was studied during rest and after ergometric exercise in 13 hypertensive or normotensive patients with obstructive sleep apnea (OSA) and in 10 sex- and weight-matched controls. All patients had undergone a complete polysomnography for the diagnosis of OSA. The controls did not undergo any sleep investigation but had no history of snoring or witnessed apneas during sleep. On antihypertensive drug wash-out, two of the patients were normotensive, whereas 11 had mild to moderate hypertension. Platelet aggregation measured by adenosine 5'-diphosphate- or adrenaline-induced aggregation, platelet factor-4 or beta-thromboglobulin did not differ between patients and controls. During exercise beta-thromboglobulin decreased significantly in both OSA patients and controls. Plasma tissue plasminogen activator activity was similar in OSA patients and controls and increased significantly in both groups after exercise. Plasminogen activator inhibitor type 1 (PAI-1) was 18.4 +/- 3.6 IU/ml in OSA patients compared with 8.2 +/- 1.7 IU/ml in controls (p < 0.029) during rest, indicating decreased fibrinolytic activity. The difference between groups remained after exercise (p < 0.017). Blood pressure elevation was more common and body mass index (BMI) was higher in patients with OSA, but there was no direct relation between blood pressure level or BMI and PAI-1. Nevertheless, differences between groups were smaller when blood pressure and obesity were accounted for. It is concluded that patients with OSA may exhibit decreased fibrinolytic activity. Low fibrinolytic activity may represent a confounding pathophysiological mechanism behind the high incidence of myocardial infarction and stroke in patients with OSA.
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PMID:Platelet function and fibrinolytic activity in hypertensive and normotensive sleep apnea patients. 761 Mar 15

To assess hemostatic risk factors for sudden death in patients with stable angina, 323 consecutive patients were recruited prospectively. Patients with clinical heart failure or recent myocardial infarction were excluded. The following clinical variables were recorded: age, gender, smoking habits, hypertension, previous myocardial infarction, left ventricular hypertrophy, and severe ventricular arrhythmia. Angiographic variables included coronary extent, assessed from Jenkins' and mean atherosclerotic scores, and left ventricular ejection fraction. Lipid variables included total cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and apolipoproteins A-I and B. Hemostatic factors included fibrinogen, fibrinopeptide A, antithrombin III, factor VIII antigen, factor VIII coagulant, protein C, plasminogen, alpha 2 antiplasmin, euglobulin clot lysis time, tissue plasminogen activator before and after venous occlusion, and plasminogen activator inhibitor. There were 34 deaths, 19 of which were sudden during the follow-up period (60 +/- 17 months). The association between each variable and the risk of sudden death was assessed by calculating the relative risk with the Cox univariate model. All significant predictors from the univariate analysis were then incorporated in a Cox multivariate model to select the independent predictors of sudden death. The independent predictors of sudden death were left ventricular hypertrophy (p < 0.04), lower left ventricular ejection fraction (p < 0.04), and shorter euglobulin clot lysis time after venous occlusion (p < 0.02), whereas fibrinogen (p < 0.07) and Jenkins' score (p < 0.08) were borderline. Determination of hemostatic variables, especially those pertaining to dynamic fibrinolysis, may thus be of value in assessing risk of sudden death.
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PMID:Predictive value of hemostatic factors for sudden death in patients with stable angina pectoris. 761 16

The effects of isradipine and atenolol on platelet function and fibrinolytic activity were studied in 10 male patients with mild untreated hypertension. After a 2-week placebo run-in period, the volunteers were randomized to either isradipine 2.5 mg twice daily or atenolol 100 mg daily for a 6-month period. Those initially receiving isradipine then received atenolol and vice versa. After each therapy regimen, blood was drawn at rest and 1 h after exercise during a maximum exercise test. Platelet activity in vivo was estimated as release of B-TG and PF-4. Fibrinolytic activity was estimated as the fast-acting inhibitor against tissue plasminogen activator usually termed PAI-1. During atenolol and isradipine therapy, blood pressure (BP) was equally reduced (p < 0.05). Heart rate (HR) decreased during atenolol treatment but was not changed by isradipine. Platelet activity in vivo estimated as B-TG and PF-4 decreased irrespective of therapy (p < 0.02). During atenolol, as during placebo therapy, exercise resulted in a significant increase in platelet activity, as shown by an increase in B-TG (p < 0.02) and in PF-4 (p < 0.01). Such increase was not observed during isradipine treatment. Both treatments tended to improve fibrinolysis, as shown by a decrease in PAI, 1 h after exercise. Reducing BP with isradipine or atenolol results in a similar decrease in platelet activity and PAI-level, tested at rest and 1 h after rest, respectively. During exercise, platelet activity increased during atenolol treatment; such change did not occur during isradipine treatment.
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PMID:Does calcium channel blockade and beta-adrenergic blockade affect platelet function and fibrinolysis to a varying degree? 772 58

At 12 centers, 395 patients, including 288 men (73%) and 107 women (27%) with acute myocardial infarction (AMI), were prospectively randomized to treatment with tissue plasminogen activator (t-PA) or primary percutaneous transluminal coronary angioplasty (PTCA). Compared with men, women were older (65.7 vs 57.7 years, p < 0.0001), more often had diabetes mellitus (19% vs 10%, p = 0.03), systemic hypertension (54% vs 39%, p = 0.005), prior congestive heart failure (5% vs 0%, p = 0.002), and presented later after symptom onset (229 vs 174 minutes, p = 0.0004). The in-hospital mortality in women was 3.3-fold higher than men (9.3% vs 2.8%, p = 0.005). After adjustment for comorbid baseline characteristics, however, only advanced age independently correlated with mortality. Among t-PA-treated patients, mortality was significantly higher in women than in men (14.0% vs 3.5%, p = 0.006). Intracranial hemorrhage after t-PA was also more common in women than in men (5.3% vs 0.7%, p = 0.037). In contrast, women and men had similar in-hospital mortality after primary PTCA (4.0% vs 2.1%, respectively, p = 0.46). No intracranial bleeding occurred in PTCA-treated patients. A univariate trend was present for reduced in-hospital mortality in women treated with PTCA rather than t-PA (4.0% vs 14.0%, p = 0.07). By multiple logistic regression analysis of 15 clinical variables, treatment with PTCA rather than t-PA, as well as younger age, were independently predictive of in-hospital survival in women.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Comparison of in-hospital outcome in men versus women treated by either thrombolytic therapy or primary coronary angioplasty for acute myocardial infarction. 774

Vascular endothelial injury associated with arterial narrowing leads to platelet adhesion and aggregation at the site of endothelial injury and to the local accumulation of several mediators that promote platelet aggregation and vasoconstriction, including thromboxane A2, serotonin, adenosine diphosphate, platelet activating factor, oxygen-derived free radicals, activated thrombin, and tissue factor. At the same sites of endothelial injury, there is a reduction in absolute or relative amounts of the endogenous inhibitors of platelet aggregation and vasoconstriction, including prostacyclin, endothelium-derived relaxing factor (nitric oxide), and tissue plasminogen activator; the loss of the effects of the endogenous inhibitors preventing platelet aggregation and vasoconstriction helps to create a prothrombotic and vasoconstrictive environment. Endothelial injury occurs as a result of atherosclerotic plaque fissuring or ulceration, flow shear stress, hypertension, diabetes mellitus, immune complex deposition, infection, and mechanical injury in the form of diagnostic and therapeutic catheterization. Endothelial injury and the accumulation of platelet- and other cell-derived mediators promotes neointimal proliferation in an exaggerated wound-healing response, resulting in further anatomic narrowing of artery in the subsequent days and weeks. Future methods that may prove useful in protecting the individual with these vascular problems from acute myocardial infarction and its consequences are inhibition of multiple mediators of platelet aggregation and vasoconstriction, restoration of the presence of the normal endogenous inhibitors of platelet aggregation and vasoconstriction, and/or rapid therapeutic regeneration of the injured endothelium.
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PMID:Conversion from chronic to acute coronary heart disease syndromes. Role of platelets and platelet products. 778 65

We have recently shown that mental stress increases local net release of tissue-type plasminogen activator (t-PA) across the forearm vascular bed. However, the mechanisms responsible for the t-PA release in man during stress are undefined. To study the effects of endothelial cell receptor stimulation and fluid shear stress we used the perfused forearm model to characterize the in vivo tissue plasminogen activator (t-PA) response in man to methacholine (Mch) and sodium nitroprusside (SNP), at doses calculated to cause similar degrees of vasodilation. The study was performed in 7 healthy young men (age 22-24 yrs) without hypertension, diabetes mellitus, or hypercholesterolemia. Each subject received double-blind step-wise i. a. infusions of Mch (0.1-0.8-4.0 micrograms/min) and SNP (0.5-2.5-10 micrograms/min) in randomized order. Each dose step was infused for 5 min. Forearm blood flow was assessed by plethysmography. Net release/uptake was expressed as the product of arterio-venous concentration gradient and forearm plasma flow. At pre-infusion baseline, there was a significant net release of t-PA antigen of approximately 0.9 ng x min-1 x 100 ml-1 and t-PA activity of 3.5 fmol x min-1 x 100 ml-1 across the forearm. I.a. infusion of Mch and SNP increased forearm blood flow from 1.9 to 14.9 and from 1.8 to 12.1 ml x min-1 x 100 ml-1, respectively (Mch vs SBP N.S.).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Release of tissue-type plasminogen activator in response to muscarinic receptor stimulation in human forearm. 787 38

Few haematological or lipid risk factors have been identified for stroke, by contrast with coronary heart disease. To find out whether a marker of endogenous fibrinolytic function might be associated with stroke risk, we measured tissue plasminogen activator (tPA) antigen concentrations in baseline plasma samples from 88 healthy participants in the Physicians' Health Study who subsequently had first-ever strokes (71 thromboembolic, 12 haemorrhagic, 5 indeterminate) and from 471 participants who remained free of cardiovascular disease during 5 years of follow-up (controls). Mean baseline tPA concentrations were significantly higher among men who later had strokes than in the controls (11.14 [SE 0.80] vs 9.59 [0.27] ng/mL, p = 0.03). The difference was largely due to an excess of abnormally high values among stroke cases. The age-adjusted relative risk for stroke among men with baseline tPA concentrations above the 95th percentile of the control distribution was 3.51 (95% CI 1.72-7.17, p = 0.0006) for total stroke and 3.89 (1.83-8.26, p = 0.0004) for thromboembolic stroke. These findings did not change substantially in analyses that also controlled for stroke risk factors (high blood pressure, body-mass index, smoking, presence of diabetes, and parental history of myocardial infarction) or the plasma lipid profile. This prospective study shows that high concentrations of tPA antigen among apparently healthy men are independently associated with high risks of future stroke, especially thromboembolic stroke. This finding is consistent with the hypothesis that activation of the endogenous fibrinolytic system occurs years in advance of arterial vascular occlusion.
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PMID:Prospective study of endogenous tissue plasminogen activator and risk of stroke. 791 Sep 26

Thrombolytic therapy has been proven to be highly effective and safe in patients presenting with acute myocardial infarction. Its use may reduce mortality rates by as much as 50%. Accelerated administration of tissue plasminogen activator (Activase) combined with intravenous heparin shows particular success in reducing mortality rates, especially in patients with anterior infarcts. However, strict compliance to the classic inclusion criteria has limited the number of patients, excluding several groups who have been shown to benefit from thrombolysis: The elderly appear to benefit from early thrombolysis even more than do their younger counterparts. Patients with inferior myocardial infarction and bundle-branch blocks also benefit. Recent trials suggest that thrombolytic therapy can be cautiously extended to patients presenting late (up to 24 hours) after onset of symptoms. Certain patients with a history of cerebrovascular disease or recent surgery, patients with severe hypertension, and those having undergone cardiopulmonary resuscitation should not necessarily be excluded from consideration.
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PMID:Thrombolysis after acute myocardial infarction. Who should be added to inclusion criteria? 799 76

In eight patients with Legg-Perthes disease, we assessed the etiologic roles of thrombophilia caused by protein C and protein S deficiency and hypofibrinolysis mediated by low levels of tissue plasminogen activator activity. We speculated that thrombosis or hypofibrinolysis were common causes of Legg-Perthes disease. Three of the eight patients had protein C deficiency; they came from kindreds with previously undiagnosed protein C deficiency. In one of these three kindreds there were six protein C-deficient family members (beyond the proband child), four of whom had thrombotic events as adults. One of the eight patients had protein S deficiency, as did his brother who had sustained mesenteric vein thrombosis at age 43. One of the eight patients who had normal proteins C, S, and antithrombin III had hypofibrinolysis, failing to elevate tissue plasminogen activator activity after 10 min of venous occlusion at 100 mm Hg. Plasminogen activator inhibitor, alpha 2-antiplasmin, and fibrinogen values were normal in all eight patients. Beyond their Legg-Perthes disease, none of the eight patients had evidence for venous thrombosis. Of the eight patients, four had thrombophilia and one had hypofibrinolysis, disorders that we believe contributed to thrombotic venous occlusion of the femur with subsequent venous hypertension and bone death that characterize Legg-Perthes disease.
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PMID:Protein C and S deficiency, thrombophilia, and hypofibrinolysis: pathophysiologic causes of Legg-Perthes disease. 804 73


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