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Arrhythmias, cardiac

An abnormal heart rhythm - rapid, slow and/or irregular - that is caused by disturbance in the heart's electrical conduction system. Symptoms include: palpitations, breathlessness, light-headedness, dizziness or blackout, chest pain, angina. Rarely, some types of arrhythmia cause sudden death. Arrhythmias in pregnancy are common and may cause concern for the wellbeing of both the mother and the fetus. For some women, the arrhythmia may be a recurrence of a previously diagnosed condition, or the first presentation in a woman with known structural heart disease. In most cases there is no previous history of heart disease. The majority of arrhythmias in pregnancy are benign and advice and reassurance is generally all that is needed. In other cases, careful treatment with antiarrhythmic drugs will ensure a safe outcome for both the woman and the baby. In women with known structural heart disease, arrhythmia is a predictor of a cardiac event during pregnancy or labour. (Adamson and Nelson-Piercy, 2007)

The heartbeat

  • Adults: normal heart rate (sinus rhythm) is 60-100 bpm at rest.
  • Sinus bradycardia is a regular but slow heartbeat (<60 beats/min).
  • Sinus tachycardia is a regular but fast heartbeat (>100 beats/min).
  • Ectopic beats are extra heartbeats, common and usually normal.
  • Palpitations are an unpleasant awareness of the heartbeat - often described as 'thumping in the chest' - and can be quite normal.

Types of arrhythmia

  • Atrial fibrillation: common; the atrial muscles flicker and the ventricles contract irregularly.
  • Ventricular fibrillation: whole heart stops beating properly and just flutters; fatal unless heart is re-started with cardioversion (using a defibrillator).
  • Atrial tachycardia and ventricular tachycardia: need urgent medical treatment.
  • Heart block: an abnormally slow beat caused by the heart's electrical impulses not reaching the ventricles properly.

Resources

Dawn Adamson and Catherine Nelson-Piercy (2007) Managing palpitations and arrhythmias during pregnancy. Heart, 93(12): 1630-1636 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2095764/

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