Ventricular Rhythms Overview

Overview

This lecture covers ventricular rhythms on ECG, including idioventricular rhythms, premature ventricular contractions (PVCs), ventricular tachycardia (VT), torsades de pointes, and ventricular fibrillation (VF), with key features and clinical implications.

Ventricular Rhythms Basics

• Ventricular rhythms originate below the bundle of His, not using the normal conduction pathway.
• These rhythms have wide QRS complexes on ECG.
• The intrinsic ventricular rate is 20–40 beats per minute (bpm).

Idioventricular and Accelerated Idioventricular Rhythm

• Idioventricular rhythm: rate 20–40 bpm, regular rhythm, absent P waves, no PR interval, wide QRS.
• Accelerated idioventricular rhythm: rate 40–100 bpm, other features same as idioventricular rhythm.

Premature Ventricular Contractions (PVCs)

• PVC: single ectopic beat from the ventricle, appears as a wide QRS without preceding P wave.
• Unifocal PVCs arise from one site; multifocal PVCs come from multiple sites.
• PVC patterns: bigeminy (every other beat), trigeminy (every third beat), quadrigeminy (every fourth beat).
• Couplets: two PVCs together; three or more PVCs in a row indicate a run of VT.

Ventricular Tachycardia (VT)

• VT: three or more consecutive PVCs at 150–250 bpm, wide QRS, regular rhythm, usually no visible P waves.
• Monomorphic VT: QRS complexes look the same; could be sustained or non-sustained; can progress to VF.
• Always check for a pulse to determine if VT is pulseless (needs CPR and defibrillation) or with a pulse (stable/unstable).
• Differentiate VT (wide QRS) from SVT (narrow QRS); management is different.

Polymorphic VT & Torsades de Pointes

• Polymorphic VT: variable QRS appearance, rate 150–250 bpm, irregular rhythm, wide QRS.
• Torsades de pointes: specific form of polymorphic VT, twisting QRS around baseline, rate 250–350 bpm.

Ventricular Fibrillation (VF) and Asystole

• VF: chaotic ventricular activity, no contraction, no cardiac output, requires immediate CPR and defibrillation.
• Coarse VF: larger amplitude, early cardiac arrest; Fine VF: smaller amplitude, later stages.
• Asystole: no electrical activity, flat line, usually seen at end of cardiac arrest management.

Key Terms & Definitions

• QRS Complex — Represents ventricular depolarization on ECG.
• PVC (Premature Ventricular Contraction) — Early ventricular beat, wide QRS, no preceding P wave.
• Bigeminy/Trigeminy/Quadrigeminy — PVCs occurring every 2nd, 3rd, or 4th beat respectively.
• Couplet — Two consecutive PVCs.
• VT (Ventricular Tachycardia) — Three or more PVCs in a row, rapid ventricular rate, wide QRS.
• Monomorphic VT — VT with identical QRS complexes.
• Polymorphic VT — VT with varying QRS shapes.
• Torsades de Pointes — Polymorphic VT with twisting QRS appearance.
• VF (Ventricular Fibrillation) — Disorganized ventricular activity, no effective contraction.
• Asystole — Absence of ventricular electrical activity.

Action Items / Next Steps

• Review ECG strips for ventricular rhythms and their distinguishing features.
• Practice identifying ventricular arrhythmias and appropriate immediate interventions.
• Prepare for questions on ECG interpretation and rhythm management protocols.