Atrial Tachycardia

Definition

  • Atrial tachycardia is a form of supraventricular tachycardia which originates within the atria but outside of the sinus node
    • Atrial tachycardia does not require the atrioventricular (AV) node, accessory pathways, or ventricular tissue for initiation and maintenance

Epidemiology

  • Occurrence in the Structurally Normal Heart
  • Occurrence in the Structurally Abnormal Heart
    • Congenital Heart Disease: especially after surgery for repair or correction of congenital or valvular heart disease

Physiology

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Classification Method Based on Endocardial Activation

  • Focal Atrial Tachycardia: arises from a localized area in the atria such as the crista terminalis, pulmonary veins, coronary sinus ostium, or intra-atrial septum
  • Reentrant Atrial Tachycardias: reentrant atrial tachycardias most commonly occur in persons with either structural or complex heart disease, particularly after surgery involving atrial incisions or scarring
    • Usually macroreentrant

Classification Method Based on Pathophysiologic Mechanism

  • Enhanced Automaticity
    • Acute Illness with Catecholamine Release
    • Alcohol Ingestion
    • Altered Fluid States
    • Drug/Toxin: caffeine, albuterol, theophylline, cocaine
    • Exercise
    • Hypoxia
    • Metabolic Disturbance
  • Triggered Activity
    • Acute Illness with Catecholamine Release
    • Alcohol Ingestion
    • Altered Fluid States
    • Drug/Toxin: caffeine, albuterol, theophylline, cocaine
    • Exercise
    • Hypoxia
    • Metabolic Disturbance
    • Digoxin Intoxication
  • Reentry
    • Structural Heart Disease: including ischemic, congenital, post-operative, and valvular heart disease
    • Iatrogenic Atrial Tachycardias: typically result from ablative procedures in the left atrium (several typical origination sites for these tachycardias have been identified, including the mitral isthmus between the left lower pulmonary vein and mitral annulus, the roof of the left atrium, and, for reentry, around the pulmonary veins)

Classification Method Based on Location of the Arrhythmogenic Focus

  • Right Atrial Origin
  • Left Atrial Origin

Diagnosis

  • Echocardiogram: useful to assess for structural heart disease
  • Chest CT: may be used to rule out pulmonary embolism, map pulmonary veins (prior to ablation), etc

Clinical

  • Chest Pain/Pressure (see Chest Pain, [[Chest Pain]])
  • Congestive Heart Failure (CHF) (see Congestive Heart Failure, [[Congestive Heart Failure]])
    • Tachycardia-Induced Cardiomyopathy: may occur in cases with frequent or incessant tachycardia
  • Dizziness
  • Dyspnea
  • Fatigue
  • Palpitations: may be paroxysmal
  • Syncope (see Syncope, [[Syncope]])
  • EKG Features
    • Narrow-Complex Tachycardia
      • QRS Morphology: usually normal (unless pre-existing bundle branch block, accessory pathway, or rate related aberrant conduction)
      • “Warm-Up” Phenomenon: tachycardia may gradually speed up soon after onset
    • Usually Regular
      • Exception: may be irregular with higher rates (due to variable condcution through AV node) -> may result in variable block or Wenckebach
      • Exception: multifocal atrial tachycardia (MAT) is typically irregular (see Multifocal Atrial Tachycardia, [[Multifocal Atrial Tachycardia]])
    • Atrial Rate: >100 BMPM
    • P-Wave Morphology: abnormal (due to its ectopic origin) and may give clue to the site of origin and mechanism of the atrial tachycardia
      • Focal Tachycardia: the P wave morphology and axis depend on the location in the atrium from which the tachycardia originates
      • Macroreentrant Circuits: P wave morphology and axis depend on activation patterns
    • P-Wave Axis: usually abnormal (ie: inverted in II, III and aVF)
    • Isoelectric Baseline (unlike atrial flutter)
    • AV Block May Be Present: due either to physiologic response to the rapid atrial rate (or in cases due to digoxin intoxication, due to the vagptonic effects of digoxin)

Treatment

  • Rate Control with AV Nodal Blocking Agents
    • Adenosine (see Adenosine, [[Adenosine]]): used for atrial tachycardia due to triggerred activity
    • Diltiazem (see Diltiazem, [[Diltiazem]]): used for atrial tachycardia due to triggerred activity
    • Metoprolol (see Metoprolol, [[Metoprolol]]): used for atrial tachycardia due to triggerred activity or enhanced automaticity
    • Verapamil (see Verapamil, [[Verapamil]]): used for atrial tachycardia due to triggerred activity
  • Anti-Arrhythmics
    • Refractory Recurrent Atrial Tachycardia: Class Ic antiarrhythmics
    • Maintenance of Sinus Rhythm: Class III antiarrhythmics
  • Cardioversion: for cases where rhythm is not well-tolerated hemodynamically and/or in whom rate-control drugs are ineffective or contraindicated
  • Radiofrequency Catheter Ablation: for symptomatic, medically refractory patients
  • Surgical Ablation: for patients with complex congenital heart disease

References

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