Abstract：Objective To explore the effect of the constant and variable nature of RR interval on the position and trend of ECG scatter plot, and to summarize the application and analytic techniques of differential method of constants and variables in rapid analysis of ambulatory electrocardiography (AECG). Methods Combined with the RR interval characteristics of classic cases such as premature ventricular contraction (PVC), consecutive PVC and atrial premature beats, we analyzed the relationship between the position and trend of the characteristic point set, and the constant and variable nature of RR interval. The analytical strategy of differential method of constants and variables were summarized. Results In the time scatter plot, when RR interval is a constant, the trend is horizontal (such as NV, VV layer, etc.); when RR interval is a variable, the scatter plot is manifested by fluctuating up and down (such as NN, SN, VN layer, etc.). In the Lorenz scatter plot, when the abscissa is a constant, the characteristic point set is vertically distributed (such as NVN, VVN point set, etc.); when the ordinate is a constant, the characteristic point set is horizontally distributed (such as NNV, VNV point set, etc.); when the abscissa and ordinate are both constants, the distribution of the characteristic point set is localized (such as NVV, VVV point set, etc.). When the abscissa and ordinate are both variables, the characteristic point set has a oblique distribution (such as VNN, NNN point set, etc.), and the slope of its principal axis depends on the ratio of the coefficients of the two variables according to the principal of the differential calculus. Conclusion The constant and variable nature of RR interval determines the position and trend of ECG scatter plot. The constant and variable rapidly identified by scatter plot technique can reveal parts of the electrophysiological mechanism of arrhythmia, which is similar to a natural electrophysiological examination. Differential method of constants and variables is an effective method for analyzing ECG scatter plot, and it is also a basic skill to analyze AECG quickly.
