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At least 757 records · Page 42Linked to original sources
PubMed1997

Guidance of radiofrequency endocardial ablation with real-time three-dimensional magnetic navigation system.

BACKGROUND: Ablation therapy for certain arrhythmias requires the formation of complex lesions based on electrical and anatomic mapping. We tested the accuracy and reproducibility of a nonfluoroscopic mapping and navigation (NFM) system to guide delivery of radiofrequency (RF) energy in the right atrium (RA) of swine. METHODS AND RESULTS: The NFM system uses an ultralow magnetic field to measure the real-time three-dimensional (3D) location of the tip of the locatable catheter. While in stable contact with the endocardium, between 30 and 40 consecutive tip locations were sampled and used for the 3D reconstruction of the RA geometry. The location of the catheter tip was presented in real time, superimposed over the RA geometry. We selected a point on the 3D reconstruction and delivered RF energy to that site via the tip of the locatable catheter. The catheter was then completely withdrawn and renavigated twice to the same point, at which RF energy was delivered again. At autopsy, the distance between the centers of the three ablation points (mean+/-SEM) was 2.3+/-0.5 mm (n=27). Similarly, we used the NFM system to guide the generation of linear lesions. The measured length of the linear lesions on the NFM 3D view was close to the actual lesion length measured at autopsy (correlation coefficient, .96; P=.002; n=6). Furthermore, the location, shape, and continuity of the linear lesions corresponded to the autopsy findings. CONCLUSIONS: We conclude that the NFM system can guide the application of RF energy without the use of fluoroscopy in a highly accurate and reproducible manner.

Animals↗
PubMed1997

Right and left ventricular volume and ejection fraction by tomographic gated blood-pool scintigraphy.

UNLABELLED: Tomographic techniques separate overlying structures, permitting measurements of absolute ventricular volumes. The purpose of this study was to determine absolute right and left ventricular volume and ejection fraction measurements with tomographic gated equilibrium blood-pool scintigraphy (TMUGA) compared to MRI and conventional planar scintigraphy. METHODS: Eighteen patients were studied. Ventricular volumes for TMUGA and MRI were calculated by modified Simpson's rule. TMUGA regions were defined by constraints including phase analysis, intensity threshold and visual inspection. MRI studies were acquired with a fast gradient-echo, ECG-gated, breath-hold technique and boundaries were defined by a semiautomated contour method. Conventional gated first-pass radionuclide angiography (FP) and planar gated equilibrium blood-pool scintigraphy (PMUGA) were performed for RV EF and LV EF, respectively. RESULTS: TMUGA absolute right ventricular volumes showed excellent-correlation with MRI for both right ventricular volumes (r = 0.91, slope = 0.90, s.e.e. = 15.7) and left ventricular volumes (r = 0.96, slope = 0.88, s.e.e. = 18.2). For left ventricular ejection fraction, TMUGA also showed excellent correlation with MRI (r = 0.94, slope = 1.10, s.e.e. = 9.0) and planar MUGA (r = 0.97, slope = 1.23, s.e.e. = 6.2). For right ventricular ejection fraction, TMUGA showed good correlation with both MRI (r = 0.88, slope = 0.79, s.e.e. = 6.0) and first-pass planar scintigraphy (r = 0.86, slope = 1.2, s.e.e. = 7.9). CONCLUSION: Tomographic gated blood-pool scintigraphy absolute right and left ventricular volumes and ejection fractions show good correlation with accepted techniques. Further studies are necessary to define the reproducibility of this method.

Cardiac Volume↗
PubMedDate not supplied

Challenges in hip joint modeling for a patient with proximal femoral focal deficiency.

We were presented with a technical challenge driven by a clinical need. A patient with proximal femoral focal deficiency required gait analysis, but our typical biomechanical model [Vicon Clinical Manager (VCM)] would not have correctly identified his abnormal right hip center (RHIP). His underdeveloped right femur was fused to his ileum, his anatomical knee functioned as his right hip, and an above-knee prosthesis provided functional knee and ankle joints. During a special calibration, we estimated the global location of RHIP as the center of the femoral epicondyles, also identifying the global location of pelvic markers. These data were used in equations after Davis et al. to establish local coordinates for RHIP. We used a system of three simultaneous equations to solve for input to VCM that would reproduce this location for RHIP. This procedure allowed for inverse dynamics in VCM, and showed the emergence of an abduction moment at the right hip postoperatively, that exceeded changes predicted by sensitivity analyses. Although our clinical need was met, we concluded that a better approach would have involved full implementation of custom models to reflect abnormal patient anatomy.

Adolescent↗
PubMed1995

Exercise-induced angina with intermittent ST-segment elevation.

A 59-year-old man was admitted for evaluation of mild exertional angina in the morning. During graded treadmill exercise stress testing, the patient had reproducibly intermittent chest pains associated with ST-segment elevations in leads II, III and aVF. A baseline coronary angiogram showed a coronary narrowing of 90% in the middle segment of the right coronary artery. The coronary narrowing was immediately resolved by an intracoronary injection of nitroglycerin. This was a very rare case of variant angina with intermittent ST-segment elevations and chest pains which were reproducibly demonstrated during exercise and the recovery phase of treadmill testing.

Angina Pectoris↗
PubMed1980

Potential pitfalls of the nuclear stethoscope.

Eleven patients (three with coronary artery disease, one with mitral valve prolapse, one with atrial septal defect, two with rheumatic mitral valve disease, one with rheumatic aortic valve disease, and three normal individuals) underwent determination of global left ventricular ejection fraction (LVEF) by 1) nuclear stethoscope (cardiac probe), 2) Tc-99m-labeled-erythrocyte gated nuclear angiocardiographic gamma camera-computer techniques, and 3) single plane RAO contrast left ventriculography--all within a 6-hour period without concurrent drug intervention. In addition, global right ventricular ejection fraction (RVEF) was determined by a similar gated technique with gamma camera-computer techniques. LVEF as determined by camera-computer techniques correlated well with that of contrast ventriculography (r = 0.95) in this heterogenous group of subjects. LVEF as determined by cardiac probe correlated somewhat less well with that of contrast ventriculography (r = 0.59). Two cases are described in which, although cardiac probe data were highly reproducible, gross overestimation of the true global LVEF was thought to occur due to the malpositioning of the probe over either the right ventricle or the most contractile portion of the left ventricle in patients with coronary artery disease.

Adult↗
PubMed1999

Comparisons of the amplitude size and the reproducibility of three different electrodes to record the corneal flash electroretinogram in rodents.

To compare corneal electrodes commonly used in rodent eyes for repeat and left versus right eye accuracy and variability to record the flash electroretinogram (ERG). Animals studied were eight C57BL/6 mice and eight rats of the Wistar strain. Scotopic ERGs were recorded from eyes of dark-adapted anesthetized rodents to compare a custom-made gold-wire contact lens electrode (CLE), a cotton-wick silver-silver chloride electrode (SCLE), and a coiled stainless steel wire electrode (SSE). Compared to SCLE and SSE. the potentials recorded by CLE are characterized by significantly larger ERG amplitudes and oscillatory potentials in both rats and mice (p <0.0001). In analyzing test-retest data comparing the three different electrodes the coefficient of variation was smaller (range, 10.3-15.5%) and the interclass correlation coefficient (0.77-0.93) showed a better agreement for the CLE. Recording scotopic ERGs with custom-made gold-wire contact lens electrodes records large amplitudes and shows a good reproducibility and reliability to monitor retinal function in rodent eyes.

Animals↗
PubMed1998

Reliability study of the Leg-O-Meter, an improved tape measure device, in patients with chronic venous insufficiency of the leg. VEINES Group.(Venous Insufficiency Epidemiologic and Economic Study).

The objective of this study was to evaluate the inter-rater reliability of the Leg-O-Meter, an instrument designed to measure the ankle or calf circumference. The Leg-O-Meter consists of a tape measure fixed to a stand attached to a small board on which the patient is in standing position. For this study the tape measure of the Leg-O-Meter was fixed at 10 cm from the board in order to standardize all measurements. Informed consent to participate in the study was obtained from 39 patients consulting the phlebology clinic of Hôpital St-Michel, Paris, France. Participants were asked to enter a closed room where four independent and blinded observers consecutively took measurements of both legs with the Leg-O-Meter. The order of the observers was randomized between patients. Under the assumption of a two-way random effects model an intraclass correlation coefficient (ICC) was used to determine the reliability or reproducibility of a measure with the Leg-O-Meter. The overall reliability coefficient calculated by the ICC for the right and left leg were estimated at 97.09% [95.52%;100%]95% and 97.08% [95.86%;100%]95%, respectively. The authors conclude that the Leg-O-Meter gives a standardized and reliable measure of the circumference of the ankle. Furthermore, it is not invasive or costly.

Analysis of Variance↗
PubMed1992

Right ventricular systolic time intervals determined by means of a pulmonary artery catheter.

OBJECTIVES: To evaluate the right ventricular systolic time interval as an index of right ventricular function and also to ascertain whether the right ventricular ejection fraction may be determined by means of a conventional pulmonary artery catheter. DESIGN: Prospective study. SETTING: Intensive care unit. PATIENTS: Eight, consecutive critically ill adult patients. METHODS: Simultaneous blind measurements, performed by two investigators, of the right ventricular systolic time interval and right ventricular ejection fraction, determined by means of a pulmonary artery catheter. Two studies, separated by an interval of 24 hrs, per patient. Linear regression analysis. Multiple regression test. RESULTS: Of the 16 studies performed, two determinations of right ventricular systolic time intervals were technically inadequate. In the remaining 14 valid studies, we found one close linear correlation between the right ventricular ejection fraction and the preejection period/ejection time quotient measured using the simultaneous display of the electrocardiogram (EKG) and pulmonary arterial pressure curve (r2 = .90, p < .001, right ventricular ejection fraction = 68.96-60.59 x [right ventricular preejection period/right ventricular ejection time]). The method proved to be simple, very accurate, with little interobserver variation (8.09 +/- 10.6% interobserver variation for right ventricular preejection period/right ventricular ejection time) and provided adequate information regarding situations in which the performance of the right ventricle is modified in a given patient. The right ventricular preejection period/right ventricular ejection time quotient was the only variable that displayed a significant relationship with the right ventricular ejection fraction in the multivariate analysis (p < .001). CONCLUSIONS: Right ventricular systolic time intervals, measured using the simultaneous display of the pulmonary artery catheter curve and EKG, provide adequate information regarding right ventricle performance in critically ill patients. The close linear correlation between the right ventricular preejection period/right ventricular ejection time quotient and the right ventricular ejection fraction enables the investigator to estimate, with a high degree of accuracy, the right ventricular ejection fraction and the values derived from the preload of the right ventricle, without the need for a modified pulmonary artery catheter.

Aged↗
PubMedDate not supplied

Interventricular differences in myocardial T2 measurements: experimental and clinical studies.

The goal of this study was to determine the accuracy, the reproducibility, and some of the tissue determinants of image-based myocardial T2 measurements. Image-based T2 calculations for the free walls of the right ventricle (RV) and left ventricle (LV), in vitro T2 determination (at 0.47 T), and water, fat, and collagen content analyses were performed in ex vivo hog hearts. T2 values of the RV and LV free walls were also determined from spin-echo images of 14 healthy human subjects. Preliminary reproducibility studies were performed with 10 sets of images acquired from a single subject. For both in vitro and image-based T2 values of hog hearts, RV T2 was significantly longer than LV T2. Water content was the only tissue factor to significantly correlate with in vitro and image-based T2 values. For the 14 human subjects studied, image-based T2 values calculated from the first- and third-echo images demonstrated a significant difference between LV and RV. The difference was not significant when the first- and second-echo images were used. Image-based T2 measurements of a single subject showed a coefficient of variation of 6.8% for the LV and 9.1% for the RV. The authors conclude that image-based T2 measurements of normal myocardium can be made with sufficient precision to identify differences of the magnitude of those found between RV and LV T2 values. Image-based T2 values of myocardium may provide useful data to aid in patient treatment.

Adult↗
PubMed1999

Interval timing performance in temporal lobe epilepsy: differences between patients with left and right hemisphere foci.

This experiment examined interval timing performance on a temporal reproduction procedure and a temporal discrimination (interval bisection) procedure in 19 patients with temporal lobe epilepsy (ten with a left-hemisphere focus [LTE group] and nine with a right- hemisphere focus [RTE group]), and 14 normal control subjects. In the temporal reproduction task, subjects were required to reproduce the durations of visual stimuli (0.5, 1, 2, 4, 8 s). In the temporal discrimination task, subjects were required to classify the visual stimuli as either 'short' or 'long'. Following exposure to the two standard durations (1 and 2 s), 'probe' trials were introduced in which the stimulus was presented for durations intermediate between the two standard durations. Psychophysical functions were derived from both timing tasks for each individual subject, as well as for the group mean data. The results showed that, compared to the normal subjects, the RTE group's timing ability was significantly compromized, as reflected by larger Weber fractions in both timing tasks. The LTE group's Weber fractions did not differ significantly from those of the control group; however they showed a leftward shift (i.e. a shorter bisection point) of the psychophysical function under the temporal discrimination task. The results suggest that the right and left hemispheres may play different roles in regulating interval timing performance.

Adult↗
PubMed2001

Reproducibility of proton magnetic resonance spectroscopy imaging measurements of normal human hippocampus at 1.5 T: clinical implications.

The authors investigate the reproducibility of metabolite signals measured with proton magnetic resonance spectroscopy (1H-MRS) acquired from the human hippocampus in controls and in a phantom. Two 1H-MRS studies separated by 3 weeks were performed in 8 healthy volunteers and in a phantom. N-acetyl compounds (NA), choline (Ch), and creatine (Cr) peak areas and ratios were measured and compared using percentage variation, and Pearson Correlation Coefficient at the level of every voxel, the level of 1 hippocampus (5 voxels), and the level of 2 hippocampi (10 voxels). Sensitivity for observing clinically significant between-session 1H-MRS changes was evaluated using the reliable change index. Reproducibility measures for metabolite peak areas were only moderately concordant with percentage variation ranging from 14% to 20% for NA, Cho, and Cr. Stability was much improved when NA ratios and sum of multiple voxels were considered. Between-session NA/(Cho + Cr) changes greater than 22%, 12%, and 10% in one given participant can be detected with a 90% confidence interval when considered at the single-voxel level, the level of a single hippocampus, or the level of both hippocampi, respectively. Left-right asymmetry indices showed similar and limited inter-hemispheric asymmetry in repeated examination. This study suggests that 1H-MRS reproducibility performance is adequate for the study and monitoring of human hippocampus function when NA ratios and the sum of multiple voxels are considered. Individual metabolite peaks and single-voxel measurements have low reproducibility at 1.5 T and should be used only with clearly established statistical parameters.

Adult↗
PubMed1997

External four channel tocography in preterm labor. First results.

In order to known more about preterm labor the objective of our investigation was to look for a correlation between the spatial and temporal pattern of uterine contractions and the duration of pregnancy. 50 patients with preterm labor between 21 and 35 weeks of gestation underwent repeated measurements using four-channel tocography in which the pressure of contractions was registered simultaneously on the left and right sides at the fundus and the lower segment of the uterus. Half of all recorded signals were locally restricted (typical labor pattern in only one or two registration tracks). The following two phenomena were significantly associated with a shorter duration of pregnancy: 1. the reproducibility of a center of dominance (defined as the locus of registration with the highest sum of amplitudes), and 2. a predominant origin of labor in the right fundal region of the uterus. Four-channel tocography indicates whether preterm labor is likely to lead to preterm delivery. It may therefore help the obstetrician in deciding whether to use tocolytic therapy.

Adolescent↗
PubMed2002

Longitudinal motion of the atrioventricular annuli in children: reference values, growth related changes, and effects of right ventricular volume and pressure overload.

The goals of this study were to characterize normal patterns of longitudinal motion of atrioventricular annuli in the young, establish reference values and assess growth-related changes (n = 40). Sensitivity to changes in right ventricular volume and pressure load was assessed in patients with atrial septal defect (ASD) (n = 25) and with primary pulmonary hypertension (PPH) (n = 20). M-mode of the annuli were obtained from apical views. In healthy subjects, longitudinal %displacement decreased with growth, lateral tricuspid annulus had highest %displacement, velocity of annular descent did not change with growth, tricuspid lateral annulus had the highest velocity of descent, only ascent velocity of the lateral tricuspid annulus decreased with growth, velocities of ascent for the lateral annuli were similar and higher than the septum, and heart rate had no effect on parameters tested. In patients with ASD, the findings were an exaggerated normal pattern. In patients with PPH, %displacement and ascent velocities were blunted. Our results demonstrate the utility of this technique to assess annular dynamics in pediatric patients.

Adolescent↗
PubMed1995

The measurements of sacroiliac joint stiffness with colour Doppler imaging: a study on healthy subjects.

RATIONALE AND OBJECTIVES: Primary peripartum pelvic and low back pain is a common complaint of females. The etiologic relation between pain and pelvic stability has been shown in previous studies, but at present there is no objective clinical testing method to evaluate pelvic stability. METHODS: In this study, a dynamic measurement method using sonoelasticity to assess the sacroiliac joint (SI) stiffness was tested in vivo in 14 healthy female volunteers. With the subjects in supine position vibrations were unilaterally applied to the anterior iliac spine. The vibrations were registered by a Colour Doppler Imaging (CDI) transducer over the ipsilateral SI joint. Since the threshold level of the apparatus has a direct relation with the power of the vibrations, the intensity of the vibrations (sonoelasticity) on the sacrum and ilium was measured indirectly in threshold units. The differences between the threshold values were accepted as the power loss of vibrations through the SI joint. One-way analysis of variance-test and T-test for paired samples were applied on the measurement results (P < 0.05). RESULTS: Statistically, the results showed a satisfactory intraindividual reproducibility and inter-individual variability. There was no significant difference between the data derived from the left SI joint and right SI joint. CONCLUSIONS: Based on the promising results on healthy female volunteers, this method will be specifically used in future studies on patients with peripartum pelvic pain.

Adult↗
PubMed1986

Reproducibility of ventricular tachycardia suppression by antiarrhythmic drug therapy during serial electrophysiologic testing in coronary artery disease.

The short-term reproducibility of pharmacologic suppression of ventricular tachycardia (VT) induced by programmed cardiac stimulation was tested in patients with coronary artery disease presenting with documented recurrent VT or ventricular fibrillation. Sixty-three consecutive patients in whom sustained VT (30 patients) or nonsustained VT (33 patients) was induced by programmed cardiac stimulation without antiarrhythmic drug treatment, and in whom at least 1 oral antiarrhythmic drug regimen suppressed the induced VT during serial electrophysiologic testing, were entered into the study. Programmed cardiac stimulation was repeated after a mean of 37 +/- 14 hours during the same antiarrhythmic drug regimen. No VT was induced in 59 of the 63 patients during the second study, resulting in a rate of 94% for short-term reproducibility of pharmacologic suppression of induced VT. Of the remaining 4 patients, programmed cardiac stimulation during the second drug study induced sustained VT in 1 patient and nonsustained VT in 3 patients. There was no significant difference in mean right ventricular effective refractory period and QT interval between the first and second drug study. Thus, in this selected population of patients, pharmacologic suppression of electrically induced VT is a reproducible phenomenon.

Aged↗
PubMed2002

Quantification of regional left and right ventricular radial and longitudinal function in healthy children using ultrasound-based strain rate and strain imaging.

BACKGROUND: Noninvasive assessment of left (LV) and right (RV) ventricular function in children could benefit from a technique that would characterize local myocardial deformation. Color Doppler myocardial imaging (CDMI) allows the calculation of either local longitudinal or radial Strain Rate (SR) and Strain (epsilon). To determine the clinical feasibility and reproducibility of longitudinal and radial SR and epsilon, the following study was carried out. METHODS: CDMI data were obtained from 33 healthy children (4-16 years). To quantify regional longitudinal and radial function SR and epsilon data were obtained from apical and parasternal views respectively. From the extracted SR curves, peak values for systole, early diastole, and late diastole were calculated. From the extracted epsilon curves the systolic, early and late diastolic epsilon values were calculated. RESULTS: LV longitudinal deformation were homogeneous for LV basal, mid and apical segments (peak systolic SR: -1.9 +/- 0.7 s(-1), systolic epsilon -25% +/- 7%). Longitudinal SR and epsilon values were significantly higher and heterogeneous in the RV (compared with LV walls) and were maximal in the mid part of the RV free wall (peak systolic SR: -2.8 +/- 0.7 s(-1), systolic epsilon -45% +/- 13%). The RV inferior wall showed homogeneous but lower longitudinal SR and epsilon values. The LV systolic and diastolic SR and epsilon values were higher for deformation in the radial direction compared with the longitudinal direction (radial peak systolic SR: 3.7 +/- 0.9 s(-1), radial systolic epsilon 57% +/- 11%; P <.0001). The interobserver variability for radial systolic epsilon and SR was 10.3% and 13.1%, respectively. CONCLUSION: Ultrasound-based Strain SR/epsilon imaging is a practical, reproducible clinical technique, which allows the calculation of regional longitudinal and radial deformation from both LV and RV segments. The combination of regional SR/epsilon indices and the timing of specific systolic or diastolic regional events may offer a new noninvasive approach to quantifying regional myocardial function in congenital and acquired heart disease in children.

Adolescent↗
PubMed2005

Evaluation of new software for angiographic determination of right ventricular volumes.

OBJECTIVES: The scope of the study was to evaluate a recent software for angiographic volume determination as compared to cardiovascular magnetic resonance imaging. BACKGROUND: A new right ventricular analysis software closes a diagnostic gap in quantitative angiography. Cardiovascular magnetic resonance imaging short axis multi slice summation is a validated reference standard. METHODS: Right ventricular angiograms were acquired in frontal and lateral projection in 15 pediatric and 17 adult patients. Additional angiograms were acquired in RAO30 degrees /LAO60 degrees projections in 10 adult patients. The tested models comprised area length with different regressions, multi-slice with different regressions, Boak, and pyramid method. Original regressions were used to calculate angiographic right ventricular volume. Right ventricular reference volumes were determined by multi-slice summation from cardiac magnetic resonance short-axis images. RESULTS: Mean inter-observer difference was -1 ml (95% confidence: -35-34 ml) and mean intra-observer difference was 0 ml (95% confidence: -22-22 ml). There was no significant difference (4 ml, 95% confidence: -22-30 ml) between geometric calibration and calibration by a sphere. The area length and multi-slice models demonstrated the best agreement with the cardiac magnetic resonance reference. Performance was best for the Onnasch Lange models. CONCLUSION: The evaluated software provides acceptably accurate volume estimates for the majority of ventricles. In a few cases larger errors may occur, however. The area length and multi-slice models preferably with Onnasch Lange regressions may be recommended. Inter- and intra-observer agreement were excellent. Geometric calibration using data from DICOM header files may be used.

Adolescent↗
PubMed2000

Measurement of subcutaneous adipose tissue topography (SAT-Top) by means of a new optical device, LIPOMETER, and the evaluation of standard factor coefficients in healthy subjects.

The quantification of obesity in respect to subcutaneous adipose tissue and fat distribution is a matter of interest. We recently reported on a new optical device, LIPOMETER, and its ability to measure the thickness of subcutaneous adipose tissue and its advantages compared with other methods. To describe the subcutaneous adipose tissue distribution of the human body in a precise, reproducible, and comparable manner, 15 well-defined body sites distributed from neck to calf on the right body side were used. This set of sites defines subcutaneous adipose tissue topography (SAT-Top). To visualize SAT-Top for subjects or groups, special SAT-Top plots were used. Subcutaneous adipose tissue distribution can be recognized easily with these techniques. SAT-Top of 590 healthy men and women was measured. Factor analysis was used to extract the essential information from these 590*15 intercorrelated single measurements and to provide standard factor coefficients for later applications. As an example of how to use the results of factor analysis, the strong SAT-Top deviation of women with clinically proven type-2 diabetes mellitus (NIDDM) from healthy controls is described. Am. J. Hum. Biol. 12:231-239, 2000. Copyright 2000 Wiley-Liss, Inc.

Journal Article↗