ACLS Rhythms: The ECG Rhythms You Need to Recognise

You do not need to be an ECG expert to pass an ACLS course, but you do need to recognise the rhythms that decide which algorithm to follow. These are the ones that matter.

Cardiac arrest rhythms

• Ventricular fibrillation — chaotic, no organised complexes. Shockable.
• Pulseless VT — wide, regular complexes with no pulse. Shockable.
• Asystole — a flat line; confirm leads and gain. Not shockable.
• PEA — any organised rhythm without a pulse. Not shockable.

See the shockable and non-shockable pathways.

Slow rhythms

• Sinus bradycardia — normal P waves, slow rate.
• First-degree block — long PR interval, every P conducted.
• Second-degree Mobitz I — PR lengthens until a beat drops.
• Second-degree Mobitz II — beats drop without PR lengthening; higher risk.
• Third-degree block — P waves and QRS complexes independent.

See the bradycardia algorithm.

Fast rhythms

• Sinus tachycardia — treat the cause.
• SVT — regular, narrow, often very fast.
• Atrial fibrillation — irregularly irregular, no P waves.
• Atrial flutter — sawtooth flutter waves.
• Monomorphic VT — wide, regular.
• Polymorphic VT / torsades de pointes — twisting wide complexes.

See the tachycardia algorithm.

How to practise

Rhythm strips, simulator practice and the precourse self-assessment. Treat the patient, not the monitor: always check for a pulse and signs of perfusion. Try ACLS practice questions.

This guide summarises what the ACLS course teaches for education only. It is not a clinical protocol: follow the current American Heart Association guidelines, linked below, and your institution’s policies.

More ACLS guides: ACLS algorithms and skills

• ACLS Course in Abu Dhabi — dates, format and booking
• ACLS Algorithms Explained: Cardiac Arrest, Bradycardia, Tachycardia and Post-Arrest Care
• The ACLS Systematic Approach: BLS, Primary and Secondary Assessment
• ACLS Cardiac Arrest: VF and Pulseless VT (the Shockable Pathway)
• ACLS Asystole and PEA: The Non-Shockable Pathway
• ACLS Bradycardia Algorithm: Atropine, Pacing and Infusions
• ACLS Tachycardia Algorithm: Stable vs Unstable Tachycardia
• ACLS Post-Cardiac Arrest Care: What Happens After ROSC
• The H's and T's of ACLS: Reversible Causes of Cardiac Arrest
• ACLS Drugs: Adrenaline, Amiodarone, Atropine, Adenosine and More
• ACLS Airway Management: From Bag-Mask to Advanced Airway
• Waveform Capnography in ACLS: What End-Tidal CO2 Tells You
• Acute Coronary Syndromes in ACLS: Recognition and First Steps
• Acute Stroke in ACLS: Recognition, Timing and First Steps
• ACLS Megacode: How It Works and How to Pass as Team Leader
• ACLS Electrical Therapy: Defibrillation, Cardioversion and Pacing
• All ACLS guides, by topic

Other life support and first aid courses: BLS Course · PALS Course · First Aid Course · Training calendar

Frequently asked questions

Which rhythms are shockable?

Ventricular fibrillation and pulseless ventricular tachycardia.

Do I need to read 12-lead ECGs for ACLS?

You need to recognise the key rhythms and understand when a 12-lead ECG is needed, for example for STEMI.

What is the most dangerous heart block?

Second-degree Mobitz II and third-degree block carry the highest risk.

What is PEA on the monitor?

Any organised rhythm without a palpable pulse.

How can I practise rhythms?

Rhythm strips, simulators and the AHA precourse self-assessment.

Sources and further reading

What we teach follows the awarding body and the UAE health authorities. For the definitive position on a course or licensing question, these are the places to check.

• CPR and ECC Guidelines — American Heart Association
• Advanced Cardiovascular Life Support (ACLS) — American Heart Association

Last reviewed 21 September 2026 by the training team at Safety First Medical Services, an American Heart Association training centre at Addax Office Tower, Al Reem Island, Abu Dhabi. Call +971 55 761 9841 or email training@safetyfirstmed.ae.