Four modules, one heartbeat
Electricity, atrial kick, ejection and refilling—one module per step, slowing a sub-second beat more than tenfold so you can stop at any moment.
Principles·Hospitals & health education
Health Education Principle Animation:One Heartbeat Lab
Hospitals and science communicators need to explain what happens inside the body—but it is fast and invisible: a heartbeat lasts under a second while electricity, valves and blood all change at once. This lab slows one beat down in code, from the SA node firing through atrial contraction and ejection to refilling, in four steps.
Pressures, volumes and flows come from the time-varying elastance heart model used in textbooks, and the ECG is built from real intervals. Drag heart rate or contractility, or switch to aortic stenosis, and the drawing, monitor and pressure–volume loop respond. Your own health topic can be made the same way—as video, GIFs or an interactive page.
ForHospitals, health commissions, disease control, health media
CARDIAC CYCLE LAB
One heartbeatElectricity, valves and blood flow
Adult at rest · 72 bpm · LV end-diastolic volume ~130 mL · BP ~120/80 mmHg · PR 0.16 s
EXPERIMENT 01EXPERIMENT 02EXPERIMENT 03EXPERIMENT 04
Every beat starts with an electrical signal
The atria squeeze the last blood into the ventricles
Ventricles contract and eject once pressure beats the aorta
The ventricles relax, valves swap, blood flows back in
SA node firesAV node delayVentricles depolarisePassive fillingAtrial contractionAV valves closeIsovolumic contractionRapid ejectionReduced ejectionIsovolumic relaxationRapid fillingLate diastoleFilling: AV valves openIsovolumic: all valves shutEjecting: outflow valves openObstructed ejection
Electrical signalECGOxygen-rich bloodOxygen-poor blood
Left ventricleLeft atriumValvesOxygen-poor blood
LV pressureAortic pressureLA pressureDepolarised muscle
Oxygen-rich bloodOxygen-poor bloodCardiac outputValves
SA node: the natural pacemakerAtria depolarise = P waveAV node holds the signal ~0.1 sMeanwhile the atria emptyHis bundle runs down the septumPurkinje fibres fire the ventricles togetherBlood flows in down the pressure gradientAtrial contraction tops up the ventricleMitral valve openMitral closes: first heart soundTricuspid valve (right heart in step)All valves shut, pressure buildsAortic valve pushed openHigh-speed jet through the narrow valveOxygen-rich blood enters the aortaVentricular wall thickensAll valves shut, ventricle relaxesAortic valve closes: second heart soundAV valves open, rapid inflowLate diastole, filling slowsVenous blood returns to the right atrium
P waveQRS complexT wave: repolarisationLV volumeLA volumeAtrial kickLV pressureAortic pressureLA pressureCardiac outputStroke volume (÷20)Too fast: diastole too short
↑ Voltage (mV)Volume (mL)Pressure (mmHg)Cardiac output (L/min)Time (s, 0 = QRS onset)Time (s, 0 = QRS onset)Time (s, 0 = QRS onset)Heart rate (bpm) →
Isovolumic contractionEjectionIsovolumic relaxationFillingEnd-systolic PV line
↑ LV pressure (mmHg)LV volume (mL) →
0%
What to watch
The SA node at the top of the right atrium fires on its own; the wave sweeps both atria (the P wave), pauses at the AV node so the atria can finish emptying, then races down the His bundle and Purkinje fibres through the ventricles (the tall, narrow QRS).
Most blood flows into the ventricles passively while the AV valves are open; after the P wave the atria contract and add about a fifth more. As soon as the ventricles start to squeeze, their pressure exceeds the atria and the mitral and tricuspid valves snap shut—the first heart sound.
With all four valves shut the ventricle can only build pressure; once LV pressure exceeds the aorta the aortic valve opens, blood is ejected and the walls thicken as the cavity shrinks. Switch to aortic stenosis: the ventricle must generate far higher pressure.
Ejection ends, the aortic valve shuts (second heart sound) and the ventricle relaxes with all valves closed; once its pressure drops below the atrium the AV valves open and blood rushes back, then slows. At very high rates diastole gets too short to refill, so each beat pumps less.
01ABOUT THIS LAB
What’s in this lab
Heart, monitor and sounds in sync
The four-chamber view, ECG and arterial-pressure monitor, the four valves and both heart sounds share the same moment in time.
Drag parameters, see results
Heart rate, contractility and aortic stenosis are adjustable; pressures, volumes, output and the PV loop are computed live.
One build, many formats
The same lab records as an explainer video, splits into step GIFs, or runs on a hospital website, waiting-room screen or patient-education page.
02WHO USES IT
How hospitals & health education clients use principle animation
Hospitals, health commissions, disease control, health media
Disease and treatment explainers, patient education, health campaigns
03MORE
Principle labs for other industries
Aerospace & automotive
Turbofan engine
Where thrust comes from
Agriculture & foodLighting and CO₂ in a plant factory
How to grow lettuce faster
Chemicals & materialsMultitubular fixed-bed reactor
Hot spot, pellets and coking
Construction & engineeringPrestressed concrete box girder
Loading, tensioning and cracking
Education & publishingKepler’s three laws
Planetary motion solved from Kepler’s equation
Energy & powerPumped storage plant
Peak shaving and valley filling
Environment & waterAAO wastewater treatment
Nitrogen and phosphorus removal
Geoscience, weather & disasterTyphoon structure and landfall
From warm-sea genesis to decay over land
Government science & industrySponge city
Storm, infiltration and storage
Patents, legal & investmentPlanetary gear reducer
Patent figures, ratios and claim chart
Medical devicesCoronary stent intervention
Stenosis, dilation, deployment and apposition
Science centers & museumsBlack holes and gravitational lensing
How a black hole bends light and spacetime
New energy & batteriesStorage battery module
Heat, cooling and thermal runaway
Pharma & biotechAntibody–drug conjugate (ADC)
Structure, targeting, release and killing
Universities & research institutesScanning tunnelling microscope
Tunnelling, feedback and atomic imaging
Semiconductors & electronicsChip lithography and etch
Five steps to one circuit layer
Telecom & computing5G massive MIMO
One antenna array, many users at once
AllAll principle animations
13 step-by-step animations and uses across 18 client types
Don’t see your need? Message us
Listed here is what we’ve done and what people ask most. For other industries or uses, add us on WeChat and send a one-line brief—we’ll reply with an approach and quote within 1–2 working days.
Page updated 2026-10-24