Skeletal muscle tissue oxygen pressure distribution during early reperfusion after prolonged ischaemia.
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OBJECTIVES: The aim of this study was to investigate the skeletal muscle tissue oxygen pressure (PtO2) distributions during early reperfusion (10-45 min) after prolonged ischaemia in a rat animal model. MATERIAL AND METHODS: Skeletal muscle ischaemia was induced in anaesthetised rats by applying a tourniquet on the left thigh for 3 h (group I) or 4 h (group II), and tissue oxygen pressure measurements were made after 10-45 min of reperfusion. Assessment of PtO2 was made by a multiwire Clark-type oxygen microelectrode, placed on the surface of the left tibialis anterior muscle. RESULTS: During reperfusion a similar PtO2 pattern was evaluated after both 3 and 4 h of total ischaemia, where the sum PtO2 distributions were shifted to the left associated with low tissue oxygen pressure values. After 10 min of reperfusion the median PtO2 was 0.28 kPa and 0.18 kPa, in groups I and II, respectively; after 45 min of reperfusion 0.61 kPa and 0.60 kPa, respectively. The median PtO2 in the non-ischaemic muscle in groups I and II were 2.19 and 2.17 Pa. CONCLUSION: The results show that local skeletal muscle oxygenation is severely impaired during the initial 45 min of reperfusion after both 3 and 4 h of total muscle ischaemia with a slow-reflow phenomenon generally present, despite pronounced needs. (+info)
In chronic nephropathies prolonged ACE inhibition can induce remission: dynamics of time-dependent changes in GFR. Investigators of the GISEN Group. Gruppo Italiano Studi Epidemiologici in Nefrologia.
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The Ramipril Efficacy in Nephropathy Core and Follow-Up Study found that > or =36 mo of continued ramipril therapy decreased substantially the risk of end-stage renal failure (ESRF) in patients with chronic nephropathies and a urinary protein excretion rate > or =3 g/24 h. This study investigates the time-dependent changes in GFR in these patients and in control subjects who were randomized to conventional therapy during the Core period and switched to ramipril during the Follow-Up study. Analyses included 150 patients (continued ramipril: n = 74; switched to ramipril: n = 76) who had at least three GFR measurements (including baseline) during the whole observation period and a subgroup of 43 patients (continued ramipril: n = 26; switched to ramipril: n = 17) who had at least six GFR measurements, including at least three on the Core and at least three on the Follow-Up study. Ramipril (1.25 to 5 mg/d) and conventional therapy were targeted at achieving a diastolic BP below 90 mm Hg. The main efficacy variables were GFR and ESRF (need for dialysis). Analysis was by intention to treat. Throughout the study, the mean +/- SEM rate of GFR decline (deltaGFR) was significantly lower in patients continued on ramipril compared to those switched to ramipril (0.51+/-0.09 versus 0.76+/-0.10 ml/min per 1.73 m2 per mo, P<0.03). In patients on continued ramipril who had at least six GFR measured--but not in control subjects--deltaGFR progressively improved with time and, in the cohort with the longest follow-up, decreased from (in ml/min per 1.73 m2 per mo): 0.16+/-0.12 (at 18 mo) to 0.10+/-0.05 (at 60 mo). This rate was about 10-fold slower compared to patients on conventional therapy during the REIN Core study. Analyses of the individual slopes found that at the end of the follow-up, 10 of 26 patients on continued ramipril therapy had a positive deltaGFR and another 10 patients had an improvement of deltaGFR while on ramipril therapy. DeltaGFR significantly improved in parallel with a significant reduction in proteinuria. Changes in deltaGFR (P = 0.0001) and proteinuria (P = 0.04) were significantly different in the two groups. Baseline characteristics and changes in systolic and diastolic BP and 24-h urine urea and sodium excretion were comparable. The present results offer evidence that in chronic nephropathies, the tendency of GFR to decline with time can be effectively halted, even in patients with remarkably severe disease. (+info)
99mTc-bicisate and 99mTc-HMPAO SPECT imaging in early spontaneous reperfusion of cerebral embolism.
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Two patients with a cerebral embolism were evaluated by using both 99mTc-ethyl cysteinate dimer (ECD, or Bicisate) and 99mTc-hexamethylpropyleneamine oxime (HMPAO) single-photon emission computed tomography (SPECT). In one patient, 99mTc-ECD SPECT images revealed hypoactivity in a reflow hyperemic area where an infarct was seen later on CT scans. In another patient, a reperfused area showed hyperactivity on 99mTc-ECD SPECT without any abnormality on follow-up CT. 99mTc-ECD represents a potential agent with which to evaluate cerebral tissue viability in early reperfusion after ischemia. (+info)
Viability and enzymatic activity of cryopreserved porcine heart valve.
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Fibroblast viability of a natural tissue valve for replacing a defective heart valve through allograft or xenograft has been suggested to affect its clinical durability. In this study, the cell viability and enzymatic activity of porcine heart valve leaflets were examined in regard to concerning to the preservation process [variable warm ischemic time (WIT), cold ischemic time (CIT), and cryopreservation]. Porcine heart enblocs were obtained and valve dissection was performed after 2, 12, 24, or 36 hours, in respective groups A, B, C, and D, as WIT. Each group was stored for 24 hours as CIT and cryopreserved. Leaflets were dissected from a valved conduit after each process, and cell viability and enzymatic activity in the leaflet were investigated using trypan blue staining and API ZYM kits. WIT extension significantly decreased fibroblast viability (p < 0.05, 92.25 +/- 2.7% at 2 hours, 84.9 +/- 6.7% at 12 hours, 57.0 +/- 10.2% at 24 hours, 55.9 +/- 7.9% at 36 hours), while CIT for 24 hours was also influenced significantly (p < 0.05), whereas cryopreservation demonstrated no effect on cellular viability. In enzyme activity observation, several enzymes related to lipid or nucleotide degradation (esterase, esterase lipase, particularly phosphatase, phosphohydrolase) were remarkably changed following the valve-fabrication process. After 24 hours CIT, these enzymatic activities in groups B, C and D significantly increased, but the activities decreased after cryopreservation. Particularly, both the viability and enzymatic activity showed remarkable changes after CIT in group B (WIT = 12 hours). These results suggest that WIT is more important than CIT in maintaining viability of the valve, and that completing all the cryopreservation process within 12 hours after acquisition is recommended. (+info)
Prevalence of myocardial viability as detected by positron emission tomography in patients with ischemic cardiomyopathy.
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BACKGROUND: Detection of myocardial viability is important in patients with ischemic cardiomyopathy. Restoration of blood flow to viable myocardium is associated with improved left ventricular function and improved patient prognosis. However, the prevalence of viable myocardium in patients with ischemic cardiomyopathy is unknown. METHODS AND RESULTS: To determine the prevalence of myocardial viability, clinical [13N]ammonia/18F-deoxyglucose PET studies performed in 283 patients (age, 63+/-10 years) with ischemic heart disease (mean ejection fraction, 26+/-8%) were visually analyzed for the presence and extent of viable and nonviable myocardium. The myocardium was divided into 19 segments. The extent of viable myocardium was considered "functionally" significant if >/=5 segments ( approximately 25% of the left ventricular myocardium) exhibited a blood flow/metabolism mismatch and "prognostically" significant if 1 to 4 left ventricular segments did so. Of all patients, 41% had no evidence of viable myocardium, 55% had viable myocardium, and 4% had normal blood flow and metabolism within an enlarged left ventricle. Functionally significant viability was found in 27% and prognostically significant viability in 28% of the patients. Multivariate analysis revealed the presence of angina to be the only clinical parameter associated with the presence of functionally significant viability. CONCLUSIONS: Revascularization might improve patient prognosis in 55% and result in improved left ventricular function in 27% of all patients with ischemic cardiomyopathy. (+info)
Prognostic value of myocardial ischemia and viability in patients with chronic left ventricular ischemic dysfunction.
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BACKGROUND: Previous studies showed that thallium scintigraphy and dobutamine echocardiography were accurate, noninvasive ways of predicting contractile recovery after revascularization in patients with left ventricular (LV) dysfunction. However, the prognostic impact of such methods remains uncertain. METHODS AND RESULTS: We prospectively studied 137 consecutive patients with coronary disease and LV dysfunction who underwent exercise-redistribution-reinjection thallium scintigraphy and dobutamine echocardiography to identify myocardial ischemia and viability. A total of 94 patients subsequently underwent revascularization, and 43 underwent medical treatment. The primary endpoint was cardiac mortality, and mean follow-up was 33+/-10 months. Twenty-four patients died of cardiac causes. By Cox's regression analysis, long-term survival was related to the extent of coronary disease, the presence of diabetes, type of treatment, the presence of ischemic myocardium as determined by thallium scintigraphy, and the presence of viable myocardium as determined by both tests. Three-year survival was greater in patients with ischemic myocardium (as determined by thallium scintigraphy) or viable myocardium (as determined by both tests) who underwent revascularization than in the other groups (P=0.018 with thallium; P<0.001 with dobutamine). Subgroup analyses indicated that among patients with 1- or 2-vessel disease, only those with ischemic or viable myocardium improved survival after revascularization, whereas in patients with 3-vessel or left main diseases, revascularization always improved survival, albeit more in the presence of ischemic or viable myocardium. CONCLUSIONS: Among the parameters commonly available in patients with LV ischemic dysfunction, the presence of ischemic myocardium (as determined by thallium scintigraphy) and that of viable myocardium (as determined by dobutamine echocardiography) are independent predictors of subsequent mortality. These observations may be useful in the preoperative selection of patients for revascularization. (+info)
Prediction of functional recovery of viable myocardium after delayed revascularization in postinfarction patients: accuracy of dobutamine stress echocardiography and influence of long-term vessel patency.
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OBJECTIVES: We sought to evaluate dobutamine stress echocardiography (DSE) for predicting recovery of viable myocardium after revascularization with cineangiography as a gold standard for left ventricular (LV) function. We studied the influence of late vessel reocclusion on regional LV function. BACKGROUND: Dobutamine stress echocardiography is a well established evaluation method for myocardial viability assessment. In previous studies the reference method for assessing LV recovery was echocardiography, long-term vessel patency has not been systematically addressed. METHODS: Sixty-eight patients with a first acute myocardial infarction (AMI) and residual stenosis of the infarct related artery (IRA) underwent DSE (mean +/- standard deviation) 21 +/- 12 days after AMI to evaluate myocardial viability. Revascularization of the IRA was performed in 54 patients by angioplasty (n = 43) or bypass grafting (n = 11). Coronary angiography and LV cineangiography were repeated at four months to assess LV function and IRA patency. RESULTS: Sensitivity and specificity of DSE for predicting myocardial recovery after revascularization were 83% and 82%. In the case of late IRA patency, specificity increased to 95%, whereas sensitivity remained unchanged. In the 16 patients with myocardial viability and late IRA patency, echocardiographic wall motion score index decreased after revascularization from 1.83 +/- 0.15 to 1.36 +/- 0.17 (p = 0.0001), and left ventricular ejection fraction (LVEF) increased from 0.52 +/- 0.06 to 0.57 +/- 0.06 (p = 0.0004), whereas in five patients, reocclusion of the IRA prevented improvement of segmental or global LV function despite initially viable myocardium. CONCLUSIONS: Dobutamine stress echocardiography is reliable to predict recovery of viable myocardium after revascularization in postinfarction patients. Late reocclusion of the IRA may prevent LV recovery and influence the accuracy of DSE. (+info)
Can the surface electrocardiogram be used to predict myocardial viability?
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OBJECTIVE: To investigate whether QRS morphology on the surface ECG can be used to predict myocardial viability. DESIGN: ECGs of 58 patients with left ventricular impairment undergoing positron emission tomography (PET) were studied. (13)N-Ammonia (NH(3)) and (18)F-fluorodeoxyglucose (FDG) were the perfusion and the metabolic markers, respectively. The myocardium is scarred when the uptake of both markers is reduced (matched defect). Reduced NH(3) uptake with persistent FDG uptake (mismatched defect) represents hibernating myocardium. First, the relation between pathological Q waves and myocardial scarring was investigated. Second, the significance of QR and QS complexes in predicting hibernating myocardium was determined. RESULTS: As a marker of matched PET defects, Q waves were specific (79%) but not sensitive (41%), with a 77% positive predictive accuracy and a poor (43%) negative predictive accuracy. The mean size of the matched PET defect associated with Q waves was 20% of the left ventricle. This was not significantly different from the size of the matched PET defects associated with no Q waves (18%). Among the regions associated with Q waves on the ECG, there were 16 regions with QR pattern (group A) and 23 regions with QS pattern (group B). The incidence of mismatched PET defects was 19% of group A and 30% of group B (NS). CONCLUSIONS: Q waves are specific but not sensitive markers of matched defects representing scarred myocardium. Q waves followed by R waves are not more likely to be associated with hibernating myocardium than QS complexes. (+info)