ACLS Algorithm 2026–2026 — Complete Guide to Cardiac Arrest, Bradycardia, and Tachycardia Algorithms

ACLS Cardiac Arrest Algorithm — VF/pVT and PEA/Asystole

The cardiac arrest algorithm is the most important ACLS pathway. It begins when a patient is unresponsive with no normal breathing and no pulse. The first step is always to activate the emergency response and begin high-quality CPR.

Step 1 — Confirm arrest and begin CPR: Immediately begin chest compressions at a rate of 100–120 per minute with a depth of at least 2 inches. Minimize interruptions — CPR quality is the single most important determinant of survival. Attach defibrillator/monitor as soon as available.

Step 2 — Analyze rhythm (every 2 minutes): The algorithm splits into 2 pathways based on rhythm:

• Shockable rhythms (VF/pVT): Ventricular Fibrillation and Pulseless Ventricular Tachycardia require immediate defibrillation. Deliver 1 shock (biphasic: 120–200J manufacturer-recommended; monophasic: 360J), then immediately resume CPR for 2 minutes before rechecking rhythm. Do not delay CPR to check pulse after a shock.
• Non-shockable rhythms (PEA/Asystole): Pulseless Electrical Activity and Asystole are not shockable. Continue CPR and administer epinephrine 1 mg IV/IO every 3–5 minutes. Search for and treat reversible causes (H's and T's).

Medications in cardiac arrest:

• Epinephrine 1mg IV/IO: Administer as soon as IV/IO access is available for both shockable and non-shockable rhythms. For VF/pVT, give after the first or second shock. For PEA/asystole, give as soon as possible.
• Amiodarone 300mg IV/IO: For VF/pVT refractory to defibrillation (after 3rd shock). Second dose: 150mg. Alternative: Lidocaine 1–1.5 mg/kg for first dose, then 0.5–0.75 mg/kg.

Airway management: Basic airway (BVM) is acceptable during CPR. Advanced airway (supraglottic or endotracheal intubation) should not interrupt compressions. Once advanced airway is placed, deliver 1 breath every 6 seconds (10 breaths/minute) with continuous compressions.

ACLS Bradycardia Algorithm

Bradycardia is defined as a heart rate less than 60 beats per minute. The ACLS bradycardia algorithm applies when the heart rate is below 50 bpm AND the patient shows signs of hemodynamic compromise (unstable bradycardia).

Signs of unstable bradycardia (the 4 Hs):

• Hypotension (systolic BP below 90 mmHg)
• Altered mental status (confusion, agitation, decreased consciousness)
• Signs of shock (cool/clammy skin, diaphoresis)
• Ischemic chest discomfort or acute heart failure symptoms

Stable bradycardia: If the patient is alert, normotensive, and comfortable — even with a rate below 50 — ACLS intervention may not be needed. Monitor and evaluate the cause. Stable bradycardia due to beta-blocker overdose, calcium channel blocker toxicity, or hypothyroidism is managed differently from primary cardiac causes.

Treatment sequence for unstable bradycardia:

• Atropine 0.5mg IV — first-line drug, repeat every 3–5 minutes to maximum 3mg. Atropine works for nodal and below-nodal blocks. It does NOT work for complete (3rd degree) heart block — pacing is required.
• Transcutaneous pacing — if atropine fails or is unlikely to work (3rd degree block, infranodal block). Sedate the patient (pacing is painful). Set rate at 60–80 bpm, increase current until capture is confirmed.
• Dopamine infusion 2–20 mcg/kg/min OR Epinephrine infusion 2–10 mcg/min — as bridge to transvenous pacing if transcutaneous pacing is not immediately available or patient cannot tolerate it.
• Transvenous pacing — definitive treatment for refractory unstable bradycardia. Cardiology consult required.

ACLS Tachycardia Algorithm

Tachycardia in the ACLS context means heart rate greater than 150 bpm causing symptoms. The algorithm first assesses stability.

Unstable tachycardia (any type): If the patient has hypotension, altered mental status, chest pain, or acute pulmonary edema — perform immediate synchronized cardioversion. Sedate first if conscious. Starting energy: narrow regular 50–100J, narrow irregular 120–200J, wide regular 100J, wide irregular (VF treatment protocol).

Stable narrow-complex tachycardia (QRS < 0.12 sec):
Most commonly SVT (supraventricular tachycardia).

• Vagal maneuvers first (Valsalva, carotid sinus massage)
• If no conversion: Adenosine 6mg IV rapid push + immediate saline flush. If no effect, give 12mg (may repeat once)
• If no conversion or recurrence: rate control with diltiazem or beta-blocker; consider cardiology consult

Stable wide-complex tachycardia (QRS > 0.12 sec):
Assume ventricular tachycardia until proven otherwise.

• Amiodarone 150mg IV over 10 minutes, then 1mg/min infusion
• Do NOT give adenosine for wide complex tachycardia of unknown origin — it can cause VF
• Expert consultation recommended before additional antiarrhythmics

Post-Cardiac Arrest Care Algorithm

After return of spontaneous circulation (ROSC), the post-cardiac arrest care algorithm begins. This phase is critical — most deaths after successful resuscitation occur in the first 24 hours due to hemodynamic instability, anoxic brain injury, and organ failure.

Immediate priorities after ROSC:

• Airway: If not already intubated, consider endotracheal intubation for airway protection. Titrate oxygen to SpO2 92–98% — hyperoxia (SpO2 100%) is associated with worse outcomes. Target ETCO2 35–45 mmHg during ventilation.
• Hemodynamics: Maintain systolic BP ≥90 mmHg or MAP ≥65 mmHg. IV fluids, vasopressors (norepinephrine, dopamine), and inotropes as needed. 12-lead ECG immediately to identify STEMI requiring emergent PCI.
• Targeted Temperature Management (TTM): For comatose survivors, target temperature 32–36°C for at least 24 hours. Avoid fever (temperature above 37.7°C) in the first 72 hours — fever worsens neurological outcomes.
• Neurology: Prognostication should not be performed before 72 hours post-arrest. EEG, CT, MRI, and somatosensory evoked potentials are used to assess neurological prognosis.

Prepare for your ACLS certification with our ACLS Advanced Cardiovascular Life Support study guide and our ACLS video questions and answers to test your algorithm knowledge. You can also take our full ACLS practice test to assess your readiness before the certification exam.