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

Abstract

Listen

Translate article

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.