Myocardial contractility

Myocardial contractility represents the intrinsic ability of the heart/myocardium to contract. Changes in the ability to produce force during contraction result from incremental degrees of binding between myosin (thick) and actin (thin) filaments. The degree of binding that occurs depends on concentration of calcium ions in the cell. Within an in vivo intact heart, it is generally the action/response of the sympathetic nervous system driven by precisely time released catecholamine that determines the concentration of calcium ions in the cytosol of cardiac muscle cells. All factors that cause an increase in contractility work by causing an increase in intracellular [Ca] during contraction.