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What is the physiological process on which ECGs are based?
Where are action potentials generated in the myocardium?
The myocardium contracts as a single unit (a functional syncytium). How is this possible?
What is the significance of the myocardium contracting as a functional syncytium for an ECG?
What does an ECG allow us to assess?
What does the P wave in an ECG correspond to?
What does the QRS peak in an ECG correspond to?
What does the T wave in an ECG correspond to?
Why is the QRS peak bigger than the P wave in an ECG?
What is Einthoven's triangle?
What is the mean cardiac vector?
How can we tell which angle of the heart we are 'looking' at from an ECG?
When plotting data in Einthoven's triangle, what number of mm of a deflection on an ECG trace is equivalent to 1 mV?
To work out the mean cardiac vector, we plotted perpendicular lines on to Einthoven's triangle at the appropriate mV for each pair of electrodes. How was the angle of the vector calculated?
How was the size of the mean cardiac vector established using Einthoven's triangle?
What is the normal range of a vector angle in a healthy person?
Using an unpaired T-test, it was established from the class data that there was no significant difference between the size and angle of the mean cardiac vector in males and females. Suggest why.
Using a paired T-test, there was no difference between normal and breath-holding vector sizes and angles. Why would one expect there to be a difference in the angle?
An axis (of the vector angle) of between -30° and -90° is referred to as what? What might cause this?
An axis (mean vector angle) of between +120° and +180° is referred to as what? What might cause this?
What is an axis (mean cardiac vector angle) between -90° and +180° referred to as? What might cause this?
