CVS: ECGs Flashcards
Describe how excitation normally spreads through the myocardium.
- SAN (sets rhythm)
- AVN
- The Bundle of His (only conducting path from atria to ventricles)
- Right and left Bundle branches
- Purkinje fibres
Describe the correct positioning of the 12 leads when performing an ECG.
CHEST
V1: 4th intercostal space to the right of the sternum
V2: 4th intercostal space to the left of the sternum
V3: Midway between V2 and V4
V4: 5th intercostal space at the midclavicular line
V5: 5th intercostal space below the armpit
V6: 5th intercostal space directly central below the armpit
LIMB Red: right arm Yellow: left arm Green: left leg Black: right leg
What kind of deflection is recorded when depolarisation spreads towards a positively recording electrode?
Upward
What kind of deflection is recorded when depolarisation spreads away a positively recording electrode?
Downward
What kind of deflection is recorded when repolarisation spreads towards a positively recording electrode?
Downward
What kind of deflection is recorded when repolarisation spreads away a positively recording electrode?
Upward
What does the P wave signal?
Atria depolarisation
What does the QRS complex signal?
Ventricle depolarisation
What does the T wave signal?
Repolarisation of the heart
Describe how the QRS complex will change if the viewing electrode is moved around a circle with the heart at its centre.
It ends as mirror image of one another as both magnitudes grow and shrink respectively until they have swapped.
What is meant my sinus rhythm?
The depolarisation of the heart is governed by the SAN.
How do you calculate the PR interval?
The space between the start of the P wave and the start of the QRS complex.
How do you calculate the QRS interval?
From the beginning to the end of the QRS complex.
How do you calculate the QT interval?
From the beginning of the QRS complex to the end of the T wave.
How many large squares are equal to a second on an ECG?
5
