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Basic ECG

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oelomar's version from 2016-03-06 14:46

Section

Question Answer
Where does electrical discharge of each cardiac cycle start?In the sino-atrial node in the right atrium.
Where does the wave of depolarisation spread to after the SA node and the atrium?The atrio-ventricular node.
Where does the wave of depolarisation spread down after the AV node?The bundle of His.
What does the bundle of His divide into?2 left bundle branches and 1 right bundle branch.
Which fibres allow spread of depolarisation through the ventricular muscle?Purkinje fibres.
What is meant by sinus rhythm?When the cardiac cycle starts in the SA node.
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Question Answer
Which wave(s) represents depolarisation of the atria?P wave.
Which wave(s) represents depolarisation of the ventricles?QRS complex.
Which wave(s) represents repolarisation of the ventricles?T wave.
What is a Q wave?A Q wave is a downward deflection that only occurs at the start of the QRS complex (not always present).
What is an R wave?Any upward deflection in a QRS complex.
What is an S wave?Any downward deflection below the baseline following an R wave.
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Question Answer
What does the horizontal axis represent on an ECG graph?Time.
What does the vertical axis on an ECG graph represent?Voltage.
How much time does a large square represent?0.2 seconds (200 milliseconds).
How much time does a small square represent?0.04 seconds (40 milliseconds).
How many large squares represent a minute?300.
If a QRS complex occurs every 1 large square, what is the rhythm?300 bpm.
If a QRS complex occurs every 2 large squares, what is the rhythm?150 bpm.
If a QRS complex occurs every 3 large squares, what is the rhythm?100 bpm.
If a QRS complex occurs every 4 large squares, what is the rhythm?75 bpm.
If a QRS complex occurs every 5 large squares, what is the rhythm?60 bpm.
If a QRS complex occurs every 6 large squares, what is the rhythm?50 bpm.
How much voltage does a small square represent?0.1mV.
How much voltage do two large squares represent?1mV (at standard gain setting).
What is the PR interval?The time between the beginning of the P wave to the beginning of the QRS complex (excitation to spread from SA node to ventricular muscle).
How long is the normal PR interval?0.12 - 0.2 seconds (3-5 small squares, 120-200 milliseconds).
How long is the normal QRS complex?0.12 seconds (120 milliseconds) or less (3 small squares or less).
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