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Biomedical subjects

P M Rautaharju

Publications and source records attributed to P M Rautaharju.

15 recordsLinked to original sources
PubMed1979

Evolution of QRS-T relationship from birth to adolescence in Frank-lead orthogonal electrocardiograms of 1492 normal children.

Patterns of evolution of QRS-T relationship were investigated by determining statistical distributions of QRS and STT integral vectors and the ventricular gradient vector in 1492 normal children divided into 12 age groups from birth to the age of 16 years. From birth to the age of 4 days, the ventricular gradient vector shifts posteriorly and to the left due to posterior shift of the STT integral vector and an increase in the spatial angle between QRS and STT integral vectors to a mean value of 103 degrees. These early neonatal changes in QRS-T relationship probably reflect the sudden reduction of hemodynamic load and the subsequent postnatal atrophy of the right ventricle while the left ventricular load slowly increases. The magnitude of the ventricular gradient vector increases from age 3 weeks until about 7 years. The increase appears to be related to a gradual increase in the magnitude of the QRS and STT integral vectors and a drastic decrease in the spatial angle between them. The spatial angle between QRS and STT integral vectors reaches it minimum (22 degrees) in the age group 1.5--4.5 years, suggesting that at that age the average direction of ventricular excitation and repolarization wavefronts are nearly opposite to each other. In addition to the shifting balance between the left and right ventricular hemodynamic load, other factors, such as the maturation of the sympathetic nervous system, may be important in determining spatial gradients in the duration of action potentials, thus influencing the relationship between ventricular excitation and repolarization.

Action Potentials↗
PubMed1978

Changing electrocardiographic recording technology and diagnostic accuracy of myocardial infarction criteria. Improved standards for evaluation of ECG measurement precision.

An analytical study was performed to estimate the magnitude of the visual Q wave duration bias produced by pressurized ink round stylus electrocardiographic (ECG) recorders. With a paper speed of 25 mm/sec and the ECG tracing width of 0.25 mm, the visually measured Q waves are on the average 8 msec too short. The corresponding error with the older type flat stylus recorder is less than 2 msec. Considerable differences can thus be anticipated in the frequency of observed ECG abnormalities in studies which use different types of electrocardiographs. The effect of the visual Q wave duration measurement bias on the diagnostic ECG classification was investigated in a group of 237 patients with old myocardial infarction and 299 subjects with no clinical evidence of infarction. An 8 msec measurement bias toward too short Q wave duration was observed to result in a potential loss of diagnostic accuracy of about 25% in some ECG coding categories. As a corrective procedure, it is recommended that the baseline width produced by a round recording stylus of uniform thickness irrespective of the vertical deflection velocity should be less.

Diagnosis, Computer-Assisted↗
PubMed1978

Use and abuse of electrocardiographic classification systems in epidemiologic studies.

An analytical study is performed to examine the utility of the Minnesota Code ECG classification for estimation of the prevalence and incidence of coronary and hypertensive heart disease. A statistical model is introduced which permits comparative analysis of the contribution of human coding errors to the overall fraction of misclassified records. It is demonstrated that the poor sensitivity and visual coding variability can seriously limit the usefulness and obscure the meaning of ECG coding results if the disease prevalence or annual event incidence is low. Gross over- or underestimation of prevalence and incidence data takes place frequently. Occasionally, reasonably good estimates are made on the basis of false evidence, for instance when false classifications 'compensate' for a high miss rate. Visual classification errors may contribute a substantial fraction to the overall misclassifications. It is pointed out that the traditional method of estimating classification errors by repeated coding of a given set of records gives a false impression of coding reliability. It is concluded that a substantial reduction of coding variation and an overall improvement of diagnostic accuracy will be required in order to justify continued use of ECG classification in population studies.

Computers↗
PubMed1978

The impact of computers on electrocardiography.

The development of the electrocardiograph was the culmination of a scientific effort aimed at perfection of a device conceived for the elucidation of a physiologic phenomenon. The development of the digital computer was the culmination of a scientific effort aimed at perfection of warfare. Both of these fairly recent innovations of modern technology have been moderately successful in their initial objectives. Electrocardiography has had a profound influence on the practice of medicine. On the global scene, computers have so far had an insignificant influence on the practice of electrocardiography. In North America, however, computer interpretation of ECGs has already made a modest impact, perhaps more in terms of commercial gains rather than producing a substantial benefits to health care. The introduction of computers into clinical electrocardiography has not resulted in any widespread application of improved diagnostic criteria. The automation of ECG interpretation has not resulted in reduction of the cost of health care, on the contrary, in general it has increased the cost. Perhaps the most dismal failure has been the negligible use of computers in epidemiologic studies and heart disease prevention efforts. Palmistry, astrology, the art of palpation of the pulse, auscultation and acupuncture have had a more profound influence on the practice of medicine than computer analysis of the electrocardiogram. On the positive side, one of the beneficial effects of the use of computers has been the increasing awareness of the limited diagnostic accuracy of currently used ECG criteria, and the recognition of the fact that a substantial improvement is warranted; if such improvement can not be achieved in the foreseeable future, electrocardiography will lose much of its current clinical utility. Computers have had a profound influence on research in electrocardiology, and although a very few tangible concrete results have thus far diffused into clinical electrocardiography, their impact can be expected during the last two decades of this century. Computers will produce at least containment of costs if not actual net cost reduction in clinical electrocardiography. Computer analysis will rapidly antiquate the present primitive visual ECG classification in epidemiologic studies and clinical heart disease intervention trials. Computer analysis will enhance the diagnostic accuracy of the electrocardiogram. However, a radical departure from the current ECG display and interpretation practice will be mandatory before any substantial breakthrough can be materialized. All these anticipated evolutionary and perhaps even revolutionary changes will require a continuing intensive research effort, a change in the professional attitude of practicing electrocardiographers and a considerable effort in professional education. Finally, the elucidation and exploration of the full diagnostic and predictive value of the ECG remains the challenge of first magnitude in electrocardiography...

Adult↗
PubMed1976

The concepts of sensitivity, specificity and accuracy in evaluation of electrocardiographic, vectorcardiographic and polarcardiographic criteria.

The concepts sensitivity and specificity are critically evaluated in the light of case studies drawn from electrocardiographic literature. These terms are often misused, and the meaning of these elementary statistical concepts is often misunderstood in studies on ECG, VCG and PCG criteria. Specificity figures reported in literature commonly refer to the fraction of true negatives with a negative test in normals. Limiting the test to two-group analysis and eliminating other disease categories tend to give overoptimistic values for specificity and diagnostic accuracy in general. It is pointed out that various performance indices for diagnostic accuracy depend heavily on the composition of the test groups and the fraction of test cases in each group. Sensitivity and specificity appear inadequate performance indices for evaluation of event detection schemes such as classification of ectopic beats. Alternative performance indices are considered, including the error ratio, association index, accuracy of positive test, accuracy of negative test, and overall diagnostic accuracy. Increased utilization of simple statistical tests for significance estimation in ECG criteria evaluation is suggested. The development and application of better diagnostic performance evaluation schemes based on concepts of cost of misclassification, entropy and information is encouraged.

Arrhythmias, Cardiac↗