Advanced Cardiac Life Support (ACLS) and ECG Rhythms

Introduction

Advanced Cardiac Life Support (ACLS) is a set of life-saving protocols and skills used in the management of cardiac arrest and other life-threatening cardiovascular emergencies. One of the most critical components of ACLS is the interpretation of electrocardiogram (ECG) rhythms, as this guides the healthcare provider in selecting the correct treatment.

Key ECG Rhythms in ACLS

1. Normal Sinus Rhythm (NSR)

• Regular rhythm with a heart rate of 60–100 beats per minute.
• Each P wave is followed by a QRS complex.
• Indicates normal electrical conduction.

2. Bradyarrhythmias

• Sinus Bradycardia: HR < 60 bpm, but with a normal P wave and QRS complex.
• Heart Blocks:
  • First-degree AV block: Prolonged PR interval (>200ms), but all impulses are conducted.
  • Second-degree AV block (Mobitz I and II): Some P waves fail to conduct a QRS.
  • Third-degree AV block: Complete dissociation of P waves and QRS complexes (complete heart block).

3. Tachyarrhythmias

• Supraventricular Tachycardia (SVT): Narrow QRS complex with a rapid heart rate (>150 bpm).
• Atrial Fibrillation (AFib): Irregularly irregular rhythm with no distinct P waves.
• Atrial Flutter: “Sawtooth” P waves, usually with a 2:1 or 3:1 conduction ratio.
• Ventricular Tachycardia (VT): Wide QRS complex at a rapid rate; can be monomorphic or polymorphic (Torsades de Pointes).
• Ventricular Fibrillation (VFib): Completely disorganized electrical activity; no identifiable QRS complexes.

4. Pulseless Rhythms (Require Immediate ACLS Intervention)

• Pulseless Ventricular Tachycardia (pVT): VT without detectable pulse.
• Ventricular Fibrillation (VFib): Chaotic rhythm leading to no cardiac output.
• Asystole: Absence of any electrical activity; a “flatline.”
• Pulseless Electrical Activity (PEA): Organized electrical activity but no mechanical contraction of the heart.

ACLS Treatment Based on ECG Interpretation

• VFib/pVT: Immediate defibrillation, CPR with epinephrine, and possible antiarrhythmic drugs like amiodarone.
• Asystole/PEA: High-quality CPR, epinephrine, and identification of reversible causes (H’s & T’s: Hypoxia, Hypovolemia, Hydrogen ion [acidosis], Hypoglycemia, Hypothermia, Tension pneumothorax, Tamponade, Toxins, Thrombosis).
• Bradycardia with symptoms: Atropine, possible transcutaneous pacing if atropine fails.
• Tachyarrhythmias:
  • Stable: Consider medications like adenosine (for SVT), beta-blockers, or amiodarone.
  • Unstable: Immediate synchronized cardioversion.

Conclusion

Mastery of ECG rhythms and appropriate ACLS interventions is critical for saving lives in cardiac emergencies. Understanding the differences in rhythms will help in making rapid, life-saving decisions.

Source recommendations

1. 2020 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care

1. https://professional.heart.org/en/science-news/2020-aha-guidelines-for-cpr-and-ecc
2. https://www.ahajournals.org/doi/10.1161/CIR.0000000000000918
3. https://cpr.heart.org/en/resuscitation-science/cpr-and-ecc-guidelines
4. https://pubmed.ncbi.nlm.nih.gov/33081530/
5. https://publications.aap.org/pediatrics/article/147/Supplement%201/e2020038505E/73495/Part-5-Neonatal-Resuscitation-2020-American-Heart

2. European Resuscitation Council Guidelines 2021

1. https://cprguidelines.eu/guidelines-2021
2. https://www.sciencedirect.com/science/article/pii/S0300957221000551
3. https://cprguidelines.eu/
4. https://pubmed.ncbi.nlm.nih.gov/33773835/
5. https://www.erc.edu/