NetLogo User Community Models

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WHAT IS IT?

This is a simulation of the electrical activity of the ventricles of the human heart. It incorporates a semi-realistic electrophysiologic model of the heart, and the impact that cardiac output has on the health of the rest of the human body.

HOW IT WORKS

The simulation uses a standard model of cardiac depolarization and repolarization to re-create the electrical waves that produce the heartbeat, and the electrical abnormalities that can cause life-threatening cardiac arrhythmia.

HOW TO USE IT

SETUP: Clears the simulation and re-sets it.

GO: Starts the simulation. Pressing it again stops the simulation.

DEFIBRILLATE: Applies an unsynchronized electric shock to the heart, simulating real-life defibrillation. This works very well against some arrhythias, but not so well against others.

SYNCHRO: Applies a shock to the heart, synchronized with its own beat. In real life, this can be very effective against such rhythms as Ventricular Tachycardia (VTach), however, in the simulation, it is almost always ineffective. Hopefully, this will be fixed in future versions.

CHARGE and PULSE: CHARGE charges a virtual defibrillator, and pulse defibrillates. This works differently from a real-world defibrillator, however, it is the only option that is effective against some of the simulated arrhythmias.

CPR: Cardiopulmonary resuscitation. Switch this on as soon as possible when a patient suffers a severe arrhythmia. This temporarily provides blood flow to the brain and body, preventing damage while the arrhythmia is corrected.

PACEMAKER: Applies an electrical stimulus to the heart at a rate of one pulse per second, simulating a ventricular pacemaker. Useful when the heart rate is too low to sustain sufficient cardiac output.

CARDIAC STRESS TEST: While this switch is on, the heart rate will steadily increase. Good for testing the virtual patient's susceptibility to arrhythmias.

ANTIARRHYTHMICS: Applies a dose of a simulated antiarrhythmic drug, which slows the heart's electrical conduction and can prevent or terminate some arrhythmias.

STIMULANT: Applies a dose of a simulated stimulant drug, which accelerates the heart's electrical conduction and increases heart rate. This can cause serious arrhythmias, but in some cases, it can increase low cardiac output.

INFARCTION: A virtual heart attack. Usually causes arrhythmias.

DAMAGE-ENABLED: When this is switched on, the heart will suffer damage when it is not pumping hard enough to supply itself with blood, which can lead to simulated heart failure.

PATIENT STATE: The state of the virtual patient. A healthy patient is "Alert." A patient suffering from mild arrhythmia is "Dizzy." A patient suffering from more severe arrhythmia or loss of cardiac function is "Confused." A patient suffering from severe arrhythmia is "Unconscious." A patient near death is "Cyanotic" (turning blue). If a patient's arrhythmia is not corrected quickly, they will die.

ECG: The standard plot of electrical activity in the heart.

CARDIAC OUTPUT: How much "blood" the heart is pumping. This decreases due to arrhythmias. If it falls too low, the patient will begin to suffer symptoms (see PATIENT STATE above).

HR

THINGS TO NOTICE

Normal Sinus Rhythm: Start the simulation, and observe its behavior. The waves on the ECG should be evenly-spaced and regular.

PVCs: Occasionally, the heart will suffer premature ventricular contractions (PVCs). These appear as irregular beats between normal beats, and can sometimes trigger Ventricular Tachycardia, an extremely fast beat with a sawtooth-shaped wave. PVCs and VTach are more common when the patient is under the effects of Stimulants (see above) and less common when the patient is under the effects of Antiarrhythmics (see above).

THINGS TO TRY

Apply a dose of Stimulant and observe the arrhythmias that result.

Press INFARCTION to simulate a heart attack.

CREDITS AND REFERENCES

Created by Asymptote: http://asymptote.wordpress.com