Loading Conditions and Left Ventricular Relaxation
Relaxation refers to the process by which the myocardium returns to its initial or resting length and tension; in the intact heart the term refers to the process by which the left ventricle returns to its presystolic or end diastolic pressure and volume. Relaxation is controlled by a complex interaction between deactivation (the time-dependent decay of active-force-generation capacity) and loading conditions (forces affecting myocardial length and tension). These forces may be subdivided into loads that are applied early in the cardiac cycle (contraction loads) and those that are abruptly applied late in the cycle (relaxation loads) (Table 14-1). Our rationale for separating early and late loads rests in the experimental observation that the application of an early or contraction load results in a more prolonged relaxation, whereas the application of a late or relaxation load results in a premature and more rapid relaxation; this latter phenomenon has been called “load dependent relaxation” .
KeywordsFilling Rate Left Ventricular Pressure Peak Filling Rate Left Ventricular Relaxation Left Ventricular Systolic Pressure
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