Electrocardiograms ECGs

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Electrocardiograms - ECGs

• Learning Objectives
• To establish what an ECG (also known as an EKG)
  is and what it measures

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Recall The Hearts Pumping Cycle

• Outline the pumping cycle of the Heart
• Put in as much detail as you can recall about how
  this is controlled by the wave of electrical
  signals that move through the heart

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An ECG and the Pumping Cycle of the Heart

• heart animation

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ECGs

• An ECG is a test that measures the electrical
  activity of the heartbeat.  With each beat, an
  electrical impulse (or wave) travels through
  the heart.
• They are used to
• measure time intervals that determine how long
  the electrical wave takes to pass through the
  heart.  This shows if the electrical activity is
  normal or slow, fast or irregular. 
• measure the amount of electrical activity passing
  through the heart muscle, a cardiologist may then
  be able to find out if parts of the heart are too
  large or are overworked.

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ECG leads attached to a person
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An ECG and the Pumping Cycle of the Heart

• heart animation

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• Electrocardiograms
• The electocardiogram or ECG is a major diagnostic
  tool for the assessment of the health of the
  heart. It is a measurement taken at the surface
  of the skin which reflects the electrical
  phenomena in the heart when the SA node triggers
  the electrical sequence that controls heart
  action.

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Further Research

• Research the symptoms of the following heart
  problems
• Sinus tachycardia
• Brachycardia
• Sinus arrhythmia
• Ventricular fibrilation
• With each problem try to predict the ECG trace
  you might get. (Wikipedia is useful)

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Sinus tachycardia

• Characterised by an abnormally high resting heart
  rate of greater than 100 bpm
• Symptoms include palpitations, fatigue and
  exercise intolerance
• Causes are related to an increased stimulation of
  the sinus node perhaps over sensitivity to
  adrenalin
• ECG trace is normal other than an increased heart
  rate
• Sinus tachycardia

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Brachycardia (also called bradycardia)

• Brachycardia is defined as a resting heart rate
  of under 60 beats per minute, though it is not
  normally symptomatic until the rate drops below
  50 beats/min.
• This is an example of cardiac arrhythmia
• Effectively either the SA node or the AV node
  function is impaired and the electrical
  conduction is affected at some point within the
  heart
• Treatment is through use of a permanent pacemaker
• Sinus Bradycardia

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Sinus arrhythmia

• Variations in the rate of the heart beat
  greater than would be expected from normal
  respiratory variation
• Cardiac Arrhythmia - Sinus Arrhythmia

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Ventricular fibrillation

• a condition in which the heart's electrical
  activity becomes disordered. When this happens,
  the heart's lower (pumping) chambers contract in
  a rapid, unsynchronized way.
• The ventricles "flutter" rather than beat.
• The heart pumps little or no blood.
• Can be treated by defibrillation which shocks the
  heart and can restore the normal heart rhythm. If
  this does not work death will occur in minutes.
• Ventricular Fibrillation

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