Computer model study of electrocardiologic manifestations in asymmetric left ventricular hypertrophy.

Electrocardiologic criteria of left ventricular enlargement do not take into consideration the eventuality of asymmetric hypertrophy. Since experimental techniques for production of this condition are not available, computer modeling was utilized to study its electrocardiologic manifestations. A computer model of human ventricles with analytically defined geometry, consisting of 142,000 elements (1.

Effect of different sources of ventricular repolarization heterogeneity on the resultant cardiac vectors. A model study.

The computer model of ventricular activation was used to study the effects of eventual differences in the repolarization pattern between the right and the left ventricle, as well as between the apical and the basal parts of the ventricles. All changes in model action potential durations (APDs) were performed in the range corresponding to the APD variability measured in myocytes. The vectorcar-diographical spatial T loop was very sensitive on the changes in the right to left ventricular gradient of APD, while the similar changes in the apico-basal gradient of APD influenced the T loop minimally.

Comparative dipolar electrocardiotopographic study of ventricular activation in Macaca mulatta monkeys and man.

Electrocardiographic correlates of ventricular activation sequence were studied in 22 Macaca mulatta monkeys, aged 1-18 years, and 145 human subjects, aged 11-72 years, using the corrected orthogonal lead system of McFee-Parungao and the dipolar electrocardiotopographic (DECARTO) data presentation, where the time series of instantaneous spatial vectors are converted into time series of areas of activation on a spherical image surface enveloping the heart. Macaques had shorter ventricular activation time (61+/-11 vs. 97+/-11 ms) that could not be explained exclusively by their higher heart rate.

[Orthogonal electrocardiography].

The orthogonal electrocardiography was a further development of Einthovens conception of electrocardiography. It eliminates the redundancy of the 12-lead ECG and offers a more precise and illustrative image of the model of an equivalent dipole. It was the prerequisite of the development of vectorcardiography.

Normal variability of the peak-to-trough amplitude of isointegral QRST body surface maps.

The peak-to-trough amplitude (sum of absolute values of maximum and minimum) of an isointegral QRST body surface map was shown, according to literary data, to be sensitive to changes in ventricular sympathetic tone. Statistics of this parameter were obtained, with an 80 electrodes array, in 135 healthy subjects of both sexes, aged from 10 to 67 years (37 +/- 16). The QRST amplitudes were smaller in females than in males in average by 28% (P < .

Quantitative characterization of the relief of body surface potential distribution.

The body surface distribution of the cardiac electric field is best represented as reliefs of positive and negative potentials, or their time integrals. The objective of this study was to design a methodology of their quantitative evaluation. QRST isointegral maps were obtained from 45 healthy subjects (35 men, 10 women, aged 10-67 years) using a 80 electrode set.

Modelling developmental changes of human cardiac electric field in early postnatal period.

In early postnatal life, human cardiac electric field undergoes dramatic changes resulting from the adaptation of the heart to new hemodynamic conditions. For the study of the effect of changes in ventricular geometry as well as in spatial orientation of the heart occurring in this period of life, on the resultant heart vectors, our computer model of propagated activation was used. This model allows to change both mentioned characteristics of ventricles so that they reflect the developmental changes in the human heart.

The role of anthropometry in the assessment of vectorcardiographic norms.

There is scarcity of quantitative studies on the relationship between somatometric characteristics of chest configuration and vectorcardiographic variables. The objective of this study was to give a quantitative description of these relations in order to improve the recognition of normal vectorcardiographic ranges and limits. The magnitude of the maximum vector of atrial depolarization is strongly influenced by chest configuration, but not by age, while declination values of atrial activation are under the influence of both factors.

Role of left ventricular geometry in the alteration of initial QRS vectors due to concentric ventricular hypertrophy.

The relation between serial magnitudes of instantaneous spatial vectors, obtained throughout ventricular depolarization, and echocardiographically estimated left ventricular (LV) mass was investigated in 64 patients with congenital aortic stenosis and in 16 patients with coarctation of the aorta. While the correlation was positive between LV mass and vector magnitudes at 50 and 60 ms after QRS onset (r = .530 and .

Computer simulation of propagated activation in different types of left ventricular enlargement.

An increase of the left ventricular mass does not always have an unambiguous effect on the electro- or vectorcardiographic image of ventricular activation. To analyse this phenomenon, three types of left ventricular enlargement were simulated by a computer model of propagated activation in cardiac ventricles. These were obtained from the reference (normal) left ventricle by an increase of its wall thickness either centripetally or centrifugally, as well as by increase of the ventricular cavity dimensions (dilatation).

Dipolar electrocardiotopographic evaluation of ventricular activation in patients with various degrees of coronary artery disease.

Dipolar electrocardiotopographic imaging of instantaneous vectorcardiographic QRS vectors represents the ventricular activation front as a bounded area on the spherical image surface. Fuzzy set treatment of the elements of this area allows for the recognition of five classes of ventricular activation: I, abnormal; II, abnormal with normal component; III, normal with abnormal component; IV, marginally normal; and V, normal. In a group of 71 patients with chest pain and various degrees of coronary artery stenosis classes II, III, and IV were most frequently observed in patients with one- or two-vessel disease.

Problems and perspectives of mapping the cardiac electric field.

The cardiac electrical field is important not only because of its diagnostic significance, but also as a biological and biophysical phenomenon. As such, it has become a research target of biologists, biophysicists and biomathematicians. It has also been an impetus for constructing more and more sophisticated measuring devices.

[Vectorcardiography of variations in localization of specific conduction systems in the left ventricle].

A realistic computer model of propagation of ventricular activation was used to study the effects of varying the position of specific conduction system terminations in the left ventricle and the septum, representing the sites of initial activation, on the resulting simulated spatial heart vectors. Three differently localized foci of initial activation, each of them represented by one model element, were considered: in the central part of the left septal surface, posteriorly at about one third of the distance from the apex to the base, and in the upper part of the anterior free wall. During the model experiments, the positions of the initial activation were shifted +/- 5 model units (ca 5 mm) in the vertical and lateral direction either separately or in different mutual combinations.

[Vectorcardiographic features of right ventricular dilatation].

Axial McFee-Parungao lead system vectorcardiograms were obtained in 55 patients with type atrial septal defect, aged 3-24 years, prior to and in average 3 years after surgical repair of the defect. Changes of the QRS loop observed after intervention led to the conclusion that the vectorcardiographic signs of right ventricular dilatation consist of a rightward shift of the posteriorly orientated horizontal plane vectors at 50-70 ms of QRS, decrease of the magnitude of vectors around the 40th ms, no changes in the magnitude and orientation of the initial (10-30 ms) QRS vectors as well abnormal departures of the spatial VCG loop from its preferential plane even in the absence of other signs of right ventricular conduction impairment. The above abnormalities vanished after normalization of hemodynamics.

[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.

[Vectorcardiographic and chronotopocardiographic study of septal hypoperfusion].

The study has been carried out in 73 patients (63 men and 10 women), aged between 22 and 59 years, suffering from angina pectoris. The localization in space of the extremities of the initial QRS vectors (10 and 20 ms) is an indicator which is relatively very sensitive to the disturbance in the myocardial irrigation in the regions around the septum and the adjacent ventricular wall. A good relationship has been found namely with the data obtained with thallium scintigraphy after effort.

[Comparison of echocardiography, vectorcardiography, electrocardiography, coronarography and ventriculography in coronary heart disease].

Fifty patients (9 women, 41 men) with angina pectoris, aged from 22 to 59 years, were examined by means of one- and two-dimensional echocardiography (ECHO), vectorcardiography (VCG) using the McFee-Parungao system of leads, standard 12 lead electrocardiography (ECG), coronarography (CAG), and ventriculography (VG). I of isolated positivity of either of these methods ans considererl as patse positivity and presence or absence of positivity in combination of at least two methods (ECG exeluted) astme positivity, or true negativity then VCG was found to have the highest sensitivity (96%), negative predictive value (80%), as well as the highest overall predictivity (83%), while ECHO had the lowest values, i.e.

Chronotopocardiography: a new method for presentation of orthogonal electrocardiograms and vectorcardiograms.

A mathematical model was developed to express and visualize signals from 3 orthogonal ECG (vectorcardiographic (VCG) leads as areas of activation on a spherical surface approximating to the walls of the cardiac ventricles, called the image surface. A computer program was compiled for presentation of orthogonal ECGs in the form of a series of instantaneous maps of cardiac activation, as well as chronotopocardiograms displaying the topography and the duration of activation on the image surface on two summary maps.