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Biomedical subjects

O Pahlm

Publications and source records attributed to O Pahlm.

At least 19 recordsLinked to original sources
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

Performance of the automated complete Selvester QRS scoring system in normal subjects and patients with single and multiple myocardial infarctions.

The automated version of the complete Selvester QRS scoring system for estimation of myocardial infarct size was evaluated in 1,344 normal subjects, 706 patients with a single myocardial infarction (366 with inferior infarction, 277 with anterior infarction and 63 with posterolateral infarction) and 131 patients with combined inferior and anterior infarction. The presence and location were determined by angiographic and ventriculographic criteria. The performance of the overall 32-point system, each of the 19 criteria and the 13 criteria sets and each of the 35 criteria within the 13 sets was examined. The mean point scores were 1.7 for normal subjects, 3.7 for posterolateral infarction, 4.1 for inferior infarction, 6.3 for anterior infarction and 6.9 for multiple infarcts. A score greater than 4 yielded a sensitivity of 67% for anterior infarction, 41% for inferior infarction, 32% for posterolateral infarction and 72% for multiple infarcts. However, 7 of 32 criteria failed to achieve 95% specificity and 10 of 35 criteria in criteria sets had a sensitivity that was even lower than their false positive rate. The automated Selvester QRS scoring system currently has limitations that are attributable to development of the original system, which used manual scoring techniques and established criteria limits from middle-aged men. Future automated analysis should use gender- and age-dependent criteria limits.

Computer Simulation↗
PubMed1991

Specificity and sensitivity of QRS criteria for diagnosis of single and multiple myocardial infarcts.

A subset of 3 criteria from the complete Selvester scoring system has been proposed earlier for electrocardiographic screening of healed myocardial infarcts. This subset yielded 95% specificity and high sensitivity for single anterior and inferior infarcts. In the present study, an automated version of these criteria was applied to 1,344 electrocardiograms from normal subjects (473 normal subjects as determined by cardiac catheterization and 871 apparently normal subjects by history and physical examination), to 706 from subjects with single myocardial infarction, and to 131 from subjects with combined anterior and inferior myocardial infarcts. Of the single infarcts, 366 had inferior, 277 anterior and 63 posterolateral locations. Presence and location of infarcts were judged from left ventriculograms and coronary angiograms. Overall specificity was only 86%, whereas overall sensitivity for the infarct population was 77%. Specificity was lower in men than in women; it was also lower in older than in younger subjects. One of the screening criteria (R greater than or equal to 40 ms in V1) may possibly be eliminated to augment specificity; this can be done with only minor loss of sensitivity. Differences in wave form measurements between the manual and computer methods account for a large part of the deterioration of specificity in this study compared with previously published results. Computer application of the screening criteria requires altered criteria limits in comparison with those used in manual application. Probably sex- and age-dependent criteria limits should be used.

Age Factors↗
PubMed1990

Limb leads of the electrocardiogram: sequencing revisited.

The six limb leads are normally presented in a format the logic of which is traditional rather than anatomical and does not allow visual interpolation such as is customary with the six chest leads. The sequence: a VL, I, -aVR, II, aVF, III was suggested years ago, and is used in some European countries, particularly Sweden. It provides a better impression of the extent of the changes of inferior infarction and makes the rather neglected lead aVR much more useful, though reversed in polarity. It also provides a more direct indication of the electrical axis, and simplifies comparisons with the frontal plane vectorcardiogram. Because modern digital electrocardiographs can provide the sequenced format, this seems a good time to review the advantages of adopting it.

Electrocardiography↗
PubMed1990

Decision rules for the ECG diagnosis of inferior myocardial infarction.

ECG measurements from 341 patients with inferior myocardial infarction (IMI) and 327 normal subjects were used to develop and test decision rules for the ECG diagnosis of IMI. Recursive partitioning provided a simple decision rule with 75% sensitivity and 97% specificity, using Q amplitude and Q duration in a VF, Q duration in III, and T-wave axis in the frontal plane as decision variables. Dropping T-wave axis from the decision rule led to a 10% decrease in sensitivity. Multiple logistic regression provided sensitivities and specificities which were similar to those for recursive partitioning. Both methods outperformed traditional noncontour criteria for IMI.

Adult↗
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↗
PubMed1990

ST changes in relation to heart rate during bicycle exercise in patients with coronary artery disease.

Exercise test on cycle ergometer and coronary angiography were performed on 190 patients with chest pain. Volunteers with a normal thallium scintigraphy (n = 47) served as controls. The load started at 20 W and increased at a rate of 10 W min-1 until exhaustion or symptoms. Conventional 12-lead ECGs were recorded by means of computer before, during and after exercise. Minimum ST amplitude 60 ms after the STJ point (ST60) at end of work with a cut-off level of -1.10 mm had a sensitivity of 69% (52/75) and a specificity of 89% (37/42) when individuals with a normal resting ECG were considered. ST80 and sum of ST60 in left ventricular leads had slightly lower values of sensitivity and specificity. Changes in ST60 during exercise discriminated less well between the groups. Final heart rate during exercise (less than 148 min-1) had a sensitivity of 88% (53/60) and a specificity of 89% (42/47). The change in heart rate during exercise (less than 66 min-1) had a sensitivity of 50/60 (only patients without beta-blockers were considered). The best discrimination was obtained by defining a test score (TS) according to the linear equation TS = 2.95-0.23 x HRE-0.301 X ST60 where a positive value indicates a positive test and a negative value a negative test. Sensitivity and specificity were 21/23 (91%) and 40/42 (95%), respectively. The test score was also calculated in those patients having significant coronary disease and an abnormal resting ECG (no bundle branch block, no beta-blockers) and this yielded a sensitivity of 30/34.

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↗
PubMed1988

Quantitative evaluation of tomographic 201-thallium myocardial scintigraphy.

Myocardial 201Tl emission computed tomography was performed on 25 normal subjects and 27 patients with angiographically significant coronary artery disease. A semi-automatic computer program was designed to define the left ventricular myocardial volume in all short axis sections. Within this volume the relative mean myocardial pixel count was calculated. This parameter was found to separate the 2 patient groups with a sensitivity of at least 81% at a specificity of 100%.

Adult↗
PubMed1988

Bedside serial comparison of electrocardiograms.

A unique method for serial comparison of electrocardiograms is introduced. A Siemens 440 or 740 electrocardiograph can be linked directly to a central minicomputer system, from which serial data for up to three previously recorded ECGs from the same patient can be retrieved and transferred back to the ECG machine. Serial comparison logic has been incorporated into the diagnostic program inside the 440 and 740 so that immediate serial comparison can be undertaken at the bedside or in the clinic.

Computers↗
PubMed1988

Vectorcardiogram synthesized from a 12-lead ECG: superiority of the inverse Dower matrix.

Vectorcardiographic (VCG) criteria for the diagnosis of, for example, myocardial infarction and right ventricular hypertrophy, are superior to the corresponding 12-lead ECG criteria. Contour and rotation of the QRS loops are important parts of these VCG criteria that have no direct counterpart in the 12-lead ECG. Therefore, attempts have been made to synthesize VCGs from 12-lead ECGs for diagnostic purposes. Visual comparison of QRS loops from the Frank VCG and three different synthesized VCGs was made by three independent observers to determine which method produces the most Frank-like QRS loops. The inverse transformation matrix of Dower proved to be the best method of synthesis. Normal limits for some clinically important measurements in VCG interpretation were calculated for this synthesis method and the Frank VCG.

Adult↗
PubMed1988

Visceral improvement following combined plasmapheresis and immunosuppressive drug therapy in progressive systemic sclerosis.

In a two-year prospective therapeutic trial, 15 patients with progressive systemic sclerosis (PSS) were treated with immunosuppressive drug therapy with or without long-term plasmapheresis. Before the trial all patients had severe involvement of either the esophagus, lungs or kidneys. One patient died of renal failure and another 2 patients withdrew unimproved. In the remaining 12 patients, objective improvement occurred in all but one. The degree and extent of skin involvement decreased significantly (p less than 0.01). Cineradiography revealed increased esophageal motility in 4 patients. Pulmonary function measured as total lung capacity and static lung compliance improved (p less than 0.01). In 4 patients the number of premature atrial or ventricular contractions at 24 h ECG monitoring decreased, as did the concentrations of immunoglobulins and ANA titres in serum. Although it could not be ascertained whether the clinical improvement was associated with combined therapy or immunosuppressive drug treatment alone, our results suggest that immunosuppressive therapy is beneficial in advanced PSS.

Adult↗