A 9-independent-leads ECG system from 10 electrodes: A practice preserving WCT-less true unipolar ECG system

Abstract

Since the invention of the 12-lead Electrocardiography (ECG) it is taught that only eight out of the twelve signals recordable from the nine exploring electrodes are linearly independent. It is also accepted practice the use of other four linearly dependent signals to add diagnostic efficacy. Unfortunately, quality and usefulness of the 12-lead signals is directly correlated with electrode placement precision and concerns have been raised around intentional misplacements of limb electrodes also for resting ECG. In this paper we show that with a simple modification to the recording front-end, nine independent signals (one per recording electrode) can be recorded. These signals can be used to reconstruct precisely the 12-lead signals (without information loss) and a plethora of other linearly dependent new signals that can open an unexplored frontier in cardiac illnesses diagnosis. While we need to carefully evaluate the clinical implications of our findings, we present here the proposed circuit and a case study (healthy subject) showing the number of signals achievable and we quantify the effect upon the ECG signals of one of the most common intentional misplacement of electrodes

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

“…In order to preserve the mentioned characteristics, the printed circuit board is designed to take advantage of the embedded active guard ring amplifier on a Teflon substrate. Although the guard ring amplifier's primary job is to reduce the noise pick-up at cable and board connections, because this offers a replica of the input signal, we also use it to measure the raw voltage of the WCT components [17][18][19][20].…”

“…In addition, we assessed the point to point correlation between limb leads reconstructed using the limb components and limb leads that are recorded directly. To reconstruct the limbs, we simply operated a point by point subtraction between recorded signals and assessed the correlation between signals using the embedded MATLAB correlation function [19,20].…”

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

“…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 ].…”

“…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 ]. Therefore, it is possible to evince that, contrary to the original definition of WCT, in modern ECG devices the WCT used is the instantaneous average of the voltages of the three limbs (RA, LA, and LL) relative to a reference voltage (see Figure 1 panel (b)) [ 3 , 17 ].…”

“…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 ].…”