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

This study was designed to evaluate the sensitivity of changes in myocardial carbon dioxide and oxygen tensions as indicators of regional myocardial ischemia and also to determine to what extent these changes can be related to changes in intramyocardial ST segment voltage. Changes in ST segment voltage recorded in unipolar epicardial electrodes proved to be a less-sensitive indicator of underlying myocardial ischemia than were changes in ST segment voltage recorded in unipolar intramyocardial electrodes. In 9 dogs, regional ischemia was produced by placing a variable constrictor on the left circumflex coronary artery; circumflex flow was monitored. Myocardial carbon dioxide and oxygen tensions were measured using a mass spectrometer. Unipolar electrograms were recorded using a multicontact plunge electrode. With progressive degrees of proximal stenosis, ranging from a critical stenosis, which is associated with a decrease in mean flow of less than 15%, to a severe stenosis associated with and 80% decrease, ST voltage increased 21 mv and carbon dioxide tension increased 84 mm Hg, but oxygen tension decreased only 7 mm Hg. The study suggests that increases in intramyocardial ST segment voltage, an index of myocardial ischemia, are associated with parallel increases in myocardial carbon dioxide tension, each providing a more sensitive quantitative correlate of regional myocardial ischemia than do decreases in oxygen tension. The local accumulation of carbon dioxide may be an important pathophysiological mechanism in myocardial ischemia.
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PMID:Changes in intramyocardial ST segment voltage and gas tensions with regional myocardial ischemia in the dog. 118 37

An evaluation of some standardized and relative indices of ergometry is presented: heart rate and oxygen consumption as percentage of individual values, indices of chrono-, isotropic, aerobic and coronary reserves. The investigation is based on the study of 113 normal individuals, 363 hypertonic patients, and 100 patients with ischaemic heart disease. In all cases the maximum tolerable workload was tested by way of its step-wise increase, conducted under pulse, arterial pressure, ECG and oxygen consumption control. Some patients were examined after Obsidan and Dopegit therapy. The use of the relative values of the heart rate and oxygen consumption was shown to neglect the role of individual factors (sex, age, body weight). The determination of the relative augmentation of these indices, as well as of the arterial pressure permits to precise the state of functional reserves of the cardiopulmonary system, and can be used for the diagnosis and evaluation of therapeutic results.
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PMID:[Evaluation of the results of ergometric studies]. 118 51

Seventeen subjects ranging from 36 to 58 years of age presented with chest pain suggestive of myocardial ischemia. Each patient had a positive double Master's two-step test with ST segment depression of 0.5 mm. or more in the postexercise ECG. In each case coronary angiography and left ventriculography were normal. Hemodynamic and metabolic investigations were carried out during sinus rhythm and atrial pacing. Thirteen patients experienced pain during pacing but only one showed an abnormal hemodynamic response. Two patients showed abnormal myocardial lactate metabolism during the control period and four during pacing-induced tachycardia. The increase in ejection fractions in this group suggests hyperdynamic ventricular contraction which could result in increased oxygen requirements and thus induce ischemic pain in the absence of arteriographically demonstrable coronary artery disease.
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PMID:Angina pectoris with normal coronary arteriograms: hemodynamic and metabolic response to atrial pacing. 119 32

The methodology for use of the mass spectrometer for the measurement of intramyocardial gas tensions in the canine preparation is described. Baseling studies were carried out initially in 36 animals, and control levels for myocardial oxygen tension and myocardial carbon dioxide tension were 19 mm Hg (S.D. 6 mm Hg) and 43 mm Hg (S.D. 10 mm Hg), respectively. Myocardial oxygen tension was not altered significantly by varying the arterial oxygen tension between 65 and 300 mm Hg. However, myocardial carbon dioxide tension increased linearly with increased arterial carbon dioxide tension. In 15 dogs placed on total cardiopulmonary bypass, a perfusion pressure 40-60 mm lower than the control mean arterial pressure resulted in myocardial ischemia with a decrease in myocardial oxygen tension and an increase in myocardial carbon dioxide tension. A subsequent increase in perfusion pressure to control levels resulted in resolution of ischemia and return of myocardial oxygen and carbon dioxide tensions to their control level. In another series of open-chest dogs on cardiopulmonary bypass, a proximal constriction applied to the left coronary circumflex artery resulted in a marked decrease in myocardial oxygen tensions and a marked increase in myocardial carbon dioxide tensions in the region supplied by the constricted vessel. In yet another series of open-chest dogs, it was found that incremental decreases in coronary flow established by constriction of the circumflex artery resulted in an exponential increase in both myocardial carbon dioxide tensions and ST-segment elevation as determined by a 25-gauge multi-contact plunge electrode placed in the posterior left ventricular wall. It appears that mass spectrometry techniques for evaluating myocardial ischemia have several advantages over myocardial biopsy techniques for assay of ATP and lactate, and also over the technique of coronary sinus lactate determination.
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PMID:Mass spectrometry for the measurement of intramyocardial gas tensions: methodology and application to the study of myocardial ischemia. 120 1

Previous investigations concerning isoproterenol infusion (PI) in the diagnosis of myocardial ischemia have shown that ischemic ECG changes are only significant if they persist or appear after discontinuing PI. In an effort to explain the mechanisms of this delayed response, hemodynamic parameters were measured in 10 patients with angiographically proven coronary disease before, during and after PI. It was found that the principal determinants of myocardial oxygen consumption (TTI and contractility) remain significantly elevated in the recuperation phase, but that aortic pressure and systemic arterial resistance, which diminish during PI, return to pre-infusion levels immediately after halting PI. The combined effects favor the late appearance of ischemic changes in the ECG. The coronary vasodilatation with resultant increased oxygen delivery to the myocardium seen during PI may be sufficient to meet the increased myocardial oxygen demand during PI but disappears immediately if PI is discontinued.
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PMID:[Proceedings: Evaluation of the hemodynamic condition during the recuperative phase after the diagnostic isoproterenol test in a patient with coronary disease]. 121 32

Direct measurement of oxygen consumption during monitored exercise can safely be used for assessment of functional reserve in established cardiorespiratory disease. Indirect prediction of aerobic capacity enables the clinical application of exercise testing to be extended outside the laboratory setting. Information so obtained can provide useful guidelines when one is prescribing exercise for the prevention and rehabilitation of ischaemic heart disease.
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PMID:Clinical application of exercise testing. 121 37

The usefulness and limitations of currently available techniques for quantitating coronary flow in ischemic heart disease are summarized. There are appreciable difficulties in assessing coronary flow solely from an arteriographic evaluation of the epicardial arteries. There is a considerable reserve mechanism for vasodilation at the arteriolar level, and a proximal occlusive lesion produces a reduction in flow only after this distal reserve has been exhausted. In addition, small increments in the severity of established lesions sometimes cause profound reductions in flow. The development of clinically useful flow measurements has been impeded by methodological problems related to nonuniformity of flow within the left ventricle in coronary artery disease. Validation of specific techniques for abnormal situations is difficult but possible and should probably be a prerequisite to the clinical application of any technique. When a methodologically appropriate technique is employed, average left ventricular flow per unit weight is found to be reduced systematically at rest in patients with double- and triple-vessel disease. This reduction is a group difference, however, and is not always evident in individual patients. Accordingly, more recent measurements have concentrated on the assessment of regional perfusion, and two general approaches, selective venous sampling and selective precordial sampling are illustrated. While only preliminary measurements of regional flow are available, it is clear that these measurements offer a more sensitive tool for detecting abnormalities of flow in individual patients and thereby for contributing to the management of specific clinical problems. Measurements of regional flow need to be performed during stress as well as at rest. For the future, there is also need for techniques which can assess transmural variations of flow in man and relate measurements of regional flow to regional oxygen demand. Because of the complexity of current techniques which are methodologically adequate, measurements of coronary flow will, for the immediate future, probably remain confined to clinical centers which have a special interest in them. The effort in these centers will hopefully include significant emphasis on the refinement of existing techniques so that they are more widely applicable.
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PMID:Quantitative evaluation of coronary perfusion in man. 122 32

On 19 test persons (10 healthy persons, 9 patients with heart diseases) mechanocardiographic and haemodynamic examinations were carried out with the new preparation Nifedipine (05-072) which effects on the coronary vessels. Insignificant positively inotropic effects with invariable heart rate and cardiac output, decreasing heart action and decreased oxygen consumption were found. Arterial blood pressure and peripheral resistance were only slightly diminished. Own results and reports from literature show that the application of Nifedipine in the ischaemic heart disease appears to be successful.
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PMID:[Clinico-pharmacological studies with Nifedipine--a new coronary substance]. 122 31

Data on pharmacology of nonachlazine-a new antianginal preparation effective in the treatment of patients with ischemic heart disease-are presented. The drug tends to greatly improve the blood supply of the heart. Its beneficial action comes from the ability to intensively and protractedly enhance the coronary blood flow, thus increasing the oxygen reserve of the heart with the contractility of the myocardium rising without any substantial changes in the cardiac output and work.
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PMID:[Pharmacology of a new anti-angina preparation, nonachlazin]. 122 83

N-Dimethylisopropyl propranolol (DMP) is a quaternary derivative which lacks significant beta-adrenergic blocking and local anesthetic effects. It has been reported, nonetheless, to be effective in treating experimental arrhythmias and in limiting the extent of ST-segment elevations following experimental coronary occlusion. The present study examined the effects of DMP on the hemodynamics and myocardial oxygen demands of anesthetized dogs. After a single dose of 3 mg/kg, heart rate fell from 146 +/- 8 to 124 +/- 6 beats/min (P less than 0.0025), and aortic systolic pressure fell from 151 +/- 11 to 141 +/- 9 mm Hg (0.05 less than P less than 0.10), resulting in a 16.8% reduction in the tension-time index. Stroke volume was reduced by 10% despite a 54% increase in left ventricular end-diastolic pressure, suggesting a negative inotropic effect. This was supported by a decrease in maximum extrapolated contractile element velocity from 9.10 +/- 1.05 to 6.61 +/- 65 units/sec (P less than 0.0025). Myocardial oxygen consumption was reduced from 12.0 +/- 1.4 to 9.9 +/- 1.5 ml/min/100 g tissue (P less than 0.05). Myocardial oxygen extraction was unchanged, indicating that the decrease in oxygen consumption resulted from a reduction in myocardial oxygen demand. When heart rate and systolic pressure were artificially restored to control levels, after the administration of DMP, myocardial oxygen consumption remained significantly below the control level. DMP, therefore, appeared to reduce myocardial oxygen demands primarily by its negative inotropic effect. This drug may have application in the treatment of ischemic heart disease.
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PMID:N-dimethylisopropyl propranolol. Effects on myocardial oxygen demands. 124 83


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