SVT | Atrial Tachycardia

Key points:

  • Atrial tachycardia is a fairly uncommon form of supraventricular tachycardia
  • It is sometimes seen in patients with diseased hearts but often occurs in patients with otherwise normal hearts
  • It is nearly always benign but can cause unpleasant symptoms
  • Medications may be used to control the arrhythmia if symptoms are troublesome, and it is often curable with a cauterising procedure (ablation)

What is atrial tachycardia?

Atrial tachycardia arises from a small area (focus) of tissue, anywhere in the atria of the heart (see diagram). This focus starts to fire and drive the heart, more rapidly than the heart's natural pacemaker. Usually, the focus fires only intermittently (this is sometimes known as paroxysmal atrial tachycardia) but occasionally it can continue for days or even persist for months at a time. In some patients (especially the elderly or those with other significant heart disease) there is more than one abnormal focus

Why does atrial tachycardia occur?

Atrial tachycardia can occur for a number of reasons. Cardiac causes include birth defects, valve problems, and damaged or weakened heart muscle (e.g. from a prior heart attack or inflammation of the heart). Episodes can also be triggered by drug/alcohol intoxication or by metabolic disturbances such as an overactive thyroid or adrenal gland. However, in most patients no particular cause is found. If you have atrial tachycardia your doctor will want do do some simple tests (blood tests, ECG, heart scan) to rule out these causes, but you should be prepared for the possibility that no specific cause is found. In older people, short bursts of atrial tachycardia are so common that they can be considered normal.

What symptoms does atrial tachycardia cause?

Symptoms vary greatly. Most people either have no symptoms at all, or are simply aware of palpitation (rapid beating in the chest). Occasionally, atrial tachycardia causes breathlessness, dizziness, or chest pain. If your tachycardia is very fast, you are more likely to notice the difference between your normal heart rhythm and an episode of tachycardia. Young people with healthy hearts are, for some reason, often more aware of symptoms than older people, in whom a modest increase in the heart rate may go un-noticed.

How is atrial tachycardia diagnosed?

The only way to diagnose atrial tachycardia is by obtaining an ECG recording during an episode. Sometimes this is recorded by chance, for example during a hospital visit for symptoms, or during an exercise ECG test. If your description suggests to your doctor that you have a tachycardia, but no ECG has been obtained, the doctor will usually try to capture an episode by ordering a 24h tape or an event monitor. Finally, it may be possible for a heart rhythm specialist to start an episode during electrophysiologic study.

Is atrial tachycardia dangerous?

Although it can cause symptoms, atrial tachycardia is almost never dangerous. The heart can usually tolerate a fast rate remarkably well and episodes of tachycardia rarely cause problems unless there are other problems such as angina. However, if the heart is forced to beat fast without a break for weeks on end, it can eventually become weakened. Even at this stage, the effect is often reversible if the tachycardia is successfully treated.

Atrial tachycardia itself has not been associated with an increased risk of blood clots or stroke, and anticoagulation (blood-thinning) is not usually required. However, your doctor may choose to recommend aspirin. Stronger medication (warfarin) may be required if there are other rhythm disturbances such as atrial fibrillation.

How is atrial tachycardia treated?

Because atrial tachycardia is not generally dangerous, treatment is only required if it is causing you symptoms. Often the rhythm disturbance is a chance intermittent finding on an ECG and no treatment is needed. However, if you experience unpleasant symptoms or a permanently increased heart rate is risking heart enlargement, your doctor may recommend treatment with medication or catheter ablation.

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