Contractility is another factor that influences cardiac output. Contractility of the myocardium represents the ability of the heart to contract independent of the influence from preload or afterload. Substances that cause an increase in intracellular calcium ions lead to an increase in contractility. Different concentrations of calcium ions in the cell lead to a different degree of binding between the actin (thin) and myosin (thick) filaments of the heart muscle.
Direct determination of cardiac contractility is not possible in the clinical setting. Therefore, surrogate parameters are used to evaluate or estimate the contractility.
Globale Ejection Fraction (GEF)
Ejection fraction represents the percentage of volume in a heart chamber which is ejected with a single contraction. The measurement of the Global Ejection Fraction offers a complete picture of the overall cardiac contractility.