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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The purpose of this study was to determine whether an exercise-induced decrease in ejection fraction in patients with coronary artery disease and left ventricular dysfunction at rest represents ischemia or the nonspecific response of a compromised left ventricle to exercise stress. Accordingly, radionuclide ejection fraction responses of 246 patients with coronary artery disease and an ejection fraction at rest of less than 0.50 were compared with those of a "nonischemic" control group of 48 patients with idiopathic dilated cardiomyopathy and a similar degree of ventricular dysfunction. The significance of the ejection fraction response in the group with coronary artery disease was further examined by relating it to the angiographic extent of coronary artery disease, severity of angina, incidence of chest pain and electrocardiographic ST segment depression during exercise and long-term prognosis. The ejection fraction decreased by greater than or equal to 0.01 and greater than or equal to 0.05 during exercise in 48 and 28%, respectively, of the patients with coronary artery disease compared with only 8 and 2%, respectively, of the patients with cardiomyopathy. When exercise was limited by fatigue at a submaximal heart rate, the ejection fraction decreased in 25% of the patients with coronary artery disease but in none of the patients with cardiomyopathy. Patients with coronary artery disease whose ejection fraction decreased during exercise had a significantly higher incidence of three vessel disease, exercise-induced chest pain or ST depression and late mortality than did patients whose ejection fraction did not decrease. These relations were confirmed equally in subgroups of patients with moderate (ejection fraction 0.30 to 0.49) and severe (ejection fraction less than 0.30) left ventricular dysfunction. Thus, in patients with coronary artery disease and left ventricular dysfunction at rest, a decrease in ejection fraction during exercise is more likely to indicate ischemia than a nonspecific left ventricular response to exercise stress. In the individual patient, a decrease of 0.05 or greater, or a decrease during submaximal exercise, appears to be highly specific for ischemia. A decrease in ejection fraction identifies a subgroup of patients with a high prevalence of multivessel coronary artery disease and a high risk of death during long-term follow-up on medical therapy.
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PMID:Mechanism and significance of a decrease in ejection fraction during exercise in patients with coronary artery disease and left ventricular dysfunction at rest. 669 May 59

To investigate the cardiac determinants of treadmill performance in patients able to exercise to volitional fatigue, 88 patients with coronary heart disease free of angina pectoris were tested. The exercise tests included supine bicycle radionuclide ventriculography, thallium scintigraphy and treadmill testing with expired gas analysis. The number of abnormal Q wave locations, ejection fraction, end-diastolic volume, cardiac output, exercise-induced ST segment depression and thallium scar and ischemia scores were the cardiac variables considered. Rest and exercise ejection fractions were highly correlated to thallium scar score (r = -0.72 to -0.75, p less than 0.001), but not to maximal oxygen consumption (r = 0.19 to 0.25, p less than 0.05). Fifty-five percent of the variability in predicting treadmill time or estimated maximal oxygen consumption was explained by treadmill test-induced change in heart rate (39%), thallium ischemia score (12%) and cardiac output at rest (4%). The change in heart rate induced by the treadmill test explained only 27% of the variability in measured maximal oxygen consumption. Myocardial damage predicted ejection fraction at rest and the ability to increase heart rate with treadmill exercise appeared as an essential component of exercise capacity. Exercise capacity was only minimally affected by asymptomatic ischemia and was relatively independent of ventricular function.
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PMID:Treadmill performance and cardiac function in selected patients with coronary heart disease. 669 16

To address the hypothesis that physical conditioning may improve left ventricular function in patients with coronary artery disease, we performed first-pass radionuclide ventriculography in 53 patients at rest and during upright bicycle exercise before and after 6 to 12 months of exercise training. The peak bicycle workload achieved before the onset of fatigue, dyspnea, or angina increased by an average of 22% (p = .0001) after training, and mean heart rate at a workload equal to the pretraining maximum workload was decreased by 10 beats/min after training (p = .0002). Of 21 subjects with angina or exertional ST segment depression before training, 15 (71%) were able to exercise to the same workload without these manifestations of ischemia after training. Whereas neither mean resting left ventricular ejection fraction (LVEF) nor LVEF at peak exertion was significantly altered, mean LVEF at the pretraining maximum workload was increased from 0.50 to 0.54 (p = .002) after training. There was a significant correlation between the magnitude of training bradycardia and the increment in LVEF at the pretraining maximum workload (p = .009). We conclude that the relative bradycardia at comparable exercise workloads produced by exercise conditioning is associated with improvements in left ventricular performance as assessed by the LVEF. This observation is compatible with the hypothesis that training bradycardia in conditioned subjects with ischemic heart disease is associated with lower myocardial oxygen demand and lesser degrees of ischemia at comparable workloads. However, training effects on ventricular afterload or on ischemia contractile performance of the heart cannot be excluded.
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PMID:Effects of physical conditioning on left ventricular ejection fraction in patients with coronary artery disease. 672 12

The workup of a patient with chronic ischemic heart disease (IHD) before the selection of medical-surgical or medical therapy depends on multiple objective and subjective factors. These include symptoms, extent of anatomic disease (degree of coronary arteriosclerosis and left ventricular abnormalities), objective evidence of ischemia, extent of left ventricular dysfunction, and recent intercurrent ischemic events. In a minority of patients, a single factor is of overwhelming importance; e.g., the presence of severe left main coronary artery narrowing in a symptomatic patient indicates surgery is a better choice, whereas evidence of advanced left ventricular dysfunction suggests that surgery is likely to be risky and of limited help to the patient. In most instances, multiple factors should be considered before making a recommendation. The patient should be placed in the appropriate clinical subset and the objective factors that are most important in determining survival should be evaluated. Hence, an exercise electrocardiographic study to evaluate symptoms and exercise tolerance in a patient with angina pectoris and radioventriculographic studies with exercise to estimate left ventricular performance in a patient who complains of fatigue and breathlessness are superior to the subjective interpretations of routine clinical examinations. Asymptomatic patients and those with excellent exercise tolerance pose the most difficult decisions. Perhaps serial (even annual) noninvasive evaluation is appropriate in such patients in light of the current uncertainty about how to manage them. Laboratory tests should be used selectively, systematically and sequentially. The high cost of many of the examinations is reason to avoid duplication. When noninvasive evaluation can answer the question being posed and the cost of hospitalization avoided, this should be done. However, there is little reason to perform noninvasive examinations that do not answer the clinical question being asked; hence, in many patients it is appropriate to proceed directly to coronary arteriography rather than to perform a variety of "screening" examinations before this procedure.
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PMID:The reasonable workup before recommending medical or surgical therapy: an overall strategy. 697 29

Aseptic osteonecrosis is observed in 25% of cases after renal transplantation. This etiological variety of osteonecrosis is unusual in that it is frequently bilateral and has multiple localisations. Apart from the classical radiological signs, attention in attracted by isolated images of osteocondensation in the metaphyses and/or the diaphyses suggesting massive bony infarction and the appearances of fatigue fractures observed frequently (14%). In 43% of cases, the obvious necrosis was proceeded by early bone pain, around the 7 th day, during massive administration of corticosteroids in the prevention or cure of graft resection. This finding suggested to us that the best time to observe ischemia of the bone or marrow is very early and led us to undertake an experimental study in the rabbit. Two series of New Zealand White rabbits were treated with massive doses of corticosteroid and sacrificed between the 3rd and the 21st day. The treated animals presented an early peak of hyperlipemia from the 7th day onwards, and diffuse lesions of hepatic and renal steatosis. Fat emboli associated with appearances of parietal thrombosis were observed in most cases. In the same animals, there were also appearances of stage I or stage II necrosis. Referring to the description of bone marrow necrosis in stages by Arlet and Ficat, there was observed in all the series, a frequency of marrow lesions of all stages much higher in treated animals (16 out of 20) than in controls. Only one lesion of stage I was observed in controls; the difference was highly significant. (0,000001 < p < 0,00001). If one only considers necroses of stage II and III (10/20 in the treated group nil in controls) the frequency was still significant p < 0.001. The preliminary results of the fixation of tetracycline are reported.
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PMID:[Cortisone-induced osteonecrosis: knowledge acquired from observations in man and comparison with the results of animal experimentation]. 700 46

Modified exercise testing within three weeks of an acute myocardial infarction has been shown to be both a safe and feasible means for identifying patients at greater risk for subsequent cardiac events. An abnormal ECG and symptomatic response to exercise correlates with a higher morbidity and mortality. An ST-segment depression as well as angina are associated with a higher risk of recurrent ischemia and death. Elevation of the ST segment as well as inappropriately high heart rates and early development of fatigue and dyspnea are seen in patients with compromised left ventricular function. Exercise-induced premature ventricular contractions raise the possibility of increased sudden death. Patients identified to be at increased risk can be considered for more intensive medical or surgical treatment to reduce their morbidity and mortality. Patients considered to be at low risk can be spared needless invasive studies and unwarranted restriction of their physical activity. Patients may also accrue psychological benefit from these stress-test procedures.
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PMID:Exercise testing soon after uncomplicated myocardial infarction. Prognostic value and safety. 723 Mar 77

Thirty-six patients with coronary artery disease were studied by first-pass radionuclide angiography to assess the effects of myocardial revascularization on exercise-induced myocardial ischemia. The radionuclide studies were performed in the 30 degree right anterior ablique position, at rest and during exercise, 1 to 3 days preoperatively and 10 to 14 days postoperatively. The mean population age was 53 years; the mean number of grafts placed was 4.0 per patient. Fifteen normal male volunteers were tested by rest and exercise radionuclide angiography to serve as normal control subjects. In all exercise radionuclide studies, progressive upright bicycle exercise was performed to symptoms of fatigue, dyspnea, or chest pain. The parameters of ejection fraction (EF), end-diastolic volume (EDV), and regional wall motion (RWM) were determined. Twenty-nine of the 36 patients had postoperative coronary arteriography that was correlated with radionuclide determinations. The results showed that in the normal subjects with maximal exercise the mean EF rose, the mean EDV increased 19%, and there was no exercise-induced regional wall motion dysfunction (ERWMD). In the patients with coronary artery disease prior to operation, the mean EF fell significantly, the mean EDV rose 24%, and 26 of 36 patients had ERWMD. After operation, the mean EF of the group rose, the EDV increased only 15%, and only two of 36 patients continued to show ERWMD. Of the eight patients who demonstrated on abnormal response postoperatively, seven had what was considered to be inadequate revascularization, and in one there was no explanation. The data demonstrate that myocardial revascularization does improve ventricular function by abolishing exercise-induced evidence of ischemia (decreased EF, increased EDV, and ERWMD) as assessed by radionuclide angiography. Failure to abolish the exercise-induced functional instability suggests incomplete revascularization.
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PMID:Improvement in left ventricular function after myocardial revascularization: assessment by first-pass rest and exercise nuclear angiography. 736 32

H reflex amplitudes, an indirect measure of the excitability of the alpha motoneuron pool, were recorded from 10 males during fatigue induced by submaximal, isotonic, voluntary contractions of the soleus muscle. H reflex changes were correlated with electromyographic changes (mean power frequency (MPF); root mean square (rms EMG)), under ischemic and non-ischemic conditions. The purpose of the ischemia was to block transmission of Ia and possibly Ib afferents to assess whether changes in sensory feedback had any effect on alpha motoneuron and EMG activity during fatigue. Significant interactions were found between ischemic and non-ischemic conditions. After an initial decrease (1.21 +/- 0.56 mV to 0.54 +/- 0.39 mV), H reflex amplitudes increased during non-ischemic trials (0.54 +/- 0.39 mV to 1.13 +/- 0.84 mV). Under ischemic conditions H reflex amplitudes decreased (2.11 +/- 1.10 mV to 0.70 +/- 0.74 mV; P < 0.003). During non-ischemic conditions, MPF decreased across 5 consecutive trials (157.7 +/- 17.9 Hz to 124.7 +/- 17.2 Hz), as compared to an increase under ischemic conditions (132.8 +/- 21.2 Hz to 197.1 +/- 53.6 Hz; P < 0.001). Root mean square amplitude decreased during the non-ischemic trials (31.07 +/- 14.62 mV to 25.98 +/- 8.26 mV). A greater decrease was noted during the ischemic trials (34.00 +/- 23.61 mV to 4.95 +/- 3.77 mV; P < 0.001). Data suggest that the CNS modulates muscle contraction in order to preserve force output and neuromuscular transmission during fatigue. This modulation appears dependent on Ia and/or Ib afferent feedback.
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PMID:Neural modulation of muscle contractile properties during fatigue: afferent feedback dependence. 751 97

Torbafylline, a novel xanthine derivative, was given to rats by gavage (2 x 25 mg.kg-1.day-1, morning and evening) to study its effect upon fast muscles (tibialis anterior and extensor digitorum longus) made ischemic by unilateral ligation of the common iliac artery and subjected to two types of activity imposed by chronic electrical stimulation at 10 Hz: (i) strenuous, 6 h.day-1 as 3 x 2 h with 90- to 120-min intervals or (ii) mild, 105 min.day-1 as 7 x 10-15 min with 90- or 85-min intervals for 12-14 days. Some of the deleterious effects on ischemic muscles of strenuous activity (reduced blood flow during contractions, less resistance to fatigue) were remedied by torbafylline treatment, and values normalized. Most notably, torbafylline significantly reduced the degree of capillary endothelial cell swelling. In addition, the degree of atrophy was reduced and fatigue resistance improved in muscles contralateral to ischemic, which had been impaired with the strenuous regime. Torbafylline treatment had little further effect on ischemic muscles subjected to mild stimulation, which on its own improved functional hyperemia, resistance to fatigue, and the capillaries per fibre ratio in tibialis anterior, although it did significantly increase the capillary per fibre ratio in extensor digitorum longus. These data indicate a possible role for torbafylline as an adjunct to exercise therapy for chronic muscle ischemia.
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PMID:Effect of torbafylline on muscle blood flow, performance, and capillary supply in ischemic muscles subjected to varying levels of activity. 782 90

Fast skeletal muscles of Sprague-Dawley rats [tibialis anterior (TA) and extensor digitorum longus (EDL)] were subjected to ischemia by unilateral ligation of the common iliac artery. In some animals, ischemia was combined with indirect electrical stimulation at 10 Hz either for 3 x 2 h (strenuous activity) or for 7 x 10-min bouts/day (mild activity). After 2 wk, muscle blood flow and fatigue were measured during 5-min isometric supramaximal twitch contractions at 4 Hz. Terminal arteriole diameters were assessed in TA by intravital microscopy at rest and during contractions. Vascular perfusion pressure in the muscles was estimated from measurements in the carotid and saphenous arteries below the site of ligation. Capillary supply was expressed in TA and EDL as capillary-to-fiber ratio on the basis of histochemical staining for capillaries. Strenuous stimulation of ischemic muscles increased their atrophy, failed to restore blood flow, and actually worsened fatigue. In contrast, mild stimulation improved perfusion pressure, increased capillary-to-fiber ratio in the glycolytic part of TA, restored dilatation of terminal arterioles during muscle contractions, and improved blood flow and muscle fatigue so that they were no longer significantly different from control muscles. Thus, an attenuated intermittent protocol may be indicated in the treatment of muscle ischemia.
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PMID:Effect of long-term electrical stimulation on vascular supply and fatigue in chronically ischemic muscles. 783 36


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