ECG

Question 1

what is an ECG?

Answer 1

recording of the electrical activity of the heart from the skin

Question 2

what is the first process of electrical conduction system that does not show up on an ECG?

Answer 2

impulse formation in SA node

Question 3

what is the P wave?

Answer 3

depolarisation of the atrial muscle

Question 4

what happens after the P wave?

Answer 4

delay through the AV node which allows pressure to build up
flat part of ECG

Question 5

what happens after the delay through AV node?

Answer 5

down bundle of His and into left and right bundle branches in the ventricular septum

Question 6

when can we see the first reflections of the first part of the CRS complex?

Answer 6

conduction through purkinje fibres and ventricular muscle begins to contract

Question 7

what is the QRS wave complex?

Answer 7

ventricular depolarisation

Question 8

what happens during the plateau phase?

Answer 8

equilibrium causes this
between end of QRS and T
ST segment

Question 9

when is the platau phase?

Answer 9

ST segment

Question 10

what happens during the T wave?

Answer 10

all ventricular action potentials depolarising
much slower wave

Question 11

why do we use 12 leads on an ECG?

Answer 11

to give a cross sectional view of the heart
we can tell how the rhythm passes through the heart

Question 11

what is a lead?

Answer 11

electrical vector
not the wire attached to the patient

Question 12

what are unipolar leads?

Answer 12

measure the potential variation at a single point

Question 13

what are bipolar leads?

Answer 13

measure the potential difference between two points

Question 14

why would everything in the wave be positive?

Answer 14

electrical current is moving towards the electrode

Question 15

why would everything in the wave be negative?

Answer 15

electrica, current is moving away from it

Question 16

why would some parts of the wave be positive and some negative

Answer 16

electrical current is passing transverse to it

Question 17

what is the systematic approach to interpratating any ECG?

Answer 17

-identify PQRST
-measure HR
-check ECG intervals
-determine QRS axis
-look at P/QRS/T morphology

Question 18

how do we determine the HR off an ECG?

Answer 18

300 divided by the number of large squares between each CRS complex
or
number of QRS complexes across ECG (10 secs) x6

Question 19

what is the normal QRS range?

Answer 19

<3 small squares
<120ms

Question 20

what is the normal PR interval range?

Answer 20

<1 large square
<200ms

Question 21

what is the normal QT interval range?

Answer 21

<11 small squares
<440ms

Question 22

what is the angle of the QRS axis relative to?

Answer 22

lead 1 - 0 degrees

Question 23

what is the QRS axis?

Answer 23

looks at the
direction of axis depolarisation
dominated by left ventricle

Question 24

what is the normal direction on the QRS axis?

Answer 24

normal is -30 to +90 degrees

Question 25

how is the axis approximated?

Answer 25

by finding the lead with the most +ve QRS

Question 26

what result is given in left axis deviation?

Answer 26

-20 to -90 degrees

Question 27

what result is given in right axis deviation?

Answer 27

+90 to +180 degrees

Question 28

what result is given in extreme axis deviation?

Answer 28

+180 to -90 degrees

Question 29

what are some normal things to look for in an ECG?

Answer 29

normal P wave is upright in inferior leads
the normal ST segment is flat
The normal T wave has the same polarity as the QRS

Question 30

what does a not flat ST segment suggest?

Answer 30

there is flow during what is meant to be the platau phase, typically caused in areas where APD is shorter than usual

Question 31

how can we describe P waves?

Answer 31

positive, negative, inverted or biphasic