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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Xamoterol, a partial agonist of beta 1-adrenoceptors, was tested as a cardiotonic drug in 10 patients with moderate chronic heart failure. The trial was double-blind drug versus placebo for 3 months and open for one year. At 3 months the patients were clinically improved with downgrading by one NYHA class, and there was a significant increase in response to a 36-second exercise, as compared with the placebo group. Haemodynamic index, a 14 per cent fall in pulmonary wedge pressure and a 7 per cent increase in left ventricular stroke work as compared with the placebo group. This clinical and haemodynamic improvement was paralleled by a reduction of the double product on exercise. In long term use, xamoterol did not seem to induce tachyphylaxis, and few side-effects were recorded during this trial.
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PMID:[Effects of xamoterol in moderate cardiac insufficiency]. 256 61

In man a close interrelationship exists between hyperadrenergic states, myocardial ischemia, necrosis, infarction and sudden cardiac death. Persistent high catecholamine levels may also be associated with increased vascular endothelial turnover and permeability to calcium and lipoproteins, increased blood velocity, abnormal blood flow patterns and atheroma formation. There are thus good reasons to predict a cardiovascular protective effect of beta-blockers. Animal data indicate that in spite of apparently adverse plasma lipoprotein changes beta-blockers retard atheromatous plaque formation under conditions of high cholesterol diet with or without stress. A slow heart rate, as well as a reduction in calcium influx and inhibition of both esterification of arterial wall cholesterol (by ACAT) and endothelial permeability to lipoproteins, may be central to this process. Beta-blockers benefit a spectrum of conditions related to the atheromatous process and myocardial necrosis. These are silent ischemia; stable (including mixed), unstable and preinfarction angina; periinfarction events (including myocardial rupture and dissection of the ascending aorta); and myocardial necrosis associated with stress conditions such as head injuries and subarachnoid hemorrhage. In one study coronary deaths in hypertensive men, particularly in smokers, were significantly reduced by metoprolol (a beta 1-selective blocker) compared to a diuretic. In contrast in the MRC study of mild hypertension only nonsmoking men with mild to moderate hypertension who received a nonselective beta-blocker appeared to experience fewer myocardial infarctions. Recent clinical data showed that moderate-severe hypertensives who were optimally controlled by atenolol-based treatment over a 10-year period were less likely to die from myocardial infarction than those suboptimally controlled, irrespective of a rise in serum triglyceride levels. Thus the net effect of acute beta-blockade in hyperadrenergic states, including myocardial infarction, is to limit cardiovascular damage. Chronic beta-blockade inhibits atheroma formation (in animals) and beneficially modifies the incidence of stroke and myocardial infarction, which in man are the long-term consequences of hypertension.
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PMID:The beta-receptor, atheroma and cardiovascular damage. 257 Apr 26

1. A bicycle exercise test was used to investigate functional capability and haemodynamics in 30 patients with heart failure (13 NYHA Class II, 17 Class III), before and after i.v. xamoterol (Corwin, Carwin, Corwil, Xamtol, ICI 118,587) 0.2 mg kg-1. 2. Resting heart rate fell from 78 to 74 beats min-1 (P less than 0.05) and cardiac index rose from 2.5 to 2.8 l min-1 m-2 (P less than 0.001) after xamoterol. Blood pressure fell slightly, and systemic vascular resistance was reduced. Stroke work index improved and double product decreased. There were no changes in pulmonary artery wedge pressure ejection fraction or plasma noradrenaline concentrations. 3. On exercise, xamoterol produced a considerable reduction in heart rate increase, improved stroke volume and left ventricular stroke index and lowered double product. Exercise duration increased by 10%, but this did not quite achieve statistical significance. 4. These results are consistent with the concept that a beta 1-partial adrenoceptor agonist with the level of intrinsic sympathomimetic activity (43%) of xamoterol provides moderate inotropic support at rest, and protects the heart against overstimulation on exercise, when sympathetic drive is high. 5. Reduction of double product on exercise implies a lowered oxygen demand, which could be of considerable importance in patients with ischaemic heart disease.
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PMID:Effects of xamoterol on resting and exercise haemodynamics in patients with chronic heart failure. 257 50

The failing heart operates with an abnormal combination of heart rate, stroke volume, and enddiastolic volume. This mismatch becomes more evident during exercise of patients with heart failure, when an increase in cardiac output is achieved with higher heart rate, a lower stroke volume and a higher enddiastolic volume. Using the beta 1-adrenoceptor partial agonist xamoterol which lacks beta 2-adrenoceptor agonism the response of the heart to sympathetic stimulation can be modulated. At rest and low levels of exercise xamoterol provides an inotropic support of the heart, whereas it reduces inappropriate tachycardia at higher levels. Thereby, xamoterol tends to normalize the balance of the inotropic and chronotropic control of the failing heart, because cardiac output is increased with a more normal combination of heart rate, stroke volume, and filling pressure. The beneficial effects of xamoterol are discussed as being especially important for failing ischemic hearts, because the balance between energy supply and energy demand may be improved by xamoterol.
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PMID:Modulation of the autonomic control of the failing heart. 257 39

To determine the effects of concurrent beta 1-adrenoceptor blocker or calcium channel antagonist administration on the haemodynamic sequelae of an inhaled beta 2-selective adrenoceptor agonist bronchodilator, we examined echocardiographically the effects of fenoterol (400 micrograms) by metered dose inhaler following oral pre-treatment with (a) placebo, (b) atenolol or (c) diltiazem. Following placebo, fenoterol produced significant decreases in diastolic blood pressure (14% +/- 6%), total peripheral vascular resistance (TPR) (31% +/- 9%) and end-systolic stress (ESS) (15% +/- 21%). Cardiac output rose significantly (42% +/- 23%) as did heart rate (25% +/- 13%). After atenolol, responses to fenoterol were significantly blunted. Post-fenoterol heart rate, systolic blood pressure, % fractional shortening, stroke volume, ejection fraction, cardiac output and pressure/volume ratio increased significantly less after atenolol pre-treatment as compared to placebo pretreatment. TPR decreased significantly less. After diltiazem pre-treatment, the response to inhaled fenoterol was not different from that following placebo pre-treatment. We conclude that atenolol blunts the haemodynamic changes induced by fenoterol inhalation whereas diltiazem has little effect.
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PMID:Effects of atenolol vs diltiazem on the haemodynamic effects of an inhaled beta 2-adrenoceptor agonist. 271 21

To assess the time course of thrombosis and fibrinolysis after acute stroke, we measured concentrations of fibrinopeptide A (FpA), B-beta 1-42 peptide (B-beta 1-42), B-beta 15-42 peptide (B-beta 15-42), and crosslinked D-dimer (XDP) in 31 patients at varying times following acute ischemic stroke and in 13 neurologically stable patients with chronic strokes. FpA levels were markedly elevated during the first week after stroke and declined slowly during the first month. Mean FpA levels were not significantly elevated in chronic stroke patients. Mean XDP levels were slightly elevated during the first week and increased during the next 2 weeks after stroke. B-beta 1-42 and B-beta 15-42 levels were not elevated at any time following acute stroke. Our data suggest that fibrin formation greatly exceeds endogenous fibrinolysis during the acute phase of ischemic stroke. Endogenous fibrinolysis develops slowly following stroke. Prolonged elevation of FpA concentration suggests that thrombin activity and fibrin formation continue for up to 4 weeks in some patients with ischemic stroke.
Stroke 1989 May
PMID:Hemostatic markers in acute stroke. 271 98

The purpose of this study was to determine the role of the autonomic nervous system's control of the heart in fitness-related differences in blood pressure regulation. The cardiovascular responses to progressive lower-body negative pressure (LBNP) were studied during unblocked (control) and full blockade (experimental) conditions in 10 endurance-trained (T) and 10 untrained (UT) men, aged 20-31 yr. The experimental conditions included beta 1-adrenergic blockade (metoprolol tartrate), parasympathetic blockade (atropine sulfate), or complete blockade (metoprolol and atropine). Heart rate, blood pressure, forearm blood flow, and cardiac output were measured at rest and -16 and -40 Torr LBNP. Forearm vascular resistance, peripheral vascular resistance, and stroke volume were calculated from these measurements at each stage of LBNP. Blood pressure was maintained, primarily by augmented vasoconstriction, equally in T and UT subjects during complete and atropine blockade. The fall in systolic and mean pressure from 0 to -40 Torr was greater (P less than 0.05) in the T subjects during the unblocked and metoprolol blockade conditions. This reduced blood pressure control during unblocked condition was attributable to attenuated vaso-constrictor and chronotropic responses in the T subjects. We hypothesize that an autonomic imbalance (elevated base-line parasympathetic activity) in highly trained subjects restricts reflex cardiac responses, which accompanied by an attenuated vasoconstrictor response, results in attenuated blood pressure control during a steady-state hypotensive stress.
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PMID:Blood pressure regulation during cardiac autonomic blockade: effect of fitness. 284 97

The influence of chronic beta 1-adrenoceptor blockade on haemodynamic and metabolic responses was examined in eight young hypertensive subjects during a 40 min submaximal bicycle test at 50% of maximal capacity. The patients were randomly allocated to one placebo and one treatment period of 6 weeks. During treatment atenolol (Tenormin, 100 mg) was given twice daily. Arterial pressure, cardiac output, leg blood flow, oxygen uptake and different metabolites in the blood were determined. The heart rate was reduced by beta 1-adrenoceptor blockade by 30% during exercise, and the decrease was related to plasma concentration of the drug. Cardiac output was decreased by approximately 10%, but the negative chronotropic effect was partly compensated for by a higher stroke volume. Blockade leg blood flow was reduced by 10%, but more oxygen was extracted, giving an unchanged oxygen uptake. Blood concentration and leg uptake of glucose were not influenced by the treatment, but plasma free fatty acids were reduced by 30-40%. Leg lactate release was decreased to half the value in the unblocked situation. Plasma renin activity did not increase at the beginning of exercise, but after 40 min an increase was seen, though only to half of the pretreatment value. It is concluded that beta 1-adrenoceptor blockade during submaximal exercise reduces blood flow to the working muscles and that this reduction is the result of a lower cardiac output. Aerobic metabolism is unchanged as a result of increased oxygen extraction, but less fat is used as lipolysis is inhibited. Glucose uptake by the working muscles is unchanged by beta 1-blockade, but there is evidence for an increased carbohydrate metabolism. As for non-selective blockade, atenolol decreases lactate release but this could be the result of non-specific action on the beta 1-receptor and/or increased carbohydrate oxidation. Furthermore, the beta 1-adrenoceptors seem to have a major influence on the renin release during exercise.
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PMID:Haemodynamic and metabolic responses to prolonged exercise after chronic beta 1-adrenoceptor blockade in hypertensive man. 286 Sep 92

beta-Adrenoceptor blockers (beta-blockers) are common first-choice drugs in the treatment of various cardiovascular disorders. Physical exercise performed during single-dose administration of beta-blockers, however, is associated with an increased rate of perceived exertion; an effect which appears to be partly reduced with long term treatment. Although clinical doses of beta-blockade may reduce heart rate by 30 to 35%, during maximal exercise cardiac output is not equally reduced. Accordingly, most studies have demonstrated increased stroke volume after beta-blockade. This reduction in heart rate is typically accompanied by a decreased VO2max (5 to 15%) in both patients and healthy, trained subjects. This smaller reduction in VO2max, as compared with the decrease in cardiac output, is the result of a partly compensating increased arteriovenous O2 difference. Work capacity as reflected by the ability to perform intense short term or more prolonged steady-state exercise is also impaired following beta-blockade. beta-Adrenoceptors can be subdivided into types beta 1- and beta 2. Blockers which are specific for either beta 1-receptors (beta 1-selective blockers) or both beta 1- and beta 2 receptors (non-selective blockers) differ with regard to their effect on exercise performance. Exercise performance ability, irrespective of exercise intensity and duration, is impaired to a greater extent following non-selective than beta 1-selective blockade at equal reductions in heart rate. This response stems from a decreased energy flux through glycogenolysis during non-selective blockade treatment. Individuals receiving beta-blockade medication therefore show greater adaptive response to physical conditioning during treatment with beta 1-selective than non-selective blockade probably because of greater training intensity with the former therapy. Neither psychomotor performance nor muscular strength and power is negatively affected by beta-blockade. Nevertheless, the ability to perform athletic events requiring high levels of motor control under emotional stress but not high levels of aerobic or anaerobic energy release, is probably increased during beta-blockade.
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PMID:Exercise performance and beta-blockade. 286 77

The effects of acute intravenous administration of ICI 118,587 (Corwin), a partial beta 1 agonist, were studied in nine patients with dilated cardiomyopathy and symptomatic congestive heart failure. Hemodynamic and metabolic parameters were measured using Swan-Ganz, arterial, and coronary sinus catheters. Repeated doses of Corwin produced no significant change in left ventricular performance, while a trend towards decreased blood pressure and stroke work was seen. No change occurred in coronary sinus blood flow, transmyocardial lactate extraction, or catecholamine release. One patient had significant depression of left ventricular function with hypotension. Thus, acute infusion of Corwin produced no beneficial inotropic responses, but rather produced features suggestive of further myocardial depression.
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PMID:Acute hemodynamic and metabolic effects of ICI 118,587 (Corwin), a selective partial beta 1 agonist, in patients with dilated cardiomyopathy. 286 73


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