Comparison of Laplacian and bipolar ECGs for R-wave detection during noise

Body surface Laplacian mapping localizes cardiac activity and provides more detailed distributions compared to body surface potential mapping. Systematic comparison of the performance of bipolar and Laplacian ECGs during noise has not been performed. To determine whether Laplacian ECGs (2.5 cm diameter concentric rings) can reduce noise (myopotential and motion artifacts) and improve signal to noise ratio (SNR) compared to bipolar (4 cm spacing) ECGs, Laplacian and bipolar ECGs were recorded from the anterior (precordial V3) and lateral (precordial V6) chest regions in 25 patients undergoing posture changes and in-office exercises. Mean peak-to-peak (Vpp), root mean square noise (Noise(rms)) and SNR were computed across all activities and patients. Sensing performance using an R-wave detector with an auto-adjusting exponentially decaying threshold was assessed. Across all maneuvers, mean Vpp was larger for the bipolar ECG compared to the Laplacian ECG on the anterior (0.65 +/- 0.07 vs. 0.14 +/- 0.07 mV, p<0.05) and lateral (0.65 +/- 0.07 vs. 0.05 +/- 0.07 mV, p<0.05) regions. Laplacian ECGs resulted in least Noise(rms) compared to bipolar ECGs (anterior: 0.02 +/- 0.01 vs. 0.05 +/- 0.01, p<0.05; lateral: 0.01 +/- 0.01 vs. 0.07 +/- 0.01, p<0.05). Bipolar and Laplacian SNRs were comparable on the anterior chest (14.05 +/- 0.95 vs. 13.49 +/- 0.95, p=NS). On the lateral chest, bipolar SNR was larger than Laplacian SNR (13.78 +/- 0.95 vs. 8.67 +/- 0.96, p<0.05). Laplacian SNR on the anterior chest was larger compared to the lateral chest, confirming that Laplacian ECGs are sensitive to mapping location. Sensing performance showed that bipolar ECGs resulted in marginally superior sensing accuracy compared to Laplacian ECGs. In conclusion, Laplacian ECGs offer no advantage in SNR compared with standard bipolar ECGs.