Load Dependence of Relaxation

  • Dirk L. Brutsaert
  • Stanislas U. Sys


The mechanical performance of the heart as a muscular pump during systole depends on the contractile properties of the contraction phase and on the time of onset, speed, and extent of the relaxation phase. Relaxation of the heart is defined by the events during systole by which the heart, as a muscle and as a pump, returns to a precontractile configuration. Relaxation of cardiac muscle includes isometric force decline and isotonic lengthening. Relaxation of the ventricle as a pump encompasses the second part of ejection, isovolumic relaxation, and rapid filling (Figure 10-1). Similarly, as for the contraction phase, a triple control mechanism also operates during the relaxation phase [1]. Relaxation of cardiac muscle and of the ventricular pump is thus governed by the dynamic interaction of the sensitivity of the contractile apparatus to the prevailing load (load dependence) and the dissipating activation (inactivation). This interaction is modulated by the regional and temporal nonuniform distribution of load and inactivation.


Sarcoplasmic Reticulum Relaxation Mode Load Dependence Relaxation Load Rapid Filling 
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© Martinus Nijhoff Publishing 1987

Authors and Affiliations

  • Dirk L. Brutsaert
  • Stanislas U. Sys

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