Biomedical subjects

B Diebold

Publications and source records attributed to B Diebold.

At least 19 recordsLinked to original sources

PubMed2002

[Value of factor analysis in a wall motion study: preliminary application in the detection of left ventricular segmental contraction ischemic disorders by echocardiography].

PURPOSE: Factor Analysis of Medical Image Sequences (FAMIS) was tested to study the regional wall motion of the left ventricle at echocardiography. MATERIALS AND METHODS: FAMIS analyzed the time signal curves of each pixel. One flat curve and one curve describing the contraction-relaxation of the left ventricle were first estimated. The contributions of the curve of each pixel to the two previous curves were computed, yielding two "factor images". The spatial distribution of positive and negative coefficients of the second factor image was analyzed. The evaluation was carried out on 222 segments (20 patients, 18 parasternal short-axis views, 17 apical four-chamber views, and 15 apical two-chamber views). A first echocardiographer reviewed the factor images and the reading was compared to the conventional reading of the cine-loops by two other echocardiographers. Each segment was scored as normal, hypokinetic, akinetic, or dyskinetic. RESULTS: On normal segments, the positive coefficients of the second factor image were on the inner side, the negative coefficients were on the outer side. Dyskinesis yields the opposite pattern. Hypokinesis and akinesis give intermediate images. An absolute concordance was obtained on 71.2% of all segments between the two types of reading. Larger discrepancies were found for akinetic and hypokinetic segments. CONCLUSION: FAMIS is a promising tool to study regional wall motion of the left ventricle.

Echocardiography, Doppler, Color↗

PubMed2001

In vitro quantification of flow using continuous infusion of Levovist and pairs of harmonic power Doppler images.

To evaluate the potential of harmonic power Doppler to quantify perfusion using a continuous infusion of contrast, two dialysis cartridges were perfused with different flow rates adjusted between 0 to 300 mL/min, corresponding to flow ratios comprised between 300:0 and 150:150. The contrast agent (Levovist, Schering) was injected at constant rates (0.6 to 5 g/h). Sequential pairs of images showing simultaneously the cross-sections of the two filters were acquired with a HDI 5000 (ATL) and the Doppler data were processed with HDI lab software (ATL). The absolute values of the signal in the different regions-of-interest (ROI) were not closely related to flow rate. At the opposite, the rapid signal decrease between the first and the second image of each pair was inversely proportional to the flow rate. An index of perfusion [PerI = image 1/(image 1 -- image 2)] was defined. It correlated closely with the absolute and relative flow rates. For the latter, the slopes of regression were found to be independent of the infusion rate of Levovist. Thus, the use of pairs of images combined with a continuous infusion of Levovist provide a quantification of perfusion.

Blood Flow Velocity↗

PubMed2001

Multigate doppler signal analysis using 3-D regularized long AR modelling.

Autoregressive (AR) modelling has already been proposed as an alternative to fast Fourier transform to process ultrasound (US) Doppler signals. Previous works introduced long AR models, set up under a regularization framework. The latter may be in 1-D (frequency) or 2-D (frequency and space or time). This study generalizes the spectrum regularization in the three dimensions frequency, space and time. The problem of the penalization function is addressed, and a new convex solution is proposed, taking into account possible nonstationarity of the Doppler signal. The parameter tuning is based on simulations using a standard Doppler signal model. The first results show that this processing improves the spectral estimation, and is well suited to flow interpretation.

Algorithms↗

PubMed2001

Determinants of right ventricular pressure in mild hypertension.

OBJECTIVE: Doppler echocardiography was used to define reference values and determinants of tricuspid regurgitation peak velocity (TRV) in hypertensive patients. A TRV value > 2.5 m/s is the threshold usually defining abnormal right ventricular systolic pressure. DESIGN AND PATIENTS: Doppler echocardiography was performed in 320 consecutive uncomplicated hypertensive patients, without overt pulmonary or heart disease. Doppler echocardiography included LV mass measurement, LV inflow and pulmonary venous flow analysis, LV systolic function and TRV measurements. RESULTS: Among 320 patients, 255 had normal TRV < 2.5 m/s and 65 had elevated TRV > or = 2.5 m/s. Compared with the normal TRV group, the elevated TRV group was older (60 versus 50 years, P < 0.0001), systolic blood pressure was higher (156 versus 151 mmHg, P = 0.02) and antihypertensive therapy was more frequent (68 versus 51%, P = 0.02); indexed LV mass was higher (45.4 versus 40.6 g/m2.7, P = 0.001), pulmonary D wave peak velocity was higher (42 versus 38 cm/s, P = 0.03). In univariate analysis, age was the most predictive variable of TRV (r = 0.36). In multivariate analysis, three variables were independently related to TRV: age, LV mass, pulmonary D wave (multiple r = 0.47). CONCLUSION: In mild hypertension, TRV is independently related to age, and to a lesser extent, to LV morphology and LV filling pressure. In clinical practice, age should be taken into account to interpret TRV.

Aging↗

PubMed2000

Fluid mechanics of regurgitant jets and calculation of the effective regurgitant orifice in free or complex configurations.

The velocity fields of turbulent jets can be described using a single formula which includes two empirical constants: k(core) determining the length of the central core and k(turb) the jet widening. Flow models simulating jet adhesion, confinement and noncircular orifices were studied using laser Doppler anemometer and the modifications of the constants were derived from series of velocity profiles. In circular free jets, k(core) was found equal to 4.1 with a variability of 1.4%. In complex configurations, its variability was equal to 15.2%. For k(turb), the value for free circular jets was of 45.2 with a variability of 6.0% and this variability in complex configurations was significantly higher (30. 1%, p=0.025). The correlation between the actual orifice size and the jet extension was poor (r=0.52). However, the almost constant value of k(core) allowed to define a new algorithm calculating the regurgitant orifice diameter with the use of outlines of the jet image (r=0.89). In conclusion, the fluid mechanics of regurgitant jets is modified in complex configurations but, due to the relative independency of the central core, velocity fields could be used to evaluate the dimensions of the effective regurgitant orifice.

Algorithms↗

PubMed2000

In vitro flow quantification with contrast power Doppler imaging.

To evaluate the effectiveness of contrast harmonic (power Doppler imaging) as an ultrasonic modality to quantify flow, an in vitro model of perfusion was studied using Optison, a second-generation ultrasound (US) contrast agent. The in vitro model was made of two dialysis cartridges placed parallel and allowed absolute and relative flow quantification on both tube (entry lines) and tissue (cartridges) simulations. Video intensity curves were generated using intermittent harmonic power Doppler imaging after bolus injection of contrast. Correlation between flow and different parameters extracted from time-intensity curves and previously defined as indicators of flow was established for both tissue and entry lines, for flow rates ranging from 0 to 400 mL/min. Single-compartment equations were also tested on the model. A good correlation for the tissue model was observed between absolute flow and onset time (O), time to maximal enhancement (TME), peak intensity (P), area under the curve (AUC), and maximal ascending slope (S) parameters, with a r = 0.94, 0.94, 0.91, 0.92 and 0.92, respectively. The correlation for O, TME, P and AUC parameters was r = 0.86, 0.90, 0.78 and 0.82, respectively for entry lines. The correlation for tissue model and entry line was slightly improved when comparing flow ratios with peak ratios (P1/P2) and slope ratios (S1/S2) (r = 0.95 and 0.94). Flow calculation using the gradient-relationship method also showed a good correlation (r = 0.88) with the experimental flow. The results obtained indicated that absolute and relative quantification of flow using PDI is feasible in tube and tissue models. Several clinical applications, namely in myocardial, hepatic and renal artery studies, could be derived from these results.

Albumins↗

PubMed2000

In vitro validation of a new approach for quantitating regurgitations using proximal isovelocity surface area.

The present work has been designed to validate the calculation of the effective regurgitant orifice (ERO) area with the use of a new formula that takes into account the velocity profile (V(r) vs r) and that is insensitive to errors in the determination of the position of the orifice. Assuming a hemispheric model, ERO = 2 pi r(2). V(r)/V(o) (with V(o) = velocity at the orifice) and (V(o)/V(r))(0.5) = (2 pi/ERO)(0.5) r. Thus, the slope of the corresponding linear regression allows ERO to be calculated as: ERO = 2 pi/slope(2). This approach was tested in vitro in pulsatile conditions on circular, conical, and slit-like orifices. The calculated ERO was compared with the actual jet cross sectional area derived from the transverse velocity profile at the jet origin. For the purpose of comparison, the "classical" ERO was calculated for all the configurations, angulations, and threshold velocities. The relationship between (V(o)/V(r))(0.5) was linear (r > 0.98) over a wide range of velocities. The nonhemispheric components were found to modify the constant and not the slope. The mean variation of the calculated ERO was 6.5%. The correlation between the calculated and the actual ERO was very close (>0.97) with slope equal to 0.96. By comparison with the new method, the classical formula gave an underestimation of the ERO that dramatically increased when studying the flow closer to the orifice or in the case of error on the measurement of r. In conclusion, a method using velocity profiles instead of isolated values improves the accuracy of the proximal isovelocity surface area (PISA) method for measuring the ERO.

Blood Flow Velocity↗

PubMed2000

[Improved left ventricular endocardial detection by a first generation contrast agent. Effect of dose].

The study of global and segmental left ventricular function forms part of every echocardiographic examination. However, this is only possible when the endocardial borders are well identified. The authors report the results of a study with Albunex, a first generation contrast agent used by intravenous injection. The object of this study was to assess the efficacy of Albunex in improving left ventricular endocardial detection compared with standard transthoracic echocardiography (TTE) and the dose-effect relationship. Forty-one patients were included prospectively at two cardiological hospital centres between 1995 and 1997, before the development of second harmonic imaging. Two patients were excluded from the study. Each patient underwent transthoracic echocardiography in the fundamental mode with an apical four-chamber view. The following procedure was adopted: 1) standard examination, 2) low dose Albunex (0.1 mg/Kg) injected via a peripheral vein, 3) high dose Albunex (0.2 mg/Kg) injected via a peripheral vein, 4) low dose Albunex injected via a central vein, 5) high dose Albunex injected via a central vein. The analysis of results was performed by two independent observers and showed that Albunex improved endocardial detection (p < 0.005); this detection was significantly better with high doses of Albunex and with central vein injection (p < 0.005); the septal border was better visualised than the lateral wall endocardium (p < 0.005) but the improvement in endocardial detection was greater for the lateral wall (p < 0.005). No complications were observed during the procedure. The authors conclude that Albunex improves left ventricular endocardial detection. This benefit is mainly due to improved lateral wall detection, and increases with higher doses of the contrast agent.

Adult↗

PubMed1999

Quantitative systolic and diastolic transmyocardial velocity gradients assessed by M-mode colour Doppler tissue imaging as reliable indicators of regional left ventricular function after acute myocardial infarction.

AIMS: The aim of this study was to determine whether myocardial velocity gradients assessed by M-mode colour Doppler tissue imaging could be of clinical relevance and represent reliable indicators of regional left ventricular function after acute myocardial infarction. METHODS AND RESULTS: Among 64 consecutive patients with a first acute myocardial infarction, in 50 who had a marked asynergy in the parasternal short-axis view at the mid-papillary muscle level, myocardial velocities and velocity gradients were assessed in the anteroseptum and posterior wall by M-mode Doppler tissue imaging. Similar measurements were obtained in 11 matched healthy volunteers who served as a control group. In patients with anterior myocardial infarction, the peak myocardial velocity gradient in the anteroseptum was significantly lower when compared with controls (mean +/- [SD] 0.0 +/- 0.5 vs 1.1 +/- 0.7 s-1 during systole, P < 0.01; and 0.3 +/- 0.6 vs 2.0 +/- 0.5 s-1 during diastole, P < 0.01). Conversely, the peak systolic myocardial velocity gradient in the posterior wall was significantly higher than in controls (2.6 +/- 1.2 vs 1.8 +/- 1.2 s-1, P < 0.05). In patients with inferior myocardial infarction, the peak velocity gradient in the posterior wall was significantly lower when compared with healthy subjects (0.9 +/- 0.6 vs 1.8 +/- 1.2 s-1 during systole and 1.4 +/- 1.4 vs 4.9 +/- 1.2 s-1 during diastole, both P < 0.01). The peak systolic tissue velocity gradient in the anteroseptum was significantly higher than in controls (2.1 +/- 1.0 vs 1.1 +/- 0.7 s-1, P < 0.01). CONCLUSION: The present study indicates that myocardial velocity gradients assessed by M-mode Doppler tissue imaging are of clinical relevance for the characterization of ischaemic myocardial dysfunction after infarction and may provide quantitative assessment of segmental left ventricular function in this clinical setting.

Aged↗

PubMed1999

Mapping of a first locus for autosomal dominant myxomatous mitral-valve prolapse to chromosome 16p11.2-p12.1.

Myxomatous mitral-valve prolapse (MMVP), also called Barlow disease, is a common cardiac abnormality and affects up to 5% of the population. It is characterized by an excess of tissue that leads to billowing of the mitral leaflets, sometimes complicated by prolapse. Typical histological findings include myxomatous degeneration and degradation of collagen and elastin. Previous reports have proposed an autosomal dominant inheritance of the trait, with age- and sex-dependent expression. By systematic echocardiographic screening of the first-degree relatives of 17 patients who underwent mitral-valve repair, we have identified four pedigrees showing such an inheritance. Genomewide linkage analysis of the most informative pedigree (24 individuals, three generations) showed a significant linkage for markers mapping to chromosome 16p, with a two-point maximum LOD score for D16S3068 (Zmax=3.30 at straight theta=0). Linkage to D16S3068 was confirmed in a second family (Zmax=2.02 at straight theta=0) but was excluded for the two remaining families, thus demonstrating the genetic heterogeneity of the disease. Multipoint linkage analysis performed, with nine additional markers, on the two families with linkage gave maximum multipoint LOD scores of 5.45 and 5.68 for D16S3133, according to a conservative and a stringent model, respectively. Haplotype analysis defined a 5-cM minimal MMVP-1 locus between D16S3068 (16p11.2) and D16S420 (16p12. 1) and a 34-cM maximal interval between D16S404 and D16S3068 when recombination events were taken into account only in affected individuals. The identification of this locus represents a first step toward a new molecular classification of mitral-valve prolapse.

Chromosome Mapping↗

PubMed1998

Vascular and cardiac remodeling in world class professional cyclists.

BACKGROUND: Numerous studies have demonstrated that left ventricular (LV) hypertrophy is often associated with conditioning. METHODS AND RESULTS: The aim of the study was to evaluate cardiac and carotid artery changes induced by professional cycling. We collected M-mode left ventricle and B-mode right common carotid artery data from 149 male professional cyclists before the 1995 "Tour de France" race and 52 male control subjects. LV mass indexed to body surface area in cyclists was double that in control subjects, with no overlap of 95% confidence intervals (cyclists 100.9 to 187 g/m2 and control subjects 51.8 to 96.3 g/m2). Both mean arterial diameter and mean arterial diastolic intima-media thickness (IMT) were 13% higher in cyclists than in control subjects, with overlap of 95% confidence intervals (for arterial IMT 0.45 to 0.65 mm in cyclists and 0.38 to 0.60 mm in control subjects). CONCLUSIONS: Our results suggest that intense cycling has an effect on the cardiovascular system, more pronounced on the left ventricle and less pronounced on large arteries. Nevertheless, athletic training should be considered as a potential determinant of carotid modification.

Adult↗

PubMed1998

Comparison of regional myocardial velocities assessed by quantitative 2-dimensional and M-mode color Doppler tissue imaging: influence of the signal-to-noise ratio of color Doppler myocardial images on velocity estimators of the Doppler tissue imaging system.

M-mode color Doppler imaging of the myocardium affords a greater sampling rate and signal-to-noise (S/N) ratio than 2-dimensional (2D) imaging. In this study, we compared myocardial velocities assessed by 2D and M-mode Doppler tissue imaging (DTI) at the same site and evaluated the influence of the S/N ratio on velocity estimates of the currently used DTI systems. In patients with and without impaired regional left ventricular function, myocardial velocities assessed by 2D DTI were lower than those obtained with M-mode DTI. The difference between regional velocities derived from both imaging techniques was positively correlated with the extent of the "black zone," which could be considered as indirectly reflecting the S/N ratio for each frame. Thus in the clinical setting and on currently used echocardiographs, 2D DTI may provide underestimated regional myocardial velocities when compared with M-mode, mainly because of the influence of the lower sampling rate and S/N ratio on velocity estimators of the imaging system.

Echocardiography, Doppler, Color↗

PubMed1998

Implementation of a fuzzy prototype-based machine learning method to predict myocardial infarction from coronary angiography.

Formal knowledge on the predictive value of morphological angiographic factors is lacking to estimate the risk of myocardial infarction. This article presents a computer system for predicting the incidence of myocardial infarction from angiographic morphological descriptions of coronary lesions. The system includes two phases. The learning phase consists in extracting from a large database of described stenoses two classes represented by one or several fuzzy prototypes. One class corresponds to stenoses leading to infarction and the other to stenoses not leading to that event. The evaluation phase consists in classifying a stenosis according to its morphological characteristics in one of these two classes. The learning method is based on a fuzzy supervised Machine Learning algorithm that combines some aspects of the K-nearest neighbours clustering approach with a defined measure of similarity, and a prototype induction function from the most similar stenoses, taking into account their degree of typicality. The current results of the evaluation phase to correctly predicted X% stenoses for their risk of myocardial infarction. This article emphasizes the feasibility of the approach, however, the learning phase relies on some heuristics that should be validated to get a formal evaluation of the system.

Artificial Intelligence↗

PubMed1998

[Recommendations of the French Society of Cardiology for the training of echocardiographers and performing echocardiograms].

The considerable advances achieved in the field of echocardiography have made this investigation an essential diagnostic tool. Under the auspices of the French Society of Cardiology, the Working group on Echocardiography publishes its practical recommendations for optimising the training of echocardiographers (theoretical instruction and practical courses) and for performing echocardiography (understanding the clinical problem, referral to previous examinations, necessary recordings and measurements, and appropriate equipment). In the future, these recommendations should be updated to take into account continuing technical improvements and changes in methods of studying cardiac disease by echocardiography.

Cardiology↗

PubMed1997

Comparison of arbutamine and exercise echocardiography in diagnosing myocardial ischemia.

Arbutamine is a new catecholamine designed for use as a pharmacologic stress agent. This study compared the sensitivity of arbutamine with symptom-limited exercise to induce echocardiographic signs of ischemia. Arbutamine was administered by a computerized closed-loop delivery system that controls the infusion rate of arbutamine toward a predefined rate of heart rate increase and maximum heart rate limit. Beta blockers were stopped > or = 48 hours before both tests. Stress was stopped for intolerable symptoms, or clinical, electrocardiographic or echocardiographic signs of ischemia (new or worsening wall motion abnormality), target heart rate (> or = 85% age predicted maximum heart rate), or plateau of heart rate response. Thirty-seven patients were entered into the study (35 arbutamine and exercise, 1 arbutamine only, 1 exercise only), of which 30 had angiographic evidence of coronary artery disease (> or = 50% lumen diameter narrowing). Rate-pressure product increased significantly in response to both stress modalities (p < 0.001) and was significantly greater with exercise (11,308 +/- 2,443) than with arbutamine (9,486 +/- 2,479, p < 0.001). The time to maximum heart rate was longer during arbutamine stress echocardiography than during exercise testing (17.3 +/- 9.4 versus 9.3 +/- 4.2 minutes, respectively, p < 0.001). There were more patients with interpretable echo data for arbutamine (82%) than for exercise (67%). Sensitivity for recognition of myocardial ischemia was 94% (95% confidence interval 70% to 100%) and 88% (95% confidence interval 62% to 98%), respectively. The most frequent adverse events during arbutamine (n = 36) were dyspnea (5.6%) and tremor (5.6%). Two arbutamine stress tests were discontinued due to arrhythmias: 1 patient had premature atrial and ventricular beats, and the other had premature atrial contractions and atrial fibrillation. Arrhythmias were well tolerated and resolved without sequelae. In conclusion, the sensitivity of arbutamine to induce echocardiographic signs of ischemia was similar to that of exercise despite a lower rate-pressure product. Arbutamine was well tolerated and provides a reliable alternative to exercise echocardiography.

Adult↗

PubMed1997

Acceleration mapping by Fourier acceleration-encoding: in vitro study and initial results in the great thoracic vessels.

Acceleration mapping can be conducted by replacing the bipolar gradient pulse of a velocity mapping sequence by a tripolar pulse. However, since the acceleration encoding pulse is longer, the image quality is altered by the requirement of a long echo time. Since Fourier encoding velocity imaging has been shown to be robust, this velocity mapping method was transformed into an acceleration mapping method. Four steps of the tripolar acceleration encoding gradient pulse were applied successively; acceleration was then obtained by Fourier transform after zero-filling. The accuracy of the method was assessed with a phantom giving a pulsatile flow. Acceleration maps of the ascending aorta and pulmonary artery were obtained in 10 healthy volunteers. The acceleration values measured were in the range of known physiologic values. The feasibility of Fourier encoding acceleration imaging was also demonstrated in four patients.

Adolescent↗

PubMed1997

Genetic polymorphisms of the renin-angiotensin system and angiographic extent and severity of coronary artery disease: the CORGENE study.

Genetic polymorphisms of the renin-angiotensin system (RAS) have been associated with coronary artery disease (CAD) but no relation between these polymorphisms and coronary atherosclerosis has yet been systematically evaluated. The CORGENE study is a cross-sectional study involving 463 Caucasians who underwent standardized coronary angiography for established or suspected CAD [156 patients with a previous myocardial infarction (MI), 307 without MI]. Four angiographic scores assessing the extent and severity of the coronary lesions were obtained from a double visual analysis of each angiogram, arbitration being achieved by a quantitative measurement. Three different genotypes were analyzed: the angiotensin I-converting enzyme insertion/deletion (ACE I/D) polymorphism, the Met to Thr change at position 235 of the angiotensinogen gene (AGT M235T) and the A to C transition at position 1166 of the angiotensin II type-1 receptor gene (AT1R A1166C). No significant association was observed between these polymorphisms and the clinical characteristics of MI and non-MI subjects. While most classical risk factors were positively correlated with the angiographic scores, no significant relationship could be established with the three genotypes (r ranging from -0.08 to 0.05). Only one significant correlation was observed: between the presence of the AGT 235T allele and the extent of the coronary lesions (r = -0.19, P = 0.04) in patients with low-risk status. These overall results are not in favor of a role of these RAS genetic polymorphisms in the development of coronary atherosclerosis.

Angiotensinogen↗

PubMed1996

In vitro flow mapping of regurgitant jets. Systematic description of free jet with laser Doppler velocimetry.

BACKGROUND: Color Doppler and magnetic resonance imaging give pictures of abnormal jets within which the respective contribution of fluid mechanics and image artifacts are difficult to establish because of current technical limitations of these modalities. We conducted the present study to provide numerical descriptions of the velocity fields within regurgitant free jets. METHODS AND RESULTS: Laser Doppler measurements were collected in rigid models with pulsatile flow conditions, giving several series of two-dimensional flow images. The data were studied with the use of two-dimensional or M-mode flow images as well as regular plots. Numerical descriptions validated in steady flow conditions were tested at the various times of the cycle. In these free jets, the momentum was conserved throughout the cycle. The transverse velocity profiles were approximately similar. A central laminar core was found at peak ejection and during the deceleration. Its length (l = 4.08 d-0.036 mm, r = .99) and its diameter (d) were proportional to the orifice diameter. At peak ejection, the velocity decay was hyperbolic, and the transverse velocity profiles were clearly gaussian. The different relations that were tested could be combined in a single formula describing the velocity field: V(x,y,t peak) = V(O,O,t peak).4.(d/x).10(-45(y/x)2) (r = .92). CONCLUSIONS: These in vitro measurements demonstrated the presence of a central laminar core and similar transverse velocity profiles in free turbulent jets. This allowed us to validate a series of numerical relations that can be combined to describe the velocity fields at peak ejection. On the other hand, further studies are needed to describe the various singularities often encountered in pathology.

Heart Valve Diseases↗