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L Christiaens

Publications and source records attributed to L Christiaens.

At least 37 records · Page 2Linked to original sources
PubMed1998

[3-dimensional reconstruction technic using power Doppler. In vitro use on normal and stenosed pulmonary artery bifurcations].

Power Doppler imaging is an ultrasonic technique representing circulating red cells as a colour signal independent of their direction and angle of analysis. This noninvasive technique provides a morphological representation of blood flow within a blood vessel. This in vitro study in pulsed flow enabled three-dimensional reconstruction of blood flow in the bifurcation of the pulmonary artery with automatic shifting of the ultrasound probe and an integral digital transfer of the echographic data. The software for treating the images and for volumic reconstruction of the flow is explained. This technique provides a quantitative method of assessing residual intrastenotic flow with a simple computer system.

Arterial Occlusive Diseases↗
PubMed1998

[Myocardial infarction by complete thrombosis of the left main coronary artery: emergency treatment with angioplasty with implantation of a coronary stent and follow-up at one year: a case report].

Acute occlusion of the left main coronary artery is usually responsible for cardiogenic shock, severe arrhythmias or sudden death. Despite the widespread use of emergency coronary angiography in acute myocardial infarction, occlusion of the left main coronary artery is rarely observed and its treatment remains controversial. The authors report the case of a young man with a previous history of radiotherapy for Hodgkin's disease, admitted for acute myocardial infarction due to complete thrombosis of the left main coronary artery treated as an emergency by percutaneous transluminal angioplasty and implantation of a Palmaz Schatz stent. There were no complications of the procedure and the patient was asymptomatic one year later.

Adult↗
PubMed1998

[Physiopathology of myocardial infarction: the acute coronary occlusion].

Rupture of the atheromatous plaque, thrombosis and local vasoconstriction are involved in the genesis of acute myocardial infarction. The vulnerability of the plaque depends on its histological structure. Its fragility is related to the size of the lipid core, the thinness of the fibrous capsule and the inflammatory reaction. External aggression favourites rupture. This triggers both thrombogenesis by bringing the blood cells into contact with thrombogenic subendothelial factors and local vasoconstriction due to endothelial dysfunction. Although rupture of the plaque is an unpredictable event, there is a circadian variability the highest incidence of infarction being between 6 a.m. and midday. Comprehension of the physiopathology of myocardial infarction has opened up new therapeutic approaches which should reduce the incidence of plaque rupture. Prevention is based on stabilisation of the plaque by dietary hygiene, lipid-lowering drugs and, maybe, in the future, by local application of antisense oligonucleotides. Finally, anti-aggregant therapy (aspirin or anti-GIIb-IIIa) could prevent the formation or extension of the thrombus.

Cholesterol↗
PubMed1998

[Coronary angiography in octogenarians. Therapeutic impact and medium-term follow-up].

In the face of the general aging of the population and technical improvements, cardiologists are more commonly faced with the decision of whether to perform coronary angiography in octogenarians who are often in good general health. The morbidity and mortality of this investigation, its therapeutic impact and medium-term survival were analysed in 145 consecutive octogenarians who underwent coronary angiography between 1988 and 1996. In this study, coronary angiography was performed essentially for angina refractory to medical treatment and confirmed the severity of the lesions with stenosis of the left main stem in 7.6% of cases and multiple vessel disease in 67.5% of cases. The mortality related to the investigation was nil in this series. Revascularisation was feasible clinically and angiographically in 38% of cases (84% by angioplasty). The actuarial survival at 3 years was 65% in the group who underwent revascularisation and in the group treated medically.

Aged↗
PubMed1997

[Reproducibility of measurements of blood gas exchange during exercise in mild cardiac failure: need for a preliminary test?].

The reproducibility of blood gas exchange measurements on exercise in chronic cardiac failure has already been established in patients familiar with this technique. The aim of this prospective study was to evaluate the reproducibility of cardiopulmonary parameters on exercise in a population of patients who had never undergone this type of investigation. Twenty patients with chronic cardiac failure in classes I to III of the NYHA classification, with a mean age of 55 +/- 11.5 years and a mean LV ejection fraction of 31.2 +/- 9%, underwent two cardiopulmonary exercise tests (CPX Medgraphic) performed on a bicycle ergometer. Patients underwent maximal exercise stress testing attaining 89% of the theoretical maximal heart rate and 1.14 of the respiratory quotient during the first test. There was no significant change in peak VO2 (22.5 ml/min/kg vs 22.6 ml/min/kg) or in ventilatory anaerobic threshold (12.8 ml/min/kg vs 12.7 ml/min/kg) between the two tests. The ventilatory anaerobic threshold could not be measured in one patient and seemed less reproducible than peak VO2 with a standard deviation of relative differences (T2-T1/T1) of 10.4 versus 7.8%. There was a significant increase in the duration of exercise (7.4 +/- 9.2%; p < 0.002) and a ventilatory flow (4.5 +/-, p = 0.03). This study shows that peak VO2 is a reproducible measurement in mild to moderate chronic cardiac failure, even in the absence of a preliminary test to familiarize the patient with the equipment. The reproducibility of the ventricular anaerobic threshold is less satisfactory than that of peak VO2. The increase in the duration of exercise is more dependent on motivation and should not be taken into account alone in the functional evaluation of chronic cardiac failure.

Adult↗
PubMed1997

[Cardiac lymphoma disclosed by tamponade and complete atrioventricular block: apropos of a surgically treated case. Heart and lymphoma].

Cardiac lymphoma is becoming increasingly frequent, especially in the context of acquired immune deficiency syndrome, and due to progress in imaging, particularly echocardiography. The authors report the case of a 49-year-old patient in whom the diagnosis of cardiac lymphoma was established in the presence of complete atrioventricular block, tamponade and right atrial tumour. The authors review the various electrocardiographic and echocardiographic features of cardiac lymphoma.

Cardiac Tamponade↗
PubMed1996

[Isolated left superior vena cava: value of intraoperative echocardiography for implantation of a cardiac pacemaker].

The authors report the case of a patient presenting with isolated left superior vena cava, for which intracardiac implantation of a cardiac pacemaker was facilitated by intraoperative transthoracic ultrasonographic detection of the course of the ventricular catheter. Transoesophageal ultrasonography confirmed the diagnosis and eliminated a possible associated malformation.

Aged↗
PubMed1995

Breakdown of the stereospecificity of DD-peptidases and beta-lactamases with thiolester substrates.

With peptide analogues of their natural substrates (the glycopeptide units of nascent peptidoglycan), the DD-peptidases exhibit a strict preference for D-Ala-D-Xaa C-termini. Gly is tolerated as the C-terminal residue, but with a significantly decreased activity. These enzymes were also known to hydrolyse various ester and thiolester analogues of their natural substrates. Some thiolesters with a C-terminal leaving group that exhibited L stereochemistry were significantly hydrolysed by some of the enzymes, particularly the Actinomadura R39 DD-peptidase, but the strict specificity for a D residue in the penultimate position was fully retained. These esters and thiolesters also behave as substrates for beta-lactamases. In this case, thiolesters exhibiting L stereochemistry in the ultimate position could also be hydrolysed, mainly by the class-C and class-D enzymes. However, more surprisingly, the class-C Enterobacter cloacae P99 beta-lactamase also hydrolysed thiolesters containing an L residue in the penultimate position, sometimes with a higher efficiency than the D isomer.

Amino Acid Sequence↗
PubMed1994

Synthesis and biodistribution of [5-131I]iodotropapride: a potential D2 dopamine receptor imaging agent.

[5-131I]Iodotropapride is a benzamidic compound which displays high affinity and selectivity for dopaminergic receptors. It was prepared from the corresponding brominated compound by a nucleophilic substitution with [131I]iodine (t1/2 = 8.02 days, E gamma = 364 keV) based on the use of Cu(I) as catalyst and high specific activity of [131I]NaI. After i.v. injection in rats the tracer crosses the blood-brain barrier (0.42 +/- 0.06% of injected dose in the total brain) and demonstrates a high affinity binding to the striatum. The striatum-to-cerebellum ratio increases with time and reaches values of 9 and 22 at 30 and 120 min after injection, respectively. This specific uptake in the striatum is saturable and can be blocked by pretreatment with different D2 antagonists. When labeled with 123I (t1/2 = 13 h, E1 = 159 keV), the corresponding [123I]iodotropapride may be useful for the investigation of the D2 dopamine receptors in humans with single photon emission computer tomography (SPECT).

Animals↗
PubMed1994

[Mammary bypass dysfunction caused by proximal stenosis of the homolateral subclavian artery: treatment by percutaneous angioplasty. Apropos of a case].

Proper function of a coronary bypass using the internal mammary artery obviously depends upon the quality of the mammary artery used and of the distal coronary system, but also the absence of any significant stenosis of the first centimetres of the homolateral subclavian artery. The authors report the case of a patient in whom angina was destabilized by dysfunction of a bypass between the left internal mammary artery and the left anterior descending coronary artery. This mammary bypass dysfunction was related not to stenosis of the bypass but to stenosis of the proximal part of the left subclavian artery. Angioplasty of this stenosis led to disappearance of anterior myocardial circulatory impairment and of angina attacks.

Aged↗
PubMed1993

Nomogram for Doppler echocardiographic assessment of mitral stenosis in atrial fibrillation.

Non-invasive assessment of the stenotic mitral valve area is often difficult when the mitral stenosis is associated with atrial fibrillation. In this study, 16 patients with mitral stenosis and atrial fibrillation were evaluated by transthoracic Doppler echocardiography. The mitral valve area calculated by the pressure half-time method was 1.65 +/- 0.73 cm2. The enddiastolic mitral gradient was obtained from the enddiastolic forward mitral flow velocity by application of the simplified Bernoulli equation. For each patient there was a linear relationship between the enddiastolic mitral gradient and the corresponding RR interval. The slope and intercept of this relationship were significantly correlated with the mitral valve area. From the regression equations describing these correlations we established a nomogram ascertaining mitral valve area from enddiastolic mitral gradient and corresponding heart rate. This nomogram was helpful in the non-invasive assessment of stenotic mitral valve area in the presence of atrial fibrillation.

Aged↗
PubMed1992

2- and 4-[18F]fluorotropapride, two specific D2 receptor ligands for positron emission tomography: N.C.A. syntheses and animal studies.

Tropapride, (exo)-2,3-dimethoxy-N-[8-(phenylmethyl)-8- azabicyclo[3.2.1]oct-3-yl]benzamide hydrochloride, has been labeled with fluorine-18 at the 2- and 4-positions of its benzylic group. Two synthetic pathways were investigated: the first one required the alkylation of the norbenzyl precursor with 2- or 4-[18F]fluorobenzyl bromide (radiochemical yield of 5% EOB, 180 min); the second method consisted of a reductive amination of norbenzyl tropapride with 2- or 4-[18F]fluorobenzaldehyde (20% EOB, 110 min). In both cases, the specific activity was found to be greater than 1 Ci/mumol (EOS). Animal studies in rats showed the percentage of the injected dose localizing in the whole brain to be 0.6 +/- 0.09 and 0.2 +/- 0.03 at 2 h post injection for the para- and the ortho-[18F]fluoro analogs of tropapride respectively. Cerebral biodistribution studies showed at 4 h a striatum uptake of 5 +/- 0.7% of the injected dose per gram of striatum for the para derivative with a low fixation into the frontal cortex and the cerebellum (% ID/g FC < 0.4 and % ID/g Cb < 0.3). The selectivity of 4-[18F]fluorotropapride for D2 dopaminergic sites was demonstrated through blocking experiments with ketanserin, spiperone and halopemide. The saturability was confirmed by the use of variable specific activities. These preliminary results showed that 4-[18F]fluorotropapride can be considered as a potent radiopharmaceutical for the study of the dopaminergic system with PET.

Animals↗
PubMed1992

[Doppler echographic evaluation of mitral valve stenosis with atrial fibrillation. Construction of a nomogram].

Doppler echocardiographic evaluation of mitral stenosis is often difficult in patients with atrial fibrillation. Sixteen patients were examined by transthoracic Doppler echocardiography and the relation between the variations in transmitral end diastolic pressure gradient and the length of the corresponding cardiac cycles was analysed. Mitral valve surface area (1.65 +/- 0.73 cm2) was determined by the pressure half-time method. The end diastolic transmitral pressure gradient was calculated from the simplified Bernouilli formula applied to end diastolic mitral flow velocity. In each patient, a linear relationship was observed between the end diastolic mitral gradient and the corresponding RR interval. The slope and intercept of the graph correlated significantly to mitral valve surface area (r = 0.72, p < 0.002 and r = 0.93, p < 0.00001, respectively). Using regression equations describing these correlations, it has been possible to construct a nomogramme indicating mitral valve surface area as a function of mitral end diastolic pressure gradient and the duration of the corresponding RR cycle. This nomogramme facilitates Doppler evaluation of mitral stenosis in atrial fibrillation.

Aged↗
PubMed1991

Accumulation of acyl-enzyme in DD-peptidase-catalysed reactions with analogues of peptide substrates.

Thioester substrates can be used to study the hydrolysis and transfer reactions catalysed by beta-lactamases and DD-peptidases. With the latter enzymes, accumulation of the acyl-enzyme can be detected directly. The efficiency of various amines as acceptor substrates was in excellent agreement with previous results obtained with peptide substrates of the DD-peptidases. The results indicated the presence of a specific binding site for the acceptor substrates. Although most of the results agreed well with a simple partition model, more elaborate hypotheses will be needed to account for all the data presented.

Acylation↗