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Computers in Cardiology 1989, Proceedings.

Date 19-22 Sept. 1989

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Displaying Results 1 - 25 of 121
  • Analysis of 24 hour heart rate variability in post-infarction patients

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    Summary form only given. The 24-h heart rate variability (HRV) in 40 Holter tapes from the Multicenter Post-Infarction Research Group Study was examined. The first 20 Holters were part of a preliminary study which analyzed various time- and frequency-domain measures of HRV. The time-domain measures were based on the RR intervals and included the 24-h standard deviations of RR/sub n/ and RR/sub n-1/-RR/sub n/. The frequency-domain measures were based on a single 24-h HR spectrum and included the LO (0.01-0.15-Hz) power, HI (0.15-0.50-Hz) power, and the alpha , which characterized the low-frequency 1/f/sup alpha / tail of the power spectrum. The other 20 Holter tapes were used to see whether the HRV measures could be used as predictors of mortality. It was found that HI power and total HRV power clearly separated the 20 patients into two distinct groups of 10 patients each. However, belonging to a group was completely unrelated to mortality: half the members of each group died.<> View full abstract»

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  • Proceedings. Computers in Cardiology (Cat. No.89CH2932-2)

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    Freely Available from IEEE
  • Integrated cardiology retrieval and storage system (ICARUSS)-a data management system for the cardiologist working in electrophysiology

    Page(s): 493 - 496
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    A data storage and retrieval system has been designed to optimize all information obtained during clinical electrophysiological evaluation in patients suffering from tachyarrhythmias. The database system has been programmed to use the fourth-generation language CLIPPER on an IBM PS2/80 but runs presently on an IBM-AT or compatible computer. In the past year data on 580 patients have been entered prospectively. Furthermore, limited information on 1660 patients admitted from 1977 to 1988 has been collected retrospectively View full abstract»

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  • Expert system for automatic phono-mechanocardiographic diagnosis

    Page(s): 393 - 396
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    An expert system has been created for collecting, controlling, and categorizing phonomechanocardiographic data. LV (left ventricle) contraction, ejection, relaxation, and ventricular filling is detected by means of an apexcardiogram. The various forms and combinations of valvular heart disease are characterized by the phonospectra of the auscultation areas. The expert system Mechano has rule-based knowledge representation, backward chaining, uncertainty handling and explanation facilities. The database consists of data on 200 patients with ischemic heart disease and 140 patients with valvular heart disease. By using question nets the digitalized knowledge elements of the apex (amplitude-time intervals) and the phonomap (location, duration, amplitude of sounds, and murmurs) are automatically collected. The diagnosis of N different forms of valvular heart disease and the evaluation of LV functions are based on diagnosis rules containing values of possibilities determined by multiple statistical models (regression, factor, and cluster). The program, implemented on a PC, is written in Turbo Prolog View full abstract»

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  • Planimetric quantification of mitral and tricuspid regurgitations by cine magnetic resonance imaging with gradient echo

    Page(s): 207 - 210
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    Cine MRI (magnetic resonance imaging) in gradient echo is able to visualize directly rapid and turbulent flows such as regurgitations. A group of 55 patients with 40 mitral regurgitations (MR) and 26 tricuspid regurgitations (TR) was explored with a 0.28 T resistive magnet. Doppler echography and contrast angiography constitute the reference explorations. Qualitative examination of the dynamic images provides a diagnostic sensitivity for MRI of 100% versus angiography and of 88% versus echography. The three techniques are compared by four-step grading of the regurgitation severity with correlation coefficients always greater than 0.70. A more precise quantification is reached by planimetry of the signal loss jets; the most accurate quantification parameter is the mean absolute surface area of the auricular signal loss during the systole, which leads to a correlation coefficient of 0.84 ( p<10-5) for MR and of 0.79 (p<10-4) for TR View full abstract»

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  • Interactive measurement of three-dimensional cardiac morphology

    Page(s): 429 - 432
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    Techniques have been developed for extracting three-dimensional (3-D) measurements directly and interactively from 3-D representations of cine CT (computer tomography) images. In order for 3-D measurements to be obtained, the anatomical surface is interrogated directly through the use of a 3-D graphical `probe' (line). The probe is interactively positioned and stretched between any visible surface points to allow direct capture of 3-D (linear) distance. Distance measurements are updated in real time as the probe dynamically `penetrates' any intervening anatomy while providing valuable depth cuing for visual feedback and probe placement. Curvilinear distance is obtained by stretching the probe over multiple surface points. The probe is implemented by a general z-buffer and is therefore applicable to a variety of 3-D imaging techniques View full abstract»

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  • Standards for electrocardiographic instrumentation

    Page(s): 69 - 71
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    Attention is given to the 1989 American Heart Association report, which focuses on the areas of digital processing and bandwidth requirements for automated ECG (electrocardiographic) analysis. Recommendations are developed for low- and high-frequency performance, sampling and quantization, and data compression. Fidelity criteria are described in relation to the intended applications, including routine visual reading, morphological diagnosis by digital program, and digital transmission or storage/retrieval of data View full abstract»

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  • A simple analytical model mimics complex physiological behavior

    Page(s): 335 - 338
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    The authors have previously described the use of nonparametric transfer function analysis in combination with broadband respiration to compute the magnitude and phase relations between respiration, heart rate (HR), and arterial blood pressure (ABP). These experimental results have led to the formulation of a model of HR and ABP control which includes the mechanical feedforward from HR to ABP, the baroreflex feedback from ABP to HR, and respiration as a noise source which directly affects HR through central modulation of autonomic activity while affecting ABP through mechanical thoracic coupling. Despite the fact that causality was not built into the ABP-HR relation, analytic transfer functions from the model closely simulate many of the observed experimental phenomena. The findings suggest that the complex transfer relations observed with a relatively simple analysis of respiration, HR, and ABP can be understood in terms of feedback loop between ABP and HR, with respiration as an external noise source View full abstract»

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  • Global and regional ejection fraction changes with CABG evaluated by stress radionuclide angiography

    Page(s): 451 - 453
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    To evaluate coronary artery bypass surgery (CABG) effects on global and regional left ventricular function, the authors studied 19 coronary artery disease (CAD) patients with stress radionuclide angiography (SRNA), before and after CABG. Global and regional ejection fraction (EF) changes, with CABG both at rest and in stress, were analyzed. The results were compared with those for a reference group of 12 normal individuals. It is confirmed that, in general, CABG does not affect left-ventricular (LV) function at rest but improves LV performance at stress. However, in individual patients the rest EF may change View full abstract»

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  • Computer filtering of an ECG signal based on the prior knowledge principle-general concept

    Page(s): 397 - 400
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    A novel computer method for ECG (electrocardiographic) signal filtering is discussed. This method is based on a concept called the prior knowledge principle (PKP). The PKP assumes that the measured signal contains the ECG signal itself and environmental noises. An artificial signal with amplitude and time resembling the real ECG signal has been constructed. Cases of white and network noise are analyzed, with the level of noise varying from 0 to 100%. The calculated errors for the techniques used do not exceed 20% View full abstract»

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  • Beat-by-beat variability of the delays between the R peak and the pressure wave onset in a peripheral artery

    Page(s): 343 - 346
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    The delay between the R peak in ECG (electrocardiography) and the pressure wave onset point (TRD) in a peripheral artery is proposed as a variability signal, in addition to the classical ones relating to heart rate (HR) and arterial pressure (AP) variability. In five hypertensive subjects, who underwent routine ECG and AP monitoring under various autonomic stimuli, it is shown that TRD duration can be determined by beat-by-beat measurement with a good precision. The spectral analysis of TRD variability revealed a dominant high-frequency component in correspondence to the respiratory frequency, which remained almost stable under the various maneuvers. This high-frequency oscillation displayed a high and stable coherence with systolic AP variability, with a constant phase opposition. The results may provide further insight into the modulation mechanisms of respiration in connection with AP View full abstract»

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  • A model of left ventricular contraction and transmural ventricular deformation

    Page(s): 15 - 17
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    The authors present a thick-wall ellipsoidal model of the left ventricle (LV) that takes into account its fiber structure in parallel with the well-known physiological properties of the muscle fibers and was constructed to describe both the transmural and global features of ventricular contraction. The model describes systolic function utilizing the force-length and force-velocity relationship of the fibers. The local oxygen consumption is simulated assuming a linear relationship with the area of the stress-length loop and the triangle between the loop and the maximum active force formed locally for each fiber. The model yields the transmural distribution of oxygen demand as a function of the loading conditions, and accounts for twist of the LV over its long axis during ejection. Thus, the model of LV function provides a comprehensive analytic tool to study the complex interactions between parameters of the ventricular function View full abstract»

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  • Shape based classification of left ventricles by spectral analysis of their geometrical cardiograms

    Page(s): 87 - 89
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    The recently introduced geometrical cardiogram (GCG) is an anatomically aligned helical vector, normalized to the size of the heart, that characterizes the three-dimensional instantaneous shape of the left ventricle. It is shown that the spectrum obtained by applying a Fourier sine series expansion to the end-systolic (ES) GCG can be utilized to classify normal, hypertension/hypertrophic (HT), and infarcted (MI) hearts. No human intervention is required once the endocardial contours are traced. The demonstrated high discriminatory potential of the |A1|, and GR8 parameters implies that a fully automated diagnostic procedure is potentially obtainable View full abstract»

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  • A real-time personal computer based system for analysis of electrocardiograms

    Page(s): 497 - 500
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    The authors have developed a real-time personal-computer-based system for analysis of single-lead electrocardiograms running on an IBM PC/AT personal computer or compatibles. It converts an analog ECG (electrocardiographic) signal coming from the ECG acquisition unit into digital form, monitors it on a video display, detects each incoming beat, displays heart rate, and recognizes some simple rhythm disorders (arrest, bradycardia, tachycardia). Each beat is classified into one of three different categories: normal, supraventricular (SVC), or ventricular ectopic (VEC). The system also computes average beats and from them determines some diagnostic parameters (R-wave amplitude, R/R1 ratio, J point level, ST slope, and ST integral). The results of the analysis are displayed and periodically updated. At the end of the analysis, histograms which show trends of global changes for heart rate, VECs/min, SVCs/min, R-wave amplitude, R/R1 ratio, J point level, ST slope, and ST integral can be viewed View full abstract»

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  • Quality control in a Holter laboratory

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    Summary form only given. The quality control program in the Holter laboratory has been on going for three years. Over this time, volume has increased from 5794 ECG (electrocardiographic) tapes/year (1987) to 6038 (1988) and 6400 (projected 1989). Technician productivity has increased from 4.8 tapes/day (1987) to 5.1 (1988) and 5.7 (1989). Because of the complex process necessary to produce a full report, an attempt has been made to examine the quality at each step, with the equipment separated from the technician component The equipment is tested for frequency response and timing, with isolated problems being identified. Since the laboratory serves 30 hospital clinics, the greatest problem is electrode placement on the patient. Eighteen hours of analyzable data were obtained from 92% of the recordings. Accuracy of analysis is measured by technicians' bi-weekly reading of a hand-counted tape from a library. Accuracy for the laboratory has increased from 87% (1987) and 90% (1988) to 93% (1989). Precision is measured by technicians' biweekly reading of a tape that they had read in the previous 2 weeks. Precision for the laboratory was 95% in 1988 and 96% in 1989 View full abstract»

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  • Left ventricular function from computer processed magnetic resonance images

    Page(s): 203 - 206
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    Cross-sectional magnetic resonance (MR) images of the heart from nine male and ten female normal subjects were computer processed to establish normal templates of left ventricular function. Ventricular volumes at end-diastole and end-systole were significantly greater in males than females but ejection fractions were identical. For analysis of regional endocardial motion, the use of a floating centroid gave more uniform values compared with a fixed centroid method. Endocardial motion values were not significantly different for males and females. The data obtained can be used to define abnormalities of left ventricular function in patients with heart disease. Male/female differences in ventricular volume will require separate templates but it appears that analysis of ejection fraction and regional endocardial motion can be performed from the same templates for males and females View full abstract»

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  • TRIAL MASTER, an expert system to control clinical drug trials

    Page(s): 361 - 364
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    An expert system has been designed to facilitate the proper application of inclusion and exclusion criteria for clinical drug trials. For six trials, these criteria were represented in rules and stored in knowledge bases. In three cases, a separate knowledge base was added, containing knowledge on ECG (electrocardiographic) criteria. For a series of 100 patients, the cardiologist and the expert system disagreed with regard to three patients. In 24 cases the patient was classified for at least one trial; 73 patients did not meet the requirements for inclusion in any trial. As an example, the evaluation of a patient with unstable angina is presented View full abstract»

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  • Microcomputer based digital image enhancement system for coronary angiography

    Page(s): 433 - 435
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    The authors have developed a microcomputer-based digital image processing system for the analysis of coronary arteriograms and ventriculograms. The system consists of an IBM-AT compatible computer equipped with an image capture board, a video camera, and a mouse. A commercially available interactive image enhancement software package with in-house written programs make-up the software environment. The image capture board is TARGA-M8, capable of grabbing images with 482×512-pixel resolution and 256 shades of gray. The video camera is of the CDD (charge-coupled-device) type. The captured images are displayed on a long persistence monitor. A mouse is used to draw regions of interest and to operate the menu-driven software. The system has been used for the densitometric and hemodynamic analysis of stenoses. Ejection fraction and wall motion analysis can be computed for ventriculograms View full abstract»

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  • Repolarization duration variability: a tool to quantify the autonomic balance at the ventricle

    Page(s): 339 - 342
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    In order to gain insight into the process of cardiac repolarization, the authors defined and studied the repolarization duration variability (RDV) on electrocardiograms. Spectrum techniques were used to evaluate the influence of the autonomic nervous system in the control of repolarization duration (RD). Coherence analysis was used to quantify common contributions between RDV and heart rate variability. The latter gave a reference of the sympathovagal balance. It was found that the autonomic nervous system acts tonically and directly to control RD. This action is mediated through both autonomic limbs View full abstract»

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  • Fetal heart rate detection by a special transform method

    Page(s): 275 - 278
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    A novel method is proposed for the detection of fetal heart rate from abdominal ECG (electrocardiography). The method resembles the computation of a discrete Fourier transform. However, the analyzing functions used have greater correlation with the signal being looked for than the standard sine and cosine functions. The functions are trains of square waves, characterized by the width of the square wave, their periodicity, and some initial phase value. Following the elimination of the maternal ECG contribution to the signal, a triple parametric transform function is computed by multiplying the signal by the analyzing functions and integrating the result. The maximum of the transform obtained this way indicates the average fetal RR interval. Thus the fetal heart rate can be detected. Preliminary application of this method to real and simulated fetal ECG signals is presented. In general, the method can be applied to handle weak, quasi-periodic, sharp signals of various origins View full abstract»

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  • A DB-based and CAI oriented edition of the knowledge on clinical arrhythmias

    Page(s): 479 - 482
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    An effort has been made to develop a teaching-oriented knowledge structure for clinical arrhythmology. The database form is based on a knowledge representation approach. Available methodologies (entity-relationship model, relational schemes, normalization of relations) are used in the analysis and planning of data. A relational database instance in a Paradox environment, comprising 43 relational schemes for the rhythm diagnostic classes, and 63 for the beat classes, was developed during a long period of cooperation with a cardiologist. As intermediate objectives some applications that search for synonyms and any functional dependence, aggregation, and disaggregation relationships have been developed, making it possible to integrate information effectively and properly. For each diagnosis considered in both the rhythm and beat domains, the database yields a detailed description of the characteristic segments of the relevant ECG (electrocardiogram) trace View full abstract»

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  • AENEAS: a standard for ECG-management and exchange in the Netherlands

    Page(s): 289 - 292
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    The Interuniversity Cardiology Institute of the Netherlands (ICIN) has set up a computer network for the exchange of ECG (electrocardiographic) data within nine large Dutch hospitals. The main goal of the project is to be able to share ECGs for both patient care and scientific research. An additional goal is standardization of ECG management and diagnostic statements. A committee was formed to investigate the proposal. It called itself and the proposed network AENEAS, which is an acronym or `automatic ECG-Analysis in the Netherlands, towards an Exclusive Authorized Standard'. Minimal requirements have been defined for electrocardiographs and management systems, and global network specifications have been written. During the course of the investigation, several types of electrocardiographs and ECG management systems were tested. It became clear that minimal standards still need to be defined for these as well. Communication between electrocardiographs and/or systems is not at all standardized and is virtually impossible between equipment of different vendors View full abstract»

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  • Quantitative shape analysis of left ventricular cine-CT images

    Page(s): 91 - 93
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    The shape of the endocardial and epicardial borders of excised dog hearts digitized and traced from cine-CT (computer tomography) images have been quantitatively compared with those obtained from actual dissected cross sections digitized and traced with a video camera. Results from a standard Fourier analysis have been compared with those obtained from the proposed boundary matching descriptor method. Both measures indicate that the LV (left ventricle) shape is not altered by the proposed reconstruction procedure. The Fourier analysis indicates that the epicardial borders are more accurately reproduced than the endocardial borders (p<0.05). Results from the introduced technique show that there is no difference in accuracy between the two borders. Reasons are offered for this disparity. The new shape descriptor allows the identification of specific regions in the borders where the shapes do not match. On the basis of these data, the shape of the LV images from cine-CT closely agree with the shape of the actual cross sections obtained by dissection. Errors in shape reproduction appear to be random and not systematic View full abstract»

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  • High frequency ECG-a new method to examine depolarization changes mediated by transient myocardial ischemia

    Page(s): 105 - 108
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    The very-high-frequency components (150-250 Hz) of the electrocardiogram were evaluated. Experiments were designed to determine the extent to which the morphology of the high-frequency QRS potentials is affected by transient myocardial ischemia. The high-frequency ECG was studied in dogs during induced ischemia and in patients undergoing angioplasty. It was found that the high-frequency ECG appears to detect evidence of transient ischemia with greater sensitivity than visual inspection of the surface ECG and may therefore provide useful information. A finite-element three-dimensional model with a self-similar (fractal) conduction system was introduced as a bridge to the understanding of these electrocardiographic phenomena. By using this model it was found that the morphological changes in the high-frequency QRS can be attributed to a slowing of conduction velocity in the region of ischemia View full abstract»

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  • HES EKG expert-an expert system for comprehensive ECG analysis and teaching

    Page(s): 77 - 80
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    An expert system for comprehensive electrocardiographic diagnosis has been developed. The system provides ECG (electrocardiogram) processing by the HES ECG program, a database with validated ECGs and their accompanying clinical findings, and a knowledge base containing established rule sets for ECG classification (Cardiac Infarction Injury Score, Romhilt Estes Hypertrophy score, the Selvester score system, etc.). For access to the database a group definition language has been developed; and a rule definition language is provided for creation of rule sets and diagnostic classification algorithms. Rule sets may be applied to single cases or groups of cases (batch processing). Reasoning is provided by using the backward chaining inference engine, which generates a structured reasoning path View full abstract»

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