• WPW Syndrome
• Orthodromic AVRT
• Decremental Conduction of the AV Junction
• Non-decremental Conduction of Accessory Pathways
• Permanent Junctional Reciprocating Tachycardia
• ECG and PJRT

WPW Syndrome

• In WPW syndrome, there is an accessory pathway (Kent bundle)
• Kent Bundle
• Present in approximately 0.5% of the population (it is the most common accessory pathway)
• Activates one ventricle earlier than the impulse from the AV junction
• Connects the atria and ventricles (Atrio-Ventricular bypass)
• On the ECG, it creates a Delta wave
• Delta Wave
• Widens the QRS complex
• Shortens the PQ interval
  
  
• Fusion Beat (fusion contraction)
• 1st impulse activates the ventricles via the AV junction (QRS complex)
• 2nd impulse activates the ventricles via the Kent bundle (Delta wave)
• Fusion beat also occurs in ventricular tachycardia

Decremental Conduction of the AV Junction

• The AV junction acts as a protective mechanism
• It protects the ventricles from high frequency
• At high ventricular frequencies (>160/min.), the heart ceases to function as a pump
• Progressively leading to ventricular fibrillation
• Decremental conduction:
• With increasing frequency of supraventricular impulses
• There is progressive delay in conduction through the AV junction up to a complete block
• Maximum ventricular frequency
• Activated through the AV junction by supraventricular impulses is 220 - age
• A 30-year-old person (220 - 30) has a maximum ventricular frequency of 190/min.
• For example, in atrial fibrillation:
• Atrial frequency is 350-600/min.
• Ventricular frequency is a maximum of 160/min. (depending on age)
• Thus, the AV junction acts as a filter for impulses and protects the ventricles

Permanent Junctional Reciprocating Tachycardia

• It is Orthodromic AVRT
• With decremental (slowed) conduction through the accessory pathway
• It is rare because accessory pathways usually have non-decremental conduction
• The accessory pathway is almost always located postero-septally
• Therefore, in tachycardia, negative P waves are seen in the inferior leads (II, III, aVF)
• The accessory pathway is hidden during sinus rhythm WPW syndrome
• Blocks anterograde impulses
• On ECG, WPW syndrome is not present (Delta wave, Shortened PQ interval)

• Permanent Junctional Reciprocating Tachycardia (Coumel's Tachycardia)
• Occurs mainly in children (around 1 year of age)
• Has a permanent character (persists almost throughout the day)
• Rarely responds to antiarrhythmic treatment
• Any heart overloaded with tachycardia (for at least 3-5 weeks) undergoes remodeling
• Leading to tachycardia-induced dilated cardiomyopathy
• Cardiomyopathy is often reversible after the tachycardia subsides
  
  
• The name of this tachycardia is not logical: Permanent Junctional Reciprocating Tachycardia:
• The mechanism of PJRT is macro re-entry and not increased automaticity as in junctional tachycardia
• A more accurate name would be: Permanent Decremental Orthodromic AVRT
• Sometimes it is also referred to as Pseudo (Slow-Slow) AVNRT, because it shows the same ECG pattern
• Definitive diagnosis is made using electrophysiological study

Sinus Rhythm and Permanent Junctional Reciprocating Tachycardia

• Initially, there is sinus rhythm
• Permanent Junctional Reciprocating Tachycardia (PJRT)
• Occurs with a rise in frequency (Activated by the accessory pathway)
• Not triggered by extrasystole
• RP interval > PR interval