New approaches to the diagnosis of left and right ventricular hypertrophy by means of dipolar electrocardiotopography.

OBJECTIVE: The aim of this work was to describe a new approach to noninvasive differential diagnosis of left and right ventricular hypertrophies (LVH and RVH) caused by the arterial or lung hypertensions. METHODS: The vectorcardiographic measurements were analyzed by means of dipolar electrocardiotopography (DECARTO) technique based upon a simplified spherical model of the heart. The characteristics of LVH and RVH are obtained from the decartograms of activation duration. The integral indices of hypertrophy for the left ventricle and right ventricle (ILVH and IRVH) are formulated on the basis of the surface integrals of activation duration calculated over the regions where left and right ventricles are projected. The diagnostic decision is made through the comparison of ILVH and IRVH with specified threshold values. For comparison, the sums of wave amplitudes used in the orthogonal vectorcardiography, Rx+Sz for LVH and Rz+Sx for RVH, were also considered. RESULTS: The study included 141 males and 191 females aged 45+/-15 years, with reliably verified state of the heart, in particular, 143 persons without hypertrophy, 129 persons with LVH, and 60 persons with RVH. The ROC curves for criteria under study were statistically analysed. As a result, the ILVH criterion is preferable to Rx+Sz with confidence level greater than 95%, and the IRVH criterion is preferable to Rz+Sx with confidence level close to 99%. CONCLUSION: The proposed DECARTO method, initially intended mainly for intelligible-pictorial visualization of vectorcardiographic data, provides also some increase of diagnostic accuracy in recognition of the left and right ventricular hypertrophies as compared to the standard electrocardiography and orthogonal vectorcardiography.

[Informative value of orthogonal electrocardiogram in the diagnosis of the left ventricular hypertrophy].

AIM: To estimate the informative value of orthogonal ECG parameters for the diagnosis of left ventricular hypertrophy (LVH). MATERIALS AND METHODS: The study comprised 142 apparently healthy individuals and 125 patients with arterial hypertension (AH) and LVH (left ventricular mass index more than 125 g/m2 for males and more than 110 g/m2 for females). Characteristic curves (ROC curves) were used to describe and compare the informative value of vectorcardiographic, demapping criteria for L VH with the informavalue of the Sokolov-Lyons criterion, the Cornelian index, and the Cornelian product. RESULTS: The informative indices of orthogonal ECG were Rx + Sz and IADIM: the area under the ROC curve was 0.89 +/- 0.02 and 0.88 +/- 0.02, respectively, which was significantly higher than with the Sokolov-Lyons criterion (0.64 +/- 0.04; p < 0.05) and similar to the Cornelian product (0.84 +/- 0.03). Of great informative value is the angle phi (area under the ROC curve was 0.88 +/- 0.04) in males and the area of QRS loop in the horizontal plane (area under the ROC curve was 0.89 +/- 0.03) in females. With 96% specificity, the male sensitivity of IADIM was 80%, Rx + Sz--73%, which was significantly higher than that of the Cornelian index (56%; p < 0.05) and the Sokolov-Lyons criterion (27%; p < 0.05). With 96% specificity, the female sensitivity of IADIM was 73%, Rx + Sz--84%, SQRSxz--70%, which was significantly higher than that of the Cornelian index (49%; p < 0.05), the Cornelian product (55%; p < 0.05), and the Sokolov-Lyons criterion (30%; p < 0.05). CONCLUSION: The threshold values of the most informative indices of orthogonal ECG are presented, which could provide the optimum sensitivity-specificity ratios. These values allow cardiac lesions to be detected in hypertensive patients with normal 12-lead ECG.

The effect of psychoemotional load on ventricular repolarization reflected in integral body surface potential maps.

The aim of the present study was to investigate the reflection of psychoemotional stress in the body surface potential distribution as documented by isointegral maps of cardiac activation and recovery. In 72 young men (18.3+/- 7.3 y.) with no cardiovascular history body surface potential maps (BSPMs) at rest and during the test of mental arithmetic were recorded. The digitalized data for each point of the QRS, STT and QRST integral maps, for each subject in both situations, were processed and evaluated by methods of univariate as well as spatial mathematical and statistical modeling. The results showed during MA a significant decrease of repolarization integral values over the sternum and right precordium, which contributed to analogically localized decrements also in the QRST BSM. The decrease occurred in more than 2/3 of lead points. The most pronounced changes were observed in the right precordial area, where potentials decreased in more than in 70 % of subjects. In conclusion, the discriminative power of the difference STT and QRST integral maps was strong enough to distinguish the mental arithmetic induced changes in the superficial cardiac electric field. These adrenergic transient alterations in ventricular recovery may be of importance in subjects at risk for ventricular arrhythmias.

[New approaches to diagnosis of left ventricular hypertrophy by dipolar electrocardiography].

AIM: To show possibilities of dipolar electrocardiography (DECG) in diagnosis of left ventricular hypertrophy (LVH). MATERIAL AND METHODS: We made DECG in 151 healthy subjects and 158 hypertensive patients. To characterize DECG quantitatively, we used the integral activation duration index (IADI) calculated as a weighted sum of the areas with different duration of activation, module of the maximal vector QRS, QRSxIADI (IADIM). RESULTS: In patients with left ventricular myocardial mass index (LVMMI) under 150 g/m2, sensitivity of DECG was 38-49%, in the index over 150 g/m2 sensitivity reached 38-75%, specificity 89-98% compared to healthy examinees and 72-82% compared to hypertensive patients without LVH. The IADIM parameter correlates directly (moderate correlation) with duration of QRS complex and LVMMI. CONCLUSION: Possibilities of using parameters IADI and IADIM for assessment of electrophysiological myocardial remodeling and their correlation with other methods need further investigations.

[A method for determining the heart moving electric center on surface distributed models of the cardioelectric generator]. / Issledovanie metoda opredeleniia podvizhnogo élektricheskogo tsentra serdtsa na poverkhnostno-raspredelennykh modeliakh kardioélektricheskogo generatora.

Using mathematical models of the bioelectric generators of the heart with surface distributed configurations, it was shown that the coordinates of the moving electric center of the heart can facilitate the recognition of the global spatial position of electrogenic zones in the myocardium. These coordinates were determined by the previously proposed method from the cardioelectric potential measured noninvasively with a multichannel lead system in the framework of electrocardiographic mapping.

Changes of decartograms under gravitational acceleration and microgravity.

The Decarto technique was used to study the orthogonal ECGs recorded in 23 subjects during parabolic flights (44 records). A parameter of the instantaneous decartograms, namely the activation area (AA), which is the total area of the depolarization front projection on the image sphere, was analyzed. We compared the values of AA during the periods of horizontal flight, upward parts of all parabolas, and the initial 10 s of microgravity of all parabolas. According to the characteristics of the vectorcardiograms and AA, all subjects were subdivided into 3 groups: with increased electric activity of the right ventricle (I), the left ventricle (II) and both ventricles (III). Changes of AA with change of gravitational levels in these groups showed some differences. In groups I and II, the AA of the initial part of the QRS complex increased during microgravity and decreased during hypergravity. In group III it decreased during microgravity and changed variously during hypergravity. The AA of the middle part of the QRS complex decreased during microgravity and increased during hypergravity, and these changes were more pronounced in group III. The changes of AA in groups I and II may be explained by the Brody effect. In group III, AA seems to be influenced by some additional factors, possibly by changes in the intramyocardial or intraventricular blood volume. The AA of the last part of the QRS complex increased during microgravity and decreased during hypergravity in all groups. This may be explained by an effect of mutual neutralization of depolarization fronts related to the changes of the QRS duration.(Fig. 3, Ref. 4)

[Mobile cardiac electrical center: a new concept and mathematical modeling]. / Podvizhnyi élektricheskii tsentr serdtsa: novaia kontseptsiia i matematicheskoe modelirovanie.

A method for determination of the cardiac electric center on the basis of noninvasive multichannel measurements and multipole description of the cardioelectric potential is proposed. The method provides a more accurate and stable spatial location of the cardioelectric generator as compared to other methods (in particular, those based on minimization of the quadrupole potential). The position of the electric center is a useful characteristic for topical diagnosis of the electrophysiological state and function of the heart. Using mathematical models, the dependence of the position of the electric center, determined by the method presented, on the configuration and spatial position of the cardiogenerator is illustrated.

[Electrical and magnetic fields of the elementary bioelectric generator in the bounded anisotropic myocardium]. / Elektricheskoe i magnitnoe polia élementarnogo bioélektricheskogo generatora v anizotropnom ogranichennom miokarde.

Using the equations of electrodynamics of stationary currents, relationships were derived for calculating the characteristics of electric and magnetic fields of an elementary (dipole) bioelectric generator in a heterogeneous medium consisting of two regions namely, an anisotropic conducting region corresponding to the excitable myocardium tissue and an isotropic conducting or dielectric region corresponding to the space outside the myocardium where the measurement is made. The shape of distributions of the electric potential and magnetic induction at the myocardium surface was determined, and the effect of anisotropy on these distributions was estimate. Formulas for the identification of the local excited zone within the myocardium from electric and magnetic measurements outside the excitable tissue or on its surface were obtained.

[Electric and magnetic fields of the closed depolarization front in the anisotropic myocardium]. / Elektricheskoe i magnitnoe pole zamknutogo fronta depoliarizatsii v anizotropnom miokarde]

On the basis of the bidomain model of anisotropic myocardium, mathematical relationships for calculating the characteristics of the extracellular electric and magnetic fields outside a closed or open depolarization front were derived on the assumption that the generator and fields are axially symmetric with respect to the longitudinal direction of the fibres making up the excitable tissue. The spatial configuration of the fields was determined and quantitative estimates were obtained for the electric potential and magnetic induction caused solely by the macroscopic anisotropy of the myocardium tissue as a volume conductor.

The remote past and near future of electrocardiology: view-point of a biomedical engineer.

The major steps of advancement in electrocardiology over a period exceeding one century of its existence are briefly summarized, and some considerations concerning the most promising trends of its current and future progress are presented. (Tab. 2, Fig. 2, Ref. 39.)

Multipole approach to the inverse problem in electrocardiology: convergence of the multipole equivalent generator on the inhomogeneous body conductor.

The multipole approach to the inverse electrocardiological problem consists of estimating the multipole components of the cardiac electric generator, starting from the measured body surface potential. This paper presents a critical investigation of the basic premise for the applicability of the multipole approach, namely the convergence of the multipole equivalent generator for the heart on the surface of an inhomogeneous body conductor. As an extension to multipole theory, a criterion for the convergence is derived. Based on realistic models for the body conductor and the cardiac electric generator, we observe that the criterion is not strictly satisfied in realistic conditions. Numerical simulations with the same models point out that the multipole equivalent generator is indeed not convergent in the strict mathematical sense. On the other hand, we show that the multipole equivalent generator yields a rather close approximation of the electrocardiological potential for intermediate values of the order of the multipole generator. A discussion is given on how to explain the apparently ambiguous results for the estimation of cardiac multipole components.

[An elementary bioelectrical generator of the anisotropic homogeneous myocardium and its extracellular field]. / Elementarnyi bioelektricheskii generator anizotropnogo odnorodnogo miokarda i ego vnekletochnoe pole.

On the basis of the bidomain model that takes into account the electric anisotropy of body tissues, analytical relationships were developed for calculating the characteristics of electric and magnetic fields produced by an elementary (dipole) bioelectric generator that arises in the electrogenic excitable tissue of the myocardium. The errors in the identification of intensity and location of the bioelectric generator in the myocardium were estimated from the measurements of its external fields (noninvasive identification of the excited region) using approximate methods based on isotropic models of the physical medium.

[A model of spherical quasi-epicardium for mapping of the electrical potential of the heart]. / Model' sfericheskogo kvasiépikarda dlia otobrazheniia élektricheskogo potentsiala serdtsa.

Possibility of determination of the heart electric potential maps on the spherical quasiepicardium from the body surface potentials measured by means of multiple leads, is estimated. The simplified models of ventricular depolarization electric generator considered in this study, consist of sets of uniform double layers representing basic configurations of the true electric generator of the heart, while allowing an analytical calculation of the multipole components, as well as potential of the generator. The contribution of the generator multipole components to the potential on the spherical quasiepicardium is evaluated. The results of the study show that it is reasonable to use the multipole components up to the 3rd order for noninvasive mapping of the potential on the spherical quasiepicardium with the radius which provides tangential touching of the quasiepicardium with the precordium surface. Because of bringing the potential observation region nearer to the generator and improving concentricity of this region with respect to the generator, the quasiepicardium mapping technique allows revealing much more complicated generator configurations than those found out by straightforward estimation of the potential measured on the chest surface, thereby facilitating more accurate noninvasive recognition of the heart electrophysiological state.

Assessment of electrophysiological state of heart in astronauts in terms of decartographic and conventional electrocardiographic characteristics.

Long-term observation of the heart state during specialized professional activities plays an important part in preventive medicine. This study is aimed at assessment of electrophysiological state of heart in astronauts by common electrocardiography, vectorcardiography, and dipole electrocardiotopography (DECARTO technique). The subjects observed were two astronauts performing a long-term flight at the Mir orbital station. DECARTO technique was used to obtain an intelligible-pictorial representation of the data in the form of so-called decartograms for visual and quantitative analysis. The observations showed rather stable chronotopography of the heart depolarization process. However, there was an increase of the maximal magnitude of the electric heart vector and a decrease of the ventricular gradient vector in the middle part of the flight. Just upon landing, a pronounced decrease of the ventricular gradient magnitude, followed by a fast restoration of its value was observed in both subjects. The DECARTO technique used in combination with vectorcardiography facilitated the detailed visual analysis of the electrocardiographic data. (Fig. 3, Ref. 3.)

Decarto technique in long-term observation of patients treated for primary pulmonary hypertension.

Techniques for noninvasive observation of heart states play an important part in experimental and therapeutic cardiology. The objective of this work is to describe a new method for intelligible pictorial representation of data acquired by an orthogonal electrocardiographic lead system and demonstration of possibilities of this method in estimating the results of longterm treatment for a cardiac disease. The method used, dipole electrocardiotopography (DECARTO), provides a set of maps (decartograms) that depict in an explicit form the instantaneous, as well as integral electrophysiological properties of the heart during the excitation cycle. The observed group of patients contained 10 females and 2 males with primary pulmonary hypertension. It was found that in all but one cases tested, the features of the maps strongly correlated with the results of the other diagnostical methods and clinical findings. The trends to improvement (6 cases), stabilization (4 cases), or deterioration (1 case) of the heart state were clearly indicated. In one case, however, the interpretation of the decartograms was ambiguous. The advantage of the DECARTO technique lays in clearness of data representation for visual analysis and facilitation of electrophysiological and anatomical interpretation of the data. (Fig. 6, Ref. 2)

High resolution electrocardiographic abnormalities as possible indexes of electric instability of the myocardium.

OBJECTIVE: To evaluate the signal-averaged high resolution electrocardiogram in the time domain and the frequency domain in various cardiac patients. DESIGN: Patients in seven clinical diagnostic categories were compared with a healthy control group. PATIENTS AND METHODS: The control group consisted of 70 clinically healthy persons. The 525 cardiac patients were divided as follows: group 1, 29 patients with surgically corrected mitralvalvular disease; group 2, 42 postinfarction patients with-bypass grafting; group 3, 57 patients with ventricular tachycardia; group 4, 198 patients with medically treated angina; group 5, 63 patients with hypertension; group 6, 46 patients with paroxysmal atrial fibrillation; and group 7, 90 patients with acute pulmonary insufficiency. The Frank orthogonal leads were used to derive the signal-averaged electrocardiogram in the usual manner by averaging over 200 complexes. Time domain and frequency domain data were recorded for both the P wave and the QRS complex. RESULTS: Ventricular late potentials were found most often in patients with postinfarction ventricular tachycardia (59%). The prevalence of ventricular late potentials in the mitral valvular disease group increased from 45% to 70% after surgery; in the bypass grafting group it also increased. Spectral temporal mapping revealed a substantial decrease of the total spectral power in the bypass grafting group, to 129 +/- 19 microV2/Hz compared with the preoperative period (205 +/- 16 microV2/Hz). The high frequency power decreased, so the ratio of low frequency to high frequency power increased. A significant correlation was found between the root-mean-square signal in the last 40 ms of the QRS complex and each of the amplitude parameter, the frequency domain localization and time domain localization of the power density peaks. CONCLUSIONS: High resolution electrocardiography including time domain and frequency domain analyses may prove helpful in diagnosis and management.

[Non-invasive mapping of cardiac electric potential of a specific quasi-epicardium]. / Neinvazivnoe kartirovanie élektricheskogo potentsiala serdtsa na sfericheskom kvaziépikarde.

A procedure was proposed for non-invasive mapping of the cardiac electrical potential or a spherical quasiepicardium from its synchronous multichannel measurement on the surface of the chest, i.e. routine electrocardiodraphic mapping. Mathematical simulation was used to demonstrate that the quasiepicardial potential can be calculated with the accuracy sufficient for clinical diagnosis by applying the multipole electric field resolution method with allowance made for three lowest resolution terms. Due to the fact that the spherical quasiepicardium is more approximate to the heart and more concentric as to its center than the chest surface, the maps of the quasiepicardial potential permit recognition of some features of the pattern of a cardiac electric process, which do not manifest themselves in the distribution of the potential on the body's surface. The examples showing that the assessment of a cardiac abnormality can be made more accurate by using this method are given in the paper.

Topographic concepts in computerized electrocardiology.

Modern approaches to automatized electrocardiological diagnostics are mostly based on topographic conception. Thus, initially measured data and the results of data processing are represented by parameters distributed over a surface instead of by the separate time-dependent curves of usual electrocardiograms. Examples of the topographic approach are found in measuring and analyzing body-surface (including precordial) potential distributions, epicardial and endocardial potential distributions, heart surface distributions of the intensity of an equivalent bioelectric generator, significant electrophysiological characteristics of the bioelectrical processes in myocardium, etc. The main advantage of using topographic methods is the ability to comprehensively collect and efficiently analyze all diagnostic information about the electrophysiological state of the heart. Rather useful additional information may be acquired by means of biomagnetic field measurements on the basis of similar topographic techniques. A critical review of recent biophysical, measuring, and computational problems, as well as theoretical and experimental results in the field of topographic electrocardiology is presented.