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G Finet

Publications and source records attributed to G Finet.

At least 37 records · Page 2Linked to original sources
PubMed2001

In-vivo prediction of human coronary plaque rupture location using intravascular ultrasound and the finite element method.

BACKGROUND: Spontaneous rupture of atherosclerotic plaques is known to be involved in the mechanism leading to acute coronary syndromes. Means to detect plaques prone to rupture and predict rupture location would then be very valuable for clinical diagnosis. DESIGN: In this study, finite element (FE) analysis based on intravascular ultrasound (IVUS) images of atherosclerotic arteries was used to predict in-vivo plaque rupture locations. In four patients with coronary artery diseases, IVUS images were recorded before and after balloon angioplasty. Pre-angioplasty images were recorded after injection of ATP. This caused a brief drop of arterial blood pressure down to values of about 20 mmHg, and thus allowed the recording of the unloaded configurations of arteries used to initiate FE analysis. Plaque rupture was triggered by balloon inflation (coronary angioplasty). FE simulations were performed under physiological loading conditions. Stress distributions within the plaque and the arterial wall were determined. The corresponding stress maps are presented. RESULTS: Circumferential tensile peak stress areas were compared with plaque rupture locations on postangioplasty IVUS images. They were found to coincide in all four studied cases. CONCLUSION: Our results agreed with those reported in previous studies based on ex-vivo postnecropsic data and showed the feasibility of in-vivo prediction of atherosclerotic plaque rupture location.

Aged↗
PubMed2001

[Efficacy and safety of low-dose heparin (30 IU/kg) during coronary angioplasty].

High doses of heparin are recommended during coronary angioplasty although platelet inhibition seems to play a role in the prevention of ischaemic complications. Low dose heparin could reduce the incidence of local complications without increasing that of major coronary events. The authors report the results of a prospective register of coronary angioplasties performed by the femoral approach with a single bolus of 30 IU/Kg of heparin and immediate withdrawal of the 6 French introducer. Only patients with recent infarction or left main stem disease were excluded. All underwent clinical examination and ultrasonic scanning of the puncture site the day after the procedure. Four hundred and eighteen patients were included (mean age: 63.3 +/- 11 years; 79% men; 77% stenting). The average dose of heparin was 2253 +/- 1056 IU; the average procedure time was 25 +/- 16 minutes, and a final activated clotting time was 174 +/- 69 ms. The duration of normal compression was 7.7 +/- 3 min. Eighty-three point five per cent of patients were discharged the day after the procedure with a global cardiovascular complication rate of 2.87%. At 1 month, 1.67% of secondary cardiovascular events was recorded. Ultrasonography of the puncture site was abnormal in 7.6% of patients. Only one serious vascular complication (0.24%) requiring transfusion and surgical repair, was observed. The authors conclude that the use of low dose heparin appears effective and safe in cases without acute myocardial infarction. This protocol allows faster mobilisation and earlier hospital discharge of patients.

Aged↗
PubMed2000

[Qualitative and quantitative descriptions of the mechanisms of action of the angioplasty balloon on coronary stenosis. An endovascular ultrasonic study].

The barotrauma induced by inflation of the balloon on an obstructive atherosclerotic plaque induces several distinct, complex effects. The object of this study was to describe these mechanisms based on endovascular echographic sections of coronary stenoses before and after balloon angioplasty. The 32 lesions analysed were richly cellular (81.2%) and associated with calcifications in 31% of cases. The remodelling index before angioplasty was used to individualize a majority of lesions with chronic arterial constriction (56.2%). The modelling of the plaque (dilatation or constriction) had no effect on the final luminal result. Global analysis of the endoluminal gain (4.38 +/- 2.28 mm2) showed that it was mainly due to reduction of plaque surface (78.2% of gain) without prejudging the mechanism, and less due to expansion of the global arterial surface (21.8% of the gain). The type of remodelling affected the mechanisms of action of balloon angioplasty. Dissection was present in 53.1% of cases. Fragmentation of the plaque with embolisation is a common phenomenon (28% of cases). The authors conclude that there are four mechanisms which coexist: 1) Reduction of plaque thickness cannot physically correspond to simple compression of tissue. The plaque is redistributed longitudinally. 2) Arterial expansion only plays a minor part in endoluminal gain. 3) Plaque rupture is directly related to the acute increase in wall stress often exceeding the thresholds of rupture of its components. Finally, 4) embolisation by parietal fragmentation, a mechanism often unknown or ignored which plays an essential part in the potentially deleterious effects.

Angioplasty, Balloon↗
PubMed2000

[Transluminal coronary angioplasty performed in patients with single vessel disease of the right coronary artery disease. Long-term results].

The patients who have only single vessel disease of the right coronary artery have an excellent prognosis, unaffected by surgery. The object of this study was to evaluate the long-term prognosis of these patients after transluminal coronary angioplasty. The criteria of analysis were survival, anginal symptoms, quality of life and ergometric parameters. Two hundred and forty eight patients with an isolated lesion of the right coronary artery who underwent angioplasty were reassessed 39.6 +/- 22 months after angioplasty. The primary success rate was 89.9% with 5.2% of severe complications during the hospital period (myocardial infarction, bypass surgery, coronary angiography +/- angioplasty). The actuarial global and cardiac survival rates at 7 years were 88.4 and 96.2% respectively with no difference between the success and failure groups. The eight cardiovascular deaths and thirteen myocardial infarctions which were observed in the long-term were all in the successful angioplasty group. From the symptomatic viewpoint, 76% of the population became asymptomatic. The same results were observed in terms of quality of life with 58% of patients estimating it to be good in correlation with anginal status. The comparison of ergometric tests showed a significant gain in performance in 67% of patients. The authors conclude that the results suggest that angioplasty in single vessel disease of the right coronary artery provides a significant symptomatic and ergometric benefit but that it is impossible to assess the eventual benefits in terms of survival which would have needed a group of similar patients assessed under anti-ischaemic treatment and taking into consideration the recent innovations (stents, statins).

Adult↗
PubMed1999

Modeling geometric artefacts in intravascular ultrasound imaging.

A model has been developed for estimating the geometric distortions in intravascular ultrasound (IVUS) imaging caused by the position of the ultrasound catheter within the artery. Geometric distortion causes degradation on cross-sectional images of the vessel wall where, for characteristic positioning of the transducer within the vessel, a circular artery is seen on IVUS images as a noncircular vessel represented by more or less complex shapes. Artefacts, therefore, have a clinical impact on the accuracy of qualitative and quantitative intravascular analyses. The main distortions are due to the inclination and the off-centered position of the transducer within the vessel. These effects are increased by two factors: first, the point of origin of the ultrasound beam does not coincide with the rotation axis of the catheter; second, in the case of a mechanical rotating transducer, the ultrasound beam is not perpendicular to the long axis of the catheter, but has an inclination such that the transducer looks forward from the emitting point. All these parameters are taken into account in the three-dimensional (3-D) geometric model developed in this paper. The model was formulated to predict the geometric deformation for artery contour of various shapes and can model artefacts during stent implantation (Finet et al. 1998). Simulations were made for various geometric configurations and compared to in vitro and in vivo IVUS images. The model results are consistent with the experimental results. Finally, the model was used for estimating the values of the geometric parameters that cause distortions on ultrasonic images.

Arteries↗
PubMed1999

[Comparison of iodixanol (Visipaque) and ioxaglate (Hexabrix) in coronary angiography and ventriculography: a double-blind randomized study].

OBJECTIVE: To evaluate and compare in a double-blinded and prospective study the incidence of adverse reactions between two contrast agents used for coronary angiography and ventriculography. The first agent was the non-ionic, dimeric, isotonic contrast medium iodixanol (Visipaque), the other was the ionic dimeric contrast medium ioxaglate (Hexabrix). METHODS: A total of 110 consecutive patients were randomized and received either iodixanol 320 mgl/ml or ioxaglate 320 mgl/ml. The efficacy, safety, tolerability and specific cardiovascular effects were evaluated. Adverse reactions were recorded during the procedure and during the first 24 hours after the examination. Hemodynamic and electrophysiological parameters were recorded before and after the ventricular injection and the first injections into the left and right coronary artery, respectively. RESULTS: The incidence of clinical adverse reactions was significantly different between iodixanol and ioxaglate (3% vs 28%, p = 0.0004). 24 patients (16 iodixanol; 8 ioxaglate) experienced no discomfort (sensation of warmth, coldness or pain), and the intensity of discomfort experienced by the remainder was similar for the two groups. No patient reported pain. During the 3 minutes after injection of contrast medium, the LV end-diastolic pressure increased but, apart from one reading, the increases with iodixanol were always significantly different (p < 0.05), and less than those for ioxaglate. During the same time period, heart rate was increased to a greater extent by ioxaglate (p < 0.05). QT interval was significantly (p < 0.05) prolonged with both ioxaglate and iodixanol, but the changes were less marked after iodixanol. The angiographic studies were of diagnostic quality for all patients and optimal diagnostic information was achieved in 92% of both groups. CONCLUSION: This randomized study shows that iodixanol and ioxaglate are of comparable diagnostic efficacy in coronary angiography and ventriculography, but that iodixanol is better tolerated by patients and results in less marked hemodynamic and eletrophysiological changes than does ioxaglate.

Adolescent↗
PubMed1999

[Endocoronary ultrasonography and angioplasty].

At the end of the 20th century, endocoronary ultrasonography has become established in many catheter laboratories. The information provided by this technique of invasive imaging has many qualitative and quantitative features. Is endocoronary ultrasonography a research or an everyday clinical tool to be used systematically or occasionally in routine procedures? Endocoronary ultrasonography is really a research tool because it is not redundant with conventional coronary angiography. Ultrasonography investigates the whole arterial wall. Its spatial resolution is twice that of angiography. Its contribution in this field in rich with many reports on arterial modelling, post-angioplasty remodelling, plaque rupture and atherothrombosis, the accurate description of the mechanical effects of angioplasty tools, two and three-dimensional quantification of atherosclerotic plaques and, finally, providing a very accurate biomechanical approach. Its use in routine procedures is only occasionally justified as there is no scientific proof in favour of a more widespread use with respect to changing the procedure or to evaluating patient prognosis. Endocoronary ultrasonography, a very rich technique, should be available in all catheter laboratories for occasional use. This technique is useful for all cardiologists performing coronary angioplasty by improving the evaluation of atheromatous plaques and countering the intrinsic ambiguities of coronary angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed1998

Artifacts in intravascular ultrasound imaging during coronary artery stent implantation.

Intravascular ultrasound imaging is able to provide direct images of the stent meshwork. However, a paradoxical question remains unanswered: Why is it not possible to correct or prevent implantation defects by ultrasound-guided implantation? We postulate that these discrepancies are due to image artifacts. We performed an in vitro experiment allowing detection, physical characterization, and computerized simulations of the various aspects of these artifacts. The width of the echo of a strut is variable, dependent on its distance from the transducer. The stent strut echo orientation is variable, and depends on the position of the transducer inside the stent. The stent contour image depends on the position of the transducer. In conclusion, knowledge of these stent intravascular ultrasound image artifacts enabled us to discriminate accurately between artifacts and real stent implantation defects, and are indispensable for accurate qualitative and quantitative analyses of stents.

Arteries↗
PubMed1998

Evaluation of an automatic intraluminal edge detection technique for intravascular ultrasound images.

Intravascular ultrasound (IVUS) imaging enables detailed analysis and precise measurements of vascular cross-sections. However, to achieve a reduction in the existing level of observer variability requires the development of quantitative IVUS. We have developed a fully automatic intraluminal edge detection technique, based on adaptive active contour models and called ADDER (adaptive damping dependent on echographic regions) that allows the quantitation of the intraluminal cross-sectional area (ICSA). Using a 30-MHz mechanically rotated transducer mounted at the tip of a 3.5-F catheter, 58 normal and pathologic arterial segments (from coronary, renal, splenic, iliac, and carotid arteries) were imaged in vitro. These images were analyzed by 2 experts, E1 and E2, who manually traced the intraluminal contour twice for each image, as well as with ADDER. Intra-observer variabilities for ICSAs were found to be excellent (-1.454 +/- 3.51% for E1, 0.96 +/- 5.4% for E2). The inter-observer variability was 2.1 +/- 4.3%. The success factor for ADDER was 89%. Its intra-observer variability was null, as the method always finds a unique contour. The correlation between the automatically detected ICSA and the manual ICSA was: r = 0.99 (y = 1.03x + 0.89 mm2). Morphometric variations between manually and automatically traced contours, analyzed by the centerline method, were 100 +/- 140 mm on average. In conclusion, the ADDER automatic contour detection applied to IVUS images is robust and characterized by small systematic and random errors; therefore, quantitative IVUS is a useful tool in clinical research trials.

Blood Vessels↗
PubMed1997

Left ventricular pressure-volume relationships before and after cardiomyoplasty in patients with heart failure.

BACKGROUND: The aim of this study was to elucidate whether beneficial effects of cardiomyoplasty (CMP) in patients with dilated cardiomyopathy are the result of a decrease in existing ventricular dilatation or a prevention of further dilatation. METHODS AND RESULTS: Combined micromanometer-conductance catheters were used to evaluate left ventricular pressure-volume relationships in six patients with dilated cardiomyopathy before and at 6 and 12 months after CMP. Acute changes in preload and afterload were induced by a standardized leg-tilting intervention and a bolus infusion of nitroglycerin. After CMP, end-diastolic volume (EDV) decreased from 138+/-10 to 103+/-18 mL/m2 (P<.01) at 6 months and to 83+/-17 mL/m2 (P<.01) at 12 months. End-diastolic pressure (EDP) decreased from 20.2+/-6.4 to 13.9+/-7.7 mm Hg (P<.01) at 6 months after CMP. Peak ejection rate and ejection fraction increased at 6 months after CMP from 594+/-214 to 799+/-214 mL/s (P<.05) and from 26.6+/-4.7% to 40.1+/-8.3% (P<.05), respectively. Peak dP/dt decreased at 12 months after CMP from -842+/-142 to -712+/-168 mm Hg/s (P<.05). Leg-tilting before CMP increased EDP from 20.2+/-6.4 to 25.6+/-5.2 mm Hg (P<.01), end-systolic pressure (ESP) from 118+/-17 to 122+/-17 mm Hg (P<.05), and tau from 50.8+/-2.8 to 53.8+/-2.3 ms (P<.05). Six months after CMP, leg-tilting also increased EDV from 103+/-18 to 110+/-22 mL/m2 (P<.05) and ESV from 62+/-14 to 66+/-14 mL/m2 (P<.05). Before CMP, nitroglycerin decreased EDP from 20.2+/-6.4 to 10.4+/-3.8 mm Hg (P<.01), ESP from 118+/-17 to 96+/-11 mm Hg (P<.05), ESV from 100+/-11 to 89+/-7 mL/m2 (P<.05), and tau from 50.8+/-2.8 to 44.5+/-3.7 ms (P<.05). Six months after CMP, nitroglycerin decreased EDP, ESP, and tau to similar values. CONCLUSIONS: Our findings show that up to 1 year after CMP, marked decreases in left ventricular volume are present. Our measurements suggest that CMP actively reduced the dilated ventricle but did not prevent a higher EDV on an increased venous return. The latissimus dorsi muscle wrap contraction results in better synchronization of contraction and more rapid emptying of the left ventricle.

Cardiomyopathy, Dilated↗
PubMed1997

Effect of the direct nitric oxide donors linsidomine and molsidomine on angiographic restenosis after coronary balloon angioplasty. The ACCORD Study. Angioplastic Coronaire Corvasal Diltiazem.

BACKGROUND: Nitric oxide (NO) donors, in addition to their vasodilator effect, decrease platelet aggregation and inhibit vascular smooth muscle cell proliferation. These actions could have beneficial effects on restenosis after coronary balloon angioplasty. METHODS AND RESULTS: In a prospective multicenter, randomized trial, 700 stable coronary patients scheduled for angioplasty received direct NO donors (infusion of linsidomine followed by oral molsidomine) or oral diltiazem. Treatment was started before angioplasty and continued until 12 to 24 hours before follow-up angiography at 6 months. The primary study end point was minimal lumen diameter, assessed by quantitative coronary angiography, 6 months after balloon angioplasty. Clinical variables were well matched in both groups. However, despite intracoronary administration of isosorbide dinitrate, the reference diameter in the NO donor group was significantly greater than in the diltiazem group on the preangioplasty, postangioplasty, and follow-up angiograms. Pretreatment with an NO donor was associated with a modest improvement in the immediate angiographic result compared with pretreatment with diltiazem (minimum luminal diameter, 1.94 versus 1.81 mm; P = .001); this improvement was maintained at the 6-month angiographic follow-up (minimal lumen diameter, 1.54 versus 1.38 mm; P = .007). The extent of late luminal narrowing did not differ significantly between groups (loss index in the NO donor and diltiazam groups, 0.35 +/- 0.78 and 0.46 +/- 0.74, respectively; P = .103). Restenosis, defined as a binary variable (> or = 50% stenosis), occurred less often in the NO donor group (38.0% versus 46.5%; P = .026). Combined major clinical events (death, nonfatal myocardial infarction, and coronary revascularization) were similar in the two groups (32.2% versus 32.4%). CONCLUSIONS: Treatment with linsidomine and molsidomine was associated with a modest improvement in the long-term angiographic result after angioplasty but had no effect on clinical outcome. The improved angiographic result related predominantly to a better immediate procedural result, because late luminal loss did not differ significantly between groups.

Aged↗
PubMed1997

Ultrasound contrast agent in intravascular echography: an in vitro study.

The intravascular ultrasound image of the intraluminal contour depends on the difference between acoustic impedances of the media which create the endoluminal interface. There are several limitations to the visualization and detection of this interface. These limitations are due to artifacts encountered during image formation and to anatomical complexity. The purpose of this study is to obtain intraluminal contour enhancement using ultrasound contrast agent (UCA). Therefore, our objective was to address the feasibility of this technique by documenting the following: (i) the acoustic properties of UCA at 30 MHz; (ii) in vitro experimentation with tube or postnecrotic artery; and (iii) suitable digital processing. The images obtained with UCA (enhanced image quality) and subtracted from those without UCA provided, after simple digital processing, accurate visualization of the arterial lumen. The image obtained exhibits an even, high-contrast intraluminal edge. Such characteristics facilitate contour extraction by the automated contour detection procedures.

Contrast Media↗
PubMed1997

Validation of a new quantitative coronary angiography analysis system used to evaluate densitometric lumen remodelling.

Arterial lumen volume, determined by sequential coronary angiography, could have advantages over more commonly used variables (such as percent stenosis or minimal lumen diameter) as a primary endpoint in clinical trials evaluating post-angioplasty restenosis or atherosclerotic plaque progression. We validated a quantitative coronary angiography analysis (QCA) system aimed at measuring lumen volume from coronary angiography films by a densitometric method. Using images of polyacrylate models filled with different concentrations of contrast medium, accuracy (mean of the differences between known and measured values of a measurement) and precision (standard deviation of the difference) were lower than or equal to 0.09 and 0.21 mm, respectively, for diameters ranging from 1.5 to 16 mm. In terms of volume measurement, accuracy was 30.2 mm3 and precision 5.7 mm3 for a known volume of 620.2 mm3. To assess the short-term variations of lumen volume measurements under conditions resembling those encountered in clinical trials, a special image comparison program of the QCA system was used to measure the same coronary artery segment on two images taken 10 minutes apart in 21 patients. The mean difference between the two measurements was 1.7 +/- 12.4 mm3, with a coefficient of variation of 15%. An error of +/-2 frames in the selection of images to be analyzed had little influence on the results. We conclude that the QCA system provides easy-to-achieve standardization of the image acquisition process and sufficient reproducibility for repeated measurement of volume of a coronary artery segment, which can serve as the primary endpoint in clinical trials evaluating atherosclerotic plaque progression or restenosis after angioplasty.

Angioplasty↗
PubMed1997

[Analysis of the diagnostic value of endovascular ultrasound with roc curves. Practical implications].

Intravascular ultrasound enables detection of the components of atherosclerotic plaques. The diagnostic value was assessed by ROC (receiver operating characteristic) curves on images acquired in vitro and correlated with the histological findings in 61 arteries. Five questions were asked of each operator; the reply was represented by a continuous variable in order to express all nuances of judgement. The area under the ROC curve, Az, was the criterion of performance (0.5 : chance response : 1.0 : all replies were accurate). Detection of plaque was satisfactory (Az = 0.89). The three layer appearance of muscular arteries was well recognised (Az = 0.94). The fibrous composition of a plaque was only just satisfactory (Az = 0.88) with 38.7% interindividual variability. The lipid composition of the plaque was poorly recognised (Az = 0.76) with large interindividual variability (52.8%) : hypoechogenicity was too ambiguous a sign from the acoustic point of view. A hypoechogenic zone must not be synonymous with a lipid plaque but a cellular zone. Calcium can almost always be detected (Az = 0.98) with a very low interindividual variability (10.7%), fibrohyaline progression of some plaques can be confusing. The authors present a more objective description of endovascular ultrasonographic images. They conclude that the diagnostic performance of 30 MHz intravascular ultrasound is satisfactory but several limitations are apparent in the interpretation of images, especially hypoechogenic zone and hyper-reflective zones with high attenuation.

Arteries↗
PubMed1996

Parameters that influence accuracy and precision of quantitative coronary arteriography.

The limited resolution of any imaging system causes edge blurring of objects acquired with X-ray. In digital angiography, this effect combined with noise gives rise to systematic and random errors in the determination of vessel dimensions. The influence of bandwidth limitation on the estimation of tube diameter is established by a theoretical approach: it leads to over and underestimations of catheter and vessel diameter dimensions. Therefore a correction is proposed that counterbalances the point spread function (PSF) offset. The residual inaccuracy and the variability of measurement of phantom tubes are analyzed and evaluated in controlled conditions. Some of the parameters which govern their extent are identified: field-of-view, catheter size, concentration of contrast agent.

Coronary Angiography↗