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Biomedical subjects

L Edenbrandt

Publications and source records attributed to L Edenbrandt.

At least 19 recordsLinked to original sources
PubMed1995

Artificial neural networks for recognition of electrocardiographic lead reversal.

Misplacement of electrodes during the recording of an electrocardiogram (ECG) can cause an incorrect interpretation, misdiagnosis, and subsequent lack of proper treatment. The purpose of this study was twofold: (1) to develop artificial neural networks that yield peak sensitivity for the recognition of right/left arm lead reversal at a very high specificity; and (2) to compare the performances of the networks with those of 2 widely used rule-based interpretation programs. The study was based on 11,009 ECGs recorded in patients at an emergency department using computerized electrocardiographs. Each of the ECGs was used to computationally generate an ECG with right/left arm lead reversal. Neural networks were trained to detect ECGs with right/left arm lead reversal. Different networks and rule-based criteria were used depending on the presence or absence of P waves. The networks and the criteria all showed a very high specificity (99.87% to 100%). The neural networks performed better than the rule-based criteria, both when P waves were present (sensitivity 99.1%) or absent (sensitivity 94.5%). The corresponding sensitivities for the best criteria were 93.9% and 39.3%, respectively. An estimated 300 million ECGs are recorded annually in the world. The majority of these recordings are performed using computerized electrocardiographs, which include algorithms for detection of right/left arm lead reversals. In this study, neural networks performed better than conventional algorithms and the differences in sensitivity could result in 100,000 to 400,000 right/left arm lead reversals being detected by networks but not by conventional interpretation programs.

Algorithms↗
PubMed1995

Reconstruction of the standard 12-lead ECG from recordings using nonstandard activity-compatible proximal limb lead positions.

Proximal or torso placement of limb leads in the 12-lead electrocardiogram (ECG) has been shown to influence the appearance of QRS waveforms considerably. A method was developed for computer-based reconstruction of standard-like waveforms from nonstandard torso-recorded waveforms. Reconstruction coefficients required by the method were determined using ECG data obtained from 30 patients. The coefficients were then applied on an independent test set of 100 patients. In 21 of these patients, a second standard EGG was obtained the next day to determine the day-to-day variation in QRS waveforms. R wave amplitudes in leads I and II, and electrical axes in the frontal plane were measured in the standard ECG, the nonstandard ECG, and the reconstructed ECG. It is shown that the reconstruction method yields ECGs that differ less from standard than do two standard ECGs recorded on consecutive days. The performance of the reconstruction method was not influenced by age, sex, height, or weight.

Adult↗
PubMed1995

Increased sensitivity for the diagnosis of healed myocardial infarction using vectorial information in the 12-lead ECG.

The aim of this study was to use the vectorial information in the conventional 12-lead electrocardiographic (ECG) recording and to investigate whether this information, in combination with well-known ECG criteria, could increase the diagnostic performance for healed anterior or inferior myocardial infarction. A total of 1,458 subjects were included in the study; 272 patients with anterior myocardial infarction, 356 patients with inferior myocardial infarction, and 830 subjects classified as normal. New 12-lead vectorcardiographic criteria for anterior and inferior myocardial infarction were developed and used in combination with well-known ECG criteria. The combined criteria showed a sensitivity of 80.0% and 72.4% for the diagnosis of anterior and inferior myocardial infarction, respectively. The corresponding sensitivities for the conventional ECG criteria were significantly lower. In conclusion, the addition of vectorial parameters into ECG interpretation programs could be of value.

Diagnosis, Computer-Assisted↗
PubMed1995

Dynamic Octreotide scintigraphy in neuroendocrine tumours.

The purpose of the present study was to investigate the optimal time for scintigraphy after injection of the radio-labelled somatostatin analogue, Octreotide. A secondary purpose was to evaluate the value of SPECT. One SPECT study and up to 4 whole body scans were performed in 22 patients with neuroendocrine tumours 0.5, 5, 24 and 48 hours after an injection of 110 MBq In-DTPA Octreotide. A total of 98 scintigrams were studied. A pathological uptake was found in 19 of the 22 patients. In 3 cases, early scintigrams (0.5 and 5 hours after injection) were of the most value whereas late scintigrams (24 and 48 hours) were the best in 4 cases. SPECT was found to be of value in 13 of 21 cases. For correct interpretation of Octreotide scintigraphy it is necessary to obtain both early and late scintigrams as well as a SPECT study.

Adult↗
PubMed1995

Esophageal scintigraphy of systemic sclerosis.

UNLABELLED: Esophageal involvement is common in systemic sclerosis, and esophageal scintigraphy can be used to detect and follow esophageal dysfunction. This study assesses the value of visual and quantitative analysis of esophageal scintigraphy performed as a multiple swallow test in normals and patients with systemic sclerosis. METHODS: Forty patients with systemic sclerosis and 40 sex- and age-matched healthy subjects (controls) were studied. A multiple swallow technique was used and both quantitative and qualitative analyses were performed. Visual analysis of condensed images was performed independently by two physicians. Each swallow was assigned a score on a scale from 1 to 4. In the quantitative analysis, time-activity curves based on the mean condensed images were used to calculate the following 3 parameters: residual activity 12 or 25 sec after the beginning of the swallow, measured with or without baseline correction, respectively, and time from onset of swallow to 50% of peak activity. RESULTS: Both visual and quantitative analysis showed a highly significant (p < 0.001) difference between the patient group and the control group. Visual analysis was best reflected by the residual activity 25 sec after the beginning of the swallow without correction for background. Receiver operating characteristic curves were used to study the ability to separate the two groups using visual or quantitative analysis. A high rate of positive tests in the patient group was achieved only at the cost of a relatively high rate of positive tests in the control group. CONCLUSION: Our results indicate high variability in esophageal motility in controls. This variability impairs the possibilities of developing a screening test to identify asymptomatic patients early in the disease course.

Adult↗
PubMed1994

Artificial neural networks for the electrocardiographic diagnosis of healed myocardial infarction.

Artificial neural networks are computer-based expert systems that learn by example, in contrast to the currently used rule-based electrocardiographic interpretation programs. For the purpose of this study, 1,107 electrocardiograms (ECGs) from patients who had undergone cardiac catheterization were used to train and test neural networks for the diagnosis of myocardial infarction. Different combinations of QRS and ST-T measurements were used as input to the neural networks. In a learning process, the networks automatically adjusted their characteristics to correctly diagnose anterior or inferior wall myocardial infarction from the ECG. Two thirds of the ECGs were used in this process. Thereafter, the performance of the networks was studied in a separate test set, using the remaining third of the ECGs. The results from the networks were also compared with that of conventional electrocardiographic criteria. The sensitivity for the diagnosis of anterior myocardial infarction was 81% for the best network and 68% for the conventional criteria (p < 0.01), both having a specificity of 97.5%. The corresponding sensitivities of the network and the criteria for the diagnosis of inferior myocardial infarction were 78% and 65.5% (p < 0.01), respectively, compared at a specificity of 95%. The results indicate that artificial neural networks may be of interest in the attempt to improve computer-based electrocardiographic interpretation programs.

Case-Control Studies↗
PubMed1992

Evaluation of changes in standard electrocardiographic QRS waveforms recorded from activity-compatible proximal limb lead positions.

Proximal limb lead positions are currently used for activity-compatible electrocardiographic monitoring of myocardial ischemia. Two previously described systems for alternate limb lead placement were studied in patients with and without QRS evidence of healed anterior or inferior myocardial infarction. An innovative method was used to simultaneously record 6 standard and 6 modified limb leads, and 3 standard and 3 modified precordial leads on a standard digital electrocardiograph. Both alternate lead placement systems showed rightward frontal plane axis shift and diminished Q-wave durations in lead aVF compared with those of their simultaneous standard controls. Furthermore, potential differences between the standard distal limb lead sites and 5 more proximal sites were explored along each limb. Differences along the left arm were accentuated relative to those along the right arm owing to differences in proximity of the arms to the myocardium. Along the lower limb, and anterior site showed less deviation from standard than did a more lateral site. It is imperative that recordings from alternate sites be labeled accordingly so that their output cannot be confused with that obtained from standard sites.

Arm↗
PubMed1992

Reconstruction of the electrocardiogram during heart surgery.

Electrocardiograms (ECG) recorded during arrhythmia surgery are used for identification of arrhythmias of different morphology. However, the interpretation of an intraoperative ECG is difficult because some leads cannot be recorded and the signals of the remaining leads often differ from those of a preoperative recording because of the sternotomy. Therefore, a method for reconstruction of a complete intraoperative ECG, which resembles a preoperatively recorded ECG, was studied in 24 patients undergoing heart surgery. The reconstruction method involves calculating coefficients for a transformation matrix, using a preoperative ECG recording and a first intraoperative ECG recording. Once this matrix has been established, further intraoperative recordings can be transformed into an ECG which strongly resembles a preoperative ECG. The correlation between reconstructed intraoperative leads and the corresponding preoperative leads was high in the leads Vx and Vy (median correlation coefficient 0.98 and 0.97) and slightly smaller in lead Vz (0.94). Further studies will prove if the method can be useful in arrhythmia surgery.

Aged↗
PubMed1992

Neural networks for classification of ECG ST-T segments.

The usefulness of neural networks for pattern recognition in electrocardiographic (ECG) ST-T segments was assessed. Two thousand ST-T segments from the 12-lead ECG were visually classified singly into 7 different groups. The material was divided into a training set and a test set. Computer-measured ST-T data for each element in the training set, paired with the corresponding classification, was input to various configurations of software-based neural networks during a learning process. Thereafter, the networks correctly classified 90-95% of the individual ST-T segments in the test set. The importance of the size and composition of the training set in determining the performance of a network was clearly demonstrated. In conclusion, neural networks can be used for classification of ST-T segments. If carefully incorporated into a conventional ECG interpretation program, neural networks may well be of value for automated ECG interpretation in the near future.

Electrocardiography↗
PubMed1992

12-lead vectorcardiography in ischemic heart disease.

The conventional approach to recording the vectorcardiogram is to use a specially designed set of electrodes that derive 3-orthogonal leads, ideally corrected with respect to lead strength and direction. This has disadvantages in that it entails a separate recording as opposed to the use of the 12-lead ECG that is universally used. On the other hand, recently developed equations allow the vectorcardiogram to be derived from the 12-lead ECG, and although there is not a one-to-one correspondence with the vectorcardiogram derived using a corrected orthogonal lead system, it has been shown that there is a high degree of similarity between the two derivations. This article discusses the advantages of utilizing the "derived 12-lead vectorcardiogram," which is claimed to have information that is complementary to that of the scalar 12-lead ECG display. It is suggested that using the combination of the 12-lead ECG and the vectorcardiogram derived therefrom, provides the optimum approach to ECG interpretation as compared to using either method alone.

Coronary Disease↗
PubMed1990

Improved ECG interpretation using synthesized VCG for the diagnosis of inferior myocardial infarction.

Electrocardiographic (ECG) criteria for the diagnosis of inferior myocardial infarction (IMI) have high specificity but low sensitivity. Vectorcardiographic IMI criteria attain higher sensitivity without sacrificing specificity. One approach to improving ECG interpretation is to synthesize VCG loops from the 12-lead ECG. The performance of synthesized VCG (SVCG) was assessed, using the Frank VCG criterion of Starr et al. ECGs and SVCGs from 351 normal subjects and 65 patients with IMI verified by myocardial scintigraphy or angiocardiography were studied. The sensitivity was 14 percentage points higher for SVCG than for ECG (72% vs. 58%).

Adult↗
PubMed1990

Vectorcardiogram more sensitive than 12-lead ECG in the detection of inferior myocardial infarction.

The vectorcardiogram (VCG) is commonly stated to be more sensitive than the 12-lead electrocardiogram (ECG) for the diagnosis of inferior myocardial infarction. However, a recent study indicated that VCG is not superior to ECG for this diagnosis. The purpose of this study was to compare the performance of VCG and ECG criteria and to indicate possible explanations for the disagreement between earlier studies. Accordingly, we studied 65 patients with inferior myocardial infarction verified by left ventriculography or 201-TI myocardial scintigraphy and 351 normal subjects. Sensitivity was 69% (45/65) and 43% (28/65) for the VCG and ECG criteria, respectively. This difference was highly significant (P less than 0.001). Among the normal subjects there were only three with false positive ECG. We conclude that both VCG and ECG criteria for the diagnosis of inferior myocardial infarction are highly specific and that VCG criteria have greater sensitivity than ECG criteria.

Adult↗
PubMed1989

Vectorcardiographic bites. A method for detection and quantification applied on a normal material.

Vectorcardiographic bites as an expression of small fibrotic or necrotic areas in the myocardium have been discussed for many years. Distinct definitions of bites and normal limits for bites have, however, not been established. Therefore, an algorithm for computer detection and quantification of bites is presented. To find a bite, sectors of the QRS loop rotating opposite the way of the main part of the loop (eg, a clockwise-rotating sector in an otherwise counterclockwise-rotated loop) are detected. The bite is then delineated, using an iterative procedure. Finally the amplitude, duration, and area of the bite are calculated. The method for detection and quantification was applied on a well-defined normal material to obtain normal limits for bites. The commonly used criterion for an abnormal bite (amplitude greater than or equal to 0.1 mV and duration greater than or equal to 10 msec in the horizontal or sagittal plane) results in a specificity of only 87%. A specificity of 95% is yielded with the criterion of bite amplitude greater than 0.15 mV in the horizontal or sagittal plane.

Adult↗
PubMed1989

An accurate exercise lead system for bicycle ergometer tests.

In order to minimize muscle noise in the exercise electrocardiogram, Mason and Likar proposed a new lead system where the limb electrodes are instead placed on the trunk. The Mason-Likar system is widely used for both the resting ECG before exercise and recordings during exercise. Several studies have, however, reported great differences between this lead system and the standard lead system. This study shows greater R wave amplitudes in leads II, aVF and III, smaller R wave amplitudes in leads aVL and I and thus a vertical shift of the frontal plane QRS axis for the Mason-Likar system compared with the standard system. For many years another lead system for exercise tests with the bicycle ergometer has been used in our laboratory. The limb electrodes are placed at the proximal part of the arms and the left iliac crest. This lead system yields ECG signals with a low level of muscle noise. The differences between this lead system and the standard ECG are much less pronounced than the differences between the Mason-Likar ECG and standard ECG. We propose our lead system for exercise tests with the bicycle ergometer.

Ankle↗
PubMed1989

On the consistency of ECG reports from two different computer-based ECG recorders.

Four consecutive computer-based ECG recordings/interpretations were made on each of 100 patients. Two of the recordings were made with the MAC II recorder (Marquette Electronics Inc., Milwaukee, USA) and two with the Cardisuny IC503FA (Fukuda M-E Kogyo Co. Ltd, Tokyo, Japan). Computer measurements of PQ interval, Q-width in III, R-amplitude in V5 and QRS axis in the frontal plane were compared between recordings, as also were diagnostic statements pertaining to the presence of atrial fibrillation and myocardial infarction. The MAC II was found to be more consistent than the Cardisuny as regards the measurements. There was a tendency that the MAC II was more specific than the Cardisuny and the Cardisuny more sensitive than the MAC II. The MAC II gave no false positive reports of atrial fibrillation and only one false positive report of myocardial infarction.

Atrial Fibrillation↗