Zang Z. Zao

A study of cardiac vectors in the frontal plane.

Abstract 1. 1. The Einthoven triangle has been set forth in the circular form. The circular form correlates easily the polarities written in the six limb leads and the corresponding heart-vector direction in the RLF plane. 2. 2. The average QRS vector was directed toward +45 degrees in normal electrocardiograms, toward +120 degrees in right ventricular hypertrophy, and toward +15 degrees in left ventricular hypertrophy. The average QRS′ vector was directed toward +30 degrees in both complete right bundle branch block and left bundle branch block. The average QRS″ vector was directed toward −165 degrees in complete right bundle branch block, and toward −30 degrees in complete left bundle branch block. 3. 3. In normal electrocardiograms the angle formed by the QRS vector and T vector did not exceed 45 degrees. In right ventricular hypertrophy and left ventricular hypertrophy this angle could range between 0 degree and 180 degrees. In complete right bundle branch block the angle formed by the QRS′ vector and QRS″ vector usually exceeded 90 degrees; the average angle was 150 degrees. In complete left bundle branch block the angle formed by the QRS′ vector and QRS″ vector usually did not exceed 90 degrees; the average angle was 45 degrees. 4. 4. The incidence of complete right bundle branch block was 2 per cent, of which 95 per cent were of the Wilson type. The incidence of complete left bundle branch block was 1 per cent. 5. 5. The T vector could not be determined in 4 per cent of right ventricular hypertrophy and in 11 per cent of left ventricular hypertrophy. 6. 6. In the RLF plane the general direction of activation of a single normal ventricle, either right or left, was nearly the same as that of the normal QRS vector. The route of activation of a blocked ventricle, either right or left, was abnormally altered: toward the right in complete right bundle branch block, and toward the left in complete left bundle branch block. 7. 7. The circular form was found to be advantageous in clinical routine electrocardiographic analysis.

Spatial vector electrocardiography: Method and average normal vector of P, QRS, and T in space

Abstract A method for spatial vector electrocardiography from 12 routine leads by means of a model is described. It is found to be useful as a practical method for quick and approximate determination and in clinical teaching. Presented are the average normal spatial vectors of P, QRS, and T obtained in this model from 1,000 electrocardiograms classified as normal under the criteria of F. N. Wilson. The average normal vectors of P, QRS, and T in space are directed to the left and downward, P and T being directed anteriorly, and QRS, posteriorly. The angle between QRS and T was 60 degrees; the angle between P and the plane defined by QRS and T was 15 degrees. The problems of the spatial counterpart of the Einthoven assumption is discussed on the basis of previous experimental work. It is anticipated that spatial vector electrocardiography may be studied on a physically founded basis by means of the Burger lead-vector concept while the electrodes on the patient remain at the routine 12-lead positions. On the average this will give more nearly accurate results than those based on the spatial counterpart of the Einthoven assumption. The present model may be adapted easily in such study for convenient visual correlation as described above.

A geometric study of the relationship between limb leads and cardiac vector in the frontal plane.

Abstract The relationship between bipolar limb leads and cardiac vector in the RLF plane was considered in five sections. 1. 1. Various Burger triangular shapes were correlated with the Einthoven triangle. Results indicated that the Einthoven triangle is inaccurate for subjects possessing Burger triangles of either scalene or isosceles shapes. As a rule, the more the Burger triangle departs from the equilateral, the more the vectorial direction, calculated in the Einthoven triangle, deviates from the true one. 2. 2. Using the criteria given in the above section, a study was made of the influence of heart vector eccentricity and length in the inaccuracy of the Einthoven triangle by means of an electrolytic model. It was observed that the inaccuracy of the Einthoven triangle was affected more by the eccentricity than by the length of the “heart vector.” Although the heart vector length also exercised an influence in this regard, the longer the vector (dipole length) the more inaccurate is the Einthoven triangle. Furthermore, the degree of inaccuracy of the Einthoven triangle, if other factors remain equal, depends not solely on the distance between the eccentric position and the geometric center, but on the position itself in the electrolytic model. 3. 3. Burger triangles were constructed directly from living toad hearts in situ, using the graphic method described by Wilson and associates. Burger triangles from toads were similar under similar conditions to those that Wilson obtained from a current dipole located on the anterior aspect of the living human thorax. Depolarization and repolarization Burger triangles from the same toads were almost identical. This suggested that the hypothesis that QRS and T vectors from the same subjects differ in length and occupy different heart regions could not be confirmed by biologic experiments, at least not on toads. 4. 4. In the fourth section a modified technique to construct a Burger triangle with coordinate scales was described. Such a triangle has some interesting features; namely, it obeys the Einthoven law, synthesizes the data of limb leads 1, 2, and 3 into a heart vector arrow within the triangle, or conversely, projects the heart vector arrow on the three sides of the triangle to yield bipolar limb lead data. 5. 5. Described in detail in the final section were two diagrams (A and B) that yielded simultaneous results for the Einthoven triangle and the “average” Burger triangle. Diagrams may also be used to convert Einthoven data into Burger data. From diagram B it is easily seen that, other factors being equal, the inaccuracy of the Einthoven triangle depends upon vectorial direction itself. In other words, the directions obtained in the Einthoven triangle are more inaccurate when referred curves are more distant from each other, less inaccurate when they approach each other, and incidently accurate when they intersect.

A vector study of the delta wave in “nondelayed” conduction☆

Abstract 1. 1. At present, the electrocardiographic syndrome discussed could be adequately described as a “nondelayed” conduction. 2. 2. The directional incidence of the delta wave vector and remaining QRS vector, as well as the angular incidence between them at the RLF plane, were studied. The study was based on 50 limb lead electrocardiograms of “nondelayed” conduction. 3. 3. The left basal ventricular wall of either ventricle may possibly be the frequent site of the premature, weak, localized contraction associated with the delta wave vector. 4. 4. A leftward tendency of the remaining QRS activation was observed.

The two main QRS vectors in the frontal plane in electrocardiograms of complete left bundle branch block

Abstract 1. The incidence in the various directions of the two main QRS vectors in the frontal plane in LBBB was investigated. The first main QRS vectors had nearly the same directions as the normalAˆQRS, the second one occupied the left upper quadrant. The angles formed by the two vectors usually did not exceed 90°, and was 45° on the average. 2. The incidence of LBBB was about 1 per cent; its incidence to RBBB was as 1 to 2. 3. The general direction of activation of a single normal ventricle, either left or right, was nearly the same as normalAˆQRS. The route of activation of a blocked ventricle, either left or right, was abnormally altered; toward left in LBBB, toward right in RBBB.

The Burger triangle in curve from

Abstract The average Burger triangle gives more accurate results than the Einthoven triangle. This paper described the average Burger triangle in curve form. It is easier to use than the triangle itself. It was pointed out that the curves may be used together with the curves derived from the Einthoven triangle to obtain simultaneous results from both triangles. The physician may check each time at a glance the inaccuracy of the Einthoven triangle in individual electrocardiograms.

A radial device for the RLF plane.

Abstract A radial device was given on the basis of the Einthoven triangle. Using the quotient e1e3 the corresponding cardiac vectorial direction in the RLF plane can be obtained. It was discussed that a similar device could be constructed on the basis of a Burger triangle. The same quotient could give almost the accurate direction.

A further study of cardiac vectors in the frontal plane

Abstract In a previous study we analyzed cardiac vectors in the frontal plane from several hundred limb-lead electrocardiograms. 1 They were selected at random from routine 12-lead electrocardiograms which were classified either as being normal or as indicating right ventricular hypertrophy, left ventricular hypertrophy, complete right bundle branch block, or complete left bundle branch block. The classification of the electrocardiograms was based on the criteria established by Frank N. Wilson and associates. This study is a continuation of the previous one. It concerns cardiac vectors in the frontal plane from a total of 400 limb-lead electrocardiograms. They were selected at random, there being 100 cases of old anterior myocardial infarction (AMI), 100 cases of old posterior myocardial infarction (PMI), 100 cases of acute pericarditis (AP), and 100 cases of digitalis effect in left ventricular hypertrophy (DE). In each case the classification was supported by clinical data. The recording instrument was a Sanborn Viso-Cardiette.

Relation between S-T segment elevation and experimental myocardial oxygen gradient

Myocardial oxygen gradient was altered variously by means of gas mixture inhalation in acute coronary artery occlusion in dog. This was correlated with the S-T segment elevation in electrocardiograms recorded in a bipolar subepicardial lead across the pink area and cyanotic area of the myocardium. The electrocardiograms revealed a positive relation between them, that is, the S-T segment increased in height with the increasing of oxygen gradient, and decreased in height with the decreasing of gradient. Occasionally there were also observed S-T segment electrical alternans and the merging of the S-T segment. Implications were briefly discussed.