Comparison of Four Orthogonal Systems of Vectorcardiography

Abstract

Four orthogonal systems of vectorcardiography that are considered to be more accurate than th(-tetrahedron and cube systems were compared. In a large majority of subjects the records made with each of the 4 systems were similar. However, in 5 of 60 subjects in whom the Z lead was studied, dissimilarities were found that were considered to be significant. The possible reasons for these dissimilarities are discussed. Comparative normalization data for the systems were obtained in the living human subject, based upon comparison of wave forms.RECENTLY 4 systems of vectorcardiography based on well-established principles of potential theory have been devised by Schmitt and Simonson,1 Frank,2 McFee and Johnston,3 and Helm.4 They each attempt to provide a more orthogonal reference frame than the cube and the tetrahedron systems. It is the purpose of this paper to report the results of a comparative study in the living human subject of these 4 systems. The study was undertaken for 2 reasons, to determine how interchangeable the results of the different systems were and to provide comparative normalization data for each system in the living subject. If the systems yielded similar results, the study would serve as a consistency cheek on the validity of the separate methods of analysis and synthesis. METHODThe 3 leads of each orthogonal reference frame were compared individually. They were paired with a common lead to produce a loop rather than being recorded as scalar leads. The latter method requires high-speed, dual-channel recording with a common lead for phase relations, and analysis of such records was found to be less obvious and informative.All studies were performed with the subject recumbent. Loops were observed directly on an oscilloscope and photographed with a Polaroid Land Z Lead. Since the anteroposterior or Z lead has been the most variable component in existing systems of vectorcardiography, the major portion of this study was devoted to it. The Z lead of each system was paired consecutively with a common X lead (Schmitt system), and the gain of the Z channel controlled so that the peak-to-peak excursion was the same for all loops. The gain was then recorded for normalization information. The Z leads of the Frank and the Schmitt SVEC III systems were employed as described by these authors in their original communications.1' 2 The sponge electrode of Helm4 and the multiple bank of electrodes of McFee and Johnston3 are described as follows.The sponge electrode consisted of a thin plastic sponge moistened with a saturated solution of sodium chloride. Two sizes of sponge were used on the anterior chest wall to record the Z lead. A large sponge 10 inches square was positioned to cover the area from the first to the seventh interspace and from approximately the right midelavicular line to a line between the V4 and V5 positions. A smaller sponge with dimensions of 8Y2 inches from right to left and 612 inches from top to bottom was placed on the precordium, extending from the level of the second to the sixth rib a...

The Corrected Orthogonal Electrocardiogram and Vectorcardiogram in 510 Normal Men (Frank Lead System)

“…20 The three orthogonal leads were recorded simultaneously on frequency modulated magnetic tape. Subsequently, they were digitized at a sampling rate of 1,000 per second for each lead.…”

Experimental Comparison of Three Corrected Electrocardiographic Lead Systems

“…As emphasized by Fischmann [5], it is possible that the electrical size of the heart in the living subject is smaller than its anatomic size. These theoretical possibilities ap pear to he supported by the results of comparative analyses of several corrected lead systems in normal subjects which failed to show significant differences in terms of variability of their values [9,13]. In this regard it is important to bear in mind that the criteria of accuracy in model studies (uniformity and orthogon ality) differ from clinical criteria (separation of normal from ab normal).…”

Modified axial lead system in children.

“…chest electrodes. Langner et al (1958) proposed that the 4th intercostal space be used as the reference level for supine patients rather than the fifth, which Frank (1956) had suggested for subjects in an erect posture. It was decided, therefore, to make a limited study with the Frank system on the effect of interspace variation in infants and children.…”