Cardiac Pump: An Introduction

International audienceThe heart is a hollow muscular organ composed of two apposed two-chamber pumps that receives blood from veins, where the driving pressure is relatively low, and then expels it into arteries, where the driving pressure is much higher, each pump being related to the systemic and pulmonary circulation.The heart has an intrinsic chaotic behavior (in the sense of deterministic chaos and nonlinear dynamics) that enables it to quickly respond to any sudden changes in the environment and adjust to physical activity. It is endowed with automatism that triggers its muscular activity under the control of the nervous system. The latter regulates its excitability (threshold of excitation), or bathmotropy; its action potential emission frequency, or chronotropy; its action potential conduction speed (conductibility), or dromotropy; its muscular contraction force, or inotropy; its diastolic relaxation, or lusitropy; and its distensibility, or tonotropy.Cardiac functioning depends on several factors, such as (1) ion carriers that determine ion fluxes and intracellular concentrations, especially in the nodal tissue that creates and propagates action potentials and myocytes that undergo contraction–relaxation cycles; (2) sarcomere activity, particularly the cross-bridge cycling rate; (3) extracellular matrix, other categories of associated cells (fibroblasts), capillaries, and nerve endings, that signals to myocytes; (4) wall perfusion responsible for nutrient inputs; and (5) cardiac loads, that is, flow conditions in upstream (veins) and downstream vessels (arteries), the so-called pre- and afterload (or postload).Functional noninvasive imaging of the heart is aimed at visualizing motions of the blood container and pump as well as its content during the cardiac cycle, using Doppler echography and echocardiographic particle image velocimetry as well as nuclear magnetic resonance imaging with its two derived techniques, diffusion tensor MRI and MR velocimetry