Coordinating the einthoven body impedance model for ECG signals with IEC 60479–1:2018 electrocution heart current factors
Section snippets
Introduction: ECG with string galvanometer
The non-invasive, low-cost, and effective process to measure the electrocardiogram (ECG) is a medical invention that has been in continuous use for more than 100 years. An ECG is a voltage-time graph of the electrical activity of the heart, obtained from recordings of measurement systems such as electrometers, galvanometers, electronic amplifiers and chart or digital recorders. In the 1910s and 1920s, string galvanometers as shown in Fig. 1 were the instruments available for ECG studies [1, 2].
Effect of path on fibrillation current
The IEC 60479–1 (2018) Standard, clause 3.2.6 [6] defines F, the heart-current factor that relates the electric field strength (current density) in the heart for a given current path to the electric field strength (current density) in the heart for a touch current of equal magnitude flowing from left hand to both feet. It provides Table I that uses the same value of F = 1 for LH-LL, LH-RL, LH-2L and 2H-2L paths where 2H refers to contact with both hands and 2L to both legs through the feet on
Inversion of the Einthoven resistor network
The slight imbalance in resistor values, with unequal values of R1 and R2 in Fig. 2 is an important aspect of the model in electrocution calculations. Consider a potential of 100 V applied to LH with both LL and RL grounded. Ignoring skin breakdown resistance, the model in Fig. 2 suggests that a current of 233 mA will flow into LH and equal currents of 116.5 mA will flow out of each leg. The imbalanced resistors lead to ac current flow of 2.6 mA through the heart, about the same magnitude as
Adding cross-hip resistance to the Einthoven resistor network
The traditional ECG circuit model in Fig. 2 can be improved further to match the heart-current split factors in Table I. This is achieved by separating the single node at the hip (H) into two nodes, RH and LH in Fig. 4. A cross-hip resistance on the order of 10–100 Ω is supported by measurements of electrocution resistance of pigs as well as by the other values of peripheral torso resistance. Resistors R3, R4, R5 and R6 now connect each side of the heart, nodes (a) and (b), to each hip,
Process for validation of heart current split factors: comparison of lead I: lead III and lead II: lead III ECG signal amplitudes
The “Einthoven Triangle” research of Mann [18] suggested the Lead I (LH-RH) peak-to-peak signal would be about one-half of the RH-L and LH-L signals. The analysis is based on the projection of the heart axis (origin to upper right) of an equilateral triangle. The quality of a set of three-lead ECG signals is established by verifying that the area of this “triangle” is greater than zero. A comparison of peak magnitudes from the three independent galvanometers could verify the heart current
Process for validation of leg-leg heart current split factor using three-lead ECG
A literature survey did not turn up any measurements of the RL-LL ECG. A preliminary investigation [23] was carried out using three subjects and a GE Case Stress System V6.51 Exercise ECG monitoring system at an ECG clinic. Each subject was measured using a standard three-lead configuration using the right leg as the body voltage reference point. In common with the results in [21], there was a considerable variation in the peak ECG Lead III signal (0.5–1.5 mV) as well as subject-to-subject
Process for validation of heart current split factors using two-lead ECG
Considerable progress has been achieved in two-terminal ECG monitors, intended for personal fitness use, as shown in Fig. 12. This ECG instrument [24] combines internal batteries, contact electrodes, internal signal conditioning, display, and storage. Data are saved and exported for additional analysis, including monitoring of peak-to-peak voltage. The instrument in Fig. 12 is configured to measure either Lead I (LH-RH), Lead II (RH-LL) or chest lead (RH-chest, giving the highest signal
Conclusions and recommendations
A traditional model for the appearance of ECG signals at the extremities in response to the electrical activity of the human heart can be inverted to estimate the effects of electrocution potentials applied at those extremities.
The “Einthoven” model with 2.5-mA current source and a network of 13 resistors provides, to first order, a good match to the path impedance values in IEC 60479–1. Some imbalance in two of the resistors is physically plausible based on distance from hip to top and bottom
Author statement
Ms. Ref. No.: EPSR-D-22–01,932
Coordinating the Einthoven Body Impedance Model for ECG Signals with IEC 60479–1:2018 Electrocution Heart Current Factors
I confirm that I am the main author of this contribution.
There was no financial or non-financial assistance from third parties.
I do not have any financial interest related to the subject matter.
I am not aware of any relevant patents or copyrights that affect this work.
The acknowledgements mention the work of a translator, and two paragraphs from
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
acknowledgements
The authors acknowledge the cooperation of Rockland Clinic, Montréal, QC; Sylvie Laprise, Directrice administrative des cliniques médicales as well as Dr. Susan Hunt in carrying out non-standard ECG tests on volunteer subjects. Professor Chris Andrews provided the Sam reference [9] used by IEC and Lesley Chisholm translated it into English.
References (25)
Willem Enithoven and the birth of clinical electrocardiography a hundred years ago
Caridac Electrophysiol. Rev.
(2003)Development of the electrocardiograph in Great Britain
Br. Med. J.
(1950)- et al.
An improved form of electrocardiograph
Rev. Sci. Instrum.
(1932) Bioelectromagnetic Phenomena
(2001)- et al.
Effect of electric shock on the heart
Trans. AIEE
(1936) Effects of Current On Human Beings and Livestock –Part 1: General Aspects
(2018)TB 694: Ground Potential Rise at Overhead AC Transmission Line Structures During Power Frequency Faults
(2017)TB 749: Substation Earthing System Design Optimisation Through the Application of Quantified Risk Analysis
(2018)- U. Sam, " Neue Erkenntnisse über die elektrische Gefährdung des Menschen bei Teildurchströmungen des Körpers," in VDRI...
Kriterien fur konventionelle vereinbarungen uber vertretbare risiken beim schutz gegen schadlichen elektrischen schlag bei wechselstrom 50/60 Hz
Elektrotech. Informationstech.
(2006)