Ventricular relaxation and diastolic function in cardiac-failure
Current opinion in cardiology. - London, 1986, currens
, p. 381-388
Relaxation in isolated cardiac muscle is regulated by triple control through load, inactivation, and nonuniformity, manifesting as load dependence. Load dependence describes different contributions of load and inactivation to control of isometric and isotonic relaxation and can be interpreted in terms of contractile protein properties and cellular calcium handling. From the extrapolation of triple control to onset, rate, and extent of relaxation in the intact left ventricle, a distinct regulation of isometric pressure fall and isotonic filling becomes evident. Slower relaxation manifests as slower left ventricular pressure fall and as impaired initial left ventricular filling. Incomplete relaxation is residual active force in ventricular muscle fibers throughout filling, manifesting as filling disturbances and increased filling pressures. Diastolic function relates to passive muscular and ventricular properties and can be evaluated only when relaxation has been completed. Diastolic dysfunction involves stiffer left ventricle and manifests as filling disturbances and increased filling pressures.