Tachycardia is a condition of the heart where the heart is beating at a rate of 100 beats per minute or faster. The tachycardia may originate from the lower heart chambers (ventricles) or from the upper heart chambers (atria). In adults, tachycardias rarely exceed 200 beats per minute.

Why does this happen and how may it affect the patient's health?

Tachycardias that originate in the lower heart chambers (ventricles) usually occur due to lack of oxygen of heart muscle; this is mostly caused by

  • Obstruction (atherosclerosis) of the coronary arteries (blood vessels supplying oxygen to the heart muscle)
  • A heart attack
  • Loss of blood volume

There may be a problem with the primary pacemaker of the heart, the SA node, located in the upper heart chambers (atria).

The fast heart rate may occur intermittently.

Other causes of increased heart rate include

  • Psychological conditions such as anxiety and emotional trauma
  • Diseases that cause generalized fever
  • Over-activity of the thyroid gland
  • Low red blood cell count (anaemia)

What symptoms may the patient experience?

  • Breathlessness
  • Feeling faint-headed
  • The heart may pound in the chest to the extent that the patient becomes aware of it (palpitations)
  • The patient may experience chest pain
  • Heart failure may become aggravated

Carotid pressure may cause gradual onset and offset of tachycardia. However, paroxysmal (intermittent) tachycardia (fast heart rate) of the upper heart chambers may start and stop abruptly with carotid massage (the carotid arteries are located in either side of the neck and deliver oxygenated blood to the brain).

How is the diagnosis made and what special investigations are required?

ECG of heart: To determine the location and type of tachycardia (fast heart rate). With a sinus tachycardia (fast heart rate that originates from the SA node, the primary pacemaker of heart, located in right upper heart chamber), the doctor will be able to see P-waves (electrical graphic caused by contraction of upper heart chambers) preceding the QRS complexes on an ECG.

What is the treatment?

It may be possible to slow the heart rate down by exerting pressure on the

  • Carotid bodies (located inside the carotid arteries on either side of the neck), or
  • Eyeballs

There are specific medications for tachycardias (fast heart rate) originating in the upper heart chambers or the lower heart chambers and for maintaining a normal heart rate.

The underlying disease that is causing the tachycardia, such as ischaemic heart disease (too little oxygen to heart muscle), needs to be identified and treated appropriately.

Medications that may be used for tachycardia (fast heart rate) include

  • Beta-blockers
  • Verapamil
  • Digitalis
  • Disopyramide

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