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Query: UMLS:C0151744 (myocardial ischemia)
 31,282 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pre-existing disease in the form of hypertension or ischaemic heart disease may increase morbidity and mortality in patients presenting for anaesthesia and surgery. The interaction of these two cardiovascular conditions in relation to anaesthesia has been studied in a series of 115 patients. The results did not support the view that antihypertensive drugs and beta-receptor blocking agents should be withdrawn before anaesthesia and surgery. The main cause for concern in providing anaesthesia for these patients is that sympathetic nervous activation induced either by anaesthetic manoeuvres or by surgical stimulation may lead to reflex cardiovascular responses which, by increasing myocardial oxygen demand, lead to episodes of myocardial ischaemia. In this respect beta-receptor blocking drugs appear to have a protective effect on the ischaemic myocardium.
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PMID:Medical problems of surgical patients. Hypertension and ischaemic heart disease. 1 Aug 25

The primary aim during anesthetic management of the patient with coronary artery disease is prevention of imbalance between myocardial oxygen supply and demand. Since oxygen supply is limited by restriction of coronary blood flow, prevention of increases in demand plus maintenance of supply, rather than increases in supply, will achieve this aim. The major determinants of myocardial oxygen demand are mechanical, i.e. (a) left ventricular wall tension, dependent in turn upon systolic pressure and ventricular volumn, (b) velocity of contraction, and (c) heart rate. Systolic pressure, pulmonary capillary wedge pressure, and heart rate monitoring will alert the anesthetist to increases associated with an enhanced oxygen demand. Decreased arterial diastolic and increased pulmonary capillary wedge pressure are associated with decreased supply. By appropriate manipulation of these variables and avoidance of episodes of myocardial ischemia, the perioperative morbidity and mortality rates associated with coronary artery disease may be decreased.
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PMID:[Anesthetic considerations in patients with CAD (author's transl)]. 1 73

Timolol, a beta-adrenoceptor blocking agent with little or no cardiodepressant activity, was studied in acute myocardial ischemia in cats. Timolol, at a dose of 25 mug/kg, blocked 75 to 80% of the cardiac response to isoproterenol. This dose also significantly reduced heart rate in cats subjected to acute myocardial ischemia by ligation of the left coronary artery. Timolol significantly prevented the spread of ischemic damage in the myocardium as assessed by (a) curtailing the increase in plasma creatine phosphokinase (CPK) activity, (b) preventing the loss of CPK from the ischemic portion of the myocardium, and (c) restoring the elevated S-T segment of the electrocardiogram toward normal. Timolol did not significantly retard the increase in fragility of lysosomes in ischemic myocardial tissue. The mechanism of the protective effect to timolol on the ischemic myocardium appears to be via reducing myocardial oxygen demand by decreasing heart rate.
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PMID:Protective action of timolol in acute myocardial ischemia. 1 35

Metabolic effects of Metipranolol, a new beta adrenergic blocking agent, have been studied in patients with ischemic heart disease, hyperkinetic syndrome, hyperthyreosis and in healthy subjects. Administration of the drug (30 mg per day for one week) resulted in the decrease of noradrenaline excretion, blood free fatty acid level, and in lowering of blood pressure and heart rate, particularly in patients with ischemic heart disease and hyperkinetic syndrome. These alterations were accompanied by alleviation of clinical symptoms. It is suggested that Metipranolol by suppressing the activity of sympathetic nervous system and thereby diminishing lypolysis, exerts favourable clinical effects, most probably related to diminution of myocardial oxygen consumption.
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PMID:Effects of beta-blocking agent Metipranolol on metabolic variables in patients with ischemic heart disease, hyperkinetic syndrome, hyperthyreosis and in healthy subjects. 3 15

The indices of central hemodynamics and myocardial contractile function were studied in 35 dogs before and in different periods after the administration of drugs which block beta-receptors: propranolol, pindolol, and talinolol. The drugs blocking the beta-adrenergic receptors were administered against the background of an intact myocardium to 15 dogs and against the background of acute coronary insufficiency to another 15; acute ischemia was induced in 5 dogs to which the drugs were not given. It was established that beta-adrenergic blocking agents have a beneficial effect in the acute stage of myocardial ischemia; they exert a marked influence on the consumption of oxygen by the myocardium, intramyocardial tension, and the contractile capacity and rhythm of the heart. Talinolol produced the most favourable effect.
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PMID:[Effect of blockaders of cardiac beta-adrenergic structures on the central hemodynamics and contractile function of the myocardium in acute experimental coronary insufficiency]. 4 59

Limited hemodilution does not affect the respiratory function of the blood, neither in vitro nor in vivo. By virtue of the unchanged affinity of oxygen for hemoglobin and increase in nutritional flow, reduction in the O2 content of the blood is completely compensated. Tissue hypoxia does not develop as long as pulmonary and circulatory compensation is ensured. As a result, maintenance of a normal blood volume is an essential parameter. Information is not yet available concerning the relationship of O2 supplies in coronary disease. Coronary disease is presently considered to be a contra-indication since a marked reduction in the O2 content of the blood could restric coronary reserves and result in myocardial ischemia.
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PMID:[Tissue oxygenation during normovolemic hemodilution]. 4 92

In order to evaluate the clinical efficacy on penbutolol (Hoe 893 d), a new adrenergic blocking agent, two groups of 10 patients (A & B) with ischemic heart disease were chosen. These were submitted to exercise testing for 3 minutes, and placebos, nitroglycerin, and propranolol were used as reference preparations. As an index of indirect consumption of oxygen we determined the maximum cardiac frequency (MCF), maximum systolic arterial pressure (MAP) and the maximum double product (MDP). An electrocardiographic control of the patients was also included to observe ST segment changes. The patients from group A received 0.8 mg. of nitroglycerin sublingual as the first treatment and 40 mg. of propranolol as the second. The patients from group B received initially a placebo P.O. and then 25 mg. of penbutolol P.O. In both groups the exercise testing was repeated 10 minutes after the administration of the first substance and 10 minutes after the second. The results showed that 25 mg. of penbutolol and 40 mg. of propranolol have similar therapeutic effects over the degree, intensity, and duration of the differences in elevation of the ST segment, MCF, MAP, and MDP when you compare the results of their own controls with those obtained with the active principle. There is no significant difference observed in the results obtained in each parameter studied between penbutolol and propranolol. During the period of this clinical study there were no undesirable collateral effects caused by the oral administration of the investigated drugs.
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PMID:[Effect of antianginal drugs on the exertion electrocardiogram]. 4 39

The actions of FR 7534, a new calcium antagonist, nitroglycerin, and dipyridamole on myocardial oxygen demand have been compared. Six anaesthetized dogs received two infusion levels of each drug which produced equivalent arterial hypotension. All three compounds reduced the tension-time index (TTI). FR 7534 and nitroglycerin but not dipyridamole produced significant decreases in myocardial oxygen consumption (MVO2). FR 7534 demonstrated oxygen-sparing actions comparable to nitroglycerin. FR 7534 may prove beneficial in alleviating myocardial ischemia.
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PMID:Effect of FR 7534, a new calcium antagonist, on myocardial oxygen demand. 10 31

Intravenous infusion of trinitrin (0.38 +/- 0.25 mg/hour) during rapid atrial pacing reduced pulmonary capillary pressures, cardiac output, coronary blood flow and myocardial oxygen consumption. At these dosages trinitrin allows patients with ischaemic heart disease to undergo atrial pacing in the best conditions by maintaining the pulmonary capillary and systemic arterial pressures and myocardial lactate production within limits close to the basal values. The beneficial effects last during the recovery period after the termination of pacing and of the intravenous infusion.
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PMID:[Effects of intravenous trinitrin infusion on systemic and coronary circulations during atrial electric stimulation]. 11 32

Myocardial ischemia occurs when there is an imbalance between myocardial oxygen demand and supply, and it is usually entirely or predominantly subendocardial. Animal experiments have shown that relative subendocardial ischemia (a reduced inner:outer flow ratio) can be predicted quite accurately from the ratio of two pressure-time areas:DPTI, the area between diastolic aortic and left ventricular pressures, and SPTI, the area beneath the systolic left ventricular pressure curve. Although the importance of relating supply and demand is obvious, care is needed in applying the results of these animal experiments to man. Recent work has shown that the critical DPTI:SPTI ratio below which subendocardial ischemia occurs is about 0.4 to 0.5 rather than 0.7 to 0.8, as originally reported. On the other hand, the critical ratio may be raised to an unknown extent by myocardial edema or hypertrophy, or by thickened or narrowed coronary arteries. Furthermore, the critical ratio is not independent of absolute coronary diastolic pressure: It is much lower than 0.4 when coronary pressures are high, perhaps because intramyocardial diastolic pressures are much higher than once thought. Further work is required to allow an important physiologic concept to be used in making decisions about patients with heart disease.
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PMID:The myocardial supply:demand ratio--a critical review. 14 25


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