The slope summarizes how strongly ventricular mechanical work rises as end-diastolic volume increases. A steeper relationship indicates that added filling produces a greater increase in stroke work, whereas a flatter relationship suggests reduced systolic performance. This makes the slope useful for characterizing contractility across several preload conditions rather than relying on one observation.
Contractility and loading conditions can both influence the heart's measured performance. Varying preload reveals how stroke work responds to changes in end-diastolic volume, helping separate the ventricular systolic response from the effect of a particular filling state. The resulting relationship is therefore more informative during changing circulation than an isolated measurement.
Ejection-based indices describe ventricular emptying under a particular loading condition, so their interpretation can change when circulation alters preload. Preload recruitable stroke work instead evaluates the relationship between stroke work and end-diastolic volume across altered filling states. That load-adjusted perspective can provide a more consistent assessment of myocardial systolic performance.
The assessment begins by producing or observing changes in ventricular preload. At each filling condition, investigators measure pressure-volume loop data and determine stroke work, while recording the corresponding end-diastolic volume. They then relate stroke work to end-diastolic volume and evaluate the slope of that relationship as the contractility index.
The principal outcome is the slope linking stroke work with end-diastolic volume. Its value provides an integrated measure of ventricular systolic performance across the tested preload range, rather than a result tied to one filling condition. Comparisons of this relationship can help identify changes in myocardial function during altered circulation or experimental intervention.
This analysis can support evaluation of heart failure and myocardial dysfunction, where ventricular contractility is a central concern. It also provides a framework for studying cardiac interventions and experimental treatments that may affect contractility. Because the method examines performance across changing preload, it is relevant when circulation or ventricular loading does not remain constant.