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Y Rudy

Publications and source records attributed to Y Rudy.

101 records · Page 6Linked to original sources
PubMed1983

Intercalated discs as a cause for discontinuous propagation in cardiac muscle: a theoretical simulation.

A theoretical model of a cardiac muscle fiber (strand) based on core conductor principles and which includes a periodic intercalated disc structure has been developed. The model allows for examination of the mechanism of electrical propagation in cardiac muscle on a microscopic cell-to-cell level. The results of the model simulations demonstrate the discontinuous nature of electrical propagation in cardiac muscle and the inability of classical continuous cable theory to adequately describe propagation phenomena in cardiac muscle.

Action Potentials↗
PubMed1982

The effect of high lung conductivity on electrocardiographic potentials. Results from human subjects undergoing bronchopulmonary lavage.

The effect of increased lung conductivity on ECG potentials was studied in human subjects undergoing pulmonary lavage of a whole lung. In this procedure, the air in the lung is replaced by physiologic saline solution, which is a highly conductive fluid. The same situation was simulated theoretically with an eccentric spherical model of the heart and torso. Both the experimental results and theoretical simulations show a decrease in body-surface potentials as the lung conductivity increases. In particular, a large decrease was observed in the posterior vector and the scalar Z lead both experimentally and theoretically. The model simulation shows that the scalar Z lead is maximal at a conductivity value that is very close to the typical normal lung conductivity, so that low voltages are predicted for low lung conductivities as well.

Cystic Fibrosis↗
PubMed1981

Electrocardiographic body surface potential maps of the QRS of normal children.

Electrocardiographic body surface potential maps (BSPM), utilizing 180 active dry electrodes imbedded in an inflatable vest, were obtained in 40 normal children, ages 8 to 18. The potential levels of the maps are displayed as different colors. A qualitative analysis indicated that the onset of right ventricular breakthrough could always be recognized in the upstroke of the QRS by a pseudopod from a right shoulder minimum extending into an anterior maximum, at an average of 24.4 +/- 4.2 msec., for an average QRS duration of 75.0 +/- 7.1 msec. However there was considerable normal variation, particularly in the mid and late QRS. At the time of depolarization of the free walls of the ventricles, the maximum often remained anterior, with an extension posterior, even through the Frank system vectorcardiogram invariably was posterior. Most remarkable was the terminal QRS of the BSPM, where the terminal maximum may be right superior anterior, anterior superior, or right posterior, presumably reflecting the right ventricular outflow tract, the superior septum, or the posterior basal left ventricle.

Adolescent↗
PubMed1979

The effects of variations in conductivity and geometrical parameters on the electrocardiogram, using an eccentric spheres model.

The effects of variations in the volume conductor properties of the torso on the electrocardiogram were studied by means of a theoretical eccentric spheres model. The model includes a blood cavity, cardiac muscle layer, pericardium, lung region, skeletal muscle layer, and subcutaneous fat. The source of the field is a double-layer spherical cap located within the myocardium. The following effects regarding the electrocardiogram (ECG) potentials were determined: (1) blood augments the potential, but less than predicted by simpler published models; (2) in anemia, high potentials are expected, whereas in polycythemia, voltages are reduced; (3) abnormally low lung conductivity (emphysema) causes low surface potentials whose magnitude is controlled by the low conductivity skeletal muscle layer; (4) low voltages result both from low and high pericardial conductivities; (5) the surface potential increases with increasing myocardial conductivity; (6) low skeletal muscle conductivity (Pompe's disease) causes high surface potentials; (7) obesity lowers the potential only slightly; (8) a thick myocardium, protruding into the lung region, slightly augments the potential; (9) an increase in the thickness of the myocardium at the expense of the blood cavity causes a decrease in potential; (10) the potential increases with increasing heart size; and (11) the location of the heart within the torso has a very significant effect on the surface potential distribution.

Action Potentials↗
PubMed1978

A note on the "Brody-effect".

The effect of a perfectly conducting sphere simulating the intracavitary blood mass on a dipole source located at the interface with the outer tissue (myocardium) is studied, utilizing image theory. The resulting enhancement factor is found to be a function of the field point location and is not a constant, as previously reported by Brody and by Rush and Nelson.

Blood↗
PubMedDate not supplied

Endocardial potential mapping from a noncontact nonexpandable catheter: a feasibility study.

In previous studies, we established methodology for reconstructing endocardial potentials, electrograms and isochrones from a non-contact intracavitary probe during a single beat. The probe was too large to be introduced percutaneously. Here we examine the possibility of similar mapping with a small multielectrode catheter that could be introduced percutaneously and does not expand inside the cavity. Cavity geometry and endocardial potentials were recorded in an isolated canine left ventricle. Simulated catheter probes were introduced into the cavity. Probe potentials were computed from the measured endocardial potentials and perturbed to include measurement noise, geometrical errors, and limited electrode density. Endocardial potentials were then reconstructed from the perturbed probe potentials and compared to the actual measured potentials. Of all probes simulated, a 3.0 mm (9F) catheter that assumes a curved geometry (e.g., a J shape) inside the cavity performed best (better than a larger 7.6 mm cylinder simulating an inflatable probe). Without bending, a straight cylindrical probe of the same size (9F, 3.0 mm) did not perform well. Sixty probe electrodes were needed for accurate reconstruction. The J-probe reconstruction was very robust in the presence of noise (10%) and of geometry errors (3 mm shift, 10 degrees rotation). The results demonstrate the feasibility of accurate single-beat endocardial mapping using a 9F percutaneous multielectrode catheter that assumes a J shape in the cavity without the need for expansion (e.g., into a balloon or a "basket"). The robustness of the procedure to noise and geometrical errors suggests its applicability in the clinical EP laboratory and the possibility of determining probe position in vivo using current imaging modalities.

Animals↗
PubMedDate not supplied

A field-compatible method for interpolating biopotentials.

Mapping of bioelectric potentials over a given surface (e.g., the torso surface, the scalp) often requires interpolation of potentials into regions of missing data. Existing interpolation methods introduce significant errors when interpolating into large regions of high potential gradients, due mostly to their incompatibility with the properties of the three-dimensional (3D) potential field. In this paper, an interpolation method, inverse-forward (IF) interpolation, was developed to be consistent with Laplace's equation that governs the 3D field in the volume conductor bounded by the mapped surface. This method is evaluated in an experimental heart-torso preparation in the context of electrocardiographic body surface potential mapping. Results demonstrate that IF interpolation is able to recreate major potential features such as a potential minimum and high potential gradients within a large region of missing data. Other commonly used interpolation methods failed to reconstruct major potential features or preserve high potential gradients. An example of IF interpolation with patient data is provided to illustrate its applicability in the actual clinical setting. Application of IF interpolation in the context of noninvasive reconstruction of epicardial potentials (the "inverse problem") is also examined.

Action Potentials↗