[Contribution of the evidence-based medicine to the solution of some problems in electrocardiography]

The paper summarizes the author's view on the possibilities to use the principles of evidence-based medicine for the re-evaluation of classical hypotheses and formulation of new hypotheses in electrocardiology. Electrocardiographic diagnostics of the left ventricular hypertrophy based on the voltage criteria, which is known to suffer by high number of so-called false negative results and low sensitivity, is shown as an example. An alternative approach is presented, based on the acceptation of these so-called false negative results as true results, reflecting changes in electrical properties of myocardium due to electrophysiological remodeling in left ventricular hypertrophy. In this context a new parameter is introduced for the quantification of the relative voltage deficit--the specific potential of myocardium. Results of experimental and clinical studies supporting the new paradigm are presented.

[Three-dimensional presentation of the electrocardiogram: new possibilities in comparative studies using cardiologic imaging methods]

The aim of the study was to demonstrate a biomathematical model for the topographic presentation of orthogonal electrocardiogram DECARTO, to present the possibilities for visualisation and processing of ECG in relation to others cardiological imaging methods. In DECARTO (Dipolar ElectroCARdioTOpography), the orthogonal ECG is used as an input signal, the signal is processed by the means of a biomathematical model and presented as areas of activated points on a spherical surface closely surrounding the heart, so-called decartograms. Decartograms can be visualised using the projection of the spherical image surface onto geometrically defined planar or 3D surfaces. The selection of the surface depends on the purpose of ECG imaging, on the evaluation of advantages and limitation of the particular possibilities, such as the degree of deformation, and their comparability with other imaging methods. Another possibility of 3D visualisation of decartograms is the utilisation of time as a 3rd dimension of the space. Additionally to analytically defined geometrical surfaces, it is possible to project decartograms onto a real surface of the heart, constructed from data of other image techniques. In this paper we present a superposition of decartogram and SPECT imaging, which combines graphic presentation of two diagnostic methods providing different but complementary information on the heart. The combination of comparable information allows to study the relationship between electrogenesis and perfusion of myocardium and its metabolism, to study diagnostic and prognostic importance of both agreements and disagreements of used methods. The fusion of information on the structure and function of the heart could potentially increase the diagnostic power of both methods.

[Role of orthogonal electrocardiography and vectorcardiography in a paradigm shift in diagnosis of left ventricular hypertrophy]

A new contingency approach to the ECG diagnostics of left ventricular hypertrophy, its theoretical background, and first results of experimental and clinical studies are presented. This approach considers false negative ECG results as a consequence of the relative voltage deficit and introduces a new parameter: the specific potential of myocardium. As well it considers nonlinear changes of non-spatial determinants with respect to the stage and progression of left ventricular hypertrophy. The potential advantages of the concept of the specific potential of myocardium can be summarized as follows: (1) It utilizes equally both electrocardiographic and echocardiographic information, without stressing the priority or neglecting any of particular methods and creates a broader basis for the clinical diagnosis of left ventricular hypertrophy, (2) It utilizes also the false negative ECG results for diagnostics and quantifies the relative voltage deficit.

[Cardiopathies of unknown origin--a cooperative interdisciplinary study]

The authors described aim. objectives, design and criteria of the study which is oriented to the clinical and research problems of heart diseases of uncertain origin. The paper presents the preliminary experience with invasive cardiological techniques in this field. At the same time the authors discuss the potential impact of the basic research on the prevention and effective treatment of cardiopathy which is until now of unknown origin.

Methodological issues in studies of air pollution and daily counts of deaths or hospital admissions

STUDY OBJECTIVE

To review the issues and methodologies in epidemiologic time series studies of daily counts of mortality and hospital admissions and illustrate some of the methodologies.

DESIGN

This is a review paper with an example drawn from hospital admissions of the elderly in Cleveland, Ohio, USA.

MAIN RESULTS

The central issue is control for seasonality. Both over and under control are possible, and the use of diagnostics, including plots, is necessary. Weather dependence is probably non-linear, and adequate methods are necessary to adjust for this. In Cleveland, the use of categorical variables for weather and sinusoidal terms for filtering season are illustrated. After control for season, weather, and day of the week effects, hospital admission of persons aged 65 and older in Cleveland for respiratory illness was associated with ozone (RR = 1.09, 95% CI 1.02, 1.16) and particulates (PM10 (RR = 1.12, 95% CI 1.01, 1.24), and marginally associated with sulphur dioxide (SO2) (RR = 1.03, 95% CI = 0.99, 1.06). All of the relative risks are for a 100 micrograms/m3 increase in the pollutant.

CONCLUSIONS

Several adequate methods exist to control for weather and seasonality while examining the associations between air pollution and daily counts of mortality and morbidity. In each case, care and judgement are required.

The association between air pollution and the daily number of deaths: findings from the Slovak Republic contribution to the APHEA project

STUDY OBJECTIVE

To analyse the short term relation between daily air pollutant values and the daily number of deaths in Bratislava, Slovak Republic, during the study period 1987-91.

DESIGN

This follows the APHEA protocol. The association between the daily number of total and cause specific deaths and daily variations in ambient air levels of sulphur dioxide (SO2) and total suspended particulates (TSP) were analysed using Poisson regression that allowed control for meterological data and variables that handle temporal and autoregressive patterns.

SETTING

Bratislava is the capital town of Slovakia, the total population was 442,999 according to 1991 census data. The dominant sources of industrial air pollution are the chemical industry and oil refinery.

MAIN RESULTS AND CONCLUSIONS

After adjustment for season, temperature and relative humidity, days of week and holidays, secular trends, and autoregressive patterns no significant associations were found between the daily variations in the air pollutants, SO2-24 h and TSP-24 h, and total mortality (RR 0.978, 95% CI 0.96, 0.99; RR 1.008, 95% CI 0.96, 0.99) and cause specific mortality in Bratislava during the study period.

Short term effects of air pollution on health: a European approach using epidemiologic time series data: the APHEA protocol

BACKGROUND AND OBJECTIVES

Results from several studies over the past five years have shown that the current levels of pollutants in Europe and North America have adverse short term effects on health. The APHEA project aims to quantifying these in Europe, using standardised methodology. The project protocol and analytical methodology are presented here.

DESIGN

Daily time series data were gathered for several air pollutants (sulphur dioxide; particulate matter, measured as total particles or as the particle fraction with an aerodynamic diameter smaller than a certain cut off, or as black smoke; nitrogen dioxide; and ozone) and health outcomes (the total and cause specific number of deaths and emergency hospital admissions). The data included fulfilled the quality criteria set by the APHEA protocol.

SETTING

Fifteen European cities from 10 different countries with a total population over 25 million.

METHODOLOGY

The APHEA collaborative group decided on a specific methodological procedure to control for confounding effects and evaluate the hypothesis. At the same time there was sufficient flexibility to allow local characteristics to be taken into account. The procedure included modelling of all potential confounding factors (that is, seasonal and long term patterns, meteorological factors, day of the week, holidays, and other unusual events), choosing the "best" air pollution models, and applying diagnostic tools to check the adequacy of the models. The final analysis used autoregressive Poisson models allowing for overdispersion. Effects were reported as relative risks contrasting defined increases in the corresponding pollutant levels. Each participating group applied the analyses to their own data.

CONCLUSIONS

This methodology enabled results from many different European settings to be considered collectively. It represented the best available compromise between feasibility, comparability, and local adaptibility when using aggregated time series data not originally collected for the purpose of epidemiological studies.

Frank electrocardiograms

Frank electrocardiograms were recorded in 426 schoolchildren (225 girls, 201 boys) aged 10 to 14 years, planar vectorcardiograms projected onto the horizontal and left sagittal planes were constructed. Spatial magnitude of instantaneous QRS vector end-points in 10 ms intervals of QRS duration, and of maximum QRS vector, as well as X, Y, Z coordinates of instantaneous QRS vector end-points in 10 ms intervals of QRS duration, and of the maximum QRS vector were analyzed in relation to weight, height and BMI. The initial part of VCG loop was not influenced by age and anthropometric parameters, respectively. The spatial QRS vector magnitude at the 30 ms of QRS decreased significantly with age and height. From the 40 ms of QRS duration the VCG parameters were significantly related to anthropometric parameters. Vectorcardiographic parameters were more influenced by the anthropometric parameters then by age.

[Reference values of QRS-complex amplitude parameters in computer evaluation of Frank's orthogonal electrocardiogram]

In 123 healthy subjects (54 women and 69 men) in the age range from 7 to 72 years the x, y, z coordinates were determined along with the magnitude of instantaneous spatial QRS vectors of the orthogonal electrocardiogram according to Frank, and that in 10 ms intervals from the beginning of the QRS complex and eighths of the duration of QRS. The values of these parameters were computed by means of Pipberger's VAH program implemented in the computer SM3-20. The results are presented as means, standard error of means, median, interpercentile interval (2 to 98 percentile) and confidence intervals.

[Reference values of dipolar electrocardiotopography of the QRS complex]

Reference values of dipolar electrocardiotopogram of ventricular depolarization are presented. The data for establishing reference values in the McFee-Parungao lead system were obtained by manual processing of 145 records of healthy subjects (64 women, 81 men) in the age range of 11-72 years, and for the Frank lead system by automatic processing of 123 records of healthy subjects (54 women, 69 men) aged from 9 to 72 years. The obtained values of the X, Y, Z coordinates of the end points of QRS instantaneous vectors recorded at 10 ms intervals were processed by means of a biomathematical model in the form of activation areas on the spherical image surface. Electrocardiotopograms were represented in the form of discrete spherical image surface in the shape of a rectangle (11 lines, 24 columns). For each point of this matrix the value of relative frequency (probability) of its occurrence in activated state in the healthy population is given.

[Agreement analysis of the results of examinations performed by a physician and automated results in the preventive care system]

The authors elaborated an automated preventive system and examined by means of it 1000 probands with regard to the incidence of cardiovascular and bronchopulmonary diseases and analyzed the results. In the submitted paper they present the results of an analysis of agreement of conclusions of examination made in the traditional way by the doctor and those obtained in the automated diagnostic preventive system. Agreement in the sense of a positive statement (presence of disease) was recorded in 54.1%, agreement in the sense of a negative finding (disease not detected) was recorded in 28.7%. Falsely negative conclusions (the doctor detected the disease, the system did not) were found in 5.6% and falsely positive conclusions (the doctor did not detect the disease, the system did) were found in 11.6% of the patients. The calculated sensitivity of the system is 0.90 and the specificity 0.72.