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

Skeletal muscle edema secondary to an increase in capillary permeability after reflow is an important cause of the compartment syndrome after acute arterial revascularization. The purpose of this study was to investigate the possible role of oxygen free radicals, generated at reperfusion, in the pathogenesis of the compartment syndrome secondary to acute arterial ischemia/reperfusion. A reproducible model of this syndrome was produced in anesthetized rabbits by femoral artery occlusion after surgical devascularization of collateral branches from the aorta to the popliteal artery. Increasing periods of ischemia from 6 to 12 hours, followed by 2 hours of reperfusion, were associated with corresponding increases in the anterior muscle compartment hydrostatic pressure and inversely proportional decreases in tibialis anterior muscle blood flow within that compartment as assessed by xenon 133 washout (n = 46) (r = -0.62, p less than 0.001). Anterior compartment pressure increased from 5 +/- 1 to 48 +/- 5 mm Hg (n = 46) (p less than 0.001) after 7 hours of total arterial ischemia and 2 hours of reperfusion. Ablation of free radicals generated from xanthine oxidase with either allopurinol (n = 8) or oxypurinol (n = 8), by scavenging the superoxide radical at reperfusion with superoxide dismutase (n = 8), or by blocking secondary hydroxyl radical formation with deferoxamine (n = 8) significantly ameliorated the rise in compartment pressure (p less than 0.05) in each case; it also significantly improved muscle perfusion in the superoxide dismutase-, allopurinol-, and deferoxamine-treated animals (p less than 0.05). These findings indicate that development of the compartment syndrome after acute arterial revascularization may be due, at least in part, to microvascular injury mediated by oxygen-derived free radicals generated from xanthine oxidase at reperfusion.
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PMID:Inhibition of the compartment syndrome by the ablation of free radical-mediated reperfusion injury. 236 Jan 89

We have previously shown that cardiac cycle-dependent variation of integrated backscatter occurs in normal myocardium. To determine whether myocardial ischemia and reperfusion can be distinguished by real-time integrated backscatter imaging we performed 10 min balloon occlusion of the Left Anterior Descending (LAD) coronary artery followed by reperfusion in 10 closed-chest anesthetized dogs. Images were obtained at baseline, during occlusion, and up to 120 min after reperfusion. We measured the magnitude and delay of cyclic variation of integrated backscatter in segments with and without asynergy. Radiolabeled microspheres were used to verify both ischemia and reperfusion. Ischemic segments exhibited decreased magnitude and increased normalized delay of cyclic variation of integrated backscatter (from 3.3 +/- 0.3 dB to 1.4 +/- 0.2 dB, mean +/- SE; and from 0.95 +/- 0.03 to 1.67 +/- 0.15, respectively, all p less than or equal to 0.001). Reperfusion promptly restored the magnitude of cyclic variation toward normal. However, the delay of the cyclic variation was restored only partially. Wall motion analysis of the ischemic sites revealed persistent abnormalities throughout the reperfusion interval despite return to normal of the magnitude and delay of cyclic variation. Thus, real-time integrated backscatter imaging permits detection and differentiation of changes in myocardial acoustic properties indicative of ischemia and of subsequent reperfusion.
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PMID:Myocardial ultrasonic backscatter for characterization of ischemia and reperfusion: relationship to wall motion. 239 28

To evaluate the significance of "reciprocal" ST segment depression resulting from coronary occlusion, 27 patients with single vessel coronary disease were studied with intravenous digital subtraction left ventriculography before and during angioplasty of the left anterior descending coronary artery. During balloon inflation, 13 patients developed inferior lead ST depression in addition to anterior lead ST elevation (Group 1), whereas the remaining 14 patients did not (Group 2). The degree of anterior lead ST elevation in Group 1 (5 mm) was greater than that in Group 2 (1.5 mm, p less than 0.001) as was the reduction in left ventricular ejection fraction (24% versus 13%, respectively; p less than 0.02). Anterior and apical regional shortening decreased in both groups similarly, but an additional decrease in anterobasal shortening was confined to Group 1 (from 38% to 21%; p less than 0.002). Despite the presence of inferior lead ST depression in Group 1, inferior regional shortening did not change and inferobasal contraction was enhanced (from 4% to 29%; p less than 0.01). Inferior lead ST segment depression during anterior descending coronary angioplasty reflects a greater degree of anterior wall ischemia. The concurrent preservation of inferior wall contraction and the augmentation of infero-basal shortening confirm that this electrocardiographic feature is a "reciprocal" phenomenon rather than a manifestation of remote ischemia.
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PMID:Significance of "reciprocal" ST segment depression: left ventriculographic observations during left anterior descending coronary angioplasty. 252 57

Patients with acute inferior myocardial infarction commonly have ST segment depression in the anterior precordial leads. This may reflect either reciprocal changes from the inferior ST elevation or primary ST depression from additional anterior subendocardial ischemia. From a biophysical perspective reciprocal changes should be uniformly anticipated from basic dipole theory. Detection will vary with the size, location, orientation, and electrical intensity of the lesion and with the ECG lead system deployed to register the anterior changes. Alternatively, acute occlusion of the right coronary artery may produce ischemia in the anterior left ventricular wall supplied by a stenotic anterior descending coronary artery. Anterior ischemia may result from the abnormal hemodynamics or the reduced collateral flow produced by acute right coronary artery occlusion. Thus both mechanisms are based on sound physiologic principles. A review of the clinical literature suggests that such patients represent a heterogeneous group. In some instances coexistent anterior ischemia is present, whereas in others the anterior ST depression is the passive reflection of inferior ST elevation augmented in many cases by a large infarct size or more extensive posterobasal or septal involvement.
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PMID:Physiologic bases for anterior ST segment depression in patients with acute inferior wall myocardial infarction. 305 9

Nine patients underwent simultaneous or staged detachment of the vertical and medial rectus muscles in the treatment of sixth nerve palsy or Duane's retraction syndrome. In five adult patients (34, 35, 41, 45, and 65 years of age), clinically significant anterior segment ischemia developed postoperatively. Known medical risk factors were present in only one case. With the exception of corectopia, there were no apparent sequelae and all involved eyes returned to preoperative visual acuity within 9 weeks of surgery. Anterior segment ischemia may be a frequent complication of strabismus surgery in adult patients when the superior, inferior, and medial rectus muscles are detached from the globe.
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PMID:Anterior segment ischemia after three rectus muscle surgery. 317 12

A case of congenital erythropoietic porphyria, with corneoscleral ulceration, a rare association in this disorder, was reported. Anterior segment ischemia is believed to play an important role in the etiopathogenesis of corneoscleral ulceration. Remarkable improvement occurred with use of topical heparin drops (500 units/ml).
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PMID:Corneoscleral ulceration in congenital erythropoietic porphyria (a case report). 341 8

Anterior segment ischemia developed in a 62-year-old dysthyroid patient after two-muscle adjustable suture repair of vertical strabismus. Because of a quiescent pulmonary tuberculous focus he was not treated with systemic steroid therapy but rather with hyperbaric oxygen in the controlled environment of our hospital hyperbaric chamber. He tolerated this treatment well, and his acute symptoms almost completely resolved in 3 days. We believe this to be the first reported case of the use of hyperbaric oxygen in the management of anterior segment ischemia. We also believe it is the first reported case of anterior segment ischemia following surgery to two opposing, not contiguous, rectus muscles in dysthyroid ophthalmopathy.
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PMID:Anterior segment ischemia treated with hyperbaric oxygen. 343 55

The relationship between inducible ventricular tachycardia in the convalescent phase of myocardial infarction and subsequent spontaneous ventricular fibrillation is uncertain. Thirty conscious instrumented dogs underwent programmed ventricular stimulation 5 days after anterior infarction; 15 had inducible ventricular tachycardia and 15 were noninducible. Following programmed ventricular stimulation, the application of a 150 uA current to the intima of the proximal circumflex artery initiated intimal damage, thrombosis, and acute ischemia of the posterolateral wall. After 20 minutes of ischemia, 73% inducible and 15% noninducible animals developed ventricular fibrillation (p less than 0.005) without previous hypotension. At 24 hours, 7% inducible and 85% noninducible animals survived (p less than 0.001). Anterior infarct size (percentage of left ventricular mass) was much larger in inducible (24.7 +/- 1.7%) than in noninducible (5.3 +/- 1.1%) (p less than 0.001) animals. Inducible ventricular tachycardia following infarction was highly predictive of spontaneous ventricular fibrillation during a later ischemic episode in this model. The mass of previously injured myocardium was a critical determinant of both.
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PMID:Postinfarction sudden death: significance of inducible ventricular tachycardia and infarct size in a conscious canine model. 396 35

The relationship between epicardial and transmural function (measured with sonomicrometers) was examined in 13 anesthetized open-chest dogs. Systolic wall thickening was used as a standard of integrated transmural function to compare with epicardial function measured as segment shortening parallel to surface fibers. Three levels of coronary inflow restriction were produced by using decrements in systolic wall thickening as an index of changes in the transmural distribution of myocardial blood flow (microspheres) in myocardium perfused by the left anterior descending artery (anterior-apical group, n = 7) or circumflex artery (posterior-basal group, n = 6). Levels 1 and 2 were characterized by reductions in systolic wall thickening of 35% and 80%, respectively, and marked decreases in deep myocardial blood flow. In the subepicardium, myocardial blood flow was minimally affected at levels 1 and 2 and there was no change in posterior-basal epicardial segment shortening, but anterior segment shortening decreased significantly (by 21% and 37%, respectively). At level 3 myocardial blood flow was reduced transmurally, producing systolic wall thinning and marked epicardial dysfunction in both groups. Parallel epicardial segment shortening underestimated the extent of transmural dysfunction in both groups at levels 1 and 2 but the degree of underestimation was greatest in the posterior-basal group. Anterior-apical segment shortening was impaired at levels 1 and 2, whereas posterior-basal segment shortening was unaffected, suggesting that significant regional variability exists in the epicardial response to nontransmural ischemia.
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PMID:Dissociation between epicardial and transmural function during acute myocardial ischemia. 399 16

This work was done to evaluate the transcutaneous oxygen tension (TcPO2) in ischaemic legs introducing two variables: O2 breathed at 40% and heating with an electric blanket (HEB). Forty nine legs were studied and divided into three different groups: Normal (N) 19 legs, Intermittent Claudication (IC) 12, and Rest Pain (RP) 13. The transcutaneous sensor was placed on the Anterior Chest Wall (AChW), High thigh (HT), Anterior Tibial Compartment (ATC) and Dorsum of the Foot (DF). Measurements were done at each area with and without 40% O2 and with and without HEB. The TcPO2 readings increased significantly (P less than 0.05) in the three groups (N, IC, RP) at all leg levels (HT, ATC, DF) when the patient breathed 40% O2 with and without HEB. In the N group no significant differences were noted between the three leg levels whether the 40% O2 or the HEB was used or not (P less than 0.05). In the RP group significant differences were obtained when the HEB was used whether the patient was breathing ambient O2 or at 40%. On the contrary, when the HEB was not used, the differences between HT and ATC disappeared but persisted at the DF (P less than 0.05). There was a good correlation at the DF and at the AChW (DF/AChW) (r: 0.8012; P less than 0.001). From these results, we conclude that the TcPO2 is a good method of differentiating different degrees of leg ischemia in vascular patients.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Assessment of transcutaneous oxygen tension in ischaemic legs by means of using an electric blanket and 40% O2. 406 35


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