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Biomedical subjects

L I Titomir

Publications and source records attributed to L I Titomir.

At least 19 recordsLinked to original sources
PubMed2006

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.

Body Surface Potential Mapping↗
PubMed2005

[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.

Adult↗
PubMed2002

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)

Acceleration↗
PubMed2000

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.

Computer Simulation↗
PubMed1996

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.

Action Potentials↗
PubMed1996

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.)

Astronauts↗
PubMed1996

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)

Adolescent↗
PubMed1992

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.

Animals↗
PubMed1987

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.

Electrocardiography↗
PubMed1984

[Evaluation of the chronotopography of cardiac excitation by means of epicardial electrocardiotopograms].

The authors described a method of the automatic construction of an epicardiac electrocardiotopogram based on measuring the distribution of the potential on the chest surface, the geometrical parameters of this surface and on the mathematical processing of the data obtained with the help of multiple expansion. The major advantages of the method include the elimination of the effect on the electrocardiotopogram of non-cardiac factors, an increase in its resolving capacity and its specific characterization of the anatomic elements of the heart. Examples are presented which illustrate the diagnostic interpretation of the epicardiac electrocardiotopogram under experimental conditions.

Computers↗