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Biomedical subjects

M Fauchet

Publications and source records attributed to M Fauchet.

At least 19 recordsLinked to original sources
PubMed1998

Broadband ultrasound attenuation at the calcaneus measured using a new contact ultrasound unit.

We evaluated a new contact ultrasound device, developed and manufactured in France, for measuring broadband ultrasound attenuation at the calcaneus. We first studied the influence on measurement results of a number of parameters including the nature of the coupling agent, heel position, transducer temperature, and foot vasodilation. We then determined the reproducibility of the measurements (2.14 +/- 1.07% in the medium-term) and established reference values in women (n = 612) and men (n = 106). Broadband ultrasound attenuation decreased between 25 and 85 years of age by 34% in women and 17% in men. Sensitivity and specificity for detection of decreased bone mass at the calcaneus were 85.5% and 81.5%, respectively. Sensitivity and specificity of the measurement at the calcaneus as compared to the lumbar spine were 90.7% and 89.1%, respectively. This unit intended for screening purposes is very easy to use, and the measurements it provides are immediately available. It can be expected to help determine the optimal strategy for use of ultrasound in the management of osteoporosis.

Adult↗
PubMed1996

Scintigraphic Study of Local Flux and Osmotic Pressure Distributions in Ultrafiltration of Blood and Plasma.

We have investigated the spatial variation of local protein concentration and filtration flux by a scintigraphic technique in the ultrafiltration of bovine albumin solutions and blood. The feed was mixed with (99m)Tc albumin macroaggregates and circulated through a polysulfone 30,000 MWCO hollow fiber filter placed in the field of a gamma-camera. Concentration profiles c(b) (x) were reconstructed from scintigraphic images and the local ultrafiltration flux was calculated by differentiating c(b) (x) and using mass conservation. Tests were run at various inlet shear rates from 472 to 1415 s(-1) and under two different filtration regimes: no net filtration (permeate valve closed) and large filtration (below the pressure independent plateau). The data confirm the filtration decay from the filter inlet to outlet but an unexpected result is the presence of high retrofiltration in the downstream part of the filter length in the case of large filtration. This retrofiltration can be explained by a high osmotic pressure at the membrane created by the protein polarization concentration. Assuming a constant pressure gradient along the fibers, it is possible to estimate the local osmotic pressure at the onset of retrofiltration and to infer from it the protein concentration at the membrane, which is found to vary from 170 to 250 g/liter when gamma(w) increases. Similar experiments were run with blood and a microfiltration membrane (0.55-µm pores). In that case no retrofiltration was obtained, which confirms our explanation since in this case the polarization layer is composed of red cells which exert no osmotic pressure.

Journal Article↗
PubMed1996

Limited activity of mini-dose interferon alpha-2a in the treatment of myelodysplastic syndrome.

Impairment in marrow function often characterizes the evolution of myelodysplastic syndrome. As a differentiating agent, interferon alpha 2a (INF alpha) has been shown to be active in the correction of cytopenias related to myelodysplastic syndromes (MDS). We report the clinical course of 9 patients with MDS treated with low-dose subcutaneous INF alpha (1 x 10(6), 3 times per week). A significant effect on anemia was only demonstrated in one patient (11%). In the other, eight, therapy was totally ineffective and four of them could not receive the complete treatment due to worsening cytopenias or leukemic transformation. In conclusion, in our study, INF alpha had only limited activity in the treatment of myelodysplastic syndrome.

Drug Evaluation↗
PubMed1990

Detection of prosthetic valve thrombosis using 111indium platelet imaging.

The diagnosis of prosthetic valve thrombosis (PVT) may be difficult in cases without valve obstruction. The aim of this study was to evaluate the diagnostic accuracy of 111indium-labelled autologous platelet imaging in the detection of PVT. We studied 41 patients with 45 prostheses, mechanical (37) or biological (8), in the mitral (26) or aortic (19) site. Mean age was 55 +/- 13 years. All these patients experienced one or several thromboembolic events (mean: 2.3 per patient). The mean interval between the last embolic event and indium test (IT) was 32 +/- 25 days. Scintigrams were recorded in two views daily for 5 days. IT showed an abnormal platelet deposition on the prosthetic area in 24 patients. Platelet half-life was 3.8 +/- 1.0 days for patients with a positive IT and 4.6 +/- 0.6 days for those with a negative IT (P less than 0.01). Anatomical data were obtained in 10 cases (surgery nine, autopsy one) 16 +/- 5 days after IT. All these patients had PVT, and IT was positive in eight cases. In the other 31 medically treated patients, recurrent embolism occurred within 12 months after IT in four cases, three of whom previously had a positive test. We conclude that IT is a useful means for detecting PVT.

Aortic Valve↗
PubMed1989

Adequate preservation of right ventricular function after coronary sinus cardioplegia. A clinical study.

Whether retrograde coronary sinus cardioplegia adequately preserves right ventricular (RV) function is still a point of concern. Using technetium Tc 99m-labeled red blood cells, we assessed global and segmental RV function by first-pass and gated blood-pool radionuclide angiocardiography before and within 24 hours after aortic valve replacement in 14 consecutive patients (age, 58 +/- 5 years; mean +/- SEM). Coronary sinus cardioplegia was given in a multidose fashion at a flow rate of 50-70 ml/min through a balloon-tipped catheter, with the inflated balloon kept seated around the intra-atrial rim of the coronary sinus orifice. Additional myocardial protection was provided by systemic (25 degrees C) and topical hypothermia. Postoperatively, none of the patients had clinical or hemodynamic patterns suggestive of RV dysfunction. The postoperative global RV ejection fraction (0.49 +/- 0.03) was similar to the preoperative value (0.49 +/- 0.01). Analysis of segmental wall motion did not reveal postoperative abnormalities of new onset in any of the three anatomically defined RV regions (free wall, apex, and septum). Similarly, RV end-diastolic and end-systolic volume indexes (ml/m2) were not significantly affected by coronary sinus cardioplegia, being 71.6 +/- 5.8 and 36.1 +/- 3.5 before, and 67.4 +/- 3.8 and 34.5 +/- 2.3 after aortic valve replacement, respectively. We conclude that retrograde coronary sinus cardioplegia does not cause a detectable impairment of RV function if the balloon catheter does not obstruct the terminal tributaries of the coronary sinus and, hence, does not impede delivery of cardioplegia to right-sided cardiac structures.

Adult↗
PubMed1988

Radionuclide exploration of dialysis amyloidosis: preliminary experience.

The noninvasive diagnosis of amyloid arthropathy in dialysis patients is still uncertain. Therefore, we investigated the potential diagnostic value of the 99mTc-methylene diphosphonate scan in seven long-term hemodialysis patients suffering from chronic joint pain who had biopsy-proven osteoarticular amyloidosis of the recently discovered beta 2-microglobulin (beta 2-M) type. In six, but in none of five control patients on short-term hemodialysis, increased tracer uptake was found at the site of one or several articular and/or periarticular regions. Increased uptake at a given joint was often, but not always, associated with joint pain. It appeared to precede radiologically visible changes. In conclusion, the 99mTc-methylene diphosphonate scan may be of help in the early diagnosis of dialysis amyloidosis.

Adult↗
PubMed1987

Left ventricular global and regional function during lumbar epidural anesthesia in patients with and without angina pectoris. Influence of volume loading.

The influence of lumbar epidural anesthesia without cardiac sympathectomy on global and regional left ventricular function was investigated prior to surgery in eight normal subjects (group 1) and in ten patients suffering from stable mild effort-related angina (group 2). In both groups, epidural blockade was performed with 10 ml 0.5% plain bupivacaine. To differentiate the effects due to epidural blockade from those related to volume expansion, three sets of measurements were obtained: control, epidural blockade without volume loading, and epidural blockade with volume loading (500 ml lactated Ringer's solution). Radionuclide angiography was used to determine cardiac output, left ventricular ejection fraction, end systolic and end diastolic volumes, and to analyse left ventricular wall motion. Peak systolic pressure-end systolic volume ratio was used as an index of myocardial contractility. Seventy-two hours postoperatively, a thallium 201 myocardial scintigraphy obtained after iv dipyridamole detected myocardial defects in all patients with a history of angina. These defects were fully redistributed in eight out of ten patients. Throughout the procedure, patients with a history of angina exhibited neither chest pain nor ECG evidence of myocardial ischemia. At control, left ventricular ejection fraction (LVEF) and systolic pressure-volume ratio (SPVR) were lower in group 2 than in group 1 (LVEF: 0.54 +/- 0.02 vs. 0.64 +/- 0.02, P less than 0.01), (SPVR: 2.3 +/- 0.2 vs. 3.3 +/- 0.4 mmHg/ml, P less than 0.05). In addition, 19 hypokinetic sectors were found in group 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

[Value of computed medical imaging in the surveillance of neo-adjuvant chemotherapy of osteogenic osteosarcoma in children and adolescents. 51 patients seen from 1984 to 1986].

The value of quantitative bone scintigraphy, digitised angiography, CT scanning and magnetic resonance imaging in the follow-up of neo-adjuvant chemotherapy for osteogenic osteosarcoma was assessed in 51 patients between 1984 and 1986. Bone scintigraphy was a very sensitive method of detecting bone metastases but of limited value in assessing the response to preoperative chemotherapy. CT scanning was very useful in small and medium sized tumours with predominantly non-calcific involvement of the soft tissue. At present, digitised angiography seems to be the best investigation for following up these patients as shown by the close histo-angiographical correlations. However, magnetic resonance imaging is a very promising method and may in future replace the more invasive aforementioned techniques in this indication.

Adolescent↗
PubMed1986

Value of the 99mTc-methylene diphosphonate bone scan in renal osteodystrophy.

The value of radionuclide bone scanning in the diagnosis of renal osteodystrophy is still debated. In order to re-examine this issue, 25 uremic patients treated by intermittent hemodialysis underwent 99m-Technetium Methylene Diphosphonate (99mTc-MDP) bone scan. They were subdivided into three groups according to quantitative bone histology. Group 1 (N = 8) had pure dialysis osteomalacia, group 2 (N = 7) mixed lesions, and group 3 (N = 10) pure osteitis fibrosa. The scintigraphic studies were interpreted by means of a five point semi-quantitative scale. Using this quantification, all but one group 1 patients had decreased bone tracer uptake, and all patients of group 3 had an increased uptake (chi square test of Yates, P less than 0.001). Among patients of group 2, bone uptake was decreased in the three patients with clearly reduced mineralization front and moderate osteitis fibrosa, but it was increased in all patients with severe osteitis fibrosa and subnormal mineralization front. A quantitative analysis of regional tracer uptake into bone was performed in two patients: one of group 2 and one of group 3. The results obtained clearly corroborated the semi-quantitative findings. Thus, in hemodialysis patients with symptomatic bone disease, the 99mTc-MDP bone scan provides useful information for the differential diagnosis between dialysis-related osteomalacia and secondary hyperparathyroidism. In patients with mixed lesions, the importance of bone tracer uptake appears to depend on the extent of the mineralization front and on the intensity of osteitis fibrosa.

Adult↗
PubMed1986

Response of left ventricular ejection fraction to recovery from general anesthesia: measurement by gated radionuclide angiography.

To test the hypothesis that, after anesthesia for noncardiac surgical procedures, the increased cardiac work during recovery induces wall motion and ejection fraction (EF) abnormalities in patients with mild angina pectoris, gated radionuclide angiography was performed in patients undergoing simple cholecystectomy under narcotic-relaxant general anesthesia. The ejection fraction was determined during anesthesia at the end of surgery, and then determined 3 min and 3 hr after extubation. A new angiography was performed 24 hr later, and a myocardial scintigraphy (Thallium 201) was performed during infusion of the coronary vasodilator, dipyridamole. In the first part of the investigation, eight patients without coronary artery disease (CAD) (group 1) and 20 patients with mild angina (group 2) were studied. In the second part of the study, seven patients (group 3) with mild angina pectoris received an intravenous infusion of 0.4 microgram X kg-1 X min-1 of nitroglycerin started before surgery and gradually decreased 4 hr after extubation. In group 1, EF remained unchanged at recovery. In contrast in group 2, EF responded abnormally to recovery: EF decreased from 55% during anesthesia to 45% 3 min after extubation (P less than 0.001). Patients in group 3, who received intravenous nitroglycerin, showed no change of EF at recovery. This study demonstrates that recovery from general anesthesia causes abnormalities in left ventricular function in patients suffering from CAD. These abnormalities are prevented by prophylactic intravenous nitroglycerin.

Aged↗
PubMed1985

Limitations of fluorocarbons in reducing myocardial infarct size.

The effects of the oxygen-carrier fluorocarbons on myocardial infarct size were assessed in non-exchange-transfused dogs subjected either to a 3-hour occlusion of the left anterior descending coronary artery (LAD) followed by 2 hours of reperfusion (protocol I) or to a 5-hour permanent LAD occlusion (protocol II). Fluorocarbon administration was begun 30 minutes after LAD occlusion and was continued over the entire period of ischemia. After 5 hours, the hearts were excised and areas of necrosis were visualized by triphenyl tetrazolium chloride staining while risk regions were assessed by radiolabeled microspheres injected after coronary occlusion just before the onset of therapy, and further, in protocol I, by thallium-201 perfusion imaging performed at the end of fluorocarbon administration. In protocol I experiments, the ratio of necrotic area to area at risk was 81 +/- 35% (mean +/- standard deviation) in control saline-treated dogs (n = 6) and 67 +/- 27% in fluorocarbon-treated dogs (n = 6) (difference not significant). There was no significant difference between risk regions measured after and before fluorocarbon treatment. In protocol II, the ratio of necrotic area to area at risk was 47 +/- 30% in control dogs (n = 5) and 63 +/- 29% in fluorocarbon-treated dogs (n = 5) (difference not significant). However, in control dogs, the ratio of necrotic area to area at risk increased from 47 +/- 30% in the dogs that underwent permanent occlusion to 81 +/- 35% in the group that underwent reperfusion (p less than 0.001) while this ratio was similar in the corresponding subsets of fluorocarbon-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Left ventricular dysfunction after non-cardiac surgical procedures in patients with ischemic heart disease.

In order to demonstrate the presence of postischemic ventricular dysfunction after non-cardiac surgical procedures, myocardial perfusion scintigraphy with thallium 201 and radionuclide ventriculography were performed before and 24 h after intervention in 20 patients suffering from angina pectoris. A long-term ECG recording was used in all patients to detect peroperative myocardial ischemia. In 14 of the 20 patients studied, both ventriculography and thallium scintigraphy were unchanged at the postoperative study. Comparison of pre- and postoperative radionuclide data revealed an increased deficit in one patient, both increased deficit and decreased ejection fraction in four others and a decreased ejection fraction in one other. In these five last patients, continuous ECG recording demonstrated the occurrence of peroperative ST segment depression. These results underline the part played by prolonged peroperative episodes of myocardial ischemia in the occurrence of postoperative left ventricular dysfunction.

Adult↗
PubMed1984

Reduction of myocardial infarct size by a fluorocarbon-oxygenated reperfusate.

This investigation assesses whether the size of an acutely revascularized myocardial infarct (MI) could be reduced by altering the composition of the initial reperfusate. Nineteen open-chest dogs underwent 4-hour occlusion of the left anterior descending coronary artery and were then assigned to a treatment group: 12 dogs to selective intracoronary infusion of the modified reperfusate over 30 minutes before resumption of blood flow for 60 minutes and 7 to a control group (90 minutes of unmodified blood reperfusion). The modified reperfusate consisted of 500 ml of a fluorocarbon-oxygenated crystalloid solution (PO2 650 mm Hg; total O2 content 5.5 vol%) whose composition was adjusted by decreasing Ca++ (0.25 mM), increasing pH (7.60) and adding glucose (1.8 g/liter). Four hours after occlusion, technetium-99m-labeled microspheres were injected into the left atrium. After 90 minutes of reperfusion, the heart was removed and sliced transversely. Areas not perfused by microspheres (areas at risk) were traced, planimetered and compared with the areas of necrosis after incubation in triphenyltetrazolium chloride. Areas were then converted into weights. In control dogs, the weight of necrotic myocardium was not significantly different from the weight at risk (5.0 +/- 0.7 vs 7.0 +/- 0.8 g, respectively [mean +/- standard error of the mean]), whereas it was markedly reduced in treated dogs (5.9 +/- 0.5 vs 9.4 +/- 0.7 g, respectively, p less than 0.001). The weight of salvaged myocardium was 3.4 +/- 0.5 g in treated dogs vs 1.9 +/- 0.4 g in the control group (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Radionuclide assessment of cardiac function. Pre-operative evaluation of patients with abdominal aortic occlusive disease undergoing aortobifemoral bypass grafting.

Pre-operative radionuclide angiography, a non-invasive technique for evaluating ventricular function, was performed on 34 consecutive patients undergoing aortobifemoral bypass grafting for abdominal aortic occlusive disease, to determine whether pre-existing coronary artery disease causes significant modification of cardiac function. Patients were divided into two groups according to medical history. Group I had 23 patients with no symptoms of coronary artery disease and Group II had 11 patients, six with previous myocardial infarction and five with angina pectoris. There was a significant difference in left ventricular ejection fraction and in cardiac output between these two groups. A flow-directed pulmonary artery catheter was inserted in eight patients in Group II who had an ejection fraction less than 50% and a nitroglycerin infusion was used in six cases to maintain pulmonary capillary wedge pressure below 20 mmHg. In the other patients, only central venous pressure was monitored. All patients had uneventful operative courses. It is concluded that left ventricular function is significantly altered in patients with symptoms of both abdominal aortic occlusive disease and coronary artery disease. By contrast, cardiac function is normal in patients free from symptoms of coronary artery disease, and central venous pressure monitoring seems sufficient in the management of these patients during aortobifemoral bypass grafting.

Aged↗
PubMed1982

[Nuclear magnetic resonance. Applications to medicine and biology (author's transl)].

Nuclear magnetic resonance (NMR) is a non-invasive exploratory technique based on a principle radically different from those of radiography, radionuclide exploration and ultrasonography. Signals coming from atomic nuclei and reflecting their density and chemical/biochemical environment are collected, thus providing information of the physiological and pathological state of tissues. The technique has multiple applications, either practical (tomographic imaging of the brain, thyroid gland and liver) or in the field of research, e.g. investigating ischaemic myocardial areas and pathological fluid composition, measuring intracellular pH, diagnosing the nature of a tumour and, broadly speaking, understanding the biochemical changes associated with malignant degeneration.

Body Fluids↗
PubMed1982

Retrograde coronary sinus perfusion: a safe alternative for ensuring cardioplegic delivery in aortic valve surgery.

During aortic valve surgery, cardioplegic solution is delivered through direct cannulation of both coronary ostia. Since this approach may cause an intimal injury leading to acute dissection or late ostial stenosis, we have evaluated retrograde coronary sinus perfusion (RCSP) as a means of delivering cardioplegia in 12 patients undergoing aortic valve replacement. The retroperfusion of the cardioplegic solution was performed with a balloon-tipped catheter inserted into the coronary sinus through the right atrium. The perfusion pressure averaged 40 mm Hg. Twelve patients undergoing antegrade coronary perfusion served as controls. Both groups were matched for preoperative and intraoperative data. The postoperative evaluation focused on hemodynamic status, as evidenced by serial measurements of right-sided pressures and cardiac output at 1, 6, 12, 18, and 24 hours after operation. The stroke volume index and the left ventricular and right ventricular systolic stroke work indexes were then calculated. There was no statistically significant difference between the two groups. We conclude that RCSP is a simple, safe, and effective means of cardioplegic protection during aortic valve surgery.

Adult↗