ECG Interpretation Made Easy: Ventricular Rhythms and Torsades de Pointes

Overview

• Focus on ventricular rhythm, polymorphic ventricular tachycardia, and torsades de pointes.

Heart's Electrical Activity

• SA Node: Produces electrical currents for atrial contraction.
• Pathways: Electrical signals travel from the SA node through internodal pathways to the AV node, then to the bundle branches, Purkinje fibers, and ventricles, causing contraction.
• Pacemaker Hierarchy:
  • SA node
  • AV node (if SA node fails)
  • Purkinje fibers (if AV node fails)
  • Ventricles (if Purkinje fibers fail, resulting in ventricular rhythm)

Ventricular Tachycardia

• Ectopic Foci: Damaged myocardial tissue can cause ectopic foci, leading to ventricular tachycardia with rapid heart rate and wide QRS complexes.
• Monomorphic Ventricular Tachycardia: Single dominant ectopic focus results in same-shaped QRS complexes.
• Polymorphic Ventricular Tachycardia: Multiple ectopic foci result in varied QRS complex shapes.

Torsades de Pointes

• Definition: A type of polymorphic ventricular tachycardia characterized by irregular grouping and morphology.
• Visual Description: "Twisting of the points" seen in ECG, with alternating pointed and round QRS complexes.

ECG Analysis

• Heart Rate Calculation: Use 6-second method; count QRS complexes in 30 large boxes and multiply by 10.
• Key Features:
  • Irregular regularity
  • Absence of P waves
  • No PR interval
  • Wide QRS complexes

Causes of Torsades de Pointes

• Medications: Antiarrhythmic (quinidine, procainamide), antimicrobial (erythromycin, clarithromycin), antipsychotic (chlorpromazine, haloperidol).

Management of Torsades de Pointes

• Unstable Patients: Immediate defibrillation.
• Stable Patients: IV magnesium sulfate (8 mmol over 15 mins, then 72 mmol over 24 hrs).
• Avoid: Amiodarone, procainamide, sotalol.
• Supportive Measures: Address underlying causes, correct electrolyte imbalances, discontinue causative drugs.

Conclusion

• Summary of ventricular rhythms, monomorphic and polymorphic ventricular tachycardia, and management strategies for torsades de pointes.
• Encouragement to view other ECG interpretation videos for further learning.