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Atrial tachycardia overview

Published: June 19, 2009. Updated: July 29, 2009

Atrial Tachycardia is a heart rhythm driven by pacemaker activity in atrial sites other than the SA node. Automatic atrial tachycardia is typically associated with heart rates ranging from 150-200 beats/minute. The heart rate may display a "warm-up" in which the abnormal rhythm gradually accelerates after initiation. Often atrial tachycardia is associated with prior heart surgery or lung diseases. The rhythm is most often associated with structural heart disease such as coronary artery diseases, myocardial infarction, severe lung disease and drug toxicity. The origin or focus of the abnormal impulses distinguishes two types of atrial tachycardia depending upon whether the origin or focus of the abnormal impulse appears to involve a single (unifocal) site or multiple (multifocal) sites.

Definition

Atrial tachycardia

A series of 3 or more consecutive atrial premature beats occurring at a frequency >100/min; usually due to abnormal focus within the atria and paroxysmal in nature. This type of rhythm includes paroxysmal atrial tachycardia (PAT).

Supraventricular tachycardia (SVT)

Usually caused by reentry currents within the atria or between ventricles and atria producing high heart rates of 140-250.

Epidemiology

Incidence

Incidence of paroxysmal supraventricular tachycardia is approximately 1-3 per 1000.

Gender

Prevalence is twice as high in women compared to men, but may occur in either sex, and the prevalence increases with age.

Age

SVT may occur at any age but often occurs in younger people in the absence of heart disease.

Causes of supraventricular tachycardia (SVT)

  • Re-entrant tachycardias (the most common type):
    • Atrioventricular nodal re-entrant tachycardia (AVNRT)

      Due to the presence of two functionally and anatomically distinct conducting pathways in the atrioventricular (AV) node. One of these is fast-conducting, the other slow-conducting.

      During an episode of SVT one of these acts as the antegrade limb of a re-entrant circuit, while the other acts as the retrograde limb. AVNRT is the most common form of SVT.

    • Atrioventricular re-entrant tachycardia (AVRT)

      Due to the presence of accessory pathways that connect the atria and ventricles, but that lie outside the AV node.

      Accessory pathways may be capable of antegrade or retrograde conduction, or both. Wolff-Parkinson-White syndrome is the most well-known type of AVRT.

  • Automatic tachycardias

Supraventricular tachycardia (SVT) is caused by abnormalities of impulse conduction (re-entrant tachycardias) or disorders of impulse initiation (automatic tachycardias), causing a narrow complex tachycardia. SVT is most often due to the junctional tachycardias, atrioventricular nodal re-entrant tachycardia (AVNRT) or atrioventricular re-entrant tachycardia (AVRT).

SVT is usually paroxysmal and episodes may occur regularly or very infrequently (sometimes years apart). Episodes may only last for a few minutes or for several months. Atrial tachycardia typically arises from an ectopic source in the atrial muscle and produces an atrial rate of 150-250 beats/min, slower than that of atrial flutter. The P waves may be abnormally shaped depending on the site of the ectopic pacemaker.

Risk factors

It is frequently observed in anxious young people and in those who are physically fatigued, consume large amounts of coffee, use alcohol or smoke heavily. It is also noted occasionally (but is uncommon) with myocardial ischemia and in the setting of acute MI. Atrial tachycardia occurs in some patients with myocardial diseases during systemic arterial hypoxia and in some patients with serious mitral valve disease.

Conditions associated with atrial tachycardia

  • Cardiomyopathy
  • Chronic obstructive pulmonary disease
  • Ischaemic heart disease
  • Rheumatic heart disease
  • Sick sinus syndrome
  • Digoxin toxicity

Risk Factors

  • Previous myocardial infarction
  • Mitral valve prolapse
  • Rheumatic heart disease
  • Pericarditis
  • Pneumonia
  • Chronic lung disease
  • Current alcohol intoxication
  • Digoxin toxicity

Diagnosis

Atrial tachycardia occurs when the atrial rate exceeds 100 bpm and the origin of electrical activity is within the atrium but outside the sinus node. Paroxysmal atrial tachycardia (PAT), especially with second-degree AV block (PAT with block) classically is associated with digitalis toxicity.

Multifocal atrial tachycardla often is associated with chronic obstructive pulmonary disease and heart failure (HF) and may be potentiated by concomitant therapy with theophylline. Therapy is targeted at the underlying pathophysiologic process.

ECG reading

The ECG typically reveals an atrial rate of 100-200 bpm and may be observed to increase and decrease over time. The P waves have an abnormal configuration and axis, the PR interval depends on the atrial rate, and the QRS pattern is either normal or reflects aberrant conduction secondary to the increased rate.

Treatment

PAT with block in the setting of digitalis therapy should be treated by discontinuing digitalis and maintaining normal serum potassium levels. If refractory and symptomatic, treatment with digoxin antibodies and (if necessary) with lidocaine, propranolol, or phenytoin should be considered.

In clinical situations not associated with digitalis toxicity calcium channel antagonists, beta-adrenergic antagonists, or digitalis may be used to slow the ventricular response rate.

If atrial tachycardia persists, class Ia, Ic, or III agents can be added. Unifocal or re-entrant atrial tachycardias often can be eliminated permanently with radiofrequency catheter or surgical ablation.


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