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Biomedical subjects

J Troquet

Publications and source records attributed to J Troquet.

At least 19 recordsLinked to original sources
PubMed1988

[Vectorcardiographic significance of three-dimensional devices ended and nevertheless without boundaries].

The circular boundary of a disk may be suppressed by connecting it to that of an other disk presenting the same characteristics (isomorph). In such a condition, energizing the first element indirectly feeds the second one by the same amount than it would be delivered to infinite surroundings. In mathematical terms, this means that summing up the potentials arising at the same points of the two connected disks leads to the potential identically located in the disk activated as before but disconnected from its isomorph: the statement being true except for a constant. In three dimensions, the problem is somewhat more difficult because a single isomorph cannot drain all the current that would be transmitted by a sphere to the infinite medium in which it is immersed. So, connecting two spheres results in a partial confinement which, however, does not rule out the aforementioned statement. On the other hand, the potential differences around the isomorph centre are well-suited to a vectorcardiographic use like Rijlant's one; this method is consequently justified as to its principle. Finally, we have studied the radial alinearity which is introduced by Rijlant to improve his instrument. We have shown the changes related to Rijlant's way of building his network and we conclude that the use of many equivalent layers bears on grounds similar to that which are developed for the linear isomorphs.

Humans↗
PubMed1987

The integrated form of the Brody effect.

We have considered the simplest model of the Brody effect: a circular inhomogeneity into a conducting medium of infinite extent energized by a source sink pair near the disk. To correlate with the reciprocal field equations, the Brody effect has been calculated in its integrated form by the Gabor-Nelson method (1954). In these conditions, our results do not depend upon any singular position on the closed contour; they are also invariable with respect to grounding the inhomogeneity and/or shifting the inhomogeneity centre from that of the compartment around it. Contrariwise, characterizing the Brody effect by an enhancement factor of local potential values is sensitive to the above factors and so, may become confusing because inducing the belief that the effect due to an inhomogeneity intrinsically depends upon removing the point from which it is viewed.

Blood Volume↗
PubMed1986

Magnitude and location of a dipole in a circular ring with non-insulating boundaries.

It was shown that the resultant dipole moment of a system of sources and sinks within a region can be found from integrations of potential and potential gradient or normal current over the surfaces bounding the region. The method was applied in two dimensions to the case of a dipole in an infinite medium of one resistivity outside a circle having a different resistivity. The results agree with the Brody theory in that potentials at remote points due to a radial dipole were increased and potentials due to tangential components were decreased. Potentials on and within the circle are more complicated, however. For a radial or oblique dipole, potentials on the "endocardium" are increased in some areas but reduced at others. In addition, the effects are non-linear, depending on the distance of the dipole from the circle. Neglecting the effects of the low resistance circle leads to false values of dipole moment. When the integrations of potential and potential gradient are used, however, accurate values of dipole moment are obtained. The low-resistivity disk makes a radial dipole appear more centric but a tangential dipole appear further away.

Electrocardiography↗
PubMed1986

[Léon Fredericq and the descending portion of the second positive wave (1st systolic wave) of the venous pulse: the negative cd or X wave in current nomenclature].

Understanding the venous pulse waves was a challenge for L. Fredericq. We show that his interpretation of the X depression previewed the nowadays visualization of the A-V valve movement through echography. We also present an a contrario demonstration on the same topic by observing that forcing a passive heart (Gad's experiment) cannot reproduce the atrial aspiration during the simulated ejection unlike it is in the beating organ.

Humans↗
PubMed1985

Experimental foundation of the Gabor-Nelson theory applied to boundaries which are non-insulating.

In order to found the application of the Gabor-Nelson theory to non-insulating boundaries, we have used a network which we have divided into two parts: a core energized by a source sink pair and an appendage, the conductivity of which may or may not differ from that of the core. By ignoring the appendage and by applying the Gabor-Nelson method to the restricted perimeter as if it were totally insulating, we stress the errors made in computing the dipole strength, orientation and position and how they are influenced by the dipole eccentricity, by its orientation with respect to the junction between the added portion and the core, and by a change in conductivity between the same compartments. Finally, we restore the dipole characteristics by using the appropriate correction derived from theory. Comparing the later results to those obtained by applying the Gabor-Nelson method to the whole insulating boundary leads to the conclusion that the correction is founded and must be taken into account.

Electric Conductivity↗
PubMed1980

Intracellular action potential changes induced in both ventricles of the rat by an acute right ventricular pressure overload.

Eleven open chest, artificially ventilated rats were used to observe and compare the intracellular potential changes induced in the right and left ventricles by an acute right ventricular overload. Graded right ventricular hypertension was produced by external constriction of the main pulmonary artery. Transmembrane potentials were obtained using floating glass microelectrodes filled with 3 mol X litre-1 KCl and connected to a cathode follower through a silverchloride-silver junction. Following right ventricular overload, the level of resting potential was depolarised by 20% on the right ventricle and by 4% on the left (P less than 0.001). The repolarisation was not significantly affected. A significant correlation (P less than 0.01) was observed between the increase of right ventricular pressure and the depolarisation of resting right ventricular potential. The right ventricular distension which occurs in our experimental model thus induces a diastolic depolarisation of right ventricular muscle cells which cannot be neglected in the interpretation of the peripheral ECG changes.

Action Potentials↗
PubMed1980

[Cardiovascular responses of the rat to a prostaglandin endoperoxide analog].

In the anaesthetized rat, injection of the prostaglandin endoperoxide analog, U 44069, in the right ventricle is vasopressor both in the pulmonary and the systemic circulation. When a moderate dose is used, the hypertensive response of the systemic vascular bed changes in an hypotension. The toxicity seems to be cumulative. At high doses, a vascular collapse is observed sometimes with pulmonary oedema. These findings correlate with the EKG pattern typical for an acute cor pulmonale.

Animals↗
PubMed1980

[Geometric representation of the human thorax in electrocardiographic theory].

An accurate representation of the thoracic surface is required to solve the inverse problem of electrocardiography. For the purpose we have searched the second degree surface which fits 55-88 positions distributed around the trunk. Over a group of 17 young men, we have found that the positions always scattered around an ellipsoid the cephalo-caudal limits of which extended far away from the zero potential gradient levels. This discrepancy is discussed and a proposal is formulated.

Adult↗
PubMed1978

[Comparison between the potential maps, first measured in a Rijlant's vectocardiographic network and secondly calculated for a homogenous sphere when, in both cases, the source and the sink are opposite on the external boundary].

In order to predict quantitatively how a Rijlant's vectocardiographic network operates, we did calculate the electrical potential map generated by two opposite poles situated at the ends of a diameter in a conducting sphere isolated on its external boundary. We also measured the potentials similarly arising at each point of the network. The relation between the corresponding values may be usefully approximated. These relations are the best ones but by no means the only ones, and thus any generalization is not yet possible.

Electric Conductivity↗
PubMed1976

Alterations of the Frank orthogonal scalar leads induced by anaphylactic shock in the rabbit.

The anaphylactic shock of the rabbit is characterized by an acute right ventricular overload, accompanied by severe alterations of cardiac electrogenesis. During shock, the mean QRS vector, as measured from the algebraic sum of the Q, R, and S deflections on the three leads, shifts to the right, inferiorly and anteriorly. An injury current quickly appears. The TQ vector points away from the right ventricle. A progressive depolarization on the right ventricular wall is displayed by suction electrodes and the suppression of right ventricular hypertension by a cross circulation produces an almost immediate disappearance of the injury current. The geneses of these electrical alterations are briefly discussed. The possibility of an anaphylactic reaction at the level of the coronary arterial wall, previously mentioned in the literature, seems unlikely. The role of the haemodynamic changes and of the increased right ventricular blood pool is thought to be predominant.

Action Potentials↗
PubMed1976

[Eccentric driving of a Rijlant's network (author's transl)].

As far as the central terminal does not interfere with the dipolar equivalent of the driving system, the zero isopotential line reaches the boundary of the network. Besides, if the emission level is at least five resistive layers "away" from the detection points, the proximity effects vanish. In these conditions the potential information available at the boundary becomes proper to be handled by the Gabor & Nelson's method. Calculating the location of the dipole leads to a fraction of the maximal "dimension" of the structure so that it directly expresses the eccentricity. The latter value may be compared with the corresponding one which is determined by the injection axis relative to the dodecahedral disposition of the connexions. From such quantitative comparisons, we conclude that an eccentricity simulating that of the heart in the thorax requires that the injection remains at least ten resistive layers "away" from the boundary if we want to view the generator through VCG leads which does not appreciably distort it.

Electrocardiography↗