In terms of cardiac output, what does a lower ESV indicate about heart performance?

A lower end-systolic volume (ESV) is indicative of a strong heart performance, primarily because it suggests that the heart is effectively emptying its chambers during systole (the contraction phase of the heartbeat). When ESV is lower, it means that there is less blood remaining in the ventricles after contraction, which typically leads to an increase in stroke volume (SV). Stroke volume is calculated as the difference between the end-diastolic volume (the amount of blood in the ventricles before contraction) and the end-systolic volume. Therefore, a low ESV contributes to a higher stroke volume, reflecting that the heart is efficiently pumping a substantial amount of blood with each beat.

A good stroke volume indicates that the heart is capable of delivering adequate blood flow to meet the body's demands, which is a sign of effective cardiac function. This efficiency in blood pumping can be especially crucial during times of physical exertion or increased metabolic need. In contrast, a higher ESV would indicate less blood being ejected, leading to decreased stroke volume and potentially less effective cardiac performance.