1.5 How to Read AHA Algorithms Under Pressure

1.5 How to Read AHA Algorithms Under Pressure

AHA algorithms are priority maps, not lists to read top to bottom. Each one follows the same rhythm: assess the patient, choose the branch, perform the immediate action, reassess, loop. Cardiac arrest reassessment occurs on a fixed 2-minute cycle anchored to compressor switches and rhythm checks. If you internalize the branch points and the loop, you can move through any scenario without losing CPR quality or stalling on a single box.

The branch points that matter

The cardiac arrest loop in detail

For VF/pVT the cadence is: deliver a shock, immediately resume CPR for 2 minutes, then rhythm check. After the second shock, give epinephrine 1 mg and continue q3-5 min. After the third shock, add an antiarrhythmic (amiodarone 300 mg, later 150 mg, or lidocaine). For PEA/asystole, there is no shock: do CPR, give epinephrine as soon as IV/IO access is available, and aggressively search the reversible causes, the H's (hypovolemia, hypoxia, hydrogen ion/acidosis, hypo-/hyperkalemia, hypothermia) and T's (tension pneumothorax, tamponade, toxins, thrombosis pulmonary, thrombosis coronary).

Reading scenarios the way the algorithm intends

The single most common error is to treat the rhythm label instead of the patient. Always pair the monitor with a clinical assessment: a patient with organized narrow complexes but no pulse is in PEA cardiac arrest, not tachycardia, so the correct branch is CPR, epinephrine, and reversible-cause hunting, with no shock and no cardioversion. Similarly, a wide-complex tachycardia in an unstable patient gets synchronized cardioversion, while the same rhythm in a stable patient may be managed with antiarrhythmics and expert consultation.

How questions exploit the branches

Exam writers love the seams between branches:

• Pulse present vs pulseless for the same rhythm strip.
• Stable vs unstable tachycardia (look for hypotension, altered mental status, ischemic chest pain, signs of shock).
• Continuing the arrest algorithm after ROSC instead of switching to post-arrest care.
• Choosing a drug before securing CPR and defibrillation timing.

Common traps

• Following the rhythm name without checking for a pulse.
• Treating stable tachycardia as if it were unstable (and shocking a patient who needed adenosine).
• Forgetting to transition to post-ROSC care the moment circulation returns.

Study action

For each algorithm, write the first branch question and the immediate action on each side, then test yourself with paired scenarios that change only one variable (pulse, stability, or rhythm class). Use the official adult ALS page as your reference for branch logic and dosing: AHA 2025 Adult Advanced Life Support Guidelines.

The peri-arrest algorithms, branch by branch

The bradycardia algorithm turns on one question: is the slow rate causing symptoms or poor perfusion (hypotension, altered mental status, shock, ischemic chest discomfort, acute heart failure)? If the patient is asymptomatic, you monitor. If symptomatic, the first drug is atropine 1 mg IV, repeatable every 3-5 minutes to a maximum of 3 mg. If atropine is ineffective or the block is unlikely to respond (for example, a high-degree AV block), move to transcutaneous pacing or a chronotropic infusion such as dopamine or epinephrine, and seek expert consultation.

The tachycardia algorithm turns on stability. An unstable tachycardic patient with a pulse gets synchronized cardioversion. A stable patient is sorted by QRS width and regularity: a stable, regular, narrow-complex tachycardia (likely SVT) is treated with vagal maneuvers then adenosine 6 mg, then 12 mg; other stable tachycardias are managed with rate or rhythm control and expert input. The recurring trap is shocking a stable patient who needed adenosine, or giving adenosine to an unstable patient who needed cardioversion.

Post-ROSC: stop the arrest loop

The instant a pulse returns, you leave the arrest algorithm and begin post-cardiac arrest care. Priorities include avoiding both hypoxia and hyperoxia (titrate oxygen to an appropriate saturation), avoiding hyperventilation, supporting blood pressure, obtaining a 12-lead ECG to identify a treatable cause such as STEMI, and, for comatose survivors, targeted temperature management with a constant target between 32 and 37.5 degrees C maintained for at least 24 hours. Continuing to push epinephrine or shock after ROSC is a classic error the algorithm is designed to prevent.

Putting it together

Every AHA algorithm is the same skeleton: a branch question, an immediate action, and a reassessment loop. If you can state the branch question and both immediate actions for arrest, bradycardia, tachycardia, and post-ROSC, you can navigate almost any scenario the exam or a real code throws at you.

Don't lose CPR quality while reading the algorithm

A subtle but critical point is that the algorithm exists to support resuscitation, not to interrupt it. While you reason through a branch, compressions should continue. The leader thinks and speaks; the team keeps perfusing. Pauses are planned and brief, scheduled for the 2-minute rhythm check, a shock, or an unavoidable airway maneuver. If your reasoning starts to create dead air over the chest, you have inverted the priority.

The best test-takers, like the best code leaders, move through the boxes quickly precisely because they have pre-decided the branch questions and immediate actions, leaving their working attention free for the patient in front of them rather than the paper in their hand.