ECG Flashcards
What does P wave represent?
Atrial depolarisation
What does PR interval represent?
Time for electrical activity to move between the atria and the ventricles
When does PR interval begin and end?
Begins at the start of the P wave and ends at the beginning of the Q wave
What does QRS complex represent?
Depolarisation of the ventricles
When does ST segment begin and end?
Starts at the end of the S wave and ends at the beginning of the T wave
What does ST segment represent?
Time between depolarisation and repolarisation of the ventricles (i.e. ventricular contraction)
What does T wave represent?
Ventricular repolarisation
When does RR interval begin and end?
Begins at the peak of one R wave and ends at the peak of the next R wave
What does RR interval represent?
Time between two QRS complexes
When does QT interval begin and end?
Begins at the start of the QRS complex and finishes at the end of the T wave
What does QT interval represent?
Time taken for the ventricles to depolarise and then repolarise
How long does each small square on ECG paper represent
0.04 seconds
How long does each large square on ECG paper represent
0.2 seconds
How long does 5 large square on ECG paper represent
1 second
How long does 300 large squares on ECG paper represent
1 minute
Placement of V1 chest electrode…
4th intercostal space at the right sternal edge
Placement of V2 chest electrode…
4th intercostal space at the left sternal edge
Placement of V3 chest electrode…
Midway between the V2 and V4 electrodes
Placement of V4 chest electrode…
5th intercostal space in the midclavicular line
Placement of V5 chest electrode…
Left anterior axillary line at the same horizontal level as V4
Placement of V6 chest electrode…
Left mid-axillary line at the same horizontal level as V4 and V5
Placement of red RA electrode….
Ulnar styloid process of the right arm
Placement of yellow LA electrode….
Ulnar styloid process of the left arm
Placement of green LL electrode….
Medial or lateral malleolus of the left leg
Placement of black RL electrode….
Medial or lateral malleolus of the right leg
Which chest leads have septal view of the heart?
V1 and V2
Which chest leads have anterior view of the heart?
V3 and V4
Which chest leads have lateral view of the heart?
V5, V6, Lead I, aVR, aVL
Which chest leads have inferior view of the heart?
Lead II, Lead III, aVF
When the electrical activity within the heart travels towards a lead, you get a…..
Positive deflection
When the electrical activity within the heart travels away from a lead, you get a……
Negative deflection
If the R wave is greater than the S wave, it suggests depolarisation is moving _________ lead
Towards the
If the S wave is greater than the R wave,it suggests depolarisation is moving ________ that lead
Away from
If the R and S waves are of equal size, it means depolarisation is travelling at exactly __________
90° to that lead
In healthy individuals, the electrical activity of the heart begins at the ________ then spreads to the ________. It then spreads down the __________ and _________ to cause ventricular contraction
Sinoatrial node (SA)
Atrioventricular (AV) node
Bundle of His
Purkinje fibres
In healthy individuals, you would expect the cardiac axis to lie between ________, axis spreads from _________
-30°and +90º
11 o’clock to 5 o’clock
The overall direction of electrical activity in a healthy individual is towards leads _________
I, II and III
In healthy individuals see positive deflection in leads __________ with __________ showing the most positive deflection as it is the most closely aligned to the overall direction of electrical spread
Leads I, II, II
Lead II