ECG Flashcards Preview

CVS > ECG > Flashcards

Flashcards in ECG Deck (12):

What do the P wave, QRS complex and T wave show

P wave: atrial depolarisation
QRS complex: ventricular depolarisation
T wave: ventricular repolarisation


why is arial repolarisation not shown?

It occurs at the same time as ventricular depolarisation


what to the different leads show?

The standard limb leads and the augmented limb leads show the frontal view electrical activity of the heart
The precordial limb leads show the transverse activity of the heart


Standard limb leads

SLL1- left arm wrt to right arm
SLL2- left leg wrt to right arm
SLL3- left leg wrt to left arm

SLL2- R wave most in line with line of depolarisation


Explain the QRS complex in SLL2

Q wave: electrical activity spreading from the left to right side of heart so -ve
R wave: down inter ventricular septum- +ve
S wave: up towards top of septum -ve


Augmented limb leads

2 limb leads tied together wrt to 1 limb lead
AVF- most +ve
AVR - most -ve
AVL- mismatch


Precordial limb leads

v4/v5/v6 positive
V1/V2/V3 negative
between v3/v4 there is a swap over called progression


how long should each section be?

PR- between start of P and end of Q- 0.12- 0.2 MS
QT- 0.42-0.6
QRS- 0.08


Rhythm strip:
-what does it show
-what can it be used to calculate?

Should run at 25mm/sec
calibrating pulse should be 0.2 sec = 1 large square
can be used to calculate HR:
-number of R waves in 30 large squares
-multiply by 10
or if QRS complexes are regular:
-count number of large squares between them
-divide by 300



Any electrical activity
Irregular or regular
Broad or narrow
Atrial activity?
Relationship between atria and ventricles


Broad/narrow QRS complexes

-should usually be less than 3 small squares
-usually lasts 0.12 s
-if more than this then indicates that depolarisation has started in the ventricles


Atrial activity in relation to QRS complex

PR interval should be <0.2s so 1 large square - 3-5 small squares