The article deals with the analysis of the monograph Evaluation of Performance and Analysis of Cyclic Work of the Heart written by B. A. Konstantinov, V. A. Sandrikov, and V. F. Yakovlev. It discusses the possible mechanism of the maintenance of the stability of hemodynamic indices--switching into action the contractions of nonfunctioning cardiomyocytes (the factor of functional heterogeneity).