Unipolar ECG circuits: Towards more precise cardiac event identification

We present a bio-potential front-end amplifier capable of recording unipolar ECG signals without making use of the Wilson Central Terminal. The circuit is compatible with both standard and dry electrodes, and is low power (requiring less than 25 mW powered at 12 V). It is therefore well suited for long-term applications The information contained in the new unipolar recordings may yield unique diagnostic capabilities as it avoids the need to measure differential signals or make use of the averaging effect imposed by the Wilson Central Terminal. Our tests on a small population (5 subjects) showed that the system also allows direct, real-time software calculation of signals corresponding to standard ECG leads, which have a correlation in excess of 92% with standard signals recorded in parallel. Comparisons between these recordings reveal that one of the most evident alterations super-imposed by the Wilson Central Terminal is a shift in the time domain of important features of the ECG signals such as the R-peak.