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Focal Atrial Tachycardia

Focal atrial tachycardia, Paroxysmal atrial tachycardia (PAT), Unifocal atrial tachycardia, Ectopic atrial tachycardia

Focus Localization

• The focus occurs in structurally altered atria
• at anatomically uneven sites
• Atrial changes are most often caused by:
• Ischemic heart disease
• Atrial infarction
• Cor pulmonale
• Atrial dilation
• Arterial hypertension
• The right atrium is more complex than the left
• Therefore, the focus more often occurs in the right atrium
• Focus occurrence:
• Right atrium (67%)
• Left atrium (33%)

ECG and Focal Atrial Tachycardia

• Heart Rate: 100-250/min.
• Narrow QRS complexes (< 0.12s)
• QRS complexes can be widened (> 0.12s) with aberrant conduction
• P wave has a different morphology compared to sinus rhythm
• Because the atrial vector is not from the SA node, but from an ectopic focus
  
  
• Based on the ECG, the mechanism of the focus can be inferred:
• Increased automaticity
• The focus "warms up": tachycardia slowly accelerates (warm up) and slowly decelerates (cooling down)
• Similar to sinus tachycardia
• Triggering activity and Re-entry
• The focus is paroxysmal: tachycardia starts and ends suddenly

Focal Atrial Tachycardia

• P wave is negative in lead II (certainly not originating from the SA node)
• The atrial vector originates from an ectopic focus outside the SA node

Focal Atrial Tachycardia

• In the atrium, there is an ectopic focus generating impulses instead of the SA node
• Frequency 100-250/min.
• P waves have a different shape compared to sinus rhythm
• In this case, the P waves are negative in lead II
• Electro-mechanism of the ectopic focus can be:
• Increased automaticity (tachycardia "warms up")
• Triggering activity (tachycardia is paroxysmal)

Multifocal Atrial Tachycardia

• Multifocal atrial tachycardia
• There are at least 3 ectopic foci in the atria
• Which generate impulses independently of each other
• Each focus creates a different P wave
• There are at least 3 different P waves present
• Frequency 100-250/min.
• Electro-mechanism of the ectopic foci is most commonly
• Increased automaticity (tachycardia "warms up")

Supraventricular Tachycardia

• Frequency: 300/min.
• P waves cannot be differentiated (they are hidden in the QRS or the T wave)

Carotid Sinus Massage

• Carotid sinus massage slows down conduction through the AV node
• This resulted in an AV block 2nd degree 2:1
• P waves became apparent on the ECG (every 2nd P wave is followed by a QRS)
• This is Focal Atrial Tachycardia
• P wave frequency: 300/min
• QRS complex frequency: 150/min.
• It could also be atrial flutter
• Atrial flutter would show typical sawtooth waves in the inferior leads (II, III, aVF)

Focal Atrial Tachycardia and Second-Degree AV Block (2:1)

• Focal atrial tachycardia can have AV block even without carotid sinus massage
• The ECG shows an AV block with 2:1 conduction to the ventricles
• Frequency of P waves: 100/min.
• Frequency of QRS complexes: 50/min.

Focal Atrial Tachycardia

• Frequency: 110/min.
• P wave is negative (II, III, aVF) and positive (V1)
• A physiological P wave is never negative in (II, III, aVF) and positive in (V1)

Sinus Tachycardia

• Sinus Tachycardia
• Frequency: 110/min.
• P wave is positive (II, III, aVF) and biphasic (aVR)
• Theoretically, it could be a focal atrial tachycardia if the focus was located close to the SA node
• If the patient had unexplained paroxysms of such sinus tachycardia, it might be:
• Focal atrial tachycardia
• Intra-atrial reentry tachycardia
• Sinoatrial nodal reentry tachycardia