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J Lefèvre

Publications and source records attributed to J Lefèvre.

13 recordsLinked to original sources
PubMed2000

[Use of echocardiography in the diagnosis of carcinoid tumors. Report of 4 cases].

Carcinoid tumours are the most common neuro-endocrine tumours but cardiac involvement is rarely symptomatic although often observed at post-mortem and rarely revelatory of the disease. The authors report 4 cases in which echocardiographic detection of characteristic right ventricular involvement led to the confirmation of the diagnosis of carcinoid tumour leading to the secondary diagnosis of the primary carcinoid tumour. The clinical, physiopathological echocardiographic and therapeutic characteristics of this condition are discussed.

Aged↗
PubMed1999

[Criteria of localization of the bundle of Kent].

The high success rate (> 90%) of radiofrequency ablation of accessory pathways is related to accurate mapping. This determines the site of the accessory pathway and the best target for ablation with the object of reducing the number of applications and the associated morbidity. Analysis of the surface ECG is the first step of localisation of a Kent bundle. Different algorithms may be used based on the correlation between the polarity of the delta wave, of the QRS and the site of the accessory pathway confirmed at surgery or during radiofrequency ablation procedures. Some of the recent algorithms allow localisation of certain postero-septal or sub-epicardial pathways, the ablation of which can only be accomplished via the coronary sinus or one of its branches, or in an abnormally dilated coronary sinus, the so-called diverticulum. A relatively accurate localisation of the accessory pathway from the surface ECG reduces the duration of an ablation procedure and may economise the need for left-sided catheterisation. However, the endocavitary electrogrammes determine the precise target of ablation whether this be the ventricular or atrial pole of the bundle of Kent. The association of the criteria obtained by bipolar and unipolar recordings in sinus rhythm, during pacing or reentrant tachycardia enables accurate localisation in the majority of cases. Ablation of some pathways may be more complex because of their site or the presence of associated congenital or acquired cardiac disease which alters the anatomical or electrical markers. In these cases, the electrical criteria, especially those of the surface ECG may be erroneous and non invasive investigations such as Doppler echocardiography, isotopic ventriculography with phase analysis are most valuable with a positive predictive value of over 90%.

Catheter Ablation↗
PubMed1983

Teleonomical optimization of a fractal model of the pulmonary arterial bed.

Modeling the pulmonary arterial tree (PAT) is considered here as an optimal synthesis problem. Firstly, a class of candidate models is specified: the three-dimensional symmetric dichotomous fractal trees of elastic tubes described by Womersley's equations. Secondly, the parameters are shown to be constrained by interactions of PAT with the rest of the body; these constraints are used to limit the volume of the parametric space to which attention will be directed in the synthesis step. Thirdly, a teleonomical hypothesis is proposed: a naturally selected PAT must have a minimal input impedance under conditions keeping total arterial volume and distensibility as small as possible. This hypothesis is translated in mathematical terms and the resulting cost-function minimized in the limited parametric volume. The optimal model has parameter values and an impedance spectrum corresponding satisfactorily with real data. Moreover this model gives a clear picture of the internal hemodynamic behavior of PAT as an impedance matching device.

Blood Flow Velocity↗
PubMed1982

Parvalbumins and muscle relaxation: a computer simulation study.

The distribution of Ca2+ and Mg2+ among the 'regulatory' cation binding sites of troponin (T-sites) and the strong, Ca2+-Mg2+ binding sites of troponin and parvalbumins (P-sites) in the sarcoplasm of a muscle was calculated. At rest, 60% of the T-sites were metal free, while 92% of the P-sites were loaded with Mg2+. In response to a Ca2+ pulse, troponin-calcium (T-Ca) complexes were rapidly formed, while the binding of Ca2+ to P-sites was limited by the slow rate of dissociation of the parvalbumin-magnesium (P-Mg) complexes. Muscle activation was not prevented by a high content of parvalbumins. Parvalbumin and the sarcoplasmic reticulum (SR) pump were complementary relaxing factors that removed Ca2+ from the cytosol and from the T-sites. Parvalbumins dominated the first part of relaxation, while the action of the SR was essential to ensure the return to a very low level of free Ca2+ ion and of T-Ca. After relaxation, a large fraction of the Ca2+ pulse was still bound to parvalbumins and returned slowly to the SR during the recovery. When the SR activity was reduced, the presence of parvalbumins preserved a fast rate of relaxation, at least for a few contractions. This may have a high adaptive value in cold-blooded animals.

Amphibians↗
PubMed1981

[An urethromanometric study using micro-pressures gauges for female urinary incontinence. A definition of the index of continence. Applications (author's transl)].

The study has resulted from comparing urethral pressure curves measured with the use of a catheter with two micropressure gauges in 34 continent and 100 incontinent women. Two types of tracing were obtained: first of all at rest and then with the woman coughing repeatedly. Of the different parameters that were measured at rest only one seems to be advantageous over the others. That is the pressure at the maximum closure which becomes less with incontinence and with ageing. The curves that have been produced with effort make it possible to analyse what happens to this pressure when maximum closure is effected. This always rises in patients who are continent and always lessens in patients who are incontinent. The ratio of these two values, Pc with maximum effort over Pc at maximum rest, allows an index of continence (IC) to be drawn; and which conveys the ability of the sphincter apparatus to adapt itself, and which gives a quantitative value to female continence. Its practical application makes if possible to confirm the diagnosis and adapt the therapy to be used in many incontinent patients in whom other tests have been unrevealing, and to unmask incontinences that have been masked by prolapse and to identify possible future incontinent patients.

Adult↗
PubMed1980

Free-wall shortening and relaxation during ejection in the canine right ventricle.

Relations between shortening, velocity of shortening, and relaxation of inflow and outflow segments of the right ventricular (RV) free wall (FW) were examined during ejection in 12 open-chest dogs after pharmacologic blockade by recording RV pressures, RVFW dimensions (piezoelectric crystals), and pulmonary blood flow. At heart rates of 113 +/0 8 (SD) beats/min, investigated segments remained isometric or even lengthened before the end of ejection. Tension-length data in the outflow tract converged at the time of peak systolic tension toward a common linear relation (average slope 65 +/- 10 cmH2O/mm, average intercept 5.9 +/- 0.9 mm), but markedly deviated from this line at the end of ejection. Consistent relations between peak tension and mean velocity of shortening were only observed during the first part of ejection. In addition the rate of segmental isometric relaxation, estimated from RV pressure fall was load dependent (e.g., +60% increase in relaxation rate when RVFW end-diastolic segment length increased from 12.9 +/- 0.8 to 13.5 +/- 0.8 mm). We conclude that under normal conditions, the tension-velocity-length relations of the RVFW are comparable to those of the left ventricle during the first part of ejection only. We also conclude that RV relaxation is load dependent and that a significant part of RV ejection occurs during RVFW relaxation.

Animals↗
PubMed1980

[Perinatal mortality in twin pregnancy. 576 case histories (author's transl)].

The authors report on the result of a retrospective survey which they carried out in 8 Hospital Centres in the West of France between 1975 and 1978 and these were concerned with 576 twin pregnancies. This study confirms that the fetal prognosis in twins is precarious. The perinatal mortality is high and is made up at the same time of a stillbirth rate of 5 per cent and a neo-natal mortality rate of 6 per cent, which is mainly due to prematurity (49.6 per cent) and to intra-uterine growth retardation in 19.3 per cent. Studying these results and the figures given in the literature, the authors analyse the ways in which this mortality can be reduced: early diagnosis, rest, screening for fetal low growth and a sensible broadening of the indications for Caesarean section. This broadening appears to them to merit consideration especially in three circumstances: intra-uterine growth retardation, premature labour between the 31 and 33 week after the last period and transverse presentation of the second twin that cannot be turned.

Female↗
PubMed1976

[Benign tumors of the pleura].

The authors report a case of benign tumour of the pleura in a 74 year old woman. This is a pediculated tumour of the right base posteriorly above the diaphragm, the pleural nature of which was recognised before surgery and which, microscopically, proved to be a localized, benign mesothelioma of fibroblastic type. Benigh tumours of the pleura are rare but raise two interesting problems: that of their precise origin which is debated, and their prognosis; the possibility of relapse should be borne in mind.

Aged↗
PubMedDate not supplied

[Isotopic study of fluid and electrolyte disturbances in decompensated chronic respiratory insufficiency (author's transl)].

The study of fluid and electrolyte disturbances by isotope radiodilution method is carried out in 22 patients with chronic respiratory insufficiency and cardiac failure. The simultaneous measurements of hydro-ionic compartments have been carried out with tritiated water (HTO), labelled sodium (22Na), labelled potassium (42K) and labelled bromine (82Br). From these measurements, the various water spaces are calculated: total water (ET) and extracellular fluids (LEC), also exchangeable electrolytes: sodium (NaE), potassium (KE), chlorine (ClE) and derived values. Results are compared to corresponding values in controls with the same obesity index. Patients with respiratory insufficiency show a fluid and sodium rise, similar to that found in cardiac failure and denutrition. The (NaE + KE)/ET ratio is not significantly decreased and the natremia is only slightly lower. There is no real potassium depletion in most patients.

Aged↗