The Role of Myocardial Contractility in Myocardial Contraction

Serena Y. Kuang ^* Gorune Geloian

• Oakland University William Beaumont School of Medicine, Rochester, United States

Myocardial contractility (MC) is an important concept that is widely used in the literature. However, the definitions of it in textbooks and research are remarkably vague, inconsistent, or mutually contradictory. By addressing the major issues with defining MC and classify them into five categories, conducting a conceptual analysis of these issues, and applying the concept of complex adaptive systems (CAS), we conceptualize MC from a higher-level in a broader scope using a theoretical, functional, three-dimensional framework of capacity/resource, adaptability, and ability (force and/or velocity resulting from the cardiac muscle contraction). The MC framework also illustrates the complex, non-linear, dynamic relationships among the three dimensions, which has great clinical implications. Understanding these relationships recognizes that interventions might not have linear effects, leading to more cautious and context-sensitive treatments, and suggests optimizing resource use rather than maximizing outputs, potentially reducing adverse events like arrhythmias or myocardial stress. Considering the MC framework as a CAS, we further highlight its system-level emergent properties (efficiency of muscle contraction and circadian rhythm-, history-, and temperature-dependencies) and their significance in cardiac muscle research, exercise training, and clinical practice. The MC framework successfully eliminates all the issues we address, differentiates MC from cardiac performance, and suggests future directions of research. A theory of MC is established at the end as a summary of the outcomes of this article, including the components of MC (the three dimensions), the relationship among the components, the system-level properties of MC, the role of MC (one of the properties that characterize cardiac muscle contraction), and the significance of our new conceptualization of MC. Moreover, we identify a non-linear A-U-O (regulated resource Allocation-regulated Utilization of the allocated resource-regulated final Output of a system) functional pattern to characterize the MC framework. The significance of the A-U-O pattern transcends the MC framework and has the potential to be universally applicable to study biological complex systems, representing a theoretical breakthrough in the study of CAS.