Otto H. Schmitt

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.

Cardiovascular stress (electrocardiographic changes) produced by driving an automobile

Abstract A review of cardiovascular changes during driving an automobile is presented. The heart rate responds instantaneously to critical situations and in stressful situations such as car racing increases rapidly to frequencies of 200 per minute or more. Blood pressure is less responsive. Significant ST depression and T wave changes were reported in healthy drivers and more so in ambulatory patients with coronary heart disease or in hyperreactors. In the experimental part, significant changes of the T wave in the ECG are reported which occurred in five men (having normal resting and postexercise ECGs) while driving an automobile over distances of 200 to 2,600 miles. The previously positive T wave of a bipolar manubrium-C5 lead, similar in pattern of V 5 , decreased to half its original size in one subject after three hours of driving. Transient flattening or inversion of the T wave developed in two other subjects after one to four hours of driving with some correlation to road events. The changes recovered partially during rest periods. The repeatability of ECG changes in eight drives over the same route (suburban and urban driving during rush hour) was quite good.

Electrocardiographic mirror pattern studies. III

Abstract 1. 1. The distribution curve of 142 cancellations in thirty-seven patients is similar to that of 106 cancellations in seventeen normal subjects, but the number of good and excellent cancellations in patients is smaller and that of poor and bad cancellations is greater. 2. 2. The significantly poorer cancellation in patients with bundle branch block is explained with a mobile dipole. 3. 3. In patients with right or left ventricular strain, the significantly poorer average cancellation is probably due in large part to technical limitations, but excellent cancellations were also frequently obtained. 4. 4. In patients with anterior or posterior myocardial infarct, the average cancellation coefficient is the same as in normal subjects. 5. 5. There is no significant difference in the cancellation coefficient or the dial reading at the bridge between patients with pulmonary emphysema and normal subjects. 6. 6. The regional distribution of good or poor cancellations over the surface of the body does not show any selective pattern in any category of pathology. 7. 7. There is no evidence that the poorer cancellation in some patients is due to the interference of local patterns. 8. 8. It is concluded that the lipole theory is a valid, workable concept for electrocardiographic interpretation of patients as well as normal subjects. 9. 9. Implications to electrocardiographic theory are discussed.

LEAD VECTORS AND TRANSFER IMPEDANCE

Biophysical theory and the technology of instrumentation have advanced so far during the last few years that we have only ourselves to blame if we are still unable to agree qualitatively and, indeed, semiquantitatively upon the relationship between the heart as a generator of action currents and the potential differences arising a t the surface of the body as a result of these currents. We are not yet prepared to understand fully the detailed physiological implications of the potentials that we measure, but we should be able to unscramble adequately the relationship between the potentials measured a t the body surface and the potentials that would be measured were we able to suspend the heart in a geometrically simple container filled with uniformly conducting fluid. We cannot yet escape the empiricism implicit in our interpretation of cardiac events in terms of electrocardiographic data, so there is room here for differences in clinical interpretation based upon extensive personal experience and intuitive understanding. However, all correct theoretical reconstructions should lead to the same heart generator for a given set of surface potentials. One theoretical treatment might be much simpler or more easily understood intuitively, and another might involve measurements that are especially easy to make, but all should be mutually consistent. I t is the purpose of this study to provide theoretical and technical means for testing objectively the degree of consistency between the several popular electrocardiographic recording systems and, incidentally, to provide a mental tool for easy understanding of the universal relationship between measured potential and active source, independent of the peculiarities of a particular lead system used in any specific study. Transfer impedance bears a simple mathematical relationship to the “leadfield vector” that has been utilized in some other theoretical developments. It is much more easily understood intuitively, however, being defined directly in terms of an action current source and the accompanying measured potential. Lead-field concept starts with the notion of an externally applied current and measures the electric field in the source region, relying upon a reciprocity theorem to guarantee that source and measurement positions can be interchanged, provided careful attention is paid to the specification of source and measuring impedance, dimensions, and proper conversions between field and potential differences. Let us start with the idea of a small bundle of active muscle fibers producing an action current somewhere in the heart and a pair of electrodes picking up a resultant action potential somewhere a t the body surface (or, if preferred, a t internal points). As long as the surrounding tissue is electrically linear, * The research reported in this paper is supported in part by research grants from the National Institutes of Health, Bethesda, Md., from the Minnesota Heart Association, St. Paul, Minn., and by a research contract with the Office of Naval Research, Washington, D. C,

Electrocardiographic mirror pattern studies. I: Experimental validity tests of the dipole hypothesis and of the central terminal theory

Abstract 1. 1. A theoretical analysis is made of the mirror image electrocardiograms which are often found at anatomically opposite positions across the heart. 2. 2. A cancellation technique is proposed whereby similar parts of presumed mirror patterns are cancelled leaving only the unbalanceable portion as a residual. 3. 3. A cancellation coefficient has been devised which permits quantitative evaluation of mirror pattern excellence. 4. 4. Use of a polar cardioscope is proposed for detailed study of electrocardiographic patterns over a lengthy observation period and is found valuable experimentally. 5. 5. A double exposure photographic method is utilized to establish cancellation axes visually within the body. 6. 6. The existence of deceptive “false” mirror patterns is pointed out and demonstrated. 7. 7. The importance of exact phase coincidence for cancellation is emphasized. 8. 8. True mirror patterns of good cancellation excellence are not rare and most patterns have good mirror images, but some noncancellable patterns are found.

Cathode‐Ray Presentation of Three‐Dimensional Data

The cathode‐ray oscilloscope is usually regarded as a means for displaying data in one or two variables as a function of time. By means of simple transformations which are easily performed electrically, it is possible to present three variable electrical data in the form of isometric or other conventional projections or as true perspective drawings. It is further possible to change the observers viewpoint in the presentation coordinate system at will by turning range, elevation, and azimuth controls.A more elaborate but similar set of transformations permits presentation of separate pictures to the two eyes. These pictures are optically superimposed but differ in such a way as to yield stereoscopically correct perspective pictures. These pictures are fully acceptable to the eye as patterns in space.

Plans for orbital study of rat biorhythms results of interest beyond the biosatellite program

Long term zero gravity effects on mammal physiologic rhythms characteristics, studying rats in biosatellite orbits

The theoretical and experimental bases of the frontal plane ventricular gradient and its spatial counterpart

Abstract 1. 1. The theoretical basis of the ventricular gradient concept is re-examined. 2. 2. The effect of changing pathway of ventricular activation is analyzed in Wilsons experiment and in a corresponding human case. 3. 3. Normal limits for the magnitude of the ventricular gradient are calculated and tabulated for a group of 107 healthy men and for corresponding material available from the literature. 4. 4. Analysis of the literature reveals that very few cases even with advanced myocardial involvement exceed these normal limits. 5. 5. No correlation is found between the manifest QRS and T areas in any of three different experimental normal groups even when the area measurements are made by means of an electronic integrator, which is described in appendix II. 6. 6. Analysis of the existing literature on the spatial gradient reveals that no adequate method of measurement has yet been described. 7. 7. A simple method for measuring the spatial ventricular gradient based on determination of a null point for the QRS-T area at the fifth intercostal space is developed. 8. 8. Some representative normal values of the spatial ventricular gradient and its components are given. 9. 9. A strong positive correlation between the spatial QRS and T areas is found in contrast with the negative correlation implied by conventional ventricular gradient theory. 10. 10. A theoretically more satisfactory definition of a spatial ventricular gradient is proposed based on the stereovector theory. 11. 11. Technical electronic means for instananeous determination of the spatial ventricular gradient are described. 12. 12. The results do not encourage further use of the frontal plane ventricular gradient in clinical electrocardiography. The value of its spatial correlate remains to be proved.

Electrocardiographic mirror pattern studies. II: The statistical and individual validity of the heart dipole concept as applied in electrocardiographic analysis☆

Abstract 1. 1. A procedure for determining accurately the degree to which electrocardiographic potentials may be ascribed to a dipolelike source has been experimentally evaluated. The method makes use of the cancellation properties of mirror patterns and has a sensitivity of approximately 2 per cent. 2. 2. In a study of seventeen normal subjects and thirty-seven cardiac patients, mirror patterns were found along approximately 100 different anatomic axes through the heart, no direction giving significantly better mirror patterns than any other direction. 3. 3. In general, approximately 90 per cent of the electrocardiographic potential appearing at any point on the body, including the precordial areas, may be ascribed to a dipolelike current source at the heart, in that only 9 per cent of any pair of mirror patterns, on the average, failed to cancel. 4. 4. Although different points on the body are at different electrical distances from the heart, a study of bodily and cardiac dimensions failed to reveal any significant correlation between physical dimensions and electrical distance. 5. 5. All of the studies were made using a Wilson central terminal. Since excellence of cancellation of mirror patterns depends on having a truly neutral central terminal as well as on having actual dipolelike activity of the heart, the Wilson terminal, accordingly, is shown to be quite satisfactory for leads in the anteroposterior direction as well as in the frontal plane. It was indicated, however, that careful derivation of a properly weighted central terminal might be expected to improve the degree of cancellation obtainable. 6. 6. Since only a dipolelike source is capable of yielding mirror patterns in a wide variety of directions through the heart, the results obtained were taken to be a verification of the dipole theory for semiquantitative, as well as qualitative, purposes. The projection areas of the so-called Unipolar Electrocardiography must be regarded as having relatively little meaning.

A note on interaction between nerve fibres.

IT has previously been shown [see Katz & Schmitt, 1939, 1940 for details of problem and methods] that the passage of an impulse in a single nerve fibre of Carcinus (fibre I) is accompanied by a triphasic excitability change consisting successively of a fall, a rise, and a second fall of excitability in an adjacent fibre (fibre II). These changes were attributed to that part of the action current which penetrates the resting fibre and which reverses in direction twice as does the excitability change. Recently, Blair & Erlanger [1940] have raised the question whether those changes may not, to some extent, have been due to a resistance decrease of the active fibre [cf. Cole & Curtis, 1939]. It is conceivable, as they point out, that the active region of fibre I may provide a more effective shunt for the test stimulus and so cause an apparent fall in excitability of fibre II, possibly masking or preceding an excitability rise due to the action current. In the case of two Carcinus fibres the question can be decided as follows. Consider the arrangement of Fig. 1 a. The test shock is applied at C and D, with cathode at D. A depression of excitability due to more effective shunting would occur as soon as the impulse reached the interpolar stretch CD. The latency of this effect, therefore, depends upon the position of the anode C. On the other hand, changes due to penetrating action currents occur only when the impulse reaches the cathode D and are independent of the position of the anode.