Effect of ECG signal gain on the detection accuracy of four common QRS detectors

The QRS complex detection methods have been extensively studied over the past several decades, and the current common QRS detection algorithms can achieve high detection accuracy on the open-access ECG database. Although massive of researches exist on the performance of QRS detectors, the effect of the ECG signal gain is usually ignored and did not attract researchers' attentions in the past studies. In this study, the effect of gain (including gain polar and gain value) on four widely used QRS complex detectors were comprehensively tested. Positive/negative gain had a significant effect on the RS-slope method and the difference operation method. Using negative gain, the accuracy of RS-slope method decreased 16.91% and 6.76% for high and low quality databases; the accuracy of the difference operation method decreased 8.86% for low quality database. It suggesting these two methods were not suitable for analyzing the inverted ECG channels such as the chest IV lead. Gain value had a slight effect on the jqrs' method due to the adding of the flat line judging procedure. Using gain value of 1 decreased the accuracy of the jqrs' method for both high and low-quality ECG databases by 2.49% and 0.48% respectively. The Pan-Tompkins method was not influenced by the gain because it was based on the peak energy. The conclusion generated by this study could potentially offer important reference for understanding the effect of ECG signal gain on those methods.