Basic ECG

Question 1

If there is no electrical impulse what happens on an ECG?

Answer 1

trace remains static

Question 2

What happens on an ECG trace when there is an impulse moving towards an electrode?

Answer 2

Upwards (+’ve deflection)

Question 3

What happens on an ECG trace when there is an impulse moving away from an electrode?

Answer 3

Downwards (-‘ve deflection)

Question 4

What happens on an ECG trace when there is an impulse moving at an angle to an electrode? (i.e. running parallel)

Answer 4

If the electrode is at an angle to the impulse it will cause both a positive and negative deflection, as the impulse moves first towards the electrode and then away from it

Question 5

On ECG paper what is a small square equivalent to in time? (on paper moving at 25mm/sec)

Answer 5

0.04 secs

Question 6

Impulse starts in the __ node and depolarises throughout the atria travelling from right to left and to the __ node via intranodal tracks

The depolarisation causes the _____ to contract and fill the _______

This causes a relatively small deflection on the ECG called the __ wave

Answer 6

SA

AV

atria, ventricles

P

Question 7

When the ___ node releases the impulse it depolarise quickly down the left and right _________ to purkinje fibers causing the ventricles to contract in an orderly fashion

This is seen on the ECG as _____

Answer 7

AV

Bundles of His

This impulse causes the much larger QRS complex of an ECG

Question 8

Because the cells have depolarised they need to repolarise before the next impulse, ________ repolarisation causes the __ wave on the ECG

Answer 8

Ventricular

T