Ventricular Arrhythmias Overview

Overview

This lecture covers the key ventricular arrhythmias, their ECG characteristics, clinical significance, and the importance of rapid identification and intervention in critical care settings.

Idioventricular Rhythms

• Idioventricular rhythm (IVR) occurs when SA and AV nodes fail or are too slow, so ventricles pace the heart.
• IVR is identified by a wide QRS complex, absent P-waves, and a heart rate of 20-40 bpm.
• IVR usually results in poor cardiac output and is potentially life-threatening.

Accelerated Idioventricular Rhythm (AIVR)

• AIVR has the same characteristics as IVR, except the heart rate is between 40-100 bpm.

Ventricular Tachycardia (VT/V-Tach)

• Ventricular tachycardia (V-Tach) is a ventricular rhythm with a heart rate >100 bpm, wide QRS, and no discernable P-waves.
• Monomorphic V-Tach has uniform QRS complexes, meaning the impulses originate from one location.
• V-Tach may be pulseless or with a pulse and is potentially lethal, requiring immediate attention.
• Causes include myocardial ischemia, R on T phenomenon, drug toxicity, ventricular irritation, or electrolyte imbalance.

Torsades de Pointes (Polymorphic VT)

• Torsades is a form of polymorphic V-Tach with varying QRS morphologies, often due to prolonged QT interval or electrolyte imbalance.
• Usually a pulseless, lethal rhythm.

Ventricular Fibrillation (VF/V-Fib)

• Ventricular fibrillation is characterized by chaotic, uncoordinated electrical activity with no organized QRS complexes.
• VF results in no effective cardiac output—always pulseless and requires immediate intervention (e.g., ACLS).
• Coarse VF has larger, erratic ECG tracings; fine VF has smaller, weaker electrical activity and is harder to reverse.

Key Terms & Definitions

• Idioventricular Rhythm (IVR) — Ventricular-driven rhythm, HR 20-40 bpm, wide QRS, no P-waves.
• Accelerated IVR (AIVR) — Same as IVR, but HR 40-100 bpm.
• Ventricular Tachycardia (V-Tach) — Fast ventricular rhythm (>100 bpm), wide QRS, no P-waves.
• Monomorphic V-Tach — V-Tach with uniform QRS appearance.
• Torsades de Pointes — Polymorphic V-Tach with varying QRS, often from prolonged QT.
• Ventricular Fibrillation (V-Fib) — Chaotic ventricular activity without organized contraction, always pulseless, lethal.
• Coarse VF — VF with larger electrical waves.
• Fine VF — VF with low amplitude, less electrical activity.

Action Items / Next Steps

• Review ECG tracings of ventricular arrhythmias for recognition practice.
• Prepare for the next lesson on heart blocks.
• Study causes and emergency response protocols for each ventricular arrhythmia, especially ACLS algorithms.