Biomedical subjects

Jos J M Westenberg

Publications and source records attributed to Jos J M Westenberg.

12 recordsLinked to original sources

PubMed2006

Assessment of left ventricular dyssynchrony in patients with conduction delay and idiopathic dilated cardiomyopathy: head-to-head comparison between tissue doppler imaging and velocity-encoded magnetic resonance imaging.

OBJECTIVES: This study sought to compare tissue Doppler imaging (TDI) with velocity-encoded (VE) magnetic resonance imaging (MRI) for left ventricular (LV) dyssynchrony assessment. BACKGROUND: Cardiac resynchronization therapy (CRT) is proposed for patients with heart failure, depressed LV function, and a wide QRS complex. Selection is based mainly on electrocardiogram criteria, but recent data suggest that intraventricular dyssynchrony may be preferred for selection. An LV dyssynchrony can adequately be assessed with TDI, but this has not been compared directly with other imaging modalities. A VE MRI potentially allows direct myocardial wall motion measurements similar to TDI. METHODS: Twenty patients with heart failure, systolic LV dysfunction, and a wide QRS complex were included, as well as 10 normal individuals with normal QRS duration and LV function. The TDI and VE MRI data were acquired to study intraventricular dyssynchrony. RESULTS: Left ventricular dyssynchrony was not observed in normal individuals (mean dyssynchrony -2 +/- 15 ms on TDI; mean -5 +/- 17 ms on MRI, p = NS). In patients, mean LV dyssynchrony was 55 +/- 37 ms on TDI; 49 +/- 38 ms on MRI (p = NS). Good correlation between both modalities was observed (linear regression TDI = 0.99 x MRI - 5, n = 30, r = 0.98, p < 0.01). The MRI showed a small, nonsignificant underestimation of 5 +/- 8 ms compared with TDI. Agreement between MRI and TDI for classification according to severity of LV dyssynchrony (minimal, intermediate, and extensive) was excellent (kappa +/- SE = 0.96 +/- 0.07, p < 0.01) with 95% of patients classified identical. CONCLUSIONS: Both MRI and TDI yield comparable information on LV dyssynchrony; MRI is useful in the selection of patients for CRT.

Adult↗

PubMed2006

SPASM: a 3D-ASM for segmentation of sparse and arbitrarily oriented cardiac MRI data.

A new technique (SPASM) based on a 3D-ASM is presented for automatic segmentation of cardiac MRI image data sets consisting of multiple planes with arbitrary orientations, and with large undersampled regions. Model landmark positions are updated in a two-stage iterative process. First, landmark positions close to intersections with images are updated. Second, the update information is propagated to the regions without image information, such that new locations for the whole set of the model landmarks are obtained. Feature point detection is performed by a fuzzy inference system, based on fuzzy C-means clustering. Model parameters were optimized on a computer cluster and the computational load distributed by grid computing. SPASM was applied to image data sets with an increasing sparsity (from 2 to 11 slices) comprising images with different orientations and stemming from different MRI acquisition protocols. Segmentation outcomes and calculated volumes were compared to manual segmentation on a dense short-axis data configuration in a 3D manner. For all data configurations, (sub-)pixel accuracy was achieved. Performance differences between data configurations were significantly different (p<0.05) for SA data sets with less than 6 slices, but not clinically relevant (volume differences<4 ml). Comparison to results from other 3D model-based methods showed that SPASM performs comparable to or better than these other methods, but SPASM uses considerably less image data. Sensitivity to initial model placement proved to be limited within a range of position perturbations of approximately 20 mm in all directions.

Algorithms↗

PubMed2006

Aortic root dysfunctioning and its effect on left ventricular function in Ross procedure patients assessed with magnetic resonance imaging.

BACKGROUND: This study evaluated the diameters and distensibility of the aortic root as well as the degree of aortic regurgitation (AR) and its effect on left ventricular (LV) function in patients 8.2 +/- 3.1 years after they underwent the Ross procedure, with a comparison of these parameters between patients and matched healthy subjects. METHODS: Eighteen Ross procedure patients (16 male patients, age [mean +/- SD] 19.2 +/- 3.8 years) and 18 matched healthy subjects (16 male patients, age [mean +/- SD] 19.7 +/- 4.2 years) underwent magnetic resonance imaging. Measurements for diameters (at 4 levels) and the distensibility of the aortic root were performed using a steady-state free precession sequence. Aortic flow was assessed with a velocity-encoded phase-contrast sequence. Left ventricular systolic function was assessed with a gradient-echo sequence in the short-axis plane. Comparison of parameters was performed using the Mann-Whitney U test. Correlations between diameters, distensibility, AR fraction, and LV systolic function were expressed with Spearman rank correlation coefficients. Linear regression analysis was used to identify predictors of LV systolic dysfunction. RESULTS: Aortic root diameters were increased in Ross procedure patients as compared with healthy subjects (mean difference 6.3-11.6 mm, P < or = .02 at all 4 levels). Distensibility of the aortic root was lower in patients (1.9 +/- 1.1 vs 7.8 +/- 3.3 mm Hg(-1), P < .01). An AR fraction > 5% was present in 14 of the 18 patients (mean AR fraction 8% +/- 5% vs 1% +/- 1%, P < .01). Left ventricular ejection fraction was lower in patients (50% +/- 6% vs 57% +/- 6%, P < .01). Dilatation, decreased distensibility, and AR fraction were correlated with impaired LV systolic function (P < .05 for all). The AR fraction predicted impaired LV systolic function (P < .01). CONCLUSIONS: Magnetic resonance imaging shows dilatation and decreased distensibility of the aortic root, AR, and consequent impaired LV systolic function in patients after the Ross procedure.

Adolescent↗

PubMed2005

MRI to evaluate left atrial and ventricular reverse remodeling after restrictive mitral annuloplasty in dilated cardiomyopathy.

BACKGROUND: Data on reverse remodeling of the left atrium (LA) and left ventricle (LV) after restrictive annuloplasty in patients with dilated cardiomyopathy are scarce, and follow-up studies are performed with echocardiography. METHODS AND RESULTS: Twenty patients with dilated cardiomyopathy and severe mitral regurgitation selected for restrictive mitral annuloplasty underwent serial MRI studies (within 1 week before surgery, and 2 months [n =18] and 1 year [n =13] after surgery). Early mortality was 10%; all patients were free from endocarditis and thromboembolism. New York Heart Association class improved from 3.2+/-0.4 to 1.2+/-0.9. Only 1 patient developed recurrent severe mitral regurgitation during follow-up and it was re-repaired. LA end-systolic volumes decreased significantly over time (from 165+/-48 mL to 109+/-23 mL to 111+/-28 mL; P < 0.01), as did LA end-diastolic volumes (from 92+/-32 mL to 71+/-22 mL to 75+/-17 mL; P = 0.01). LV end-diastolic volumes decreased significantly (from 244+/-56 mL to 184+/-54 mL to 195+/-67 mL; P < 0.01), whereas end-systolic volumes did not change significantly. LV ejection fraction increased significantly (from 35+/-8% to 46+/-13% to 46+/-15%; P < 0.01) and LV mass decreased significantly (from 150+/-43 grams to 132+/-39 grams to 136+/-33 grams; P = 0.02). CONCLUSIONS: Restrictive annuloplasty in patients with dilated cardiomyopathy yielded excellent clinical results associated with significant LA and LV reverse remodeling over time as demonstrated by MRI.

Adult↗

PubMed2005

Influence of positional and angular variation of automatically planned short-axis stacks on quantification of left ventricular dimensions and function with cardiovascular magnetic resonance.

PURPOSE: To theoretically and experimentally investigate the influence of the automated cardiovascular magnetic resonance (CMR) scan planning pitfalls, namely inaccurate positioning and tilting of short-axis (SA) imaging planes, on quantification of the left ventricular (LV) dimensions and function. MATERIALS AND METHODS: Eleven healthy subjects and eight patients underwent CMR. Manually and automatically planned SA sets were acquired. To obtain the quantitative measurements of LV function, one observer performed image analysis twice. The agreement between planning methods, as well as the decomposition of the total variation into interstudy and intraobserver components was measured. RESULTS: The decomposition of the total variation showed that the interstudy factor accounts for 70-85% of the total variation, while the rest is due to the intraobserver factor. Moreover, the relative contribution of the interstudy factor remains independent from errors in slice positioning and small angular deviation of SA stacks from the optimal orientation. Good agreement between the theoretical and measured variability factors was observed. CONCLUSION: Global LV function derived from the automatically planned CMR acquisitions yield accurate quantification of the human cardiovascular system. Inaccurate positioning and tilting of SA images does not affect the quantitative measurements of LV function. The computer-aided system for automated CMR has proven clinical applicability.

Adult↗

PubMed2005

3D model-based approach to lung registration and prediction of respiratory cardiac motion.

This paper presents a new approach for lung registration and cardiac motion prediction, based on a 3D geometric model of the left lung. Feature points, describing a shape of this anatomical object, are automatically extracted from acquired tomographic images. The "goodness-of-fit" measure is assessed at each step in the iterative scheme until spatial alignment between the model and subject's specific data is achieved. We applied the proposed methods to register the 3D lung surfaces of 5 healthy volunteers of thoracic MRI acquired in different respiratory phases. We also utilized this approach to predict the spatial displacement of the human heart due to respiration. The obtained results demonstrate a promising registration performance.

Algorithms↗

PubMed2005

Atrioventricular conduction in mammalian species: hemodynamic and electrical scaling.

OBJECTIVES: The purpose of this study was to investigate scaling of the duration of late diastolic left ventricular (LV) filling in relation to AV conduction time (delay) (PR interval on the ECG) in mammals. BACKGROUND: From mouse to whale, AV delay increases 10-fold, whereas body mass increases one million-fold. The apparent "mismatch" results from scaling of AV delay versus body and heart mass. METHODS: We measured (1) mitral orifice diameter in 138 postmortem hearts of 48 mammalian species weighing between 17 g and 250 kg and (2) transmitral diastolic flow using magnetic resonance imaging (MRI) recordings of 10 healthy human individuals. (3) We visually inspected early and late diastolic LV filling. (4) We developed two physical models to explain scaling of late diastolic LV filling time. RESULTS: (1) Diameter of the mitral orifice proportionally relates to heart length (third root of heart mass). (2) Atrial contraction starts at a fixed instant (+/- 80%) of the (normalized) cardiac cycle and contributes 31% +/- 5% to LV filling. (3) MRI shows that during diastole, the left atrium (LA) and LV form a single space. (4) The physical models relate the duration of late diastolic LV filling directly to heart length, the third root of heart mass. CONCLUSIONS: (1) Late diastolic (LV) filling time scales with heart length (third root of heart mass). (2) No "mismatch" exists between AV delay and heart size. (3) Knowledge of the actual starting time of atrial contraction may contribute to better treatment of patients with heart failure. (4) The findings suggest that in evolution of mammalian species, hemodynamics commands electrical behavior of the heart.

Animals↗

PubMed2005

Operator induced variability in cardiovascular MR: left ventricular measurements and their reproducibility.

PURPOSE: To assess the intra- and inter-operator variability of the manual planning of cardiovascular magnetic resonance imaging and to evaluate the influence of these factors on the functional parameters of the left ventricle (LV). METHOD: The study population consisted of 10 healthy volunteers. For each subject the manual planning of the short-axis cine acquisitions was carried out twice by one operator and once by a second operator. Left ventricular volume, mass, and function were manually evaluated twice by one experienced observer, resulting in an approximation of the intra-observer variability factor. The intra- and inter-operator variation factors were estimated as the difference between the total and intra-observer variation components. RESULTS: LV end-diastolic volume varied by 3.3% and 4.16%, and LV end-systolic volume by 5.84% and 6.23% for intra- and inter-operator studies, respectively. The variability for LV mass at end-diastole was equal to 4.23% in both studies. For the ejection fraction the variability was 3.56% and 2.97% for intra- and inter-operator studies, respectively. Comparison of reproducibility between intra- and inter-operator studies resulted in insignificant statistical differences. Bland-Altman limits of agreements revealed no systematic bias in differences between measurements with respect to their means. Reliability of the planning expressed as the angular deviation of the short-axis imaging planes amounts to 2.67 -/+ 1.5 degrees and 4.99 +/- 2.17 degrees for the intra-operator and inter-operator studies, respectively. For EDV, ESV, and EF approximately 75-80% of the total variation can be explained by the within or between operator variation, while the same percentage is 60% for LVM. CONCLUSIONS: Our study confirms the excellent inter- and intra-operator reproducibility of the cardiovascular magnetic resonance measurements of the left ventricular volumes and mass in a group of healthy volunteers.

Adult↗

PubMed2004

Accurate quantitation of regurgitant volume with MRI in patients selected for mitral valve repair.

OBJECTIVE: Echocardiography, the currently preferred diagnostic approach for mitral valve regurgitation, cannot accurately quantify the amount of regurgitation. Flow quantification with MRI is possible, but the conventional method (1-directional velocity-encoding) acquires the flow at a fixed location during the cardiac cycle, which is not necessarily the location of the mitral valve during the whole cycle. In this study, the exact flow through the mitral valve was quantified with a 3-directional velocity-encoded MRI approach. METHODS: Ten patients with severe mitral valve regurgitation (class 3-4+with echocardiography) resulting from systolic restrictive motion of both leaflets (Carpentier IIIb) which were selected for valve repair and 10 healthy volunteers without cardiac valvular disease confirmed with echocardiography were included in this study. The intra-ventricular flow was sampled with a radial stack of six acquisition planes parallel to the long-axis of the left ventricle. Three-directional velocity-encoded MRI was performed resulting in the intra-ventricular flow velocity vector field for 30 phases during the cardiac cycle. The position of the mitral valvular plane in this vector field was indicated manually for each phase. Velocity values perpendicular to this plane determined the flow through the mitral valve. Both the 3-directional encoded mitral valve flow and the 1-directional encoded mitral valve flow were compared with the flow determined with MRI at the ascending aorta. RESULTS: One-directional velocity-encoded MRI showed a mean overestimation (P<0.01) of 25 ml/cycle compared to the aortic flow. Correlation was very poor (r(P)=0.15, P=0.68). The 3-directional velocity-encoded MRI on the other hand, showed no over/underestimation and a good correlation (r(P)=0.91, P<0.01 for volunteers, r(P)=0.90, P<0.01 for patients). The regurgitant flow fractions were between 3 and 30%. CONCLUSION: With 3-directional velocity-encoded MRI, measurement of the flow through the mitral valve is accurate and reproducible. This is a valuable tool for diagnosing and absolute quantification of regurgitant volume.

Adult↗

PubMed2004

Enhanced circadian ACTH release in obese premenopausal women: reversal by short-term acipimox treatment.

Several studies suggest that the hypothalamo-pituitary-adrenal (HPA) axis is exceedingly active in obese individuals. Experimental studies show that circulating free fatty acids (FFAs) promote the secretory activity of the HPA axis and that human obesity is associated with high circulating FFAs. We hypothesized that HPA axis activity is enhanced and that lowering of circulating FFAs by acipimox would reduce spontaneous secretion of the HPA hormonal ensemble in obese humans. To evaluate these hypotheses, diurnal ACTH and cortisol secretion was studied in 11 obese and 9 lean premenopausal women (body mass index: obese 33.5 +/- 0.9 vs. lean 21.2 +/- 0.6 kg/m(2), P < 0.001) in the early follicular stage of their menstrual cycle. Obese women were randomly assigned to treatment with either acipimox (inhibitor of lipolysis, 250 mg orally four times daily) or placebo in a double-blind crossover design, starting one day before admission until the end of the blood-sampling period. Blood samples were taken during 24 h with a sampling interval of 10 min for assessment of plasma ACTH and cortisol concentrations. ACTH and cortisol secretion rates were estimated by multiparameter deconvolution analysis. Daily ACTH secretion was substantially higher in obese than in lean women (7,950 +/- 1,212 vs. 2,808 +/- 329 ng/24 h, P = 0.002), whereas cortisol was not altered (obese 36,362 +/- 5,639 vs. lean 37,187 +/- 4,239 nmol/24 h, P = 0.912). Acipimox significantly reduced ACTH secretion in the obese subjects (acipimox 5,850 +/- 769 ng/24 h, P = 0.039 vs. placebo), whereas cortisol release did not change (acipimox 33,542 +/- 3,436 nmol/24 h, P = 0.484 vs. placebo). In conclusion, spontaneous ACTH secretion is enhanced in obese premenopausal women, whereas cortisol production is normal. Reduction of circulating FFA concentrations by acipimox blunts ACTH release in obese women, which suggests that FFAs are involved in the pathophysiology of this neuroendocrine anomaly.

Adrenocorticotropic Hormone↗

PubMed2004

Accurate and reproducible mitral valvular blood flow measurement with three-directional velocity-encoded magnetic resonance imaging.

A new method for quantifying the transvalvular flow through the mitral valve (MV) based on three-directional velocity-encoded magnetic resonance imaging (MRI) is presented. For thirty time phases during one cardiac cycle, the three-dimensional (3D) velocity vector field of the blood flow is reconstructed from the MRI measurement. Retrospectively, for each time phase, the MV-plane is indicated manually in the velocity data and the flow through this plane is determined, representing the MV flow. Measurements are performed in 10 healthy volunteers. The new method is compared to the conventional, one-directional velocity-encoded MRI method for which an acquisition plane is positioned at the mitral valve at end-systole and remains fixed during the acquisition. The flow measurements with the new method correlate very well with the flow measured in the aorta (r(p)=0.92, p<0.01), whereas the conventional method shows no statistically significant correlation (r(p)=0.15, p=0.68). The low differences between the flow measured at the MV and the flow in the aorta proves high accuracy of the new method. Also, the new method shows very low intra- and interobserver variation, proving the high reproducibility. Three-directional velocity-encoded MRI is a patient-friendly and easy-to-use method suitable for quantifying accurately and reproducibly the transvalvular MV flow.

Adult↗

PubMed2004

Automated short-axis cardiac magnetic resonance image acquisitions: accuracy of left ventricular dimension measurements in normal subjects and patients.

RATIONALE AND OBJECTIVE: This study investigates the use of an automated observer-independent planning system for short-axis cardiovascular magnetic resonance (MR) acquisitions in the clinical environment. The capacity of the automated method to produce accurate measurements of left ventricular dimensions and function was quantitatively assessed in normal subjects and patients. METHODS: Fourteen healthy volunteers and 8 patients underwent cardiovascular MR (CMR) acquisitions for ventricular function assessment. Short-axis datasets of the left ventricle (LV) were acquired in 2 ways: manually planned and generated in an automatic fashion. End-diastolic volume (EDV), end-systolic volume (ESV), ejection fraction (EF), and left ventricular mass (LVM) were derived from the 2 datasets. The agreement between the manual and automatic planning methods was assessed. RESULTS: The mean differences between the manual and automated CMR planning methods for the normal subjects and patients were 5.89 mL and 1.93 mL (EDV), 1.14 mL and -0.41 mL (ESV), 0.81% and 0.89% (EF), and 4.35 g and 3.88 g (LVM), respectively. There was no significant difference in ESV and EF. LVM significantly differed in both groups, whereas EDV was significantly different in the normal subjects and insignificantly different in the patients. The variability coefficients were 2.8 and 3.59 (EDV), 3.3 and 5.03 (ESV), 1.79 and 2.65 (EF), and 4.36 and 2.27 (LVM) for the normal subjects and patients, respectively. The mean angular deviation of the LV axes turned out to be 8.58 +/- 5.76 degrees for the normal subjects and 8.35 +/- 5.15 degrees for the patients. CONCLUSIONS: Automated CMR planning method can provide accurate measurements of LV dimensions in normal subjects and patients, and therefore, can be used in the clinical environment for functional assessment of the human cardiovascular system.

Adult↗