What it is
Cardiac preload describes the filling and stretch of the ventricle before contraction.[1]
Why it matters
Preload shapes stroke volume because a ventricle that fills more can usually eject more blood up to physiological limits.[1,2]
Root causes of abnormal values
- Filling relation: More venous return and circulating volume fill and stretch the ventricle more, often raising stroke volume; too little return or volume underfills the ventricle and lowers stroke volume.[1,3]
- Timing relation: Preload also depends on time available for filling, so rhythm and rate can change preload even before muscle strength is considered.[1,4]
What it affects
- It connects venous return, blood volume, filling time, stroke volume, and cardiac output.[1]
Interpretation traps
- Preload is a hemodynamic mechanism, not a standalone home measurement.[1]