Kérdö Autonomic Index: Role of Initial Parameters, Areas, and Limitations of the Use

Abstract

The Kerdo Autonomic Index (KAI) was developed by the Hungarian physician I. Kerdo and was used by Russian physiologists to assess the balance of tone between the sympathetic and parasympathetic nervous systems. KAI gives an indirect characteristic of the vagosympathetic balance in the body without revealing the mechanisms of this balance. It was found that in athletes and patients with hypertension, the correlation between KAI and heart rate (HR) is positive, and between KAI and diastolic blood pressure (BPd) negative, which confirms the ideas of I. Kerdo. A theoretical graphical analysis of the dependence of KAI on its constituent parameters showed that KAI has a decreasing rectilinear dependence on BPd and increasing inverted hyperbolic dependence on HR. KAI reflects vagosympathetic balance in the body to a greater extent in terms of HR and to a lesser extent in terms of BPd. KAI correctly characterizes the vagosympathetic balance in the body of athletes before and after physical activity. The use of KAI to assess vagosympathetic balance in patients with hypertension is not recommended. With high blood pressure in hypertensive patients, KAI values can lead to an erroneous conclusion about the vagosympathetic balance in the body.