Session PB4.2

Waveform Phase Shift Study on Extremities to Compute the Relation between the Mason-Likar and the Standard Limb Lead Electrode Placement

M Sagiroglu*, S Thiagarajan

Cardiac Science Corporation
Bothell, WA, USA

It is well known that the ECG recordings using standard limb electrode placement and the Mason-Likar configuration present differences in amplitude and waveform morphology especially in the QRS complex. Anisotropic characteristics of the human body partially contribute these variations in the observed ECG waveforms between the two configurations.
In this study the authors have investigated the nature of this variation as a function of electrode locations along the limb, between the shoulder and the wrist to formalize a non-linear, space-variant relationship to characterize the amplitude and the phase components of ECG waveform that can transform one electrode placement to the other. Estandard (t, x) = L(t, x){Emason-Likar(t, x)} Where; L (t, x) is the complex transfer function that will map ECG between standard and Mason-Likar configuration.
This approach utilizes scalar wave equation to represent the observed ECG waveform as a complex function of time and location; E(t, x) = A(t, x) exp[iwt + f(t, x)] Where; E(t, x) : is the observed ECG signal, A(t, x) is the amplitude and f(t, x) is the phase angle at time t and electrode location x.
Cardiac Science Q-Stress ECG system is used to collect 12-Lead ECG data from two subjects. The limb electrodes were placed on the torso per Mason-Likar configuration, and the chest electrodes (V1-V6) were placed along the limb to observe the waveform transition. It was observed that the variation on the QRS complex is not only a “linear” amplitude change but in addition it also involves a “phase-rotation”. This phase-rotation displays a visible progression of Q and S-Wave amplitudes as a function of electrode position. Using the above equations, authors analyze QRS waveforms to determine the complex transfer function that can be used to map the ECG signals between the torso and the limb electrode positions. Initial trials indicated the need for a unique transfer function for each individual limb electrode position to transform the waveform transition.

(Abstract Control Number: 66)