Biomedical subjects

P Peronneau

Publications and source records attributed to P Peronneau.

At least 19 recordsLinked to original sources

PubMed1995

Quantification of erythrocyte aggregation by blood echogenicity: a preliminary study.

Many techniques were proposed to assess erythrocyte aggregation in clinical and experimental investigations in view of in vitro determination. However no methodology until now is available to measure erythrocyte aggregation in flowing blood in vivo. High resolution ultrasonography provides an original way to quantify erythrocyte aggregation using the echogenicity of blood. We have developed and A-mode ultrasound scanner coupled with an oscilloscope and a computer allowing the analysis of ultrasonic signals produced by erythrocytes. A closed measurement chamber connected to a calibrated roller-type blood pump where blood was perfused was used. The echogenicity of blood was determined at different shear rates. Dextran, fibrinogen and other high molecular weight substances were added to increase erythrocyte aggregation. Changes in red blood concentration was also tested. An increase in blood echogenicity rate was observed at low shear. At a given shear rate blood echogenicity increased when fibrinogen or dextran were added. Such determination of the echogenicity of flowing blood in vitro will provide an approach to the quantification of erythrocyte aggregation in vivo circulation, especially in the veins where low shear rates are observed.

Biomechanical Phenomena↗

PubMed1992

Segmentation, modelling and reconstruction of arterial bifurcations in digital angiography.

The paper presents a method to model an arterial bifurcation from a pair of X-ray angiographic images. It is the initial step of a reconstruction process aiming at detecting and quantifying abnormal sites located on bifurcations. The method proposed consists of two steps. First, each image is independently segmented to extract the vessels in the images. The algorithm uses dynamic programming first to find the bifurcation centrelines from the original images, and secondly to extract vessel edges from the morphological gradient images, under a constraint of parallelism with the previously detected centrelines. Then, a three-dimensional bifurcation model is built by adapting cylinders around the three-dimensional bifurcation centrelines. These cylinders are obtained as a stack of binary orientable ellipses fitted to the projection densities in the corresponding cross-sections. Results obtained on simulated data, phantom and femoral bifurcations are displayed.

Angiography, Digital Subtraction↗

PubMed1992

[Use of extracorporeal circulation oxygenators (CEC) in the European Economic Community (EEC)].

This study analyses the growth of CPB in the EEC. The study situates its position in the world taking into account several indexes such as the Gross National Product and its growth the life expectancy and other technical or economic factors. Only a broad analysis could be performed for Europe to the irregular development of CPB. A more detailed analysis was performed for France thanks to a greater number of data. In this type of study the most important problem is to estimate the relevance and consistency of the data provided either by companies or by other organizations because they can change very quickly.

Cardiopulmonary Bypass↗

PubMed1991

Smoothed power spectrum estimate applied for analysis of the Doppler signal from blood flow.

A simple method for the improvement of the definition of the instantaneous spectrum estimate of Doppler signal is proposed. A short review of the stochastical properties of FFT spectrum estimates is presented. This review allowed us to develop a concept of the 'estimation noise' as an interpretation of the stochastic uncertainty of the estimation. This, in turn, permitted us to propose a method of adaptive filtering of spectral estimation to minimise the effects of the 'estimation noise'. Proposed filtering in the frequency domain corresponds to a procedure known as smoothing of the estimate. Two different smoothing procedures are presented: classical, linear smoothing and nonlinear, homomorphic smoothing. The performances of the smoothed spectrum estimate are theoretically and experimentally studied, showing that their effectiveness depends mostly on the shape of the Doppler spectrum. Although smoothing always reduces the spectral resolution, the important limitation of the variance of estimation can be achieved without meaningful deterioration of the resolution in our application. Thus, the proposed procedures may sensibly improve the accuracy of the relationship between the shape of the spectrum and the flow parameters. As a result, more exact determination of flow characteristics such as stability or maximum velocity, even in cases of low signal-to-noise power ratio, should be possible.

Algorithms↗

PubMed1991

In vitro uptake of dicarboxylic porphyrins by human atheroma. Kinetic and analytical studies.

Human atheromatous aorta segments as well as presumably disease-free control aorta were obtained at autopsy. They were incubated with solutions of various purified dicarboxylic porphyrins including hematoporphyrin (HP) and hydroxyethylvinyldeuteroporphyrin (HVD), and with solutions of Photofrin. Selective labelling of the atheroma was shown by macroscopic and microscopic observations of the characteristic porphyrin fluorescence associated with the atheromatous plaques. The time dependence of the uptake, monitored by absorption spectrophotometry or by high performance liquid chromatography, was inferred from the disappearance of the porphyrins in the incubation medium. Significant binding was observed in the absence of albumin or serum proteins. The uptake of HP was less than that of the more hydrophobic compounds HVD or Photofrin when these porphyrins were used alone. The presence of albumin or serum drastically reduces atheroma labelling. Some competition between HP and HVD for binding sites is also seen. The present results do indicate that hydrophobic porphyrins have an intrinsic affinity for atheroma and that they can be taken up through passive processes. Taking into account previous data on animal models (Photochem. Photobiol. (1989), 731-737), it appears however that, in vivo, interactions with proteins and pharmacokinetics will primarily determine plaque labelling.

Aorta↗

PubMed1991

[Thrombosis of atrioventricular prosthesis. Contribution of transesophageal echocardiography].

The aim of this study was to assess the diagnostic value of transesophageal echocardiography for the detection of thrombosis of a mechanical mitral or tricuspid valve prosthesis. Twelve patients (mean age 54 +/- 12 years) out of a series of 39 patients operated between April 1988 and June 1989 for prosthetic valve dysfunction had valve thrombosis at operation (11 mitral and 1 tricuspid valve prosthesis). Transesophageal echocardiography was routinely performed preoperatively in addition to transthoracic Doppler echocardiography to search for an abdominal mass on the prosthetic valves. The largest diameter of the diastolic jet at the level of the prosthetic valve annulus was measured using transesophageal color flow Doppler in the 8 Starr-Edwards mitral valve prostheses and compared with 5 control valves. The results of transthoracic Doppler echocardiography and transesophageal echocardiography were compared with the operative findings. The specificity of transthoracic echocardiography for the positive diagnosis of prosthetic valve thrombosis was 18%. A thrombosis could be suspected in 10 of the 12 cases by transthoracic echocardiography giving a sensitivity of 83%. Eleven of the 12 abnormal masses on the prostheses were visualised by transesophageal echocardiography, a sensitivity of 91%. Detection of the masses on the arterial side was possible in all cases (10/10) but 5 of the 6 extensions of the thrombus into the ventricle could not be visualised. The diameter of the transprosthetic jet was less than 12 mm in 7 of the 8 thrombosed valves compared with greater than 15 mm in the 5 normal control prostheses.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1990

Cellular electrophysiological effects of flecainide on human atrial fibres.

STUDY OBJECTIVE: The aim of the study was to examine the electrophysiological characteristics of human atrial specimens collected during heart surgery and to investigate the effects of the class I antiarrhythmic agent flecainide on their electrical activity. DESIGN: Atrial specimens were studied using standard microelectrode techniques, with and without superfused flecainide (5 x 10(-7) M) or the transient outward current inhibitor 4-aminopyridine (0.5 mM). EXPERIMENTAL MATERIAL: Atrial fragments 0.5-1.0 cm2 were obtained at operation from 34 patients, mean age 30 years. There was no history of previous atrial arrhythmia in any patient and drug therapy was stopped 24 h before surgery. MEASUREMENTS AND MAIN RESULTS: Two types of transmembrane action potential were identified: (1) triangular shaped potentials (group A, classically found in animal models); (2) potentials with a large plateau preceded by a notch (group B). The effect of flecainide was compared on the the two types of action potential. In both, flecainide lessened the depolarisation rate. In group B, but not in group A, it increased the action potential duration at 50% and 90% repolarisation (APD50, APD90) and the effective refractory period. The notch in group B action potentials is generated by transient outward currents (Ito). Inhibition of these currents, either by increasing the pacing rate or by adding 4-aminopyridine, limited the increase in APD50, APD90, and effective refractory period generated by the presence of flecainide. CONCLUSIONS: The effects of flecainide on the atrial repolarisation process depend on the shape of the action potential. These effects are more marked in cells with a plateau, where Ito is activated.

4-Aminopyridine↗

PubMed1990

Is pulsed Doppler echocardiography an adequate method to evaluate left ventricular function during filling in hypertensive patients?

Pulsed Doppler tracings of the mitral inflow are often proposed to describe left ventricular function during filling in hypertensive patients. The tracings are determined by the complex interaction of left atrial pressure and left ventricular relaxation, diastolic compliance and contractility of the left atrium. They strongly depend on preload and, thus, do not allow precise characterization of the left ventricle. In addition, they vary with age, heart rate and the site of measurement. The modifications caused by the presence of hypertensive hypertrophy are not specific: similar changes are seen for example, in the presence of hypertrophic cardiomyopathy or coronary heart disease, but are absent in highly trained athletes in spite of very significant physiologic hypertrophy.

Aging↗

PubMed1990

[The value of recording the pulmonary insufficiency flow by continuous Doppler for the evaluation of systolic pulmonary artery pressure].

Systolic, diastolic and mean pulmonary artery pressures can be evaluated by Doppler recordings of the maximal velocity of tricuspid regurgitation and early and late diastolic pulmonary regurgitant flow. The aim of this study was to assess the reliability of the calculation of systolic pulmonary artery pressure from pulmonary regurgitant flow by comparing the values with those obtained from the tricuspid regurgitant flow in the same patient. With this objective in mind, we investigated 70 patients with an average age of 45 +/- 34 years, in sinus rhythm, all of whom had tricuspid and pulmonary regurgitant jets which could be recorded with continuous wave Doppler. Systolic pulmonary artery pressure was calculated as follows: from tricuspid regurgitation: maximum pressure gradient + 10 mmHg; from pulmonary regurgitation: 3 x early diastolic gradient - 2 x late diastolic gradient + 10 mmHg. The systolic pulmonary artery pressures calculated from tricuspid and pulmonary regurgitation were: 42 +/- 16 mmHg and 43 +/- 17 mmHg respectively (r = 0.97) with an estimated standard error of 4.7 mmHg. These results show that the recording of pulmonary regurgitation by continuous wave Doppler allows accurate estimation of pulmonary artery pressures. The calculation by the two methods using tricuspid and pulmonary regurgitant jets increases the reliability of the results and provides a means of internal validation of the Doppler technique.

Adolescent↗

PubMed1990

[Demonstration of muscular activity in the human aorta. Effects of trinitrin].

The human thoracic aorta is usually considered to be a purely elastic vessel. Transoesophageal echo-cardiography (TEE) provides a new approach to study the mechanical properties of the descending aorta. The aim of the study was to evaluate the reproducibility and accuracy of M mode recordings of the human descending thoracic aorta and to appreciate the changes produced by an infusion of glyceryl trinitrate (GTN). The reproducibility of M mode recordings was studied in vitro on plexiglass tubes of different calibre, and also in vivo, the inter and intra-observer error was estimated to 0.6% in vitro and 1% in vivo. The accuracy of the method was evaluated in vitro by comparing the measured values (MV) with the actual diameters of the plexiglass tubes (T): MV = 1.012T + 0.9; r = 0.99; SE = 0.8 mm. The systolic and diastolic diameters of the descending thoracic aorta were measured in 8 healthy volunteers by TEE, before and during continuous intravenous infusion of GTN at a rate of 0.9 mg/hr and then 1.35 mg/hr after a 10 minutes interval. Systolic and diastolic blood pressures were recorded automatically every minute. The results showed a very significant increase in the systolic (from 20.3 +/- 0.7 to 20.9 +/- 1.3 and 22.1 +/- 2.2 mm) and diastolic diameters of the aorta (from 18.3 +/- 0.7 to 19.1 +/- 1.4 and 20.1 +/- 2.4 mm) despite a fall in systolic blood pressure (from 121.3 +/- 7.7 to 114.5 +/- 6.6 and 108.4 +/- 5.4 mmHg). This study shows that TEE is a reliable and reproducible method of measuring the diameter of the human descending thoracic aorta.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Transcatheter radiofrequency ablation of atrial tissue using a suction catheter.

Closed chest ablative technique that avoid barotrauma would be attractive for ablation at thin walled cardiac structures, such as the atrial free wall or coronary sinus. Transcatheter radiofrequency (RF) currents produce tissue necrosis the size of which is dependent on the contact between the tissue and the electrode. In order to assess the effects of transvenous RF ablation of atrial free wall using a suction electrode catheter, we delivered in ten dogs, one single unmodulated RF pulse 1.2 MHz, in a unipolar mode, through the distal electrode of a lumen catheter (USCI 8F) (USCI, Billerica, MA USA) located in the right appendage. During the pulse an 80 KPa vacuum depression was applied to the lumen of the catheter. Each pulse had a 10 seconds duration and the mean delivered power was 4.3 +/- 1.4 W. Aortic pressure and electrocardiogram were monitored during the procedure. A right atrial electrophysiological study was performed at the ablated site, at control, after suction application and after RF pulse delivery. The animals were sacrificed after 14 or 21 days. Atrial pacing threshold values decreased after suction application in comparison to control values after the pulse (0.42 +/- 0.06 vs 0.60 +/- 0.23 mA, P less than O.05) but increased after the pulse delivery (2.60 +/- 1.85 mA, P less than 0.01). In contrast, the atrial effective refractory period did not significantly change after suction, nor after RF pulse delivery. Aortic pressure remained unchanged throughout the procedure. Complex arrhythmias were not observed during or after RF pulse delivery. One dog died suddenly at the first day after ablation, but this death was most probably unrelated to RF ablation. Anatomic lesions had a length of 8.8 +/- 3.3 mm, a width of 4.6 +/- 2.5 mm and a depth of 3.6 +/- 1.1 mm. They were transmural in nine of the ten dogs but without atrial wall perforation in any case. Lesions suggesting tissue volatilization were present in four dogs. These results demonstrate that low energy RF currents delivered with a suction electrode catheter can produce transmural necrosis of free wall, without risk of perforation. Such ablative technique would be of interest for ablation of right sided accessory pathways or atrial ectopic foci. Further experimental data are required in order to define the optimal energy level required to avoid tissue volatilization.

Animals↗

PubMed1989

Photofrin II uptake by atheroma in atherosclerotic rabbits. Fluorescence and high performance liquid chromatographic analysis on post-mortem aorta.

Atherosclerotic lesions were induced in normal and Watanabe rabbits by atherogenic diet and stripping of aorta endothelium. The rabbits were injected with Photofrin II and sacrificed two days later. Atheromatous aorta as well as normal aorta from control animals were characterized by their fluorescence spectra using front face excitation. Characteristic emission peaks at 631 and 694 nm were displayed at atheromatous plaques. The excitation spectrum shows a strong band at 394 nm and weaker bands at 446, 504, 536 and 574 nm. Although no fluorescence of normal aorta can be seen by visual inspection, emission with a maximum at 626 nm was detected by spectrofluorimetry. Normal phase high performance liquid chromatography analysis of extracts from atheroma and control aorta were also carried out. The specific labelling of atheroma involves mainly protoporphyrin, hematoporphyrin and also minor components of Photofrin II which are accumulated. Some other components are accumulated but do not appear to be specifically retained by atheroma.

Animals↗

PubMed1989

Detection of pulmonary hypertension by Doppler echocardiography of the inferior vena cava in chronic airflow obstruction.

Pulsed Doppler echocardiography of the inferior vena cava is an accurate method for the diagnosis of tricuspid regurgitation and impaired right ventricular compliance, two features of pulmonary hypertension. The purpose of this study was to assess the value of Doppler echocardiography of the inferior vena cava for the detection of pulmonary arterial hypertension in patients with chronic obstructive lung disease. Pulse Doppler echocardiography of the inferior vena cava and right heart catheterisation were performed in 29 patients with severe chronic obstructive lung disease. The mean pulmonary arterial pressure was 27 (10) mm Hg for the entire group; 62% of patients (18/29) had pulmonary arterial hypertension (mean pulmonary arterial pressure greater than 20 mm Hg). An adequate Doppler signal could be obtained in 25 of the 29 patients (86%). Pulsed Doppler echocardiography of the inferior vena cava gave normal results in 10 patients and disclosed tricuspid regurgitation in seven patients, impaired right ventricular compliance in seven patients, and both of these abnormalities in one patient. An abnormal Doppler echocardiogram of the inferior vena cava (tricuspid regurgitation or impaired right ventricular compliance, or both) predicted the presence of pulmonary arterial hypertension with a sensitivity of 87% and a specificity of 80%. These results suggest that pulsed Doppler echocardiography of the inferior vena cava may be a useful though imperfect method of detecting pulmonary arterial hypertension in patients with chronic obstructive lung disease.

Echocardiography, Doppler↗

PubMed1989

[Clinical application of echocardiography using a transesophageal approach].

Transesophageal echocardiography is a new method of cardiac imaging with well-defined indications. In view of the absence of hindering anatomical obstacle between the probe and cardiac structures, the images obtained are of high definition, especially as regards the atria and atrial appendages, the mitral, aortic and tricuspid valves and the thoracic aorta. Being easy to perform and little traumatic, this method can be used in ambulatory patients. It is also valuable in intensive care patients and in the peri-operative period. Transesophageal echocardiography is primarily indicated to explore cardiac valve prostheses, notably those of the mitral valve, to identify vegetations and abscesses in infective endocarditis, to detect intra-atrial tumours and thrombi, to evaluate dissections of the aorta, to study the mechanism of mitral regurgitation, to investigate some congenital cardiopathies in adults, such as interatrial septal defects, and to monitor left ventricular function before and after surgery. Owing to its major contribution to the diagnosis of these potentially dangerous diseases, it should soon become a very useful and even indispensable complement of transthoracic exploration in certain cases.

Aortic Diseases↗

PubMed1989

[Electrocoagulation of the His bundle node junction in dogs by a high-frequency current delivered by suction catheter].

High-frequency currents constitute an attractive form of energy for transcutaneous myocardial destruction, but their potential for creating lesions varies with the nature of contact between electrode and skin. The adequacy of a suction catheter for electrocoagulation of the AV node-His bundle junction was assessed in 7 dogs. The high-frequency current (1.2 MHz) was delivered as bursts of 6 watts lasting 30 seconds, between the distal electrode of a bipolar catheter containing a central lumen (USCI 8F) and a wide skin electrode. During firing, an 80 kPa depression was applied to the lumen. Electrophysiological testing was performed before and immediately after firing. Continuous 24-hour Holter recording was carried out before, immediately after, then between the 2nd and 20th days post-firing. Following another electrophysiological study, the animals were killed on the 15th or 21st day for anatomical study. Complete atrioventricular block was obtained in all dogs during the first (n = 4) or second (n = 3) firing and persisted in 6 dogs up to the time of anatomical study. The atrial and right ventricular electrophysiological parameters remained unmodified after firing, and no severe ventricular arrhythmia was recorded during the study. The histological lesions were 4.7 +/- 0.7 mm in mean diameter and 3.1 +/- 0.6 mm in mean depth. It is concluded that electrocoagulation of the AV node-His bundle junction performed with high-frequency currents is a safe and selective technique. Using suction catheters makes this technique well reproducible with moderate amounts of energy. The development of preformed catheters should reduce the duration of the procedure.

Animals↗

PubMed1988

[Indirect approach of stenosis of transplanted kidneys by Doppler echography].

Pulsed Doppler ultrasound for the detection of rejection and renal artery stenoses involving transplanted kidneys was evaluated. Using mean velocity curves, the time interval between the ECG R wave and the onset of peak velocity was measured successively on the renal and ipsilateral iliac arteries and divided by the R-R interval. In 27 patients, a Doppler index defined as the ratio of the standardized renal artery and iliac artery time intervals, was determined and compared to angiographic data. The DI index failed to detect stenoses associated with rejection; conversely, in the absence of rejection, clear separation of patients without (n = 14, DI = 1.03 +/- 0.6) and with (n = 6, DI = 1.24 +/- 0.05) stenosis (t = 7.48, p less than 0.001) was achieved. Thus renal artery stenoses in transplant recipients can be detected by the comparative study of time intervals calculated for renal vessels and for the neighbouring iliac artery.

Adult↗

PubMed1987

Quantification of aortic regurgitation using Doppler imaging.

Aortic insufficiency induces the development of a jet within the left ventricular outflow tract. The cross sectional area of this jet at its origin is the major determinant of the severity of the regurgitation. M mode Doppler imaging reportedly allows the measurement of jet diameter. This study was designed to evaluate the quantification of aortic regurgitation using a measurement of the jet diameter by M mode Doppler imaging. The left ventricular outflow tract of 32 patients was imaged using either a multigate pulsed Doppler velocimeter of color flow mapping system (Hewlett Packard). The jet diameter was compared to a 4 grade semiquantification derived from supravalvular aortography. Adequate imaging was obtained in the 32 patients. Four of them had no regurgitation: no diastolic flow image could be found during their Doppler investigation. A clear jet image was obtained in the 28 remaining patients. We found a close relationship between the jet diameter (jd in mm) and the angiographic grade (ag): jd = 2.4 + 6.1 ag, r = 0.88, the most significant differences being found between grade 0 and grade 1, and grade 1 and grade 2. In conclusion, direct M mode measurement of the regurgitant jet of aortic insufficiency at its origin offers an additional approach of the severity of the leak.

Adult↗

PubMed1987

Limitations of ultrasound imaging and image restoration.

The definition of medical ultrasound images is strongly limited by the need for low examination frequencies which is imposed by the high attenuation of acoustic waves in tissues. The filtering effect of imaging systems is described and quantified for echography, transmission tomography and reflection tomography. Improvement of image definition is demonstrated to be the result of a numerical restoration of the received echoes implemented, in the present case, by a simplified Kalman filter. The improvement in definition obtained is emphasized on simulated data and tissue images. The comparison between the results obtained from the three techniques shows that: if only echography provides a real-time acquisition of signals, tomographic methods lead to faster processing associated with a better signal-to-noise ratio on the reconstructed images, and reflection tomography offers the best definition.

Animals↗