Poincare plot: A simple and powerful expression of physiological variability

Abstract

“Variability is the sign of life” is the principle being followed by all living beings on the earth. The study of variability came into existence in 1965 with Hon and Lee’s observation of the need for rapid delivery after a decrease in fetal heart rate variation. The field has grown phenomenally since then and has become an essential part of patient care. Heart rate variability is the most studied and explored for its physiological origin and subsequent clinical applications. It has been followed by blood pressure variability, blood flow variability, morphology index variability, and so on. These variabilities are expressed in the time domain, frequency domain, and nonlinear domain by different parameters and geometric shapes. Poincare representation is one of the nonlinear domain representations of variability. Elliptical, torpedo-like, or fan-shaped central conglomeration of points in Poincare plots are generally considered normal. The shape distorts considerably in different diseases. Not much effort has been made to classify these distortions since the time domain and frequency domain presentations have dominated most of the studies due to their numerical expression. Poincare presentation in arrhythmias is very interesting to the extent that a diagnosis can be made based on the Poincare plot. The point plots are now being extended to curve plots or line plots for better detection of arrhythmia and its understanding. Owing to large scatter in the time domain and frequency domain parameters of variability, extended Poincare plots are currently being explored as substitutes. Some of these features of Poincare plots and their clinical applications are briefly described in this article.

Keywords

• arrhythmia detection
• blood flow variability
• heart rate variability
• morphology index variability
• poincare plot