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Multifocal Atrial Arrhythmia

Multifocal atrial arrhythmia, Wandering pacemaker, Wandering atrial pacemaker

Automaticity of the Atria

• Every part of the conduction system and working myocardium
• has the ability to generate impulses (automaticity)
• Impulses are generated with the highest frequency by:
• SA node: 60-100/min. (Sinus rhythm)
• Atria: 55-60/min. (Multifocal atrial rhythm)
• AV junction: 45-50/min. (Junctional rhythm)
• Increased parasympathetic tone (vagus nerve) decreases the automaticity of the SA node
• Foci in the atria are activated and begin to generate impulses
• in place of the SA node (or together with the SA node)
• Increased parasympathetic tone is seen in
• Athletes
• Young individuals

Physiological P Wave

• Atrial vector originates in the SA node and directs
• AWAY from the aVR lead
• TOWARDS the II lead
• Physiological P wave is
  • Positive in the II lead
  • Negative in the aVR lead
    
    
• In the case of wandering pacemaker
• P waves of varying shapes alternate
• Each P wave has a different vector (from a different focus)

ECG and Multifocal Atrial Rhythm

• Frequency < 100/min.
• If the frequency > 100/min., it is multifocal atrial tachycardia
• Narrow QRS complexes (< 0.12s)
• QRS complexes may be widened (> 0.12s) in case of aberrant conduction
• Heart rhythm is irregularly irregular
• 3 P waves of different shapes alternate (usually 3 waves, but sometimes 4)
• Each ectopic focus generates a different P wave
• PQ interval varies
• Each ectopic focus is at a different distance from the AV node

Multifocal Atrial Rhythm

• Frequency: 40/min.
• Heart rhythm is irregularly irregular (various RR intervals)
• The ECG shows 3 P waves of different shapes
• Because each ectopic focus generates a distinct vector, which has a different direction
• PQ interval varies

Wandering Pacemaker and Bigeminal Rhythm

Multifocal Atrial Rhythm (Wandering Pacemaker)

• There are 3 ectopic foci in the atria (usually 3)
• They generate impulses independently of each other with f: < 100/min.
• The SA node may also alternately generate impulses
• The mechanism of the foci is automaticity
• 3 P waves of different shapes are present (each focus generates a different P wave)
• The heart rate is irregularly irregular (RR intervals of varying lengths)

Multifocal Atrial Rhythm

• Frequency: 80/min.
• 4 P waves of different shapes
• Narrow QRS complexes (< 0.12s)
• Heart rhythm is irregularly irregular (even though it may seem regular)

Multifocal Atrial Rhythm

• Frequency 80/min.
• 3 P waves of different shapes
• Narrow QRS complexes (< 0.12s)
• Heart rhythm is irregularly irregular

Multifocal Atrial Rhythm

• Frequency: 80/min.
• 3 P waves of different shapes (the 3rd P wave is hidden in the T wave)
• Narrow QRS complexes (< 0.12s)
• Heart rhythm is irregularly irregular

Multifocal Atrial Tachycardia

• Frequency: 130/min.
• 4 P waves of different shapes
• Heart rhythm is irregularly irregular

Multifocal Atrial Tachycardia

• Frequency: 140/min.
• 3 P waves of different shapes (some P waves are hidden in the T wave)
• Heart rhythm is irregularly irregular

Atrial Fibrillation

• Frequency: 90/min.
• Heart rhythm is irregularly irregular
• P waves cannot be differentiated
• This is atrial fibrillation (which is often confused with multifocal atrial tachycardia)
• Atrial fibrillation never has P waves