Cardiac Cycle & Ejection Fraction Simulator

Heart Condition

Controls

Heart rate 72 bpm

Preload (end-diastolic vol.) 140 mL

Contractility 100%

DIASTOLE — filling

Live Hemodynamics

Stroke volume

0 mL

Ejection fraction

Cardiac output

0.0 L/min

End-systolic vol.

0 mL

How it works

Each heartbeat is a cycle of two mechanical phases. In diastole the ventricles relax, the mitral and tricuspid valves open, and blood fills them from the atria. In systole the ventricles contract, the mitral/tricuspid valves shut, and the aortic/pulmonic valves open to eject blood into the aorta and pulmonary artery.

Stroke volume:     SV = EDV − ESV
Ejection fraction: EF = SV / EDV
Cardiac output:    CO = SV × HR

The Frank-Starling law says a healthy ventricle contracts harder when it is stretched by a larger end-diastolic volume (EDV) — up to a point, after which over-stretching stops helping. This simulator applies that relationship to the preload slider, then scales the result by a contractility factor:

Heart rate — beats per minute; sets how fast the cycle repeats.
Preload (EDV) — how full the ventricles are just before they contract.
Contractility — the intrinsic squeezing strength of heart muscle, independent of stretch.

A normal EF is roughly 55-70%. Heart failure with reduced ejection fraction (HFrEF) comes from weakened contractility — the ventricle fills normally but can't squeeze out its usual share, so EF and cardiac output both fall even though EDV may rise. An athlete's heart adapts the opposite way: a larger, more compliant ventricle fills to a bigger EDV and beats more slowly at rest while still moving the same or more blood per minute.

Oxygenated (left heart) Deoxygenated (right heart)

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