• Wide QRS Complex
• Wide Complex Tachycardia
• Differential Diagnosis
• Probability of Mechanism
• ECG and Ventricular Tachycardia
• Diagnostic Algorithms

Wide QRS Complex

• Occurs in disorders of impulse conduction in the ventricles
• The ventricles are not depolarized only through the conduction system
• But also through the working myocardium
• The impulse spreads slowly through the myocardium
• Therefore, the ventricular depolarization will be slower (>0.12s)
• On the ECG, there will be a wide QRS complex (>0.12s)

Differential Diagnosis

• Diagnostic algorithms are used for the differential diagnosis of the mechanism of wide complex tachycardia (Brugada algorithm for ventricular tachycardia vs aberrant SVT)
• 10% of wide complex tachycardias (WCT) cannot be definitively specified
• Diagnosing the mechanism is crucial for treatment
• WCT is an emergency, often life-threatening, and requires urgent and immediate treatment
  
  
• For wide complex tachycardia:
• 80% of cases are ventricular tachycardia
• If the patient is older than 50 years, then 90% of cases are ventricular tachycardia
  
  
• The principle is: unclear wide complex tachycardia should always be treated as ventricular tachycardia

ECG and Ventricular Tachycardia

• Ventricular tachycardia (VT) displays characteristic ECG features
• Each feature has a specific sensitivity and specificity
• VT does not have all features on the ECG at once
• Mechanism of wide complex tachycardia
• Must be clear within several seconds (for treatment purposes)
• For rapid diagnosis of wide complex tachycardia
• Diagnostic algorithms are used
• These differentiate VT from supraventricular wide complex tachycardia
• ECG features of ventricular tachycardia:
• Heart rate > 100/min.
• Wide QRS complexes (≥ 0.12s, often > 0.16s)
• There are 2 types of VT with narrow QRS complexes (≤ 0.12s), which is a paradox:
• VT from the ventricular septum
• Fascicular VT
• Absence of typical ECG pattern of bundle branch block (LBBB, RBBB)
• RSr' in V1 (Left bunny ear is larger)
• Extreme right axis deviation "north-west"
• AV dissociation
• Capture beats
• Fusion beats
• Precordial concordance (positive or negative)
• Brugada sign
• Josephson's sign
• R wave duration in lead II (≥ 50ms)

Wide Complex Tachycardia

• QRS width 0.2s
• Heart rate 160/min.
• The ECG shows typical signs of ventricular tachycardia
• QRS width 0.2s (QRS > 0.16s is typical for VT)
• Negative precordial concordance (all QRS V1-V6 are negative)
• The ECG indicates ventricular tachycardia
• Brugada Algorithm (most commonly used diagnostic algorithm)

Wide Complex Tachycardia

• QRS width 0.2s
• Heart rate 200/min.
• The patient has WPW syndrome
• On ECG during sinus rhythm, there was a delta wave
• Ventricular Tachycardia and SVT with accessory pathway
• They are morphologically almost identical on ECG
• Brugada-Stuerer Algorithm (VT vs. PXT)
• Used to differentiates VT from PXT (Pre-excited SVT)
• With high probability, the ECG shows antidromic AVRT
• Because the patient has WPW syndrome (on ECG during sinus rhythm)
• During AVRT, the impulse circles between the atria and ventricles
• However, patients with WPW syndrome can also have ventricular tachycardia
• The impulse does not circle but originates from an ectopic ventricular focus