Calvin F. Kay

Recommendations for Standardization of Leads and of Specifications for Instruments in Electrocardiography and Vectorcardiography

By COMMITTEE MEMBERS: CHARLES E. KOSSMANN, M.D., CHAIRMAN, DANIEL A. BRODY, M.D., GEORGE E. BURCH, M.D., HANs H. HECHT, M.D., FRANKLIN D. JOHNSTON, M.D., CALVIN KAY, M.D., EUGENE LEPESCHKIN, M.D., HUBERT V. PIPBERGER, M.D., AND by MEMBERS OF THE SUBCOMMITTEE ON INSTRUMENTATION: * HUBERT V. PIPBERGER, M.D., CHAIRMAN, GERHARD BAULE, PH.D., ALAN S. BERSON, M.S., STANLEY A. BRILLER, M.D., DAVID B. GESELOWITZ, Ph.D., LEO G. HORAN, M.D., AND OTTO H. SCHMITT, Ph.D.

Specific Resistance of Body Tissues

The resistive properties of various tissues surrounding the heart were investigated in a number of living dogs. Alternating currents of a frequency varying between 10 and 10,000 c.p.s. have been used for this purpose. Technical problems associated with such measurements are analyzed. The results show that the resistive properties of most tissues are comparable and that the resistivity decreases slowly as the frequency increases.

Capacitive Properties of Body Tissues

The electric capacity of various tissues surrounding the heart has been investigated in living dogs, using frequency ranges from 10 to 10,000 c.p.s. Electrode polarization, a serious source of error in such measurements, has been corrected for. Discussion of our results and of resistivity data previously obtained in body tissues proves that the electric properties of body tissues are primarily resistive ones.

A reference potential for unipolar electrocardiographic measurements on models

Abstract 1. 1. Measurements of potentials produced by a finite dipole immersed in an insulating torso model filled with a homogeneous conducting fluid are discussed. 2. 2. The need for a reference potential is presented as well as a discussion of the accuracy with which the reference potential must be determined. 3. 3. The equivalent bridge viewpoint is introduced and is shown to give considerable insight into the electrical nature of both unipolar and bipolar measurements. 4. 4. A center-electrode reference system is described which has several advantageous features. The inherent defect of this system, a shift of equipotentials between the two current electrodes owing to the distant boundary, is pointed out and analyzed. 5. 5. The experimental difficulties and interrelationship of the more important design factors of a practical reference potential system are presented.

The Electrical Conductivity of Living Tissues as it Pertains to Electrocardiography I. Review of the Problem of Homogeneity vs. Nonhomogeneity, an Outline of the Technical Aspects of Tissue Resistivity Measurements, and a Critical and Experimental Analysis of Certain Pertinent Experiments

Field analysis methods provide a convenient mathematical process for organization of electrocardiographic observations. The degree of divergence of calculated spatial orientations of heart forces from true orientations is dependent upon the magnitude of inaccuracy of the assumption that body tissues are electrically homogeneous. Preliminary to undertaking quantitative measurements of tissue resistivities in situ, technical difficulties of the problem have been surveyed, and previous studies have been analyzed. It is concluded that an accurate, quantitative measurement of such resistivity has not been made. If major inhomogeneity were found, current methods of application of field theory to electrocardiography might require extensive modification.

The Electrokymograph: Studies in Recording Fidelity

Several electrokymographs were subjected to study of their recording fidelity. Distortions were found in respect to time and amplitude of recorded response. The recording defects were analyzed quantitatively, and the degree to which the various components of the electrokymograph contribute to these distortions was measured. The significance of these deviations in recording fidelity is discussed in reference to the application of the electrokymograph to the study of cardiovascular dynamics.

A National Self-Assessment Program in Internal Medicine

The Medical Knowledge Self-Assessment Program of the American College of Physicians is one of the largest continuing medical education programs in the United States. The scope and educational rationale for each of the components of the program are described. More than 32,000 physicians used one or more components during 1977 and 1978. Performance on the self-assessment examinations showed that, on the average, participants who submitted answer sheets scored in the range of 65% to 75% correct responses. Participants performed better in areas reflecting their special interests and, in general, performance appeared to improve for groups that were closer to the completion of formal training in internal medicine. Specific suggestions have been made as to how the program might be improved in future years.

Myocardial complications of cutaneous diphtheria.

Abstract 1. 1. The myocardial complications which developed in a group of 140 patients with cutaneous diphtheria have been considered. 2. 2. Shortly after cutancous diphtheria was first observed in this hospital we became impressed with the gravity of the myocardial complications, and measures were instituted in an effort to recognize this complication early and to prevent death from this cause. The measures adopted may have been more stringent than necessary. 3. 3. Definite myocarditis appeared in four patients, one of whom died. The diagnosis was considered probable in three additional patients, an incidence of 5 per cent. In seven other patients the diagnosis could not be exeluded entirely. 4. 4. The symptoms, signs, laboratory studies, and electrocardiographic findings in these patients are discussed. 5. 5. Cardiac complications developed from the fourth to seventh week after the onset of the skin lesions. Their duration was from one to three months. All patients who survived showed no evidence of cardiac abnormality after four and one-half months from the onset of the skin lesions. The electrocardiograph is an essential in the diagnosis and evaluation of the myocarditis. 6. 6. A definite parallel relationship existed between the severity of the cutaneous lesions and development of cardiac complications. Of 18 patients with very severe cutaneous diphtheria, four (22 per cent) developed myocarditis: whereas the complication did not appear in any of the 50 patients in whom the cutaneous lesions were mild. 7. 7. Neuritis developed as a complication in the three patients with definite myocarditis who survived, and in one of the three patients in whom the diagnosis of myocarditis was probable. The onset of neuritis either preceded, or coincided with, or followed the onset of the myocarditis. 8. 8. It is concluded that myocarditis is an infrequent complication of cutaneous diphtheria, but one which must be especially considered in any patient in whom the degree of cutaneous involvement is severe.

Cardiopulmonary Resuscitation: A Chain of Many Links

Excerpt Recently, while I was dining in a suburban restaurant near a large midwestern city, an elderly man at a nearby table slumped in his chair and was unconscious and pale. His stertorous breath...

Panel discussion I

Since their rise in the 90s, SoCs have been fueling the rapid growth of mobile devices, consumer electronics, medical equipment, and network infrastructure devices.