ACM Extended Wiki | Cardiac rhythms

01

Choose the treatment path

Finding	Rhythms	Action
Organized rhythm with a pulse	Sinus, AFib, AFib with RVR, atrial tachycardia, SVT, VT with a pulse	Assess stability and treat the cause. Use SYNC for cardioversion of an appropriate organized tachyarrhythmia.
Shockable arrest	VF, pulseless VT, torsades	CPR and ventilation; defibrillate with SYNC off. Correct reversible causes.
Nonshockable arrest	PEA, asystole	CPR, ventilation and correction of the cause. Do not defibrillate.
Moving or recently shocked trace	CPR/motion artifact or the brief post-shock display	Reassess once the transient clears. An electrical number or a brief flat trace alone does not establish recovery or death.

How to read these monitor examples

Each strip spans six seconds and uses the mod’s ECG shapes, sampling interval and bright green monitor color. The examples hold the electrical rate steady; AFib uses variable intervals. Pulse status must be assessed separately. Motion, compressions and poor electrode contact can change the live display.

The vertical scale shows relative monitor deflection, with upward deflections positive. It is not a calibrated millivolt scale. The torsades strip shows its established appearance; the rhythm’s entry transition is described below.

Sources: native rhythm shapes, custom rhythm shapes, beat timing and monitor color, checked at commit dd50edf.

02

Sinus rhythm

Pulse: Present if perfusion is adequate

Organized P-QRS-T pattern at slower rates. At faster rates the monitor uses a compressed narrow complex pattern.

ECG example75 BPM example

Regular P waves, narrow QRS complexes and T waves. Confirm perfusion with a pulse check. Hover, tap or enter a time to inspect. Vertical scale is relative, without mV calibration.

Reference	What happens in game
Rate	Follows the patient's actual heart rate
Entry / transient rhythm	Appears directly on recovery or when an induced perfusing rhythm terminates. There is no separate timed entry rhythm.
Common causes	Normal rhythm after stabilization. Pain, blood loss, oxygenation, temperature and medications can move the rate while it remains sinus.
What to do	Assess perfusion, breathing and injury. A normal looking ECG does not prove normal blood volume or adequate ventilation. No shock is indicated for sinus rhythm.
Conversion / deterioration	Changes as physiology changes. If the rate becomes critically high or low, or pressure/oxygenation fails, the native deterioration rules can take over.

03

Sinus bradycardia

Pulse: May be weak; check directly

Organized sinus complexes with longer R-R intervals. This is a rate presentation of sinus rhythm, not a separate selectable electrical rhythm.

ECG example45 BPM example

The same sinus morphology with more time between beats. Check the pulse and pressure. Hover, tap or enter a time to inspect. Vertical scale is relative, without mV calibration.

Reference	What happens in game
Rate	Slow sinus rate; below 60 BPM is a descriptive band
Entry / transient rhythm	Rate slows progressively according to the cause. There is no fixed countdown or separate entry waveform.
Common causes	Hypoxia, hypothermia, drug depression/toxicity and late circulatory failure. A head injury with a Cushing response can also slow the rate.
What to do	Correct oxygenation/ventilation and assess pressure, temperature and medication exposure. Atropine can raise rate; identify whether the underlying cause needs reversal, rewarming or another intervention.
Conversion / deterioration	Below 40 BPM outside an existing critical vitals grace period, the game enters its fatal rate pathway. VF is the usual electrical selection; active adenosine can instead select asystole. This is game behavior, not a requirement to wait for that threshold.

04

Sinus tachycardia

Pulse: Present until perfusion fails

Regular narrow complexes, with less room between beats. P and T detail compresses at high rates.

ECG example130 BPM example

The game compresses the sinus complex at this rate. The underlying cause still determines perfusion. Hover, tap or enter a time to inspect. Vertical scale is relative, without mV calibration.

Reference	What happens in game
Rate	Fast sinus rate; above 100 BPM is a descriptive band
Entry / transient rhythm	Tracks the patient's changing rate. Hemorrhagic tachycardia does not automatically become SVT under the default settings.
Common causes	Blood loss, pain, hypoxia, physiological stress, epinephrine or distress during inadequate sedation/paralysis.
What to do	Control hemorrhage, replace volume, treat pain, support ventilation and reassess any pressor or sedative delivery. Adenosine does not treat the underlying sinus response.
Conversion / deterioration	A sustained pressor surge can induce atrial tachycardia or SVT. A native rate above 220 BPM can enter VT with a pulse and then the critical vitals pathway.

05

Atrial fibrillation

Pulse: Usually present

Irregularly irregular narrow complexes with a fibrillatory baseline and no consistent P wave.

ECG example90 BPM nominal example

Uneven beat spacing and a fibrillatory baseline. The rate is a nominal example; individual intervals vary. Hover, tap or enter a time to inspect. Vertical scale is relative, without mV calibration.

Reference	What happens in game
Rate	Controlled target about 90 BPM
Entry / transient rhythm	Can be induced directly or follow rate control of AFib with RVR. The rhythm label changes immediately when treatment is effective; the actual heart rate can settle progressively. No separate timed entry stage is drawn.
Common causes	Rate controlled AFib with RVR, or an instructor created scenario. Severe hypothermia can initiate the faster RVR presentation.
What to do	Follow pulse, pressure and symptoms. Correct cold exposure and other physiological problems. Synchronized cardioversion can convert this modeled rhythm to sinus when intervention is appropriate.
Conversion / deterioration	Rate control does not itself restore sinus rhythm. Successful synchronized cardioversion restores sinus; native critical deterioration overrides the perfusing rhythm.

06

Atrial fibrillation with RVR

Pulse: Present, with impaired perfusion possible

Fast, irregularly irregular narrow complex rhythm. Uneven R-R intervals and a fibrillatory baseline distinguish it from regular SVT.

ECG example150 BPM nominal example

Fast, uneven beat spacing with a fibrillatory baseline. Assess whether the patient remains perfusing. Hover, tap or enter a time to inspect. Vertical scale is relative, without mV calibration.

Reference	What happens in game
Rate	Default target about 150 BPM
Entry / transient rhythm	Starts directly when induced. At core temperature 32°C or lower there is a 15% chance on each eligible cooling check; this is probabilistic, so there is no fixed onset time.
Common causes	Severe hypothermia and instructor induction. The modeled rhythm adds a 28 mmHg pressure penalty and can produce discomfort and brief obtundation.
What to do	Rewarm and assess perfusion. Esmolol or amiodarone can rate control it to AFib. Synchronized cardioversion can restore sinus. Adenosine does not terminate AFib.
Conversion / deterioration	Rate control targets AFib near 90 BPM after enough medication effect develops. Successful cardioversion restores sinus immediately, followed by the short post-shock display period. Ongoing native deterioration can still produce arrest.

07

Atrial tachycardia

Pulse: Present

Regular fast narrow complexes. The small atrial deflection is easiest to see when the rate leaves enough space between complexes.

ECG example185 BPM example

Regular narrow complexes with a small atrial deflection before the main spike. Hover, tap or enter a time to inspect. Vertical scale is relative, without mV calibration.

Reference	What happens in game
Rate	Default target about 185 BPM
Entry / transient rhythm	Can be induced directly, or after about 6 seconds of a sustained qualifying pressor surge. The rhythm appears directly once induced; no additional timed entry pattern follows.
Common causes	Excess epinephrine related drive or stacked measured push dose support, with the patient already tachycardic. It adds a 12 mmHg pressure penalty and discomfort.
What to do	Check medication concentration and actual infusion rate. Esmolol or amiodarone can terminate it; synchronized cardioversion is available. Adenosine's dedicated conversion effect is limited to SVT.
Conversion / deterioration	Successful medication conversion or cardioversion returns to sinus. Reducing the original surge is still necessary, because conversion alone does not remove the cause.

08

Supraventricular tachycardia (SVT)

Pulse: Present, may be poorly perfusing

Regular rapid narrow complexes, generally without a clearly separated P wave. It should not look like the broad complexes of VT.

ECG example190 BPM example

Regular, rapid narrow complexes. The trace does not determine whether pressure is adequate. Hover, tap or enter a time to inspect. Vertical scale is relative, without mV calibration.

Reference	What happens in game
Rate	Default target about 190 BPM
Entry / transient rhythm	Direct induction, or about 6 seconds of a stronger qualifying pressor surge. There is no separate timed narrow to wide entry sequence. The old optional rate only trigger is disabled by default and is not an exposed Addon Option.
Common causes	A sufficiently strong epinephrine/push dose surge or instructor induction. The rhythm adds an 18 mmHg pressure penalty and can cause discomfort or obtundation.
What to do	Rapid IV / IO adenosine can terminate the modeled regular SVT. Complete the required flush when enabled. Esmolol and amiodarone are additional modeled conversion paths; synchronized cardioversion can restore sinus.
Conversion / deterioration	A qualifying adenosine dose attempts conversion after about 1 second of systemic effect. It briefly slows rate without deliberately creating asystole. Other drug conversions depend on active effect rather than a fixed bag hanging timer.

09

Ventricular tachycardia with a pulse

Pulse: Present; verify before choosing shock mode

Regular broad ventricular complexes with little normal P-QRS-T separation.

ECG example230 BPM example

Broad ventricular complexes. This example has a pulse; pulse assessment determines the treatment path. Hover, tap or enter a time to inspect. Vertical scale is relative, without mV calibration.

Reference	What happens in game
Rate	Uses the patient's actual heart rate
Entry / transient rhythm	The native fatal rate pathway selects VT when heart rate exceeds 220 BPM outside a critical grace period. No separate timed entry morphology is implemented for this rhythm.
Common causes	Extreme physiological or drug related tachycardia. The underlying circulatory condition determines whether the patient remains perfusing.
What to do	Use synchronized cardioversion for an unstable perfusing VT. IV / IO lidocaine has a conversion path in the current mod. Correct the cause of the extreme rate. The AED's automatic analysis does not advise defibrillation for this perfusing VT.
Conversion / deterioration	Critical deterioration can lead to pulseless VT or another arrest rhythm. The native recovery check can clear VT when heart rate is above 45 and below 200 BPM and MAP is above 60 and below 180 mmHg. There is no extra fixed six second recovery hold in the current observer.

10

Pulseless ventricular tachycardia

Pulse: Absent

Broad, rapid ventricular complexes. The waveform alone does not establish whether a pulse exists.

ECG example230 BPM electrical example

The same broad waveform can occur without a pulse. This example is cardiac arrest. Hover, tap or enter a time to inspect. Vertical scale is relative, without mV calibration.

Reference	What happens in game
Rate	Displayed electrical rate generally 200–240 BPM
Entry / transient rhythm	Selected at arrest or after deterioration from a critical fast rhythm. There is no separate timed entry waveform.
Common causes	Deterioration of severe tachycardia, critical injury or an induced arrest scenario.
What to do	CPR, effective ventilation, defibrillation with SYNC off, and correction of reversible causes. Amiodarone and IV / IO lidocaine can improve defibrillation response.
Conversion / deterioration	Without effective CPR, it can deteriorate to VF and then asystole through randomized checks. Successful defibrillation still requires the patient's ROSC conditions to be met. Repeating a native VF/pulseless VT shock within 60 seconds of the previous recorded shock can instead cause asystole in the current game.

11

Ventricular fibrillation

Pulse: Absent

Continuous chaotic deflections without organized QRS complexes. The electrical display can vary roughly 100–220 BPM, but this is not a pulse.

ECG exampleNo organized rate

Chaotic activity without consistent QRS complexes. A displayed electrical number would not be a pulse. Hover, tap or enter a time to inspect. Vertical scale is relative, without mV calibration.

Reference	What happens in game
Rate	No organized ventricular rate; the monitor may show an electrical number
Entry / transient rhythm	Appears directly at arrest or after deterioration from pulseless VT. No separate timed coarse to fine entry sequence is implemented.
Common causes	Critical injury, severe physiological deterioration, progression of another arrest rhythm, or an unsynchronized shock to an organized perfusing rhythm.
What to do	CPR, ventilation and defibrillation with SYNC off. Check blood volume, oxygenation and chest causes. Amiodarone/lidocaine can improve the modeled shock response.
Conversion / deterioration	Can deteriorate to asystole when CPR is absent and randomized deterioration checks succeed. A successful shock does not guarantee ROSC if circulation remains inadequate.

12

Torsades de pointes

Pulse: Absent from the moment it is induced

Polymorphic ventricular complexes with changing amplitude and polarity, forming the characteristic twisting pattern.

ECG example220 BPM electrical example

Established torsades after its entry transition: complexes change shape, amplitude and polarity. The patient is pulseless throughout the entry stage too. Hover, tap or enter a time to inspect. Vertical scale is relative, without mV calibration.

Reference	What happens in game
Rate	Default electrical target about 220 BPM
Entry / transient rhythm	Starts with a narrower, SVT like rapid pattern. Every fourth beat becomes more ventricular early, then the whole run gradually widens and develops its twisting amplitude. The default entry transition lasts 15.84 seconds, equivalent to three 5.28-second monitor sweeps.
Common causes	Marked hypocalcemia, raised ICP or cumulative amiodarone exposure of at least 2.2 g. The trigger is probabilistic, including the severe tier; it is not guaranteed to fire immediately. It can also be induced for training.
What to do	Treat as pulseless arrest throughout the entry transition: CPR, effective ventilation and defibrillation with SYNC off. Magnesium can terminate it once sufficient active effect develops. Correct low calcium or raised ICP and stop excessive amiodarone exposure.
Conversion / deterioration	Magnesium suppresses recurrence while enough active effect remains. After magnesium assisted conversion there is a short default 20-second recurrence protection period; defibrillation uses a separate short protection period. The underlying cause can re-induce torsades after protection/effect fades. Amiodarone does not treat this modeled rhythm.

13

Pulseless electrical activity (PEA)

Pulse: Absent despite organized ECG activity

Organized abnormal complexes with beat to beat variation. The monitor's BPM is an electrical rate and does not establish mechanical circulation.

ECG example80 BPM electrical example

Organized abnormal complexes with no mechanical pulse. PEA can have several appearances; the monitor alone cannot diagnose perfusion. Hover, tap or enter a time to inspect. Vertical scale is relative, without mV calibration.

Reference	What happens in game
Rate	Electrical display varies within 60–100 BPM
Entry / transient rhythm	Appears directly when reversible circulatory failure selects PEA. There is no separate fixed bradycardic entry rhythm in the current build.
Common causes	Severe blood loss, severe hypoxia, tension pneumothorax or a large hemothorax. The ECG alone does not identify which cause is present.
What to do	CPR, effective ventilation and rapid correction of the cause. Control bleeding and restore circulating volume; treat obstructive chest injury. Do not defibrillate PEA.
Conversion / deterioration	Eligibility is rechecked every 5 seconds. Corrected PEA can attempt ROSC without waiting for a shock. After 6 minutes, the reversible PEA handling expires and the general arrest selection resumes; this does not guarantee a particular next rhythm.

14

Asystole

Pulse: Absent

Near flat baseline with small monitor noise; no organized ventricular complexes.

ECG example0 BPM

Low baseline noise without organized complexes. Reassess the patient and monitor connection. Hover, tap or enter a time to inspect. Vertical scale is relative, without mV calibration.

Reference	What happens in game
Rate	0 BPM
Entry / transient rhythm	Can appear directly with profound blood loss or another severe arrest cause, or after VF deterioration. No separate timed entry waveform is implemented.
Common causes	Profound blood loss, progressive untreated arrest, severe lidocaine toxicity or an inappropriate/refractory shock. Blood volume below 3.1 L can select asystole in the arrest handler.
What to do	CPR, effective ventilation and correction of reversible causes. Defibrillation is not indicated. Use actual pulse and circulation findings to assess recovery.
Conversion / deterioration	A flatline alone does not determine whether the unit is dead. Recovery requires a living patient and successful resuscitation with adequate circulation; dead units cannot regain medication effects or ROSC.

15

Transition timing

Transition	Default timing	How to interpret it
Pressor surge > atrial tachycardia or SVT	About 6 s after a sustained qualifying surge	The patient must already be tachycardic and perfusing. A stronger surge selects SVT. A 90-second refractory period limits repeated automatic induction.
Cold patient > AFib with RVR	Random eligible cooling checks at ≤32°C	15% per eligible cooling check. No fixed delay can be promised.
Torsades entry > developed twisting pattern	15.84 s	A visual transition across three monitor sweeps. Arrest begins immediately, so do not wait for the broad twisting pattern before treating.
Adenosine > SVT conversion attempt	About 1 s after effective rapid delivery	For a 6 mg reference push delivered over 5 s, conversion strength is sufficient in this model. Required line flush and actual delivery determine when the clock starts.
Esmolol > rate control/conversion	Dose- and delivery dependent	A full reference IV dose reaches the current rate control threshold at roughly 4.6 s; its reference peak is 20 s. An infusion reaches that effect later.
Amiodarone > atrial rhythm response	Dose- and delivery dependent	A full reference IV dose reaches the AFib-RVR/atrial tach response threshold at roughly 2.6 s and the SVT threshold at roughly 5 s. These are modeled effect thresholds, not a delay from connecting a bag.
Magnesium > torsades termination/suppression	Dose- and delivery dependent	For a fully delivered 2 g reference: about 21 s to termination effect, about 15 s to suppression effect, 90 s to peak. Conversion still requires ROSC eligibility.
Critical vitals > worsening instability	Initial grace 15–30 s; persistent severe values can cause arrest after roughly 30–45 s	Checks run every 1 s. Very extreme rate/pressure or a nonperfusing rhythm can end the grace sooner.
Pulseless VT > VF > asystole without CPR	Random checks every 15–30 s	A check must also pass a randomized 30–60 s minimum since deterioration gate and the deterioration chance. This is not a fixed per rhythm countdown.
Reversible PEA > ROSC check	Every 5 s, up to a 6 min handling window	Correction can produce an earlier attempt. Expiry returns to general arrest selection, rather than guaranteeing asystole.
Shock > live monitor/pulse display	About 2 s	The short post-shock display is shared by defibrillation/cardioversion. It is separate from the 60 s native repeat shock consequence.

Conversion changes the rhythm state when the treatment succeeds. The monitor then displays the new pattern as it redraws. Heart rate can settle over time, so electrical conversion and normalization of rate or pressure are not the same event.

16

Critical vitals progression

Finding during the critical period	Current behavior
Heart rate >245 or <10 BPM, or MAP >220 or <30 mmHg	Can trigger arrest on the next 1-second critical vitals check.
Heart rate >240 or <30 BPM, or MAP >200 or <55 mmHg	If still present beyond the initial 15–30 s grace plus 15 s, the critical handler can trigger arrest.
Heart rate >45 and <200 BPM, MAP >60 and <180 mmHg, no arrest	The critical handler can resolve; perfusing VT can return to sinus.
Severe hypoxia or class IV hemorrhage	Separate native pathways can cause arrest without waiting for the rate/pressure grace.
No effective circulation when the patient deteriorates	PEA is selected. With circulation present, a rate above 200 BPM favors a pulseless VT target; lower rates favor VF. General arrest selection can still choose between VF and pulseless VT.

These boundaries explain the game’s transitions. They are not treatment targets to wait for. A patient can already be unstable well before crossing an arrest threshold.

17

Monitor transients and artifacts

Trace or transient	What you see	Duration / response
Torsades entry	Narrower rapid complexes with increasing ventricular ectopy, then broader twisting complexes	15.84 s by default; pulseless throughout.
After a shock	Brief near flat trace and unavailable pulse/electrical rate reading	About 2 s, then the live rhythm. Successful ROSC may clear the recent shock state sooner.
Adenosine	Brief slowing; conversion to sinus only if the SVT treatment conditions are met	Effect builds for about 1 s, holds briefly and decays within 15 s. No deliberately programmed standstill strip.
CPR	Compression related deflections and movement artifact	Present while CPR is active. Compression activity does not prove spontaneous circulation.
Direct pressure, suction, bagging or hands on treatment	Baseline disturbance layered over the rhythm	Follows movement/procedure activity. Recent bagging contributes for about 1.2 s.
PEA rate drift	Organized complexes with a slowly varying displayed rate inside 60–100 BPM	The electrical rate is refreshed about once a second; it is not a hidden palpable pulse.
Ordinary rhythm switch	The new waveform enters the advancing sweep	No named intermediate rhythm or fixed multi second morph is implemented for sinus, AFib, atrial tachycardia, SVT, VT, pulseless VT, VF, PEA or asystole.

18

Cardioversion and defibrillation

Rhythm	Mode	Modeled response
AFib / AFib with RVR	SYNC on	90% conversion chance per synchronized shock.
Atrial tachycardia / SVT	SYNC on	97% conversion chance per synchronized shock.
VT with a pulse	SYNC on	90% fallback conversion chance. Check that the rhythm is perfusing.
Torsades	SYNC off	95% chance to attempt conversion, followed by the shared ROSC check.
VF / pulseless VT	SYNC off	Response depends on resistance, current amiodarone/lidocaine effect and CPR history. Current full lidocaine effect can make a conversion attempt certain; ROSC still requires adequate circulation.
Organized perfusing rhythm shocked with SYNC off	Wrong mode	55% default chance of inducing VF. A lack of immediate VF does not make this the correct mode.
VF / pulseless VT / torsades with SYNC on	Wrong mode	The shock is blocked because there is no suitable R wave for synchronization.
Sinus, PEA or asystole shocked	No indicated shock	The current manual shock path can place the patient into asystolic arrest.

The short 2-second post-shock display period does not remove the separate native repeat shock rule. For VF/pulseless VT, a shock within 60 seconds of the previous recorded shock can select asystole. The current transaction records synchronized shocks too, so check recent treatment history before another shock.

19

ROSC and reversible causes

Requirement	What to assess or correct
Living patient with circulating volume strictly above 4.2 L	Control hemorrhage and restore volume. A shock cannot compensate for an empty circulation.
SpO2 at least 67% in the native circulation check	Open/clear the airway and provide effective ventilation and oxygen. Adequate numbers require actual delivered breaths.
No active tension pneumothorax	Assess the chest and decompress the obstructive injury.
Hemothorax not above 1.2 L in the native check	Treat the chest injury and blood loss.
[HARDCORE] Cardiac Rhythms enabled	Also requires temperature at least 30°C, modeled arterial CO2 below 85 mmHg, and resolution of the lidocaine toxicity arrest restriction.

Find [HARDCORE] Cardiac Rhythms under Addon Options > ACM Extended: Systems > Hardcore. It changes the extra ROSC requirements; it does not increase torsades frequency or shorten its entry pattern. An attached ventilator does not prevent starting CPR in the current mod.

20

Addon options and scenario testing

Location	Available option	What it changes
ACM: Circulation > Cardiac Arrest	Rhythm Deterioration Multiplier	Changes the chance of deterioration during arrest. Default 1.0 gives a 40% roll when the other no CPR/time requirements pass. Range 0–2.
ACM: Circulation > Cardiac Arrest	Critical Damage Cardiac Arrest Chance	Chance of arrest from critical damage. It does not change every physiological arrest threshold.
ACM: Circulation > CPR	CPR Effectiveness Multiplier	Changes overall CPR effectiveness. Default 1.0.
ACM Extended: Systems > Hardcore	[HARDCORE] Cardiac Rhythms	Adds the extra reversible cause ROSC restrictions listed above.
ACM Extended: Circulation > Medications	Require saline flush after push	Changes when selected IV / IO pushes reach the patient and begin taking effect.
ACM Extended: Systems > Blood	Cold blood causes hypothermia	Unwarmed blood can lower temperature and contribute to the conditions that trigger AFib with RVR.
ACM Extended: Debug > Overlay	Debug menu	Opens the diagnostic display used to compare rhythm, medication delivery and patient state during a test.

Rhythm entry durations, per rhythm cardioversion percentages and automatic surge thresholds are current build defaults. They do not have corresponding end user sliders in this build. Use the exposed options above for mission tuning.

For a repeatable test, use the same patient, medication concentration, delivery rate and addon settings. Record the pulse, blood pressure, displayed rhythm, time of systemic medication delivery, and time of conversion. For torsades, record arrest onset separately from the end of its 15.84-second entry pattern.