Lecture Notes: Ventricular Tachycardia (VT)

Overview of Ventricular Rhythms

• Ventricular rhythms include:
  • Premature Ventricular Complexes (PVC)
  • Ventricular Tachycardia (VT)
  • Ventricular Fibrillation
• This session focuses on Ventricular Tachycardia.

Normal Cardiac Electrical Activity

• SA Node: Main pacemaker, causes atrial depolarization.
• AV Node: Takes over if SA node fails.
• Purkinje Fibers: Assume control if both SA and AV nodes fail.

Ventricular Rhythm

• Occurs when ventricles generate electrical activity due to failure of SA, AV nodes, and Purkinje fibers.
• Produces wide, bizarre-looking QRS complexes on ECG.

Characteristics of Ventricular Rhythms

• Wide QRS complex (>0.12 seconds or >3 small boxes on ECG)
• T waves opposite direction to R wave.
• P waves may be hidden by wide QRS complex.

Premature Ventricular Complex (PVC)

• Occurs when an ectopic focus in the ventricles disrupts normal sinus rhythm.
• Results in a wide, bizarre QRS complex interrupting normal beats.

Ventricular Tachycardia (VT)

• Defined as three or more PVCs in a row.
• Can be sustained (>30 seconds) or non-sustained (<30 seconds).
• Sustained VT: Continuous without returning to normal sinus rhythm.
• Non-sustained VT: Short bursts, returns to sinus rhythm quickly.

Pulse and Consciousness in VT

• VT can occur with or without a pulse.
• Pulseless VT: Requires immediate defibrillation.
• VT may deteriorate into ventricular fibrillation or asystole.

Causes of VT

• Re-entry circuits: Positive feedback loop of electrical activity.
• Increased automaticity: Often due to myocardial injury or hypertrophy.
• Afterdepolarization: Ventricles depolarize again before completing repolarization.

ECG Characteristics of VT

• Heart Rate: >100 bpm, often 150-300 bpm.
• Regular rhythm, absence of P waves.
• Wide QRS complexes (>3 small boxes).

Management of VT

Unstable VT

• Immediate defibrillation (DC cardioversion).
• Follow ACLS protocol, including CPR and epinephrine administration.

Stable VT

• Pharmacologic intervention:
  • Amiodarone, Lidocaine, or Procainamide.
• Consider implantable cardioverter-defibrillator for recurrent VT.

ACLS Protocol for VT

• Start CPR immediately.
• Give oxygen, attach monitor and defibrillator.
• Shockable rhythms (VT/VF): Defibrillate, continue CPR, administer epinephrine, amiodarone or lidocaine as needed.
• Non-shockable rhythms: Continue CPR, give epinephrine.

General Management Measures

• Correct electrolyte imbalances (hypoxia, acidosis, hypomagnesemia, hypokalemia).
• Beta-blockers can prevent non-sustained VT.

These notes provide an overview of ventricular tachycardia, including its characteristics, causes, and management strategies, which are crucial for interpreting ECGs and understanding cardiac emergencies.