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Atrial Tachycardia
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.
Types of
atrial tachycardia
- Benign
- Incessant ectopic
- Multifocal
- Atrial tachycardia with block (digoxin
toxicity)
Conditions associated with
atrial tachycardia
- Cardiomyopathy
- Chronic obstructive pulmonary disease
- Ischaemic heart disease
- Rheumatic heart disease
- Sick sinus syndrome
- Digoxin toxicity
Multifocal atrial tachycardia
occurs when multiple sites in the atria are discharging
and is due to increased automaticity. It is
characterised by P waves of varying morphologies and
PR intervals of different lengths on the
electrocardiographic trace. The ventricular
rate is irregular. It can be distinguished from
atrial fibrillation by an isoelectric baseline
between the P waves. It is typically seen in
association with chronic pulmonary disease.
Other causes include hypoxia or digoxin
toxicity.
Atrial tachycardia with
atrioventricular block is typically seen with digoxin
toxicity. The ventricular rhythm is usually
regular but may be irregular if atrioventricular
block is variable. Although often referred to
as "paroxysmal atrial tachycardia with block"
this arrhythmia is usually sustained.
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