Rhythms to Know and How to Treat Them

Global ACLS principles (apply to all rhythms)

For any suspected arrest or peri‑arrest situation:

• Start high‑quality CPR (rate 100–120, full recoil, minimal pauses), give oxygen, attach monitor/defibrillator.

• Check rhythm quickly (≤10 seconds) and decide: shockable vs non‑shockable vs organized with a pulse.

• Give epinephrine 1 mg IV/IO every 3–5 minutes in all cardiac arrest rhythms (VF/pVT, PEA, asystole).

• Treat reversible causes (H’s and T’s: hypoxia, hypovolemia, hydrogen ions, hypo/hyperkalemia, hypothermia, tension pneumo, tamponade, toxins, thrombosis, etc.).

VF and pulseless VT (shockable arrest)

Key actions:

• Start CPR immediately, give oxygen, attach monitor/defibrillator.

• Rhythm shows VF or pulseless VT → this is shockable.

• Charge defibrillator while continuing compressions; deliver shock (120–200 J biphasic or 360 J monophasic per local protocol).

• Resume CPR immediately after shock for 2 minutes; do not pause to check pulse after the shock.

• During CPR:

  • Establish IV/IO access.acls+1

  • Give epinephrine 1 mg IV/IO every 3–5 minutes.safetytrainingseminars+3

  • After the third shock, give antiarrhythmic: amiodarone 300 mg IV bolus, may repeat 150 mg; or lidocaine as alternative per protocol

• After each 2‑minute CPR cycle: brief rhythm check (≤10 sec):

  • If still VF/pVT → charge, shock, back to CPR.

  • If organized rhythm → quick pulse check. If pulse present, move to post‑arrest care.acls+1

  • If PEA/asystole → switch to non‑shockable algorithm.

Asystole and PEA (non‑shockable arrest)

Key actions:

• Start CPR, give oxygen, attach monitor.

• Rhythm shows asystole (flat line) or PEA (organized electrical activity but no pulse) → do NOT shock.

• Immediately resume/continue CPR for 2‑minute cycles; minimize interruptions.

• Give epinephrine 1 mg IV/IO as soon as non‑shockable rhythm recognized, then every 3–5 minutes.

• Aggressively search for and treat H’s and T’s (hypoxia, hypovolemia, tension pneumo, tamponade, toxins, thrombosis, etc.).

• After each 2‑minute CPR cycle: rhythm and pulse check (≤10 sec):

  • If rhythm becomes VF/pVT → move to shockable algorithm.acls+1

  • If organized rhythm with a pulse → post‑arrest care.

Symptomatic bradycardia (including high‑grade blocks)

Key actions:

• Maintain airway, give oxygen if needed, monitor rhythm and BP, get IV access.

• If asymptomatic and stable → observe, treat underlying cause (e.g., meds).

• If symptomatic/unstable:

  • Atropine 1 mg IV bolus; repeat every 3–5 minutes to max 3 mg

  • If atropine ineffective, consider:

    • Transcutaneous pacing.

    • Dopamine infusion (e.g., 5–20 mcg/kg/min) or epinephrine infusion (2–10 mcg/min), titrate to response.

• Prepare for expert consultation and possible transvenous pacing if persistent or high‑grade AV block.

Unstable tachycardia (with a pulse)

Unstable signs: hypotension, acute altered mental status, signs of shock, ischemic chest discomfort, acute heart failure.advancedmedicalcertification+1

Key actions:

• Maintain airway, give oxygen, attach monitor, get IV access.

• If tachycardia is unstable (regardless of whether it’s SVT, AF with RVR, or VT with a pulse):

  • Perform immediate synchronized cardioversion, using appropriate energy based on rhythm and device.

Stable Tachycardia

• Narrow‑complex (likely SVT): vagal maneuvers, then adenosine if appropriate.

• AF/flutter: consider rate control (beta‑blockers or calcium‑channel blockers) and anticoagulation based on scenario; in megacodes they focus on rate control and possible cardioversion if unstable.

• Wide‑complex (VT with a pulse): consider antiarrhythmic (amiodarone, procainamide, or sotalol) and prepare for cardioversion.

Post–cardiac arrest care (ROSC)

Once any arrest rhythm converts to a perfusing rhythm with a pulse (ROSC):

• Optimize oxygenation and ventilation, avoid both hypoxia and hyperoxia.

• Maintain systolic BP ≥90 mm Hg and MAP ≥65 (fluids, vasopressors as needed).

• Obtain ECG, treat STEMI or suspected coronary cause (consider cath lab).

• Manage glucose temperature, and provide ICU‑level monitoring.

one mental flow for shockable arrest (VF/pVT)

“CPR → shock → CPR + epi → rhythm check → shock + amio if still shockable.”

one mental flow for non‑shockable (PEA/asystole)

“CPR + epi ASAP → rhythm check q2 min → treat H’s & T’s → switch to shockable algorithm if rhythm changes.”

One Mental Flow Bradycardia

“symptomatic → atropine → pacing/pressors.”

One Mental Flow Tachycardia

“unstable → sync cardioversion; stable → meds based on narrow vs wide.”

Unstable SVT/PAT

Immediate synchronized cardioversion (follow device energy recommendations; many sources list 100–200 J for narrow‑complex SVT).

Stable SVT/PAT

• Airway, oxygen if hypoxemic, monitor, IV, consider 12‑lead ECG.

• Vagal maneuvers first (Valsalva, coughing; carotid sinus massage with caution).

• If vagal maneuvers fail and rhythm is regular narrow‑complex:

  • Adenosine: 6 mg rapid IV push + 20 mL NS flush, elevate arm; if needed, second dose 12 mg.

  • Adenosine terminates most reentry SVTs; if rhythm converts, you’ve likely treated a reentry SVT.

• If SVT persists or recurs:

  • Consider longer‑acting AV‑nodal blockers (beta‑blockers or non‑DHP calcium channel blockers) and expert consultation.

Unstable AFib (RVR)

Immediate synchronized cardioversion, starting around 200 J in many guides (follow local/device recommendations).

Do not delay cardioversion for anticoagulation in a crashing patient.

Stable AFib (RVR)

Airway, oxygen if hypoxemic, monitor, IV, 12‑lead ECG.

Rate control:

• Beta‑blocker (e.g., metoprolol) or non‑DHP calcium channel blocker (e.g., diltiazem) for narrow‑complex AFib.

Anticoagulation and rhythm‑control decisions (cardioversion vs rate‑control only) are generally beyond ACLS and handled by the physician, but megacodes emphasize rate control and recognizing when cardioversion is indicated

Unstable atrial flutter

Immediate synchronized cardioversion, typically starting around 200 J per many ACLS tachycardia resources.

Stable atrial flutter

Management is similar to AFib: control ventricular rate with beta‑blockers or calcium channel blockers; consider cardioversion if appropriate.

• Adenosine may not terminate flutter but, like AFib, can transiently slow AV node conduction and help you see flutter waves more clearly.

Accelerated junctional rhythm

• rate roughly 60–100 bpm (so not necessarily tachycardic for ACLS, but can be a “weird” rhythm you see).

If junctional rhythm is fast (junctional tachycardia) and unstable → treat as unstable tachycardia:

• Immediate synchronized cardioversion.

If fast and stable → treat like other stable narrow‑complex tachycardias:

• Airway, oxygen, monitor, IV, 12‑lead ECG.

• Consider vagal maneuvers; adenosine may be used if regular and narrow, with expert consultation, especially since junctional tachycardias can be triggered by drugs or structural issues.

Junctional tachycardia

rate >100 bpm; can be narrow‑complex and may behave like other SVTs in terms of hemodynamics.

If junctional rhythm is slow (escape) and symptomatic → you follow the bradycardia algorithm (atropine, pacing, pressors).