Abstract:
The paper presents the main principles for obtaining enhanced resolution in standard ECG records, constructing of high-resolution vectorcardiogram and determining of activities of particular segments of the cardiac muscle. Standardized electric activities of the ventricles and septum in healthy people are given. Electric activities of particular fragments of the cardiac muscle were measured by the HRVEC method for a group of healthy subjects and for people subjected to SPECT or coronarographic examination.

Introduction
In view of the high rate of ischaemia disease and the immanent danger of fatal cardiac arrest, early diagnosis and identification of patients requiring coronarography and/or surgical treatment is of great importance. As has been established the standard electrocardiogram is sometimes of dubious diagnostic worth. Literature provides descriptions of many computer methods for enhancement of resolution of various signals which thus give more information on the object of the study. Such methods are most often based on Fourier transformation, convolution and deconvolution techniques, filtration, etc. [1] One of such programs, based on the method of convolution and deconvolution, called RKU was written by us [2].

Methods and Results
This program was applied for analysis of electrocardiographic signals. The results were curves similar to standard ECG records, however, of much increased resolution of the QRS complex [3]. In order to facilitate interpretation of these high-resolution ECG signals we applied the well known method of vectorcardiography [4].The high-resolution vectorcardiogram (HRVEC) proposed in this work combines the records from particular electrodes, each of computer enhanced resolution [5]. The spatial vector loops are shown in three mutually perpendicular planes: the transverse, sagittal and frontal planes. The curve corresponds to the motion of the end of the transient vector of depolarization of the intraventicular septum as well as the left and right ventricle during a single evolution of the cardiac muscle. Gradual expansion of the excited region causes certain changes in the direction and transient resultant vectors of depolarization of ventricles. High-resolution vectorcardiogram allows viewing of the region of the depolarization wave propagation during the cardiac muscle evolution, so provides an opportunity to detect even relatively small changes in electric activity of particular segments of the cardiac muscle caused by ischaemia, hypertrophy and/or administered drugs. The amplitude of high-resolution signals was normalised so that a single simulated peak of a Gaussian curve of 20 ms in width and 1 mV amplitude had the same final amplitude of 1 mV after processing. At the subsequent step, quantitative analysis of activities of particular regions of the cardiac muscle was made. In order to perform this analysis the left and right ventricle and septum were divided into particular walls and segments to which specific directions in the orthogonal Frank lead system (Table I) were ascribed. The activity of a given region of the cardiac muscle, was calculated within the bulk angle of 600 about the directional vector of this region (directional cosines of the inferior layer: 0, 1, 0), according to the following equation:

Akty = (R) ² _* cos (R,F)

where: Akty- total electric activity of a given segment during a single cardiac muscle evolution, cos(R, F) - cosine of the angle made by the direction of the transient depolarization vector and the directional vector of a given cardiac muscle segment, R- transient depolarization vector in 1mV, F- directional vector of a given cardiac muscle segment (Table 1). The activity defined as above is measured in mV2. The aim of the first series of measurements was to establish criteria of a correct high-resolution vectorcardiogram on the basis of standards of activity of particular cardiac muscle segments of healthy people (Table 2). All those people were subjected to clinical, radiological and echocar-diographic examinations which gave no indication of coronary artery disease, systemic hypertension or any cardiac muscle defect. ECG of these people gave a correct picture.

The specificity and sensitivity of the HRVEC method as well as the positive predictive values (PPV) and negative predictive values (NPV), were determined. A similarly good correlation was obtained between the results of SPECT examination and the decrease in electric activity of particular fragments of the cardiac muscle observed by the HRVEC method (Table 4).

In the attempt at verifying the HRVEC method by the results of SPECT, the indeterminate value of specificity and negative predictive value (NPV) of the former are the consequence of a small number of subjects qualified as healthy by the two latter methods.

Conclusions
Preliminary analysis of the sensitivity and specificity of hig-resolution vectorcardiogram in IHD diagnostics has proved the method much promising in the diagnostic of ischaemic disease.