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Biomedical subjects

M Amiel

Publications and source records attributed to M Amiel.

At least 73 records · Page 4Linked to original sources
PubMed1989

Effect of iodinated contrast media on blood clotting.

Recently, blood clot formation in catheters used for the injection of nonionic contrast media (CM) during angiography has been reported as being due to activation of hemostasis in the catheter. However, CM exhibit inhibitory properties regarding coagulation and platelet functions. The effect on blood clotting of iohexol, iopamidol, ioxaglate, diatrizoate, and ioxitalamate at a ratio of 10% v/v with nonanticoagulated human whole blood was evaluated using the kinetics of fibrinopeptide A (FpA) generation. Blood aliquots were taken every 2 minutes until blood clot occurred. Two groups of contrast media were identified: (1) iohexol and iopamidol, which increased the clotting time, and (2) ioxaglate, diatrizoate, and ioxitalamate, for which all clotting times were over 30 minutes and no FpA generation occurred.

Blood Coagulation↗
PubMed1989

[Automatic quantitative analysis of vascular stenosis. Experimental study of a digital angiography system applied to cardiology].

The purpose of this study was to test the measurement reliability of the automatic stenosis quantitation program present in a digital angiography system (DG 300 General Electric CGR SA). The experimental study was performed on models mimicking circular, elliptic and irregular stenoses; it made it possible to measure the percentage of stenosis by geometric and densitometric methods. The parameters studied were the size and shape of the stenoses, the contrast medium concentration, the positioning of the stenosis in relation to the image intensifier, the number of Kvp and the angle of projection of X-ray beams in the case of elliptic and irregular stenoses. The results showed a perfect linear correlation between the thickness traversed by the X-ray beams and the value in grey level at the output of the optico-radiological chain (r between 0.987 and 0.997, p less than 0.001), using different Kvp (65 Kvp, 85 Kvp, 90 Kvp) and different X-ray doses (1 milliRoentgen and 80 microRoentgen). With all concentrations of contrast medium (320 mg I/ml to 5 mg I/ml), the values of the circular stenoses measured were very close to real values (75 p. 100) for vessels of all diameters, except those of 1.5 mm in a 22 cm field. When 16 cm and 11 cm fields were used, the results were very close to the 75 p. 100 real value (3 to 4 p. 100 of relative error), even with the 1.5 mm diameter. The values of elliptic stenoses measured by densitometry were very close to real values (1 to 4 p. 100 of relative error) with contrast medium concentrations ranging from 320 mg I/ml to 20 mg I/ml) and with three angles of projection (0 degrees, 30 degrees, 60 degrees). In contrast, the geometric method gave very different results with the three angles of projection. In the case of irregular stenosis (17 percentages of stenosis ranging from 26.2 p. 100 to 77.1 p. 100) the real values correlated very well with the estimated values (r = 0.999, p less than 0.0001). Some of the results were compared with those obtained with a digital cineradiology system (Pie Data) and were found to be equivalent.

Angiography↗
PubMed1989

[Early occlusion and dissection in coronary angioplasty. Apropos of 855 patients].

Between June 1981 and may 1987, 855 patients were treated by transluminal coronary angioplasty at the Cardiovascular Hospital, Lyon. 778 primary successes (84 p. 100) were obtained, 84 of the 855 patients (9.8 p. 100) developed occlusion and/or angiographically proven dissection within the first 24 hours. These patients fell into two groups; group A (n = 35) with occlusion and occlusive dissection, group B (n = 49) with dissection but without coronary blood flow reduction. Among the parameters examined, only three concerning the morphology of the stenosis were associated with a statistically more frequent occurrence of occlusion: eccentric stenosis (p less than 0.05), irregular stenosis (p less than 0.01) and stenosis in a curvilinear segment (p less than 0.01). In addition, among the 84 patients with occlusion and/or dissection, 14 had myocardial infarction and 2 died during the 24 hours following angioplasty. Emergency aorto-coronary bypass was performed in 12 cases, mostly after failure of redilatation. Redilatation was carried out in 26 cases and was effective in 14.

Angioplasty, Balloon↗
PubMed1989

[Pediatric angiocardiography. Randomized, controlled study of 2 iodinated contrast media: iopromide 300 and ioxaglate 320 mgI/ml].

Thirty-one children were included in a prospective randomized trial comparing a new non-ionic contrast medium, iopromide 300 and the ionic low osmolar contrast medium, ioxaglate 320 mgI/ml in pediatric cardiac catheterisation. There were fewer adverse effects with iopromide but no statistically significant difference was demonstrated in this small population, with a very low incidence of allergoïd reactions; this tendency was confirmed by meta-analysis of the multicentre study.

Angiocardiography↗
PubMed1988

Iodinated contrast agents: effect on acetylcholine hydrolase. In vitro study.

Several conventional and new contrast media were studied in vitro in order to evaluate their effects on acetylcholine hydrolase. Iohexol proved to be the most potent inhibitor of cholinesterase; all other conventional ionic agents are not inhibitors or they are weak inhibitors at the concentrations that are apparently achieved locally in clinical practice. The full clinical significance of the relationship between cholinesterase inhibition in vitro and contrast media toxicity must be reviewed.

Animals↗
PubMed1988

In vitro interactions of gadolinium DOTA meglumine and gadolinium DTPA meglumine on hemostasis.

The interactions of two gadolinium complexes (Gd-DOTA meglumine and Gd-DTPA meglumine) with hemostatic function have been analyzed using: (1) coagulation reactions (extrinsic and intrinsic pathways and fibrinoformation) and (2) platelet function investigations (aggregation, release of Ca++ and ATP after stimulation with collagen 2.5 micrograms/mL). The data obtained with Gd-DTPA meglumine (Mgl) exhibited a significant increase of the intrinsic coagulation pathway and a delay in fibrinoformation, although there is no alteration of the effect of thrombin on fibrinogen (fibrinopeptid A determinations). Platelet aggregation and release are moderately modified. In contrast, Gd-DOTA Mgl exerts no effect on the coagulation system and only minor effects on platelet functions. It is suggested that at least one mechanism involves the complexation of ionized calcium because Gd-DTPA Mgl and Gd-DOTA Mgl complex, respectively, 45% and 23% of ionized calcium in plasma. However, other mechanisms such as an alteration of fibrin polymerization are not unlikely.

Contrast Media↗
PubMed1988

[The concept of critical arterial stenosis: value of a model of measures obtained by an angiographic method and the Doppler technic before and after transluminal angioplasty of the iliac arteries].

INTRODUCTION: Numerous studies in the literature have proven the fact that a critical size appears during the stenosis evolution. The work presented is a non invasive approach of this value, with correlation to the invasive results. The study was realized on a homogeneous group of 23 arteriopathic patients, selected for iliac artery angioplasty procedure. MATERIAL AND METHODS: Patients selection: twenty-three patients including 24 angioplasty procedures have been selected on a 21 month time study. Invasive data: two measurements are realized during angioplasty: trans-stenotic pressure gradient before and after angioplasty. stenosis calibration: both diameter and section have been calculated on radiological films. Non invasive data: a standard Doppler test is performed on lower limbs. Two parameters are compared with the invasive data: the ascending time of velocity curve at the common femoral level. the systolic pressure index (peripheral pressure/radial pressure). RESULTS: 1) Critical stenosis--invasive techniques (fig. 1): trans-stenotic pressure gradient versus stenotic measurements shaw an hyperbolic correlation. The critical stenotic level is found to be 60% in diameter and 80% in section. 2) Critical stenosis--non invasive techniques: stenotic measurements compared to ascending time (fig. 2) as well as pressure index at rest (fig. 3) shaw the same type of curve. The critical stenotic level is found to be the same than with invasive techniques. DISCUSSION: Some discordant results open the discussion about angioplasty as a "gold standard", specially with a geometrical analysis. Bad precision in non regular stenosis. Hemodynamic consequences of turbulent stenosis are not evaluated. Clinical interest of critical stenotic notion is underlined.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

[New imaging technics in dissection of the thoracic aorta].

The multiplicity of imaging for investigation of the thoracic aorta requires that the physician choose a strategy adapted to the disorder involved: this is the case, for example with dissection of the aorta. A critical study of the new methods available which include digital angiography; echocardiography; CT scan; magnetic resonance imaging (MRI), should be compared to "the" reference technique of conventional methods: aortography and two-dimensional cineangiography. In addition, the decision must take into account specific characteristics of the disorder: natural history of the disease and anatomopathological form which are useful for the surgeon in case surgery is decided upon. The strategy proposed remains faithful to two-dimensional cineangiography during the first 72 hours of acute dissection because this disorder is a true surgical emergency at this stage if the ascending aorta is involved. Later, or if the ascending aorta does not appear to be involved, MRI has now proven this efficacy as a first-line diagnostic procedure. The judiciousness of preoperative aortography is still the subject of debate.

Aortic Dissection↗
PubMed1988

[Digital arteriography of the lower limbs by sequential, automatic table translation. Feasibility. Preliminary results].

Digital subtraction angiography (DSA) as a method of evaluating lower limb arteries required examination of one limb at a time up to now. Moreover repeated injections of contrast material were necessary. This problem was mainly due to the relative small image intensifier field available and to the difficulty of repositioning the patient between mask and image acquisition. The authors report the preliminary results obtained with 24 patients studied on angiographic unit equipped with: A DSA system (DG 300-CGR) using 512 X 512 matrix size, an angiographic table (Angix M 200) allowing an automatic sequential translation, a removable image intensifier using a 16 inch field below the table. Thus, all those characteristics allow DSA of lower limb arteries. Only one injection of contrast material (Ioxaglate: 80 ml at 8-10 ml/second) was used per procedure. This, usually, allows good quality examination of lower limb arteries.

Angiography↗
PubMed1986

[Comparative study of external methods (Doppler, rheography, flow using Xe) and arteriography of the legs, in the evaluation of stenoses. Statistical evaluation by the Kappa test].

On a thirty five homogeneous group of arteriosclerotic patients, the authors study by means of the Kappa test the validity of arteriographic and non invasive techniques data interpretation by two trained observers. Then they compared between the conclusion of these methods again with Kappa test. The viability of arteriographic and Doppler interpretation is good. The comparison between arteriographic and external techniques results needs strong reduction of the arteriographic data in large classifications. Doppler (with distal pressure) is the best of non invasive techniques, the others staying less selective. The good correlation between arteriography and doppler data observed in main arteries is maximum for femoral arteries and decreases in distal arteries mainly because of a poor filling due to proximal lesions.

Angiography↗
PubMed1986

[2 cases of coronary embolism. Angiographic diagnosis and anatomopathological confirmation].

The authors report two cases selected from a series of 61 cases of coronary embolism observed over an 18 year period at the Cardiovascular Hospital (Lyon) out of 4,860 autopsies of adult patients who died of cardiovascular causes. These two cases underwent coronary angiography, the results of which correlated with the autopsy findings. The authors review the causes and clinical manifestations of coronary embolism and compare their results with previously reported data, to establish the radiological features of coronary embolism. They notice the regular appearance of obstruction due to embolism and underline the importance of the associated negative signs (normality of the rest of the coronary circulation, absence of collateral vessels...) which makes the angiographic diagnosis one of elimination.

Adult↗
PubMed1986

[Contrast media in angiography: present and future].

The review proposed here is not an raised up work. Its purpose is to summarise a lot of data concerning clinical trials and some toxicity factors about uro-angiographic contrast material (CM) used in radiology. the accent has been put on physico-chemical properties, particularly hypertonicity, of iodinated CM in clinical use; the natural history of a CM molecule after intravascular injection explains the repartition of drugs, according to time, in a bicompartmental model (interstitial and vascular) with urinary excretion; the pharmacological basis of side effects are known from a lot of experimental studies; these works allow to dissociate general (or systemic) toxicity and particular side effects for targets organs (heart, nervous system, kidney). Finally the future of CM molecules, specifically for angiography, is evoked about some research ways.

Angiography↗