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PubMed1999

Prognosis in myocardial infarction survivors with left ventricular dysfunction is predicted by electrocardiographic RR interval but not QT dispersion.

OBJECTIVES: The aim of the study was to assess if QT dispersion and RR interval on the standard 12-lead electrocardiogram (ECG) predict cardiac death and late arrhythmic events in postinfarction patients with low left ventricular ejection fraction (LVEF). QT dispersion on a standard electrocardiogram (ECG) is a measure of repolarization inhomogeneity, but its prognostic meaning in myocardial infarction (MI) survivors is unclear, especially in patients with left ventricular dysfunction. RR interval has been shown to predict mortality in post-MI patients, but its prognostic power has not been compared with other noninvasive risk factors. METHODS: Retrospective cohort study. Ninety patients were identified, from a series of 547 consecutive postinfarction patients admitted to our institution for phase II cardiac rehabilitation, as having a LVEF of <0.40 at two-dimensional echocardiography (mean LVEF 0.35+/-0.04; range 0.20-0.39). QT dispersion and RR interval were analyzed on the admission 12-lead electrocardiogram, 20+/-10 (range 8-45) days after MI, using specially designed software. Additional risk markers were collected from clinical variables, signal-averaged ECG and Holter recording. RESULTS: During 24+/-18 (range 1-63) months of follow-up, 10 of 90 patients (11%) died, all from cardiac causes, and there were 18 late arrhythmic events, defined as sudden death or the occurrence of a sustained ventricular arrhythmia > or =5 days after the index MI. QT interval and dispersion were not significantly prolonged in patients who died compared to survivors and not significantly different between patients with and without arrhythmic events. Mean RR interval from standard ECG was significantly shorter in patients with both cardiac death (682+/-99 vs. 811+/-134 ms; P=0.004) and arrhythmic events (720+/-100 vs. 818+/-139 ms; P=0.006). A Cox proportional hazards model identified RR interval from standard ECG (P<0.001) and a history of more than one MI (P=0.002) as significant predictors of cardiac death independent of thrombolytic therapy, LVEF, filtered QRS complex duration at signal-averaged ECG, mean RR and its standard deviation at 24-h Holter monitoring. CONCLUSIONS: Measurement of QT interval and dispersion 3 weeks after MI has no prognostic power in patients with LV dysfunction after a recent MI. RR interval on standard 12-lead ECG is as good a prognostic indicator as other, more expensive, noninvasive markers. These findings may be relevant in this era of limited health care resources.

Chi-Square Distribution↗
PubMed1997

C.A.S.M. and C.A.S.T. A new information based approach to clinical audit.

This paper outlines a research project currently being conducted at the University of Central Lancashire. The project's aims are to develop a detailed structured method for clinical audit and to construct a supporting computer based toolset to automate the process. A discussion of the background to the research and an outline of the method and toolset is portrayed.

Database Management Systems↗
PubMed1998

Computer-based assistance in family medicine.

In this paper, the fully integrated General Practitioner (GP) Information and Research System HIOS and Decision Support System HIOS+ are described. Both systems were developed with the Phased Development Methodology (PDM), which is also presented. HIOS consists of an administrative module, medical modules, and a research module to support GPs in daily practice activities and research. It was implemented at a general practice and a health centre, and was evaluated positively. HIOS+ was developed by extending HIOS with modules which offer several types of decision support to assist GPs in (diagnostic) decision making. The modules offer passive and active decision support. HIOS+ can present textbook information, generate advice and warnings, support the creation of models, generate reports, and can be used in education. Some HIOS+ modules were evaluated by GPs in evaluation studies, all with positive results.

Computer Systems↗
PubMed1999

A software implementation for detailed volume conductor modelling in electrophysiology using finite difference method.

There is an evolving need for new information available by employing patient tailored anatomically accurate computer models of the electrical properties of the human body. Because construction of a computer model can be difficult and laborious to perform sufficiently well, devised models have varied greatly in the level of anatomical accuracy incorporated in them. This has restricted the validity of conducted simulations. In the present study, a versatile software package was developed to transform anatomic voxel data into accurate finite difference method volume conductor models conveniently and in a short time. The package includes components for model construction, simulation, visualisation and detailed analysis of simulation output based on volume conductor theory. Due to the methods developed, models can comprise more anatomical details than the prior computer models. Several models have been constructed, for example, a highly detailed 3-D anatomically accurate computer model of the human thorax as a volume conductor utilising the US National Library of Medicine's (NLM) Visible Human Man (VHM) digital anatomy data. Based on the validation runs the developed software package is readily applicable in analysis of a wide range of bioelectric field problems.

Body Composition↗
PubMed2001

Comparison of carotid vessel wall area measurements using three different contrast-weighted black blood MR imaging techniques.

Measuring carotid artery plaque burden from MRI is a reliable method for monitoring regression and progression of atherosclerosis. However, to measure all available images would be very time consuming, and in practice the image quality (IQ) of these images may be inconsistent, which can directly impact the quality of measurement. It is hypothesized that if IQ is comparable among different contrast weighted images, then carotid artery area measurements obtained from different contrast images of the same location will produce identical results. To test this, T1, proton density and T2 weighted images were acquired from ten patients (51 +/- 7 years old). Carotid lumen and vessel wall area was measured using a custom designed software program. The results showed strong agreement evidenced with only small differences on both lumen (mean: 40.5 mm(2)) and wall (mean: 52.6 mm(2)) area measurement among different weighted images. The maximum absolute mean differences are less than 2.7 mm(2) and 4.4 mm(2), and 90(th) percentile of the absolute differences are 5.6 mm(2) and 8.2 mm(2) respectively. In conclusion, different contrast weighted images with high and comparable IQ will yield similar results in lumen and vessel wall area measurement. At each matched location, it is recommended that the image with the highest IQ be used for area measurement.

Carotid Arteries↗
PubMed2002

QRST subtraction combined with a pacemap catalogue for the prediction of ectopy source by surface electrocardiogram in patients with paroxysmal atrial fibrillation.

OBJECTIVES: This study evaluated the use of ectopic P-wave morphology to localize pulmonary vein (PV) and non-PV sources of atrial ectopics in patients with paroxysmal atrial fibrillation (PAF). BACKGROUND: The vectorial information embodied in the morphology of ectopic P waves is concealed by overlying T waves. METHODS: The P-wave morphology of 56 ectopics was prospectively analyzed in 44 patients with PAF (age, 52 +/- 12 years; 36 male) by subtracting the adjacent QRST from the QRST-ectopic P-wave complex using custom-designed software. Subtraction fidelity was validated in 15 other patients (55 +/- 19 years, 11 male) by comparing drive beats with simulated ectopics (S2 from the same site) unmasked by subtracting overlying QRST. An algorithm combined with PV pacemaps was used to predict PV sources. Subtracted ectopic P-wave morphologies after PV disconnection were compared with PV and non-PV site pacemaps. Localization was confirmed by mapping and successful ablation. RESULTS: A > or =10-lead electrocardiogram (ECG) match was observed in 92% of 644 simulated ectopics (coupling intervals: 190 to 520 ms). In PAF patients, 37 spontaneous ectopics originated from the PV, while 19 were noted after PV disconnection. Using the P-wave algorithm alone, correct prediction of PV origin was achieved in 30/37 ectopics (81%). Combination with PV pacemaps allowed correct prediction in 34/37 (92%). After PV disconnection, ECG localization predicted successful ablation sites in 16/19 (84%). CONCLUSIONS: Comparison of subtracted ectopic P waves with a pacemap catalogue provides a simple and accurate 12-lead ECG-based method for localization, which can facilitate ablation of arrhythmia triggers irrespective of origin from the PV or elsewhere.

Adult↗
PubMed1985

Correlation of continuous wave Doppler velocities with cardiac catheterization gradients: an experimental model of aortic stenosis.

The purpose of this study was to use a canine preparation of experimental aortic stenosis to compare estimates of pressure gradient derived from continuous wave Doppler ultrasound with gradients measured directly by catheterization. Aortic stenosis was created in six mongrel dogs by placing an elastic band around the aorta. Eighty-eight different pressure gradients, ranging from 5 to 160 mm Hg, were produced by variable tightening of the aortic band. Pressure gradients were measured by micromanometer-tipped catheters placed in the left ventricle and aorta. Doppler spectral signals were simultaneously obtained using a 2.0 MHz nonimaging transducer placed directly on the surface of the ascending aorta. Doppler and pressure recordings were analyzed using a custom-designed software program to measure maximal instantaneous, mean and peak to peak gradients, as well as ejection and acceleration times. Maximal instantaneous Doppler gradient showed an excellent linear correlation with maximal instantaneous catheterization gradient (r = 0.98, SEE = 5.3 mm Hg). The correlation of Doppler-estimated maximal gradient to peak to peak catheterization gradient was also linear (r = 0.97, SEE = 6.2 mm Hg) but resulted in a systematic overestimation of pressure drop (mean overestimation = 9.0 mm Hg). Measurement of the Doppler gradient at mid-systole resulted in a more accurate correlation with the peak to peak catheterization gradient (r = 0.98, SEE = 6.1 mm Hg) and eliminated the problem of overestimation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1999

Diurnal fluctuations in corneal topography 10 years after radial keratotomy in the Prospective Evaluation of Radial Keratotomy Study.

PURPOSE: To correlate clinically observed fluctuations in manifest refraction, visual acuity, keratometry, and intraocular pressure (IOP) with changes in the anterior corneal surface as measured by videokeratography in patients 10 years after radial keratotomy (RK). SETTING: Four clinical centers in the United States that participated in the Prospective Evaluation of Radial Keratotomy (PERK) study. METHODS: Thirty-two eyes of 20 PERK patients who noted diurnal fluctuations in vision had clinical examination and videokeratography (TMS-1, Computed Anatomy Inc.) in the morning and evening of the same day a mean of 10.3 years (range 7.8 to 11.7 years) after RK. The videokeratographs were analyzed in terms of various indexes generated by custom-designed software. Morning-to-evening changes in the means of the various clinical and videokeratographic values were assessed using pairwise methods. RESULTS: The mean increase in myopia was 0.36 diopters (D) +/- 0.58 (SD) from morning to evening (P < .01). Analysis of the videokeratographs showed a corresponding increase in average corneal power (ACP), reflecting a steepening of 0.52 +/- 0.45 D (P < .001). The change in ACP was correlated with a change in the manifest spherical equivalent refraction (R = 0.39, P = .03) and a change in best spectacle-corrected visual acuity (R = 0.38, P = .03) over the same period. Similarly, simulated keratometry (SimK) readings correlated with the change in the manifest spherical equivalent refraction (R = 0.38, P = .03 for SimK1; R = 0.37, P = .35 for SimK2; R = 0.4, P = .02 for average SimK), although the standard clinical keratometric data did not (P = .26 for K1, P = .11 for K2, and P = .09 for the mean K). The elevation depression magnitude, a measure of the low-frequency irregularities of the cornea, showed a decrease of 0.32 +/- 1.59, which also correlated with the change in the manifest spherical equivalent refraction (R = 0.37, P = .04). Intraocular pressure tended to decrease from morning to evening (mean change of -0.97 +/- 3.29 mm Hg), but the difference was not significant. Variations in IOP in individual patients, however, were correlated with changes in the manifest spherical equivalent refraction (R = 0.37, P = .04). CONCLUSIONS: Diurnal fluctuations in corneal topographic indexes can be used to evaluate the diurnal fluctuations in refraction and visual acuity after RK. The study findings provide statistical support for the idea that IOP contributes to the diurnal fluctuation in visual acuity after RK.

Adult↗
PubMed1998

A custom designed system to measure corticospinal tract jitter.

Typical latency of an individual limb muscle response to magnetic or electric stimulation of the human cortex is in the range of 10-50 ms. For the latency variability, i.e., jitter studies, a resolution of at least 20 micros is needed. Commercially available EMG equipment needs custom-designed upgrading to allow for such studies. Two solutions were designed: (i) a hardware unit allowing an adjustable delay of data acquisition after the delivered stimuli; and (ii) diverting of the amplified biological signal and the EMG equipment trigger to an external computer equipped with an analogue-to-digital conversion (ADC) module. Custom-designed software made fast ADC possible during the whole period of data acquisition. Both concepts were applied to a Vickers Medical Mystro electromyograph, and have been successfully used in the Ljubljana (Slovenia) Institute of Clinical Neurophysiology for the last 2 years.

Brain Mapping↗
PubMed1999

Bioanalytic applications of mass spectrometry.

Mass spectrometry has suddenly expanded out of research and assay laboratories into biology, medicine and therapeutics. Electrospray ionization and matrix-assisted laser desorption/ionization yield increased mass-range and sensitivity, leading to novel applications and sparking new analyzer designs, software, and robotics.

Carbohydrate Sequence↗
PubMed1999

Vertebrate exon trapping methods: implications for transcript mapping with mosquito DNA.

Exon trapping methods have played an important role in the development of transcript maps. In one in vivo vertebrate method, exons in a genomic DNA clone are transcribed, and they are recovered without any a priori information on the nature of the expressed transcript. The only requirement is that the genomic DNA clone contains exons separated by intervening introns that are removed by splicing during mRNA transcription and that the splice donor and acceptor site sequences follow those used by vertebrates. It is not known whether invertebrate splice donor and acceptor sites from genes that contain short introns will be processed correctly using an in vivo vertebrate exon trapping method. In this report, an analysis of mosquito splice sites using software designed to identify exons in genomic DNA sequence suggested that the vertebrate exon trapping method could recognize mosquito introns and exons. When a mosquito genomic DNA clone containing the D7 gene was tested experimentally, this method failed to recognize and process small introns (< 63 bp) faithfully. In spite of this failure, exons and exon fragments were recovered. The implications of these findings and their application to map-based positional cloning in mosquito genomics is discussed.

Animals↗
PubMed2004

Variability of step kinematics in young and older adults.

Fall-related injuries are the most common and serious medical problems facing older adults. Recent studies of older adults have focused on the variability of step kinematics and the relationship to falling. The accuracy of step variability estimates is proportional to the number of steps that are collected. The use of an instrumented treadmill allows simultaneous collection of spatial and temporal step kinematics for a large number of continuous steps. The current study was conducted to determine the influence of age, walking velocity and handrail use on the variability of step kinematics using a treadmill protocol. Eighteen young adults (average age: 27.7 +/- 3.3 years) and 12 healthy older adults (average age: 73.4 +/- 2.3 years) were recruited from the community. Temporal and spatial gait parameters were quantified using custom designed software from measurements collected during treadmill walking. The primary independent variables were the variability of step length, step width, and step time. Step width variability of older adults was significantly larger than that of young adults. Walking velocity did not influence step kinematic variability. Handrail usage influenced the variability of step length and step width, but not of step time. The present results, and those of previous studies, point to a consistent relationship between age and step width variability. Since step width variability has been implicated in falls, further research is warranted.

Adult↗
PubMedDate not supplied

Gated planar technetium 99m-labeled sestamibi myocardial perfusion image inversion for quantitative scintigraphic assessment of left ventricular function.

BACKGROUND: Quantitative assessment of left ventricular systolic performance in conjunction with myocardial perfusion scintigraphy would significantly expand the clinical information obtained from these studies. METHODS AND RESULTS: Left ventricular function was evaluated in 264 patients in whom planar 99mTc-labeled sestamibi myocardial perfusion images were obtained in the best septal left anterior oblique projection. Digital inversion of these perfusion images allows semiautomated evaluation of the left ventricular cavity, with the commonly available edge-detection software designed for equilibrium blood pool imaging. In this study, ejection fractions derived from this technique were compared with those obtained from a myocardial perfusion phantom, first-pass radionuclide angiography, and contrast ventriculography. In vitro validation demonstrated that the myocardial perfusion image inversion ejection fractions correlated linearly with those obtained from a double-chamber phantom (r = 0.999). In vivo, there was good linear correlation between image inversion and first-pass (r = 0.88; image inversion = 0.98 first-pass +0.11), with 95% agreement on the presence or absence of significant left ventricular systolic dysfunction. There was also very good correlation between image inversion and contrast ventriculographic ejection fractions (n = 35; r = 0.85; image inversion = 0.8 contrast +0.05). Intraobserver and interobserver variability of the image inversion ejection fractions was very small (mean difference of 0.4 +/- 0.8 and 2.8 +/- 4.7 units, respectively). CONCLUSION: Gated 99mTc-labeled sestamibi myocardial perfusion image inversion allows evaluation of the dynamics of the left ventricular chamber changes during the cardiac cycle, providing a method for evaluation of systolic function during myocardial perfusion imaging, with highly reproducible results that correlate well with established techniques.

Adult↗
PubMed2004

Clinical application of quantitative analysis in real-time MCE.

The introduction of stable microbubble contrast agents and technological advances have recently made it feasible to perform quantitative measurements of microvascular damage by myocardial contrast echocardiography (MCE). Qontrast is a new software system far such measurements. It includes physiological filters, global rescale, regional rescale, automatic myocardial tracking, manual ECG trigger and parametric imaging. Qontrast was tested on 5 pigs given sulphur hexafluoride bubbles (I ml/min) and fluorescent microspheres (reference) after the induction of 50% and 100% stenosis of left anterior descending coronary artery. The image sequences were repeated four times using different ultrasound (US) equipment. A close correlation was found between the ratio risk area/control area by microspheres and the equivalent ratio risk area/control area (Sl x beta) by MCE, being approximately 0.9 far any contrast modality tested. Parametric MCE and SPELT were compared in 12 patients with recent myocardial infarction, including 119 segments. Agreement amounted to 83% (kappa: 0.53 far peak SI and 0.55 far SI x beta). The sensitivity and specificity of peak SI far detecting abnormal segmental tracer uptake were 67% and 88%; the values far Sl x beta were 70% and 87%. Parametric MCE is a promising imaging technique far the assessment of myocardial perfusion in patients with suspected or known coronary artery disease.

Animals↗
PubMedDate not supplied

Effective drug-allergy checking: methodological and operational issues.

Adverse drug events cause a large number of injuries, and adverse events caused by medications administered in the face of known allergies represent an important preventable cause of patient harm. Computerized systems can effectively prevent reactions due to known allergies, but building an effective allergy prevention feature is challenging and presents many interesting informatics issues that have both methodological and operational implications. In this paper, we present the experiences from one large delivery system in delivering allergy-related decision support, discuss some of the different approaches that we have used, and then propose a future approach. We also discuss the methodological, behavioral, and operational issues that have arisen which have a major impact on success. Key factors in drug-allergy checking include storing patient allergy data in a single common repository, representing allergy data using suitable terminologies and creating groups of allergies for inferencing purposes, being judicious about which allergy warnings to display, conveying the reaction that the patient has experienced when exposed to the drug to inform the provider of the importance of the warning, and perhaps most important, implementing strategies to optimize the likelihood that allergy information will be entered.

Database Management Systems↗
PubMed2003

Topographic study of extracted molars with advanced furcation involvement: furcation entrance dimension and molar type.

This study investigated the topography of the furcation entrance dimension (FED) on molars with advanced furcation involvement (FI). The sample pool consisted of 169 maxillary and mandibular molars from a group of 165 individuals with severely advanced periodontal destruction. The subjects included men and women aged 24 to 84 years (mean, 47.8 +/- 7.2 years). The FEDs of the maxillary buccal, mesial, and distal surfaces as well as the mandibular buccal and lingual surfaces were measured under a stereomicroscope and clarified into grades I (FED < 0.55 mm), II (0.55-0.75 mm), and III (> 0.75 mm) using automatic grading system software designed by our research associates. The differences and relationships among molar location, furcation site, and FED grade were analyzed using the chi-square test. There was a significant difference among buccal (BFED), mesial (MFED), and distal (DFED) FEDs in both the maxillary first (chi2(4) = 58.915, p < 0.001) and second (chi2(4) = 66.839, p < 0.001) molars. The relationship between molar type and FED grade was statistically significant for both the BFED (p < 0.001) and the DFED (p < 0.001) of maxillary molars, as well as for both the BFED (p < 0.0001) and LFED (p < 0.0001). The difference in FED grade between the first and second molars was statistically significant in both maxillary (p < 0.001) and mandibular (p < 0.0001) molars. There was a significant relationship between FED grade and tooth location at molars with advanced FI.

Adult↗
PubMed2002

Effect of a rigid ankle-foot orthosis on hamstring length in children with hemiplegia.

Eighteen children with hemiplegia, mean age 8 years 5 months, underwent gait analysis and musculoskeletal modelling using specially designed software. The maximum lengths of the hamstrings were determined for each child walking in and out of an ankle-foot orthosis (AFO). The muscles were deemed to be short if shorter than the normal average -1SD. In bare feet 8 participants had short medial hamstrings with a higher proportion of these in the less involved individuals. All participants showed an increase in maximum hamstring length when wearing an AFO. In all but one child this was sufficient to restore hamstring length to within normal limits. These finding suggest that hamstring pathology in hemiplegic gait is usually secondary to more distal lower limb pathology.

Ankle Joint↗