Leonid I. Titomir

On the Possibility to Determine Integral Characteristics of the Cardiac Electric Generator from Extracardiac Electric and Magnetic Measurements

The relation between the electric and magnetic fields of the heart outside the body is considered on the assumption that the primary bioelectric generators impressed membrane currents may be represented as geometrically curvilinear thread-like flows. An approach based substantially upon the multipole expansion of scalar potentials is developed for distinguishing between two parts of a measured total magnetic field, the first part being uniquely joint with the electric field, and the second being independent and containing information about curvilinearity of the elementary generators.

Electrocardiographic diagnosis of left ventricular hypertrophy on the basis of dipole electrocardiotopography method.

PURPOSE The aim of this study was to verify a new criterion of hypertension-related left ventricular hypertrophy (LVH) on the basis of the dipole electrocardiotopographic technique, which provides intelligible pictorial patterns and efficient quantitative parameters for recognition of pathologic states of the heart. METHODS Standard 12-lead and vectorcardiographic measurements with the McFee-Parungao lead system were carried out for 289 echocardiographically accessed healthy subjects and hypertensive patients with LVH. The proposed parameter index of left ventricular hypertrophy for recognition of LVH is a product of the following 3 characteristics: maximum magnitude of depolarization vector, total duration of ventricular depolarization, and local spatial integral of activation duration. This parameter was compared with several other parameters commonly used for LVH diagnosis. The diagnostic efficiencies of these parameters were statistically estimated and compared using the receiver operating characteristics (ROC curves), area under the ROC curve, and partial areas under the ROC curve (pAUC). The area under the ROC curve values were compared by the standard nonparametric method, and pAUC comparison was performed by bootstrap methodology. RESULTS The ROC curves display the definite advantage of the proposed criterion, especially for the specificities greater than 0.7. Statistical comparative analysis showed that the corresponding pAUC for the index of left ventricular hypertrophy is greater than for R(x) + S(z), Cornell product, and Sokolow-Lyon criteria at confidence level > or = .95. CONCLUSION The dipole electrocardiotopography-based diagnostic criterion of LVH is demonstrated to be statistically more accurate as compared to other criteria studied. The advantage of this criterion suggests that with the use of decartograms, it is possible to reveal some additional information not accessible for other diagnostic tools. Decartograms help to visualize and quantify the redistribution of activation duration over the myocardium, thus providing a valuable instrument for heuristic analysis and dynamic observation of the heart state affected by LVH.

Biophysical Model for Beat-to-Beat Variations of Vectorcardiogram

Biophysical Model for Beat-to-Beat Variations of Vectorcardiogram Linear deformation of the myocardium results in a linear transformation of orthogonal electrocardiosignals under the condition of topological invariability of the depolarization and repolarization processes in the myocardium. The relation between the linear transformations in the physical and functional spaces was found. Several practically important conclusions follow as a logical consequence of these statements. The parameters of linear transformations of the vectorcardiogram (eigenvectors, eigenvalues, rotation angles, determinants) may be used as indices of the heart position and haemodynamic changes.

Atrial late potentials in patients with paroxysmal atrial flutter

Possibility of identification of the patients with paroxysmal atrial flutter (PAF) by the methods of high-resolution electrocardiography applied to the P wave, is studied. Dependence of the criteria on the trigger mode is estimated. The importance of the filtered P wave duration as an indicator for prediction of PAF is substantiated.

Pictorial representation of local events in the heart on the basis of noninvasive spherical-quasiepicardium potential mapping

An improvement of the electrocardiographic body surface potential mapping technique is proposed to provide more explicit recognition of excitation processes in the heart by means of calculation of the potential distribution on the spherical quasiepicardium and separation of its extremum regions. The method is illustrated with cases of ventricular extrasystole and preexcitation syndrome.