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Biomedical subjects

L Philippe

Publications and source records attributed to L Philippe.

At least 37 records · Page 2Linked to original sources
PubMed1989

[Significance of isotopes in the study of pre-excitation and ventricular tachycardia].

In normal patients, Mac Carthy has demonstrated that there was a very close correlation between the ventricular contractile activity, evaluated by Fourier's isotopic phase analysis, and electrical depolarization, evaluated by endocardial mapping. It has therefore been possible to study asynchronisms or asymmetries of the ventricular contraction-depolarization and particularly the syndromes of ventricular pre-excitation and ventricular tachycardias. In Wolff-Parkinson-White syndromes (WPW), the mapping obtained by heart cavity tomography in addition to dual-plane gamma-angiography, provides most useful informations, due to additional section planes permitting tridimensional location of the earliest site of ventricular activation. It is quite useful to locate the bundle of Kent always difficult on surface electrocardiogram, or when the endocardial exploration does not permit to precisely locate the site of the excentric atrial activation in case of multiple bundles of Kent or without retrograde conduction. When the left bundle of Kent is barely identified, the isotopic image may be improved by oesophageal stimulation. Additional parameters (use of several harmonics, factorial analysis) will permit to improve the localization of accessory pathways, to be destroyed by fulguration or surgery. In case of ventricular tachycardias with limited functional tolerance, only gamma-angiography, lasting only 3 to 5 minutes, may be used. Combined with endocardial tomography or even gamma-angiography performed in sinus rhythm, not only the site of origin of the ventricular ectopy may be localized, but it also can be correlated with ventricular kinetics abnormalities and the cardiopathy in question may be identified. Most authors consider that there is a close relationship between isotopic site, electrocardiographic appearance and the site found by endocardial mapping or "pace-mapping". In patients with ventricular tachycardias of different morphologies, isotopic mapping permits to differentiate those originating from a same lesion (which may be treated by surgery of fulguration) from those originating in remote areas. Therefore, this technique is a non aggressive and rapid method providing accurate informations on severe rhythm disorders currently treated by eradication of their anatomical substratum.

Electrocardiography↗
PubMed1988

Characterization of right or left ventricular contraction heterogeneity using Fourier phase analysis. Application to a group of patients with severe ventricular arrhythmias.

The standard deviation of the first harmonic Fourier phase histogram is an indicator of the contraction heterogeneity of the heart ventricles. This approach has been applied to analyse tomographic blood pool (99mTc) examinations in a group of 32 patients with angiographically verified mainly right (RV) but also left (LV) kinetic disorders in relation to severe ventricular arrhythmias and suspicion of arrhythmogenic right ventricular dysplasia (ARVD). The reference group consisted of ten patients with low probability of cardiac kinetic abnormalities. Thick tomographic slices including both ventricles have been reconstructed in the horizontal long axis orientation from a series of 32 gated projections recorded over a 360 degrees rotation. Separately for each ventricle the Fourier phase histograms have been computed and characterized by their standard deviations (PSD). Normal values (mean +/- standard deviation, LV = 11 degrees +/- 5 degrees, RV = 12 degrees +/- 5 degrees) were significantly lower (P less than 0.01 and P less than 0.001) than those measured in abnormal cases (LV = 19 degrees +/- 10 degrees and RV = 31 degrees +/- 17 degrees). Detailed analysis of the data supports the hypothesis of a primary RV disease in ARVD, with secondary LV extension. PSD seems to be a good predictor of an organic cardiac disease underlying ventricular arrhythmias and may be used for screening the patients.

Adult↗
PubMed1988

Evaluation of valvular regurgitation by factor analysis of first-pass angiography.

We have evaluated left ventricular regurgitation by means of factor analysis of 99mTc first-pass radionuclide angiography (FPRNA) and time-activity curve deconvolution. The FPRNA regurgitant fraction (RF) was computed in 26 individuals: 13 patients (eight mitral, three aortic, and two mitral-aortic) and 13 controls. The reference method was contrast ventriculography (CV) performed within 1 hr after FPRNA. In 19 patients, CV was preceded by the determination of cardiac output, using indocyanine green dye (n = 16) or thermodilution technique (n = 3), to determine a catheterization regurgitant fraction (CATH-RF). Lung and left ventricular (LV) time-activity curves were gathered by factor analysis and the FPRNA regurgitant fraction assessed by a lagged normal deconvolution of these curves. In valvular regurgitation, the LV deconvolved curve demonstrates the appearance of a long transit time component that is amenable to quantification. The presence of regurgitation was determined by contrast ventriculography. With a 10% RF as an acceptable upper limit of normal for nonregurgitant patients, FPRNA yielded one false-negative and no false-positive studies (n = 26), while CATH-RF yielded two false-negative and four false-positive determinations (n = 19). The following are results of quantitative determination of RF (mean +/- s.d.): FPRNA 0.39 +/- 0.19 (n = 13 Valvular), 0.01 +/- 0.03 (n = 13 Controls); CATH 0.34 +/- 0.24 (n = 11 Valvular), 0.13 +/- 0.12 (n = eight controls). FPRNA was able to differentiate (p less than 0.001) between control patients (CV grading 0) and mild/moderate regurgitation (CV grading 1+ or 2+) and severe regurgitation (3+ or 4+) (p less than 0.025).

Adult↗
PubMed1988

[Isotope angiocardiographic study of 30 cases of ventricular tachycardia with Fourier phase analysis].

Twenty-seven patients (15 men, 12 women; mean age 48.9 years) suffering from ventricular tachycardia (VT) (n = 30) were studied by radionuclide angiocardiography with Fourier phase analysis, both in sinus rhythm and during tachycardia. VT was spontaneous, electrically inducible, sustained, haemodynamically stable and monomorphous, with a mean rate of 174 beats/min (range: 115-260 beats). Heart diseases responsible for VT were: non-obstructive cardiomyopathy (n = 7), hypertrophic cardiomyopathy (n = 1), ischaemic heart disease (n = 5), probable right ventricular arrhythmogenic dysplasia (n = 4), congenital left ventricular aneurysm (n = 2), sequela of myocarditis (n = 2) and aortic valve regurgitation (n = 1); no heart disease was detectable in 5 patients. On surface electrocardiogram there was good concordance between the initial radionuclide site of VT activation and the configuration and electrical axis of QRS. At Fourier phase analysis all 17 VT of the right lag type originated in the left ventricle, arising from the apical septum (n = 7) or lateral segment (n = 2) in case of left axis, from the basal segment (n = 6) or the lateral segment (n = 1) in case of vertical or right axis, and from the middle left septum (n = 1) in case of normal axis. Nine VT of the left lag type originated in the right ventricle, arising from the basal septum or the latero-basal region in case of vertical or right axis (n = 6), from the apical septum or the inferior-apical region in case of left axis (n = 2) and from the middle septum in case of normal axis (n = 1). Four of our patients (3 with coronary disease and 1 with congenital left ventricular aneurysm) had VT of the left lag type and an initial radionuclide site of activation in the middle part of the left septum in case of left axis (n = 2) and in the basal part of that septum in case of right axis (n = 2). Seven patients were operated upon for recurrent VT: 4 had intra-operative mapping which in every case confirmed the results of radionuclide angiocardiography, a method which in the other 3 patients was the only surgeon's guide. Correlations between the site of origin of VT at radionuclide mapping and kinetic abnormalities visualized at radiological angiography and gamma-ray angiocardiography were common in our study. In one of our patients the same lesion gave birth to 2 VT of different morphologies.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1986

The curve-shift paradigm in self-stimulation.

Eleven rats were trained to press a lever in an operant chamber in order to earn rewarding trains of cathodal rectangular pulses of fixed intensity and variable frequency. The rate-frequency functions were examined under administration of two neuroleptics (pimozide and chlorpromazine) and three manipulations that interfered with bar pressing (muscular relaxation with methocarbamol, increased lever weight, and limitation of maximum response rates by an F1 reinforcement schedule). Chlorpromazine, and pimozide at low dosages produced a near parallel shift of the rate-frequency functions on the logarithmic axis of pulses, suggesting that these drugs decreased the reinforcing efficacy of the stimulation. The three conditions that interfered with bar-pressing decreased the asymptotic rates and produced small or moderate lateral shifts. Changes in the reinforcing efficacy of the stimulation following the above manipulations were inferred from the shift in the number of pulses required at zero and half-maximal performance (theta 0 and M50 indices, respectively). In the cases of the manipulations that interfered with bar-pressing, M50 indicated a larger artifactual change in the efficacy of the stimulation, compared to theta 0. This phenomenon was mainly due to the fact that the asymptote of the altered functions was shifted towards higher pulse numbers.

Animals↗
PubMed1986

Diagnosis and quantitation of pulmonary arteriovenous malformations by factor analysis.

The diagnosis of a pulmonary arteriovenous malformation (AVM) was made by performing a computer-assisted first-pass cardiopulmonary imaging procedure using Tc-99m pertechnetate and processing the image information using factor analysis. This analytical technique is capable of separating partially overlapping structures by automatically extracting factors with different temporal behavior (time-activity curves) which correspond to functional areas without anatomic constraint. This procedure was accomplished successfully despite the presence of four-chamber enlargement, mitral stenosis and regurgitation, tricuspid regurgitation, chronic obstructive pulmonary disease and pulmonary hypertension. The magnitude of the right-to-left shunt resulting from the AVM was quantitated using both the factor analysis data and an independent Tc-99m MAA computer-assisted imaging procedure. Both methods gave comparable values.

Arteriovenous Malformations↗
PubMed1986

Use of factor analysis in the evaluation of left to right cardiac shunts.

We have compared two methods of data processing for the quantitation of left-to-right cardiac shunts using first-pass radionuclide angiography. These two methods are used for curve generation in the deconvolution analysis. The standard method involves manual definition of regions of interest. A newer method--factor analysis--provides automatic curve generation and is therefore more operator-independent. Both techniques yield curves of the venous input, lung, and background. The venous input curve is deconvolved by the lung curve, and the resultant unit impulse response is fitted by the gamma variate method to quantitate the left-to-right shunt fraction. Both techniques--factor analysis and regions of interest (ROIs)--separated the shunt patients (n = 16) from the control subjects (n = 20) with a p less than 0.001. There was less interobserver variability with the curves obtained by factor analysis than with those obtained by regions of interest. The coefficient of correlation of factor analysis results with oximetry, r, was 0.90. High sensitivity and specificity, each 94%, was achieved with curves generated by factor analysis. Time vs. activity curves generated by ROIs can achieve high sensitivity and low specificity, or vice versa, depending on the cutoff level defined for separation of the left-to-right shunt patients from the control group.

Adult↗
PubMed1985

[Complex ventricular arrhythmia in apparently healthy young subjects].

The aim of this study of 20 young subjects (28 +/- 10.6 years) with no apparent cardiac disease on clinical examination and chest X-ray was to determine the origin of complex ventricular arrhythmias: monomorphic or polymorphic ventricular extrasystoles, isolated or in valves (average 18 158 +/- 12 388 per 24 hours) and/or ventricular tachycardia (5 cases, sustained in 3). These arrhythmias were aggravated (N = 6), disappeared (N = 8) or remained unchanged (N = 5) during exercise. The inter-critical ECG showed ST changes in 5 cases. The extrasystoles had a left bundle branch block configuration in 14 cases and a right bundle branch block configuration in 9 cases. Nine patients were Grade 2 (45%) and 11 patients Grade 4B of Lown's classification. Complementary investigations (echocardiography), radionuclide investigations, right and left heart catheterisation, selective right and left ventriculography and coronary angiography) showed a high incidence of arrhythmogenic right ventricular dysplasia (N - 14) associated with left ventricular abnormalities in 13 cases: hypofixation of Thallium (N = 14) associated with left ventricular abnormalities in 13 cases: hypofixation of Thallium (N = 11), abnormal global left ventricular function (N = 13) with decreased ejection fractions in half the cases, left ventricular dilatation in a third of cases (average and diastolic volume: 109.8 ml/m2), mean velocity of circumferential fibre shortening decreased in 86% of cases (average 0.88 cir/sec), angiographic abnormalities of segmental left ventricular wall motion in 36% of cases; 2 clinically silent cases of mitral valve prolapse were associated with these left ventricular changes; these cases represent forms of arrhythmogenic cardiac disease localised to the right ventricle or involving both ventricles which should be searched for routinely in young patients with apparently normal hearts but with idiopathic and severe ventricular arrhythmias. The diagnosis can only be established by angiography. In other cases, isolated left ventricular abnormalities are detected: two cases of hypertrophic non obstructive cardiomyopathy including one apical form, a condition which may be suspected from analysis of the surface ECG and careful 2D echocardiographic study; phonomechanography may be normal; one idiopathic left ventricular aneurysm which was only diagnosed at ventriculography; one dilated cardiomyopathy affecting the left ventricle. In our series, none of the patients had coronary artery disease and two patients even had no abnormality of any of these investigations.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1984

The pontine substrate of circling behavior.

Single or twin movable stimulating electrodes were implanted in 9 rats in order to investigate the pontine substrate of circling behavior. The region located between the caudal part of the interpeduncular nucleus and the fourth ventricle was examined. The electrodes were implanted 6 mm below the surface of the skull and subsequently moved down by steps of 0.13 or 0.16 mm. The stimulating current consisted of trains of cathodal rectangular pulses of constant intensity and width (100 microA and 0.1 ms respectively) and of variable frequency. The effectiveness of the stimulation in eliciting a circling reaction was inferred from a psychophysical determination of the pulse period required at each site in order for the animal to maintain a criterion rotation speed. In the average, 48 brain sites were investigated per animal. Stimulation of 166 out of a total of 387 sites elicited ipsiversive rotation. Depending on the coronal plane of implantation, the dorsal boundary of the circling substrate was located within the pedunculus cerebellaris superior or the floor of the substantia grisea centralis. In addition, the positive region extended 1.7-2 mm ventrally and 1.9 mm from the midline. The distribution of the positive sites seems to suggest that the circling substrate is a large bundle which runs sagittally through the medial part of the reticular formation.

Animals↗
PubMed1984

Phase quadrature shift between left and right ventricles during a ventricular tachycardia attack.

Equilibrium gated nuclear angiography was performed on a patient during an attack of ventricular tachycardia and then after conversion to sinus rhythm. Global and regional wall motion was assessed by means of isocontours, Fourier phase analysis and factor analysis. Ventricular phase histograms showed a 100 degrees difference between ventricles: left ventricular filling time occurred during right ventricular contraction. The earliest phase was located in the septum and the sequence of activation showed a large delay of left ventricular activation. After conversion to sinus rhythm, a right bundle branch block was observed, being almost the inverse of the latter situation.

Adult↗
PubMed1984

[Radioisotopic tomography in the study of cardiac function].

Dynamic tomographic images of the heart may be obtained by computerised treatment of a number of projections and planes recorded by a gamma camera rotating around a patient whose blood is labelled with radioactive technetium. This new technique of assessing cardiac function was tested in a group of 40 coronary patients and the results compared with standard contrast angiography. The following parameters were compared : LV volume, global and regional ejection fractions. The zones of interest were easily defined on the tomographic images and correction for background noise was negligible. Two different methods have been developed to measure volume. The first consists in counting the matrix units in three dimensions on serial planes through a given cavity. The second is based on the reconstruction of thick slices integrating all the ventricular radioactivity, the counting of which is calibrated with reference to an orthogonal plane. The correlations with angiography were excellent with both methods (R = 0,85 and 0,87 respectively). An equally good correlation was observed for ejection fraction (r = 0,85). A segmental model acceptable for both gamma line angiography, gamma tomography and contrast angiography comprises 6 segments : septal, apical, antero-lateral, postero-lateral, posterior, and inferior. The sensitivity and specificity of both isotopic methods of detection of major wall abnormalities (akinesia and dyskinesia) were assessed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Beat-to-beat assessment of left ventricular ejection in atrial fibrillation.

Beat-to-beat left ventricular ejection was evaluated in a group of 20 patients with chronic atrial fibrillation using a computerized single probe detector. The reference group consisted of 10 patients with sinus rhythm. For each patient 30 successive cardiac cycles were analyzed and the relative variations of four parameters were assessed: R-R interval, diastolic and systolic time intervals, and ejection amplitude, corresponding to the left ventricular stroke volume. The mean variations were respectively 3.4%, 10.4%, 8.4%, and 11.8% in patients with sinus rhythm, and 21.9%, 37.9%, 10.6% and 30.5% in patients with atrial fibrillation. This demonstrates that changes in ejection are mainly related to the duration of the filling phase, with nearly constant systolic times. Correlations between R-R intervals and systolic ejection amplitudes were highly significant (P less than 0.001) in patients with atrial fibrillation in 85% of cases. This information complements the average ejection fraction obtained from multiple cycle superimposition.

Adult↗
PubMed1983

A dual moveable stimulating electrode and its application to the behavioral version of the collision test.

The construction and testing of a dual moveable electrode for chronic stimulation in small mammals are described. The assembly is lightweight (0.9 g), its components are completely re-usable, and the two electrodes may be independently advanced in steps as small as 80 microns over a maximum vertical excursion of 6 mm. The unit performed as well as fixed electrodes do in daily behavioral tests conducted over a 3 month period. Ipsiversive rotation was elicited by stimulation of 15 pontine-mesencephalic sites in a single rat. Behavioral evidence for the collision of heterodromic action potentials in circling-relevant fibers was obtained in 4 position sets.

Animals↗
PubMed1981

[Initial results of dynamic gamma-tomography of heat cavities].

After blood pool labeling using technetium albumin, 32 scintigraphic projections are recorded by means of a rotating gamma-camera. An electrocardiographic multi-gating acquisition procedure selects the dynamic pictures during the cardiac cycle of the patient. The computer processing of this set of data and the reconstruction of multiple tomographic slices through the thorax allow a precise kinetic analysis of the cardiac walls.

Electrocardiography↗
PubMed1977

The radiospirometric flow-volume diagram recording technique and comparative study with conventional spirometry.

The spirometric flow-volume diagram recorded for a forced expiration gives information which is used in assessing obstructive or restrictive pulmonary diseases. Regional data of the same kind can be achieved using a simple radiospirometric technique and scintillation camera. A series of images during inspiration and expiration are defined and a time-activity curve with an integration time constant of about 100-200 ms is obtained from the images during the forced expiration phase. The equivalent of the flow-volume diagram, i.e., the time derivative of the activity vs. activity is computed. There were 21 subjects studied in this series. Normal subjects or patients with various diseases underwent classical spirometry, so that the global radioactive diagram could then be compared to the spirometric flow-volume diagram and its parameters expressed in terms of volumes and flow: vital capacity, peak flow, mean flow, flow at mean volume. The correlation with classical spirometry is highly significant. Similarly regional data are consistent with the pulmonary results.

Adult↗