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Biomedical subjects

D B Geselowitz

Publications and source records attributed to D B Geselowitz.

At least 55 records · Page 3Linked to original sources
PubMed1982

Active electric properties of cardiac muscle.

A model of electrical activity in the heart has been developed that treats the intracellular domain and the extracellular domain as electrical syncytia with anisotropic resistivities (bi-syncytial model). At the microscopic level, propagation is assumed to proceed primarily along the axes of individual cells. Considerations at the macroscopic level relate the transmembrane current to the intracellular and extracellular resistivity and the transmembrane potential. The result is a relationship between instantaneous extracellular potentials and cardiac action potentials.

Animals↗
PubMed1978

Simulation studies of the electrocardiogram. I. The normal heart.

A digital computer model is presented for the simulation of the body surface electrocardiogram (ECG) during ventricular activation and recovery. The ventricles of the heart are represented in detail by a three-dimensional array of approximately 4000 points which is subdivided into 23 regions. Excitation sequence and cellular action potential data taken from the literature are used to determine the spatial distribution of intracellular potentials at each instant of time during a simulated cardiac cycle. The moment of the single dipole representing each region is determined by summing the spatial gradient of the intracellular potential distribution throughout the region. The resulting set of 23 dipoles is then used to calculate the potentials on the surface of a bounded homogeneous volume conductor with the shape of an adult torso. Simulated isopotential surface maps during both activation and recovery are in good agreement with data for humans reported in the literature.

Action Potentials↗
PubMed1978

Simulation studies of the electrocardiogram. II. Ischemia and infarction.

Experimental studies of the myocardial action potentials following coronary artery occlusion have shown that the resulting regional ischemia is reflected by characteristics changes in the shapes of the action potentials in the ischemic region. The principal changes are decreases in the magnitude of the resting potential and in the action potential duration. Action potentials with prolonged durations have been observed in the infarcted regions of experimental animals after the development of inverted T waves in the surface electrocardiogram (ECG). We use such abnormal action potentials in our digital computer model to study the effects of acute myocardial ischemia and infarction on the surface ECG. The heart is represented in sufficient detail to allow variations in the location and size of the ischemic injury and in the distribution of the severity of injury within the injured region. The evolution of acute infarctions is simulated by progressively modifying the abnormal action potentials assigned to the injured region. Calculated standard 12 lead ECGs and torso isopotential surface maps for simulated acute ischemia and infarction are in good agreement with patient data reported in the literature. Typical simulations include anterior and inferior transmural ischemia and infarction and anterior subendocardial ischemia. The model is used to examine relationships between torso surface potentials during ventricular activation and recovery and the site and size of the ischemic injury.

Action Potentials↗
PubMed1977

A dipole plus quadrupole lead system for human electrocardiography.

A lead system was constructed to extract dipole and quadrupole components of cardiac sources from surface electrocardiograms (ECGs) recorded at 16 sites. The lead system was based on an analysis of a computerized model of a multipole equivalent cardiac generator in a homogeneous torso. The model was previously determined from extensive geometric and electrocardiographic data obtained from one subject. Dipole components estimated with the lead system were 89% accurate for the original subject. Evaluation of the lead system on this subject and in 59 other subjects included calculation of the effect of non-dipolar sources on the values of the estimated dipole components, comparison of the consistency of equivalent sources found independently at two origins in the heart region, and reconstruction of ECGs from lead system components. Dipole consistency at the origins was maintained over the wide range of age, weight, and body shape which characterized the subject population. Whereas quadrupole terms did not agree as well as the dipole terms, inclusion of the quadrupole reduced ECG reconstruction errors by a factor of about three compared to errors for the dipole alone. Together, the dipole and quadrupole accounted for almost 90% of the electrocardiographic information measured on the body surface with the D/Q lead system.

Computers↗
PubMed1975

A device for producing high frequency electrocardiograms on a conventional direct writing electrocardiograph.

A device has been developed which can be used in conjunction with a direct-writing electrocardiograph to record the high frequency electrocardiogram (ECG) including notches and slurs in the waveform. The device operates on the principle of temporarily storing the QRS complex and then reproducing it at a rate 10 times slower than real time. Increasing the ratio to 80 to 1 permits registration of pulse artifacts from implanted cardiac pacemakers.

Coronary Disease↗