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Biomedical subjects

G Prieur

Publications and source records attributed to G Prieur.

7 recordsLinked to original sources
PubMed2002

Catheter ablation using very high frequency current: effects on the atrioventricular junction and ventricular myocardium in sheep.

BACKGROUND: Radiofrequency ablation is currently used in the treatment of various cardiac arrhythmias. However, this technique is limited by impedance rise, leading to coagulum formation and desiccation of tissue. We developed a new generator, providing very high frequency (27 MHz) current, which is in the intermediate range between radiofrequency and microwave energy. The aim of this study was to evaluate the results for catheter ablation of the atrioventricular junction and characteristics of the lesions obtained at ventricular sites. METHODS AND RESULTS: The generator was coupled to a specially designed 7-French coaxial catheter. The study included experiments performed on 10 sheep (Wt. 31- 42 kg). In seven sheep, the catheter was introduced into the femoral vein and advanced across the tricuspid annulus to record the largest possible His electrogram. VHF current was applied for 25 s, with increasing energies. The energy needed to obtain complete atrioventricular (AV) block ranged from 60 to 100 Watts. Six animals were observed for 6 to 21 days. Complete AV block was found to be persistent. In those seven sheep in whom AV junction was ablated and in three additional sheep, the ablation catheter was positioned toward the right ventricular apex using the same approach and into the left ventricle via the femoral artery, and 20 to 90 Watts energy was delivered in order to assess the size of the induced lesions. Side effects included ventricular tachycardia degenerating into ventricular fibrillation in six cases, but the same effect was observed in this animal model with radiofrequency energy. No cardiac perforation was noted. No thrombus was observed at the catheter tip. The size of the lesion ranged from 3 to 45 mm in width and 1 to 15 mm in depth. CONCLUSIONS: Catheter ablation using VHF current is feasible and appears effective in producing stable AV block when applied at the AV junction and results in substantial myocardial lesions. Further studies are needed to define its clinical interest and side effects.

Animals↗
PubMed1995

Intracardiac high-frequency catheter ablatherapy: technical aspects.

Arrhythmia and conduction disorders can be treated by intracardiac ablation. The paper presents an original intracardiac catheter ablation method using a high-frequency (HF) electromagnetic power source. A high-frequency signal is emitted through an electrophysiological catheter introduced into the femoral vein and passed along the course of that vein into the heart. To prevent impedance rise, a problem encountered with other techniques, HF signal wave trains are used for half-period impedance match control and, where necessary, automatic impedance adjustment. Fully automated impedance matching combined with frequency-specific catheter design prevents power reflection between load and source. Resulting lesions can be controlled as to location, area and depth. In addition, HF pulses can be released independently of cardiac rhythm. Additional comprehensive animal experimentation is currently going forward.

Animals↗
PubMed1992

[Analgesic effect of transcutaneous cranial electrostimulation in patients treated by Nd:YAG laser for cancer of the rectum. A double-blind randomized trial].

The aim of this double blind cross-over randomized trial was to assess if transcutaneous cranial electrical stimulation by Limoge current could decrease the dose of fentanyl required in patients with rectal cancer treated by Nd:YAG laser. Fifty patients, 29 women, 21 men, 78 +/- 10 years old (range: 53-96 years), were treated by 2 laser sessions with an interval of 48 hours between each session. Active and sham electrostimulation were given in random order for the 2 laser sessions. The major end point was the quantity of fentanyl injected when the score of pain was greater than or equal to 5 according to a visual analgesic scale. Age, sex, body weight, tumor location and length, tumor circumferential extent and luminal patency, duration of laser session, amount of energy delivered per session (watt-seconds), and number of patients with deep sedation did not differ between the 2 groups. There was no interaction between the order of treatments and the treatments. The mean quantity of fentanyl was 29 micrograms and 42 micrograms when sham electrostimulation was given. There was a decrease of 31 percent in the quantity of fentanyl with active electrostimulation (P less than 0.05). Results were not affected either by the treatment order nor by tumor location. There were no side effects in either group.

Aged↗
PubMed1990

Improved subtraction technique in intravenous digital left ventriculography: comparison with radionuclide studies.

Adequate processing of left ventricular angiograms depends on the visualisation of all segments of the ventricular wall. At the same time, subtraction of different images can enhance different heart segments but commercially available methods do not allow simultaneous viewing of several images masked by different processes. Using our software, for each studied frame, a four quadrant display permits the simultaneous visualisation of a mask mode image, a diastolic-systolic difference image, an image obtained by subtraction of a frame at the same cycle time and a composite mask subtracted image. The composite mask image is obtained by weighting three images according to videodensitometric measurements by reference to previously acquired data. This method facilitates contour delineation and computation of the ejection fraction by area-length method. Correlation with radionuclide estimates of left ventricular ejection fraction is higher (n = 60, r = 0.90, SEE = 8%) than using the classical mask mode display (n = 60, r = 0.82, SEE = 11%). In a subgroup of 30 patients the contrast medium was injected in an antecubital vein and the correlation coefficient remained satisfactory (n = 30, r = 0.89, SEE = 7%) when compared with the classical subtraction technique (n = 30, r = 0.70, SEE = 12%). We therefore conclude that the composite mask method gives comparatively similar values for left ventricular ejection fraction to those acquired by radionuclide angiography.

Angiography, Digital Subtraction↗
PubMed1989

[Value of digital subtraction of left ventriculographies by the venous route. Comparison with balanced scintigraphy of the heart cavities].

The development of numerisation material in radiology currently permits to perform usual cardiovascular tests. The authors report a series of 48 patients who benefited from the determination by numerised left ventriculography, of their stroke volume (SV). In 37 cases, the peripheral venous route is used while in 11 cases the central venous route is used, in the pulmonary artery trunk. The SV values obtained with both methods (one advocated by the manufacture and another one developed by the authors), are correlated with the SV values obtained with the isotopic method, used as reference. The correlations are satisfactory, approximately 0.79 for all patients of the study, and markedly improve when the injection of the contrast material is performed in the pulmonary artery (approximately 0.95). The authors conclude that determination of the left ventricle SV by numerisation is an interesting technique in centers where there is no department of nuclear medicine, and is absolutely necessary to complement right catheterisation.

Female↗
PubMedDate not supplied

Practical interstitial method of heating operating at 27.12 MHz.

A practical interstitial capacitive method of heating using thin flexible coated electrodes operating at 27.12 MHz is described. Advantages compared to classical interstitial methods are: uniform heating, control of the inserted length, compatibility with curie therapy, simplicity and low cost. The electrode geometry could be designed according to tumour site and volume. Restriction of longitudinal heating to a part of the wire is also possible. A simple matching circuit can be connected to the active wires to obtain a standing wave ratio (SWR) of less than 1.5. Individual power regulation of the electrode should be used and is feasible at this frequency. Numerical, experimental and clinical results demonstrate the practical value of this method.

Animals↗