Studying the significance of cardiac contractility variability

Based on the relationship between the amplitude of the first heart sound (S1) and the cardiac contractility, we propose a concept of cardiac contractility variability (CCV) and a method of analysis. This study was carried out to examine the regularity of the amplitude variability of the first heart sound and to evaluate the practical significance of the CCV. This article considers only three factors: respiration, exercise, and psychological activity. Other factors influencing cardiac contractility are left for further study.