extensions [ sound ] globals [ y ylast ydiv smoothed-ydiv since-last to-next rate beatwait interval hr stimer pulsetimer antiarrhythmics stimulant total-output smoothed-output limit brain patientstate ] patches-own [ potential pnext decayrate output health strength output-decay infarct automaticity] to setup ca set patientstate "Alert." set brain 1 set s-t false set cpr false set limit 45 set smoothed-output limit * 2 set rate 1 set since-last 250 ask patches [set decayrate 0.95 set strength 1 set health 1 set automaticity 0.000000025] end to go if (brain < 1) [ set brain (brain + 0.000001) ] if (brain < 0.85 and brain > 0.75) [ set patientstate "Dizzy." ] if (brain < 0.75 and brain > 0.5) [ set patientstate "Confused." ] if (brain < 0.5 and brain > 0.25) [ set patientstate "Unconscious."] if (brain < 0.25 and brain > 0.1) [ set patientstate "Cyanotic." ] if (brain < 0.1) [ user-message "The patient has died." stop] ask patches [ if potential < 0 [ set potential 0 ] if potential > 1 [ set potential 1 ] set output (output + 0.001 * health * (rate ^ 0.8 + 2 * stimulant - antiarrhythmics)) set output-decay (output-decay + 0.0005) if (pxcor = 0 and pycor = int ( max-pycor / 2)) [set to-next int(250 / (rate + 2 * stimulant - antiarrhythmics)) set since-last (since-last + 1) if (since-last >= to-next) [ set pnext 1 set since-last 0 ] ] set strength (rate) if (potential < 0.1) [ if any? neighbors with [ potential > 0.25 or random-float 1 < (automaticity + 0.00000025 * stimulant - 0.00000025 * antiarrhythmics) ] [ if random-float 1 < 0.75 [ set pnext 1 set output 0 set output-decay 0] ] ] ] ask patches [ set pnext pnext * decayrate + (0.25 * antiarrhythmics - 0.25 * stimulant ) * ( 1 - decayrate) set potential pnext set pcolor scale-color white potential 0 1 ] set antiarrhythmics (antiarrhythmics * 0.9999) set stimulant (stimulant * 0.9999) if (s-t) [ set rate (rate + 0.0013) ] if (rate > 1) [ set rate (rate - 0.001) ] set ylast y set y mean [ potential * sgn(pycor + 0.1) ] of patches set ydiv y - ylast set smoothed-ydiv smoothed-ydiv * 0.5 + 0.5 * ydiv ;;diffuse decayrate 0.0001 set total-output sum [output - output-decay ] of patches set smoothed-output smoothed-output * 0.99 + 0.01 * total-output if (damage-enabled?) [if smoothed-output < limit and not cpr [ ask patches [ damage ] set brain (brain * 0.99999) ] ] ifelse (ydiv > 0.005) [ if (beatwait > 10) [ set beatwait 0 set hr int(60 * (250 / (interval + 0.001))) set interval 0 ] set beatwait 0 ][ set beatwait (beatwait + 1) set interval (interval + 1) ] set-current-plot "ECG" set-plot-x-range (ticks - 3000) ticks plot y set-current-plot "plot 1" set-plot-x-range (ticks - 3000) ticks plot smoothed-output if smoothed-output < 0 [ set smoothed-output 0 ] if total-output < 0 [ set total-output 0 ] tick end to-report sgn [ x ] report (1 / (1 + exp(-10 * x))) - 0.5 end to synchro ifelse (stimer > 10) [ if y > 0.01 [ defib set stimer 0 stop]][set stimer stimer + 1 ] end to defib ask patches [ set pnext (pnext + 1) ] end to pace if ticks mod 250 = 0 [ ask patches with [ pxcor = 0 and pycor = min-pycor ] [ set pnext 1 ]] end to damage set health (health * (0.995 + random-float 0.01)) set decayrate (decayrate + random-float 0.0001 * (1 - decayrate)) if random-float 1 < 0.00000001 [ simple-infarct ] end to do-infarct ask patches [ set infarct 0 ] ask one-of patches [ set infarct 1 ] repeat (10 + random 25) [ ask one-of patches with [infarct = 0 and any? neighbors4 with [infarct = 1 ]] [ set infarct 1 ] ] ask patches with [ infarct = 0 and count neighbors with [ infarct = 1 ] >= 5] [ set infarct 1 ] ask patches with [ infarct = 1 ] [ set health (health * 0.9) set decayrate (decayrate + 0.5 * (1 - decayrate)) ] ;;diffuse decayrate 0.1 end to simple-infarct ask one-of patches [ ask patches in-radius 2 [ set health (health * 0.9) set decayrate (decayrate + 0.5 * (1 - decayrate)) ] ] end @#$#@#$#@ GRAPHICS-WINDOW 85 10 347 293 15 15 8.13 1 10 1 1 1 0 1 1 1 -15 15 -15 15 0 0 1 ticks BUTTON 12 10 76 43 Setup setup NIL 1 T OBSERVER NIL NIL NIL NIL BUTTON 13 44 76 77 Go go T 1 T OBSERVER NIL NIL NIL NIL PLOT 40 303 1130 538 ECG NIL NIL 0.0 0.0 0.0 0.0 true false PENS "default" 1.0 0 -16777216 true MONITOR 40 539 156 620 Heart Rate hr 17 1 20 BUTTON 489 35 595 68 Synchro synchro T 1 T OBSERVER NIL NIL NIL NIL BUTTON 364 35 479 68 Defibrillate defib\n NIL 1 T OBSERVER NIL NIL NIL NIL PLOT 160 543 1132 704 Cardiac Output NIL NIL 0.0 0.0 0.0 0.0 true false PENS "default" 1.0 0 -16777216 true SWITCH 924 48 1027 81 s-t s-t 1 1 -1000 SWITCH 367 82 470 115 CPR CPR 1 1 -1000 BUTTON 482 157 598 202 Stimulant set stimulant (stimulant + 1) NIL 1 T OBSERVER NIL NIL NIL NIL BUTTON 646 36 732 69 Charge set pulsetimer 10 NIL 1 T OBSERVER NIL NIL NIL NIL BUTTON 646 70 731 103 Pulse ifelse (pulsetimer > 0) [\nif (ticks mod 10 = 0) [\nset pulsetimer (pulsetimer - 1)\ndefib ]][ stop] T 1 T OBSERVER NIL NIL NIL NIL BUTTON 360 158 478 201 Antiarrhythmics set antiarrhythmics (antiarrhythmics + 0.1) NIL 1 T OBSERVER NIL NIL NIL NIL TEXTBOX 367 18 480 36 Unsynchronized shock: 11 0.0 1 TEXTBOX 491 17 597 35 Synchronized shock: 11 0.0 1 TEXTBOX 648 16 798 34 Repeated pulse: 11 0.0 1 TEXTBOX 368 134 518 152 Antiarrhythmic drug: 11 0.0 1 TEXTBOX 486 140 636 158 Stimulant drug: 11 0.0 1 TEXTBOX 926 27 1076 45 Cardiac Stress Test: 11 0.0 1 BUTTON 762 52 862 85 Pacemaker pace T 1 T OBSERVER NIL NIL NIL NIL BUTTON 646 160 795 204 Infarction do-infarct NIL 1 T OBSERVER NIL NIL NIL NIL SWITCH 847 162 1001 195 damage-enabled? damage-enabled? 0 1 -1000 MONITOR 359 209 506 290 Patient State patientstate 20 1 20 @#$#@#$#@ 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. 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