On the “Zero of Potential of the Electric Field Produced by the Heart Beat”. A Machine Capable of Estimating this Underlying Persistent Error in Electrocardiography

Abstract

Modern electrocardiography (ECG) uses a constructed reference potential for the majority of leads. This reference potential, named after its inventor as the Wilson central terminal, is assumed to have negligible value and to be stationary during the cardiac cycle. However, the problem of its variability during the cardiac cycle has been known almost since the inception of 12-lead electrocardiography. Due to the cumbersomeness of the measurement system required to fully appreciate these variations, this topic has received scant research attention during the last 60 years. Taking advantage of modern electronic amplifiers' capability to detect small voltages, drawing only femtoamperes from physiological equivalent signal sources and of the right-leg connection availability, we developed a complete electrocardiography device that, aside from the eight independent signals of the standard 12-lead ECG, allows direct recording of the Wilson central terminal components. In this paper, we present details of the circuit together with its initial clinical evaluation. For this trial, we recorded data from 44 volunteer patients at Campbelltown Hospital (Campbelltown, Australia) and we found that the Wilson central terminal amplitude, as foreseen by Frank and others in the 1950s, is not negligible, its amplitude in relation to the lead II is, on average, 51.2%, and thus it may be clinically relevant.

On the Einthoven Triangle: A Critical Analysis of the Single Rotating Dipole Hypothesis

“…For this paper, we employed a total of 599 ECG recordings. The first 549 were taken from the online Physionet databank [ 5 ] PTB database [ 7 ], while the remaining 50 were selected from one of our recent studies [ 2 ]. All subjects volunteered for our study and gave written consent (this study was approved on 23 September 2015 by the National Human Ethics Committee of Liverpool Hospital with the protocol number HREC/15/LPOOL/302).…”

“…As we aim to make our research entirely reproducible, the necessary processing scripts are included, together with the results of the processing for each single dataset we employed as additional material. The new data that we recorded during our clinical evaluation [ 2 ] are also available for download in Matlab format upon request.…”

“…Before delving into the full explanation of our method, we must mention that Wilson’s hypothesis and the related triangle to star transformation has been challenged at both the theoretical [ 8 , 9 , 10 , 11 , 12 , 13 ] and practical level [ 2 , 3 , 6 , 10 , 11 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ] several times in the past 80 years, with several researchers confirming that, contrary to what Wilson’s principal postulates [ 1 , 22 , 23 ], the amplitude of the WCT can be comparable to (or even larger than) the limb leads, and can exhibit variability during the cardiac cycle similar to any other ECG signal [ 2 , 8 , 10 , 16 , 24 , 25 , 26 , 27 , 28 ]. Still, as already mentioned, one may note that the original instrument that both Einthoven and Wilson used to formalize the triangular ECG model and the WCT was measuring the current impressed by the heart to the body surface, while modern electrocardiography uses voltage amplifiers [ 28 ].…”

“…As one may note, the Right Leg (RL) is not included in the original electrical activity of the heart model [ 1 , 2 , 3 ]. This is because the original instrument used to demonstrate the limbs’ ECG by Einthoven was an extremely sensitive galvanometer (Ampere-meter) [ 1 , 4 ].…”

“…We prove this research hypothesis by analysing a total of 599 12-lead ECG recordings that include 549 recordings taken from the PTB database (freely available of Physionet [ 5 ]), and 50 recording taken the pilot study for our ECG device which is capable of recording the components of the WCT [ 2 , 6 ]. Using these recordings, we first assess where the limb leads form a triangle, and calculate the inner angles.…”