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At least 595 records · Page 33Linked to original sources
PubMed2005

Accuracy of quadratic versus linear interpolation in noninvasive Electrocardiographic Imaging (ECGI).

Electrocardiographic Imaging (ECGI) is a cardiac functional imaging modality, noninvasively reconstructing epicardial potentials, electrograms and isochrones (activation maps) from multi-channel body surface potential recordings. The procedure involves solving Laplace's equation in the source-free volume conductor between torso and epicardial surfaces, using Boundary Element Method (BEM). Previously, linear interpolation (LI) on three-noded triangular surface elements was used in the BEM formulation. Here, we use quadratic interpolation (QI) for potentials over six-noded linear triangles. The performance of LI and QI in ECGI is evaluated through direct comparison with measured data from an isolated canine heart suspended in a human-torso-shaped electrolyte tank. QI enhances the accuracy and resolution of ECGI reconstructions for two different inverse methods, Tikhonov regularization and Generalized Minimal Residual (GMRes) method, with the QI-GMRes combination providing the highest accuracy and resolution. QI reduces the average relative error (RE) between reconstructed and measured epicardial potentials by 25%. It preserves the amplitude (average RE reduced by 48%) and morphology of electrograms better (average correlation coefficient for QI approximately 0.97, LI approximately 0.92). We also applied QI to ECGI reconstructions in human subjects during cardiac pacing, where QI locates ventricular pacing sites with higher accuracy (< or = 10 mm) than LI (< or = 18 mm).

Animals↗
PubMed1986

Scalar, planar, and spatial measurements of the Frank vectorcardiogram in normal infants and children.

Frank-lead vectorcardiograms (VCGs) were obtained from 1222 normal infants and children. By means of the Pipberger computer system, 176 different scaler and vector measurements obtained from each VCG were correlated with height, weight, race, sex, torso length, chest circumference, and chest diameters to determine the effect of anthropometric indices on the VCG wave forms. Because 5509 tests of statistical significance were performed, correlation coefficients and tests of statistical significance are reported only with p less than 0.001. Height, weight, torso length, and chest circumference show good correlation with QT interval, but these findings are reflective of the decrease in heart rate with age. The VCG does not show consistent correlations with constitutional variables when stratified by age, sex, or race. There were six instances of VCG parameters significantly greater in black children, and four instances of VCG parameters significantly greater in white children. All racial differences, while statistically significant, are small by clinical, hand measurement standards. There were 22 VCG values in boys which exceeded those in girls and only one VCG value in girls which exceeded those in boys. In the pediatric age group, racial differences in VCG wave forms are small and clinically insignificant. The Frank-lead system adequately corrects for constitutional variables in infants and children. Adequate evaluation of pediatric VCGs requires stratification of data according to age and sex.

Adolescent↗
PubMed1987

Qualitative and quantitative analysis of characteristic body surface potential map features in anterior and inferior myocardial infarction.

Body surface potential maps were recorded from 120 electrode sites in 236 normal subjects and 258 patients with initial evidence of either anterior myocardial infarction (MI) or inferior MI to identify characteristic map patterns in both groups. After time normalization, averaged map distributions were displayed at 18 equal time intervals during both QRS and ST-T waveforms from the normal, anterior MI and inferior MI groups. At each time instant, the 120-point averaged normal map was subtracted in turn from the corresponding anterior and inferior MI maps; the resulting differences at each electrode site were divided by the pooled standard deviation and the obtained values (discriminant indexes), plotted as contour lines with 1 standard deviation increments, producing discriminant maps for each bi-group comparison. The most consistent discriminant patterns in 114 patients with anterior MI were observed in early QRS in the upper left anterior chest where abnormal negative voltages reflected loss of electric potentials while reciprocal changes were noticed in the lower back; by mid-QRS, both distributions had moved jointly and vertically, the former in the lower torso on the midsternal line, the latter in the upper back. In 144 patients with inferior MI, abnormal positive distributions were observed in early QRS in the upper back, followed later by excessive negative voltages in the inferior right anterior chest; at mid-QRS, both distributions had migrated horizontally, the former proceeding toward the upper anterior torso, the latter to the lower left dorsal area.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Diagnostic body surface potential map patterns in left ventricular hypertrophy during PQRST.

Body surface potential maps were recorded from 117 thoracic sites and 3 limb electrodes in 173 normal subjects older than 30 years of age and 122 patients with clinically "pure" left ventricular (LV) hypertrophy. Typical LV hypertrophy map patterns were identified at successive instants during the PQRST waveform by removing from sequential LV hypertrophy maps the corresponding normal variability range at each electrode site. The presence in individual patients of 1 or more patterns typical in time and location of LV hypertrophy allowed retrospective assignment to the LV hypertrophy group. The most consistent discriminant patterns were excessive negative voltages in the anterior torso with reciprocal excess of positive voltages in the upper right chest during the second half of the P wave, excessive negative voltages in the lower right anterior torso at mid-QRS and excessive negative voltages in the left precordium with reciprocal excess of positive voltages in the upper right chest throughout ST-T. Best classification results were achieved with ST-T features, followed by features from the P wave, the QRS waveform and the PR segment. Cumulative use of ST-T and P features yielded a specificity of 94% with a sensitivity of 88%. Little improvement was obtained by the addition of QRS and PR information. The discriminant map criteria were applied to body surface potential maps from 169 new subjects (77 normal subjects ages 20 to 30 years and 92 patients with complicated LV hypertrophy). Little modification in specificity (93%) and sensitivity (90%) was observed. The performance of commonly used standard lead criteria was also tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1989

Invalidation of the resting electrocardiogram obtained via exercise electrode sites as a standard 12-lead recording.

The difficulty in interpreting the standard 12-lead electrocardiogram (ECG) due to the interference from muscle potentials produced by arm and leg motion makes it unsuitable during the exercise treadmill test. Likewise, the exercise lead placement ECG cannot substitute for the standard ECG due to significant errors in the former's diagnostic interpretation. This study compares the ECGs recorded via standard and exercise sites regarding frontal and horizontal plane axes, diagnosis and location of myocardial infarction and estimation of infarct size using the complete 54-criteria and 32-point Selvester QRS scoring system. The altered limb lead locations on the exercise ECG caused the QRS vectors to artifactually appear to be directed more inferiorly, posteriorly and rightward, producing a marked rightward mean frontal plane axis shift of +48 degrees (p less than 0.00001). No false positive or false negative anterior infarct was seen on the exercise lead placement ECG, whereas inferior and posterior infarcts were lost in 69% and 31% of patients, respectively. A false lateral infarct was seen in 19% of patients. Estimation of infarct size differed between the 2 ECG sets, with 11 patients increasing their infarct size by 3 to 9% and 14 others decreasing it by 3 to 15% on the exercise lead placement ECG. This study demonstrates that use of body torso positions for limb leads results in substantial QRS waveform variations that disqualify the exercise lead placement ECG as a "standard" recording. Such ECGs should therefore be labeled as "torso positioned" or "nonstandard" to prevent misuse for clinical and investigative purposes.

Adult↗
PubMed1980

Rhythmic fetal movements.

In recent years, studies have confirmed that rhythmic movement of the fetal torso occurs. These movements have been investigated with respect to a large number of factors, but no conclusive evidence of their significance has been documented. Much effort has been directed at developing better methods of measuring these movements. In this paper, examples of preliminary clinical results utilizing an advanced real-time B-scan phase-locked tracking scheme are presented. These traces represent a significant advancement in our ability to record rhythmic fetal torso movements and should enable us to enhance our knowledge of the physiology and clinical significance of this phenomenon.

Adult↗
PubMed1993

Frequency and volume of resistance training: effect on cervical extension strength.

Quantification of cervical extension (CERV EXT) strength is complicated by the inability to stabilize the torso and isolate the CERV EXT muscles. A newly developed machine designed to stabilize the torso and isolate the CERV EXT muscles was used to evaluate the effect of frequency and volume of resistance training on CERV EXT strength. Fifty men (age, 26 +/- 9 years; height, 174 +/- 16 cm; weight, 74 +/- 9 kg) and 28 women (age, 30 +/- 9 years; height, 152 +/- 32 cm; weight, 62 +/- 7 kg) volunteered to participate. Subjects were randomly stratified to one of four training groups or a control group (CONT, n = 19) that did not train. Each training group exercised for 12 weeks as follows; once per week using one set of dynamic exercise (DYN 1x/wk, n = 14), once per week using one set of DYN and one set of maximal isometric (IM) exercise at eight angles through a 126 degrees-range of CERV EXT (DYN-IM 1x/wk, n = 16), DYN 2x/wk (n = 19), or DYN-IM 2x/wk (n = 10). Maximal IM torque was measured at eight angles initially and after 12 weeks of training. All training groups improved CERV EXT strength (p < or = 0.05) at all angles tested compared to the CONT except for DYN once per week at 0 degree of CERV flexion. A greater increase in strength was found when the groups that trained two times a week were compared to those that trained once per week.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

A pupal lethal mutation with a paternally influenced maternal effect on embryonic development in Drosophila melanogaster.

The maternal effect and zygotic phenotype of l(1)pole hole (l(1)ph) is described. l(1)ph is a zygotic lethal mutation which affects cell division of adult precursor cells in Drosophila larvae. The locus is located in 2F6 on the salivary gland chromosome map and four alleles have been characterized. Germ-line clonal analysis of amorphic alleles indicates that l(1)ph has a maternal effect lethal phenotype. Two lethal phenotypes are observed among embryos derived from female germ-line clones homozygous for amorphic alleles dependent upon the zygotic activity of l(1)ph+ introduced via the sperm. Class 1: If no wild-type dose of the gene is introduced, embryos form abnormal blastoderms in which nuclear migration and cell formation is disrupted leading to an ill-defined cuticular pattern. Class 2: If a wild-type copy of the gene is introduced, blastoderm cells do not form beneath the pole cells (the pole hole phenotype); subsequently such embryos are missing cuticular structures posterior to the seventh abdominal segment (the torso phenotype). When the zygotic activity l(1)ph+ is modulated using position effect variegation a new phenotype is observed among class 2 embryos in which torso embryos are twisted along their longitudinal axis.

Alleles↗
PubMed1982

Identification of human lower extremity dynamics in torsion.

A four degrees of freedom, damped, linear oscillator model of the lower extremity in torsion was identified through laboratory frequency response tests. The foot was rotated sinusoidally in the medial-lateral plane through the 1-20 HZ frequency band at the constant amplitudes 2, 4 and 6 degrees. Weight bearing on the foot, muscle-induced bias torsion and knee flexion were also test variables. Identification was undertaken by minimizing the squared difference between the measured and predicted transfer functions of the pelvis and foot. The model specification and the laboratory identification procedures were the focus of this work. Variations greater than 30% in the identification stiffness, damping and inertia values were predicted over the test variable ranges. The transfer functions recorded in these tests indicated the lower extremity can be modeled as a compliance between a foot inertia and the pelvis-torso inertia. Joint compression, induced by weight bearing, and muscle contraction, measured by the bias torsional moment at the foot, increased the torsional stiffness of the knee, ankle and pelvis model elements, and they had an indeterminate influence on the hip stiffness. The model knee and hip stiffnesses and the model pelvis-torso inertia were maximized, and the model ankle stiffness was minimized at the maximum foot rotation amplitude.

Adult↗
PubMed1989

Progressive pathology of the caudate nucleus, the substantia nigra pars reticulata and the deeper layers of the colliculus superior: acute behavioural and metabolic effects of intrastriatal kainic acid.

The acute behavioural and metabolic consequences of functional changes following unilateral intracaudate kainic acid at the level of the feline caudate nucleus, the substantia nigra pars reticulata and the deeper layers of the colliculus superior were investigated. The present study became possible since it was previously found that unilateral changes in neurotransmission processes in these structures all result in behavioural alterations that can be distinguished from each other. During the first 17 min after kainic acid, all animals displayed contralateral forced staccato head turning; these movements are characteristic for an activation of dopamine receptors and/or inhibition of GABA receptors in the rostromedial caudate nucleus. Between 15 and 50 min, all animals displayed fast, uninterrupted contralateral forced head, torso or body turning; these movements are characteristic for an activation of nigral GABA receptors. From about 48 min, all animals displayed sequences of short contralateral forced ear, head, torso and body turnings; these movements are characteristic for an inhibition of collicular GABA receptors. Furthermore, most cats displayed ipsilateral orofacial dyskinetic movements during the whole 180 min observation period. Metabolism was analysed in three cats that received [14C]2-D-deoxyglucose immediately before, 5 min after, or 70 min after kainic acid. Metabolism was increased in the ipsilateral caudate nucleus; this effect was most pronounced in the cat that received deoxyglucose immediately before kainic acid. Metabolic activity was increased in the ipsilateral substantia nigra pars reticulata; this effect was most pronounced in the cat treated with deoxyglucose 5 min after kainic acid. Metabolism was increased in the ipsilateral deeper layers of the colliculus superior in the cat that received deoxyglucose 70 min after kainic acid. The present behavioural and metabolic data suggest that kainic acid produces an increasing pathology resulting successively in functional changes in the caudate nucleus, its output-station the substantia nigra pars reticulata and the nigral output-station the deeper layers of the colliculus superior. It is suggested that the successive appearance of the latter effects is inherent in the hierarchical order of the brain structures under study. The occurrence of orofacial dyskinetic movements during the whole observation period suggests that the former movements were not mediated via the striato-nigro-collicular pathway. Finally, apomorphine injected in the ipsilateral caudate nucleus 1 week after kainic acid was significantly less effective compared to apomorphine injected 1 week before kainic acid. The c

Animals↗
PubMed1996

Postmortem diffusion of ingested and aspirated paint thinner.

Post mortem diffusion of paint thinner (toluene/ethyl acetate/isobutanol 8:1:1 v/v) from gastric residue (25 ml or 100 ml) and airways contamination (25 ml) was assessed in a human cadaver model, with sampling after 24 h at room temperature. Four torso blood samples showed less toluene diffusion after gastric instillation (0.5-3.8 micrograms/ml) than after tracheal instillation (10.5-421 micrograms/ml). Isobutanol diffused more readily than toluene with four torso blood samples 1.8-256 micrograms/ml after gastric instillation and 26-576 micrograms/ml after tracheal instillation. Following 25 ml gastric instillation, toluene concentrations (microgram/ml or microgram/mg) were: pericardial fluid 0.7-4.0; bile 0.5-0.6; urine 0-0.6; brainstem 1.1; lung 0.4-4.4; liver 0-162; spleen 0.6-0.7; kidneys 0.4-0.6; peri-renal fat 0.3-30.3; psoas muscle 0.3-0.8; concentrations of toluene and isobutanol were markedly higher in the left lobe of the liver than the right. Ethyl acetate was mostly undetectable in tissue samples but variably present in five blood samples: 0-21.2 micrograms/ml following 25 ml or 100 ml gastric instillation and 0-198 micrograms/ml following 25 ml tracheal instillation. Ethyl acetate was always detectable in pericardial fluid but not always detectable in gastric contents. We conclude that post mortem diffusion of toluene from gastric residue or airways contamination is unlikely to compromise the analytical validity of femoral venous blood samples, brain, or liver from deep within the right lobe. Analysis of pericardial fluid and gastric contents allows identification of ethyl acetate and isobutanol thus implicating thinner solution.

Acetates↗
PubMed1995

A comparison of bone mineral densities among female athletes in impact loading and active loading sports.

The purpose of this study was to compare bone mineral densities (BMD) of collegiate female athletes who compete in impact loading sports; volleyball players (N = 8) and gymnasts (N = 13), to a group of athletes who participate in an active loading sport; swimmers (N = 7), and a group of controls (N = 17). All of the volleyball, swimming, and control subjects were eumenorrheic (10-12 cycles/year), whereas two of the gymnasts were amenorrheic (0-3 cycles/year), eight were oligomenorrheic (4-8 cycles/year), and three were eumenorrheic (10-12 cycles/year). Lumbar spine, proximal femur, and total body BMD were measured with dual-energy X-ray absorptiometry. The groups were compared with respect to the following regions: lumbar spine (L1-4); femoral neck; Ward's triangle; right and left arms; right and left legs; pelvis; and torso. When controlling for differences in height and weight the impact loading group (volleyball and gymnastic) had significantly greater BMD at the lumbar spine, femoral neck, Ward's Triangle, and total body when compared to the active loading (swimming) and control groups. The regional analysis from the total body scan revealed that the gymnasts had significantly (p < 0.05) greater BMD than all other groups at the right and left arm sites. The impact loading groups (gymnastic and volleyball) had a greater BMD in the legs and pelvis than the active loading (swimming) and control groups. Furthermore, the impact loading group had a greater torso BMD than the control group. There were no differences at any site between the active loading group (swimming) and control groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorptiometry, Photon↗
PubMed2006

Injury profiles of road traffic deaths.

The objective is to describe injuries of road traffic deaths in Barcelona and identify injury profiles by road user type, through a cross-sectional study including road traffic deaths for the period 1997-2004. The data source was the Institut de Medicina Legal de Catalunya. Diagnoses were coded using the International Classification of Diseases, 9th revision, Clinical Modification, and classified using the Barell Matrix. Of the 719 deaths studied, 45% were pedestrians, 32% two wheel motor vehicle users, and 23% car occupants. The injury profile of the road traffic deaths in Barcelona is internal injuries and fractures to the torso and to the head/neck. This profile is repeated in all the road user groups, although pedestrians present higher frequencies of fractures and contusions to extremities and contusions to the head/neck, and fewer internal torso injuries than car occupants or two wheel motor vehicle users.

Accidents, Traffic↗
PubMed2005

The prediction of lumbar spine geometry: method development and validation.

OBJECTIVES: To develop and validate a new method of predicting the neutral lumbar spine curve from external (non-invasive electrogoniometer) measurements. BACKGROUND: Non-invasive techniques for lumbar spine geometry prediction suffer from a lack of a complete geometry description, problems with applicability to field conditions, or both. METHODS: The study consisted of three steps. First, utilizing lateral imaging (MRI and X-ray pictures) of the lumbosacral junction, the torso geometry was described using measures of lumbar lordosis via the Cobb method. Second, the relationship between imaging based measurement of lumbar spinal curvature and externally measured torso flexion angle in the sagittal plane using a goniometer was determined. Finally, method validation was performed with an independent set of nine subjects. The predicted lumbar spine curve was determined and the prediction errors were analyzed against the measured curves from digitized lateral X-ray images of the lumbosacral junction. RESULTS: The shape of the lumbar curve was described as function of three externally measured parameters. The lumbar spine Cobb angle, segmental centroid positions (S(1)-T(12)), and segmental orientations were predicted from the external lumbar motion monitor measurements, with average precisions of 5.8 degrees , 4.4 mm, and 3.9 degrees , respectively. CONCLUSIONS: The position and orientation of each segment (vertebrae and disc), along with the lumbar spine lordosis, can be predicted in the neutral posture using data from back angular measurements. RELEVANCE: The consideration of the spine as a curve is necessary to accurately quantify and describe the forces acting along the (lumbar) vertebral column for any given loading. The method could be a very useful prediction tool for industrial and laboratory experiments, as well as analytical models.

Adult↗
PubMed2005

A mechanism of lateral flexion distraction injury of the spine.

Flexion distraction fractures or Chance fractures are well described in the literature. We present an unusual pattern of injury of a pure lateral flexion distraction fracture of the T12 vertebra with no posterior element disruption following a blow to the right torso to a passenger in a road traffic accident. The diagnosis was made intra-operatively as the potential for this injury pattern following the described mechanism was not initially recognised. We suggest that this type of injury be suspected in any patient where a fulcrum has acted at any point around the torso.

Accidents, Traffic↗
PubMed2006

Role of reflex dynamics in spinal stability: intrinsic muscle stiffness alone is insufficient for stability.

Spinal stability is related to both the intrinsic stiffness of active muscle as well as neuromuscular reflex response. However, existing analyses of spinal stability ignore the role of the reflex response, focusing solely on the intrinsic muscle stiffness associated with voluntary activation patterns in the torso musculature. The goal of this study was to empirically characterize the role of reflex components of spinal stability during voluntary trunk extension exertions. Pseudorandom position perturbations of the torso and associated driving forces were recorded in 11 healthy adults. Nonlinear systems-identification analyses of the measured data provided an estimate of total systems dynamics that explained 81% of the movement variability. Proportional intrinsic response was less than zero in more than 60% of the trials, e.g. mean value of P(INT) during the 20% maximum voluntary exertion trunk extension exertions -415+/-354N/m. The negative value indicated that the intrinsic muscle stiffness was not sufficient to stabilize the spine without reflex response. Reflexes accounted for 42% of the total stabilizing trunk stiffness. Both intrinsic and reflex components of stiffness increased significantly with trunk extension effort. Results reveal that reflex dynamics are a necessary component in the stabilizing control of spinal stability.

Humans↗
PubMed2006

Effects of abdominal stabilization maneuvers on the control of spine motion and stability against sudden trunk perturbations.

Much discussion exists about which is the most effective technique to improve spine stability. The purpose of this study was to evaluate the effectiveness of abdominal bracing and abdominal hollowing maneuvers to control spine motion and stability against rapid perturbations. Eleven healthy males were posteriorly loaded in different experimental conditions: resting with no knowledge of the perturbation timing; performing each of the stabilization maneuvers at 10%, 15% and 20% of internal oblique maximum voluntary contraction with no knowledge of the perturbation timing; and naturally coactivating the trunk muscles when perturbation timing was known. An EMG biofeedback system was used to control the pattern and intensity of abdominal coactivation. The muscular preactivation of seven trunk muscles (bilaterally registered), the applied force, and the torso muscular and kinematic responses to loading were measured; and the spine stability and compression were modeled. The hollowing maneuver was not effective for reducing the kinematic response to sudden perturbation. On the contrary, the bracing maneuver fostered torso cocontraction, reduced lumbar displacement, and increased trunk stability, but at the cost of increasing spinal compression. When the timing of the perturbation was known, the participants were able to stabilize the trunk while imposing smaller spine compressive loads.

Abdomen↗
PubMed2005

Intrasexual selection in Verreaux's sifaka (Propithecus verreauxi verreauxi).

Studies of sexual selection show that both female choice and male-male competition can influence the evolution and expression of male phenotypes. In this regard, it is important to determine the functional basis through which male traits influence variation in male reproductive success. In this study, we estimate the strength and type of sexual selection acting on adult males in a population of wild lemur, Verreaux's sifaka (Propithecus verreauxi verreauxi). The data used in this study were collected at Beza Mahafaly Special Reserve, southwest Madagascar. We conducted paternity analyses on 70 males in order to estimate the distribution of reproductive success in this population. Paternity data were combined with morphometric data in order to determine which morphological traits covary with male fitness. Five morphological traits were defined in this analysis: body size, canine size, torso shape, arm shape, and leg shape. We utilized phenotypic selection models in order to determine the strength and type of selection acting directly on each trait. Our results show that directional selection acts on leg shape (a trait that is functionally related to locomotor performance), stabilizing selection acts on body mass and torso shape, and negative correlational selection acts on body mass and leg shape. We draw from biomechanical and kinematic studies of sifaka locomotion to provide a functional context for how these traits influence male mating competition within an arboreal environment. Verreaux's sifaka and many other gregarious lemurs are sexually monomorphic in body mass and canine size, despite a high frequency and intensity of male-male aggressive competition. Our results provide some insight into this paradox: in our population, there is no directional selection acting on body mass or canine size in males. The total pattern of selection implicates that behaviors relating to locomotor performance are more important than behaviors relating to fighting ability during intrasexual contests.

Animals↗