Running an ACLS megacode when the monitor won't hand you the diagnosis

What a megacode actually tests

A megacode puts one candidate alone in front of a simulated cardiac arrest while an evaluator watches and, usually, a second person controls the monitor out of the candidate's eyeline. The point isn't really the ECG. A candidate who can rattle off every rhythm name from a flashcard can still fail a megacode by missing a pulse check, skipping a rhythm reassessment, or going quiet at the exact moment the evaluator needs to hear a decision out loud. The rhythm is the trigger; the sequence, the timing and the talking are what actually gets scored.

Same station, two names

In the US this is an ACLS megacode, run against the American Heart Association's cardiac arrest algorithm. In Australia and New Zealand the equivalent station sits inside an ALS course built on ANZCOR's guidance, and most instructors there would never use the word "megacode" even though the station looks almost identical: one candidate, one simulated arrest, one evaluator with a checklist. Both versions split the first decision the same way, shockable rhythm or not, and both run compressions in two-minute blocks with a rhythm and pulse check at the end of each one. A few drug-timing details differ between the two guidelines, but the station itself, and nearly everything below, works the same under either one.

The rhythm sequence a megacode station actually runs

A typical sequence starts with a shockable rhythm, ventricular fibrillation or pulseless VT, so the first thing being tested is whether the candidate calls it shockable and gets a shock delivered without stalling compressions to get there. After a shock and a two-minute CPR cycle, many stations switch to a non-shockable rhythm, PEA or asystole, specifically because the correct response flips: no shock, keep compressing, give the next dose of epinephrine (adrenaline outside the US), and start naming reversible causes out loud instead. A station that never makes that switch is only testing half the algorithm. Some scenarios go further and bring the rhythm back toward something resembling return of spontaneous circulation, or ROSC, or hand the candidate a post-arrest bradycardia or tachycardia, to check whether they stop compressions and shift into post-ROSC care instead of continuing a resuscitation that's already over.

Why the switch happens where it does

The rhythm change isn't supposed to land whenever is convenient for whoever is holding the monitor. It lands at the rhythm and pulse check, the moment both algorithms already schedule, at the end of a two-minute block. Whoever is running the scenario needs their own stopwatch on the compression cycle, independent of the monitor, and should only change the rhythm at that checkpoint, the same way a real arrest only reveals its next rhythm when someone actually checks. Changing the rhythm mid-cycle, or skipping the two-minute mark, breaks the one piece of realism the whole station depends on.

What the candidate has to say, not just do

Verbalization carries as much weight in a megacode as the actions themselves, because an evaluator can only score what they can hear. A candidate should say the rhythm interpretation out loud the moment they see it, shockable or not, state each intervention as a request rather than silently doing it, charging, clearing, delivering the shock, resuming compressions, calling for the next drug, and flagging when a two-minute block is ending. A candidate who reads the rhythm correctly, makes every right call, and says almost none of it out loud still fails the actual point of the station, which exists to check that someone can lead a resuscitation other people can follow, not just run one inside their own head.

Why a live monitor beats a printed strip or a slide

A printed ECG strip or a slide deck shows the same rhythm no matter what the candidate does, which turns the station into a memory test instead of a decision test. A phone-controlled monitor lets whoever is running the scenario hold a rhythm steady for as long as the candidate's actions warrant, and change it only at the right checkpoint, the way a real patient's rhythm doesn't move just because a textbook page turned. The screen never prints a rhythm name, so the candidate reads rate, regularity and QRS shape off the waveform itself, the same skill the 22-rhythm ECG library is built to drill outside a megacode station too.

Where candidates get caught out

The same trap shows up in megacode stations again and again: a rhythm check lands on PEA, the strip looks organized and the rate looks almost normal, and a candidate who's been treating "normal-looking rate" as reassuring calls it something other than what it is. PEA is built to be missed exactly this way, which is why some stations insert it deliberately instead of only running the obvious flat-line asystole. The other common breakdown happens when an instructor inserts an AV block or a wide-complex rhythm mid-sequence to see whether a candidate gets distracted chasing a diagnosis instead of sticking with the algorithm in front of them; drilling AV blocks on their own, outside the pressure of a megacode, is what makes that kind of mid-scenario curveball survivable instead of derailing.

Debriefing without inventing a score

There's no universal numeric pass mark for a megacode on this page, because the real one belongs to whichever accredited course issued the checklist, and that's the one that counts. What's worth watching for regardless of which program's sheet the evaluator is holding is simpler: did the candidate call the rhythm correctly and out loud at every check, did the intervention match the branch of the algorithm the rhythm actually called for, did a two-minute block ever run long or short without anyone noticing, and did the candidate recognize a shift toward ROSC instead of continuing compressions on a patient who already had a pulse back. A debrief built around those four points works whether the course is ACLS, ALS, or something else, and it's the version of a megacode this page is set up to help you practice.