Intro to EKG and interpretation Flashcards
1
Q
Automaticity
A
produce impulse without outside stimulation
2
Q
excitability
A
ability to respond to an electrical stimulus
3
Q
conductivity
A
ability to transmit electrical signal from cell to cell
4
Q
pacemaker cells
A
- SA node/ R atrium
- normal electrical power source
- automaticity
- 60-100 bpm
5
Q
electrical conduction cells
A
- hardwiring of the heart
- excitability and conductivity
- AV node, HIS branch, LBB/RBB, anterior and post fascicles, purkinge fibers
6
Q
myocardial cells
A
- contractile machinery of heart
- excitability and conductivity
7
Q
what determines HR?
A
- innate electrical characteristics of the cell
- external neurohormonal input
8
Q
factors that influence rate of pacemaker cell discharge
A
- catecholamines (increase HR)
- acetylcholine (decrease HR)
9
Q
what does the P wave represent?
A
- atrial depolarization
- Should proceed each QRS complex
10
Q
what does the QRS complex represent?
A
ventricular depolarization
11
Q
what does the T wave represent?
A
ventricular repolarization
12
Q
Lead I
A
- L arm is positive
- R arm is negative
13
Q
Lead II
A
- leg positive
- R arm negative
14
Q
Lead III
A
- leg positive
- L arm negative
15
Q
AVL
A
- L arm positive
- other limbs negative (-30)
16
Q
AVR
A
- R arm positive
- other limbs negative ( -150)
17
Q
AVF
A
- Leg positive
- other limbs negative (+90)
18
Q
what are the standard limb leads?
A
I, II, III
19
Q
what are the augmented limb leads?
A
AVR, AVL, AVF
20
Q
inferior leads
A
II, III, AVF
21
Q
left lateral leads
A
- I, AVL
- V5, V5
22
Q
Right leads
A
- AVR
- V1
23
Q
Anterior leads
A
V2, V3, V4
24
Q
how many seconds is one small square?
A
0.04 seconds
25
how many seconds is one large square?
0.2 seconds
26
in what leads is there a positively deflected P wave?
- I, II
- AVL, AVF
- V5, V6
27
in what leads is there a biphasic P wave?
III and V1
28
in what leads is there a negatively deflected P wave?
AVR
29
in what leads is the P wave variable?
V2, V3 and V4
30
what is a normal P wave amplitude and duration?
- amplitude= 0.5-2.5 mm
| - duration= 0.06-0.10 seconds
31
right atrial enlargement
- taller than 2.5 mm
- initial component of biphasic P wave is taller in V1
- normal duration
32
left atrial enlargement
- wide, often notched
- wide biphase wave in V1
- amplitude is normal or increased
33
what does the PR interval represent?
- the time from the start of atrial depolarization to start of ventricular depolarization
- is the distance from beginning of P wave to beginning of Q wave
34
what is a normal PR interval?
- 0.12- 0.2 seconds or up to one big box
| - larger than one box means heart block
35
what does the PR segment represent?
- time from end of atrial depolarization to beginning of ventricular depolarization
- from end of P wave to beginning of Q wave
36
what does the Q wave represent?
- septal depolarization
| - negative deflection at start of QRS complex
37
what is a pathologic Q wave?
- abnormally large Q wave
- generally indicates previous MI and irreversible damage
- occurs hours to days after MI
- can have simultaneous loss of R wave
38
what are the criteria to be considered a pathologic Q wave?
- duration greater than 0.04 seconds
| - depth > 1/3 the height of the R wave
39
what is the average vector of current flow?
0 degrees to +90 degrees
40
what is R wave progression?
- R wave progressively increases in amplitude moving L to R in precordial leads
- usually largest in V5 at apex of the heart
41
what is considered a normal QRS complex duration?
- 0.06- 0.1 seconds
| - should not be larger than 3 small boxes
42
why would someone have a wide QRS complex?
- impulse generated in ventricle
| - impulse takes an aberrant pathway through the ventricle
43
what does the ST segment represent?
- time from end of ventricular depolarization to start of ventricular repolarization
44
what does ST segment elevation represent?
MI
45
what does ST segment depression represent?
ischemia
46
what is the J point
termination of QRS complex at start of ST segment
47
what are the criteria to be considered a STEMI
- 1 mm in heigh in limb leads
- 2 mm in height in precordial leads
- has non-concave shape
48
what does J point elevation look like?
concave in appearance
49
what does the T wave represent?
- ventricular repolarization/ relaxation
| - variable in appearance
50
what does the QT interval represent?
- from beginning of ventricular depolarization to end of ventricular repolarization
- inversely proportionate to HR
- normally 40% of cardiac cycle
51
what is an easy way to check the QT interval?
should be less than half way between the two QRS complexes
52
AV Node pacemaker rate
40-60 bpm
53
ventricular pacemaker rate
20-40 bpm
54
methods for determining HR
- 300, 150, 100, 75, 60, 60
| - count QRS in 6 sec interval then multiply by 10
55
common reasons for cardiac hypertrophy
- chronic HTN
- congenital
- more common in ventricles
56
common reasons for cardiac enlargement
- volume overload
| - more common in atria
57
mean axis
- summation of all vectors in the heart
- normally falls between 0-90 degrees
- positive QRS in leads I and aVF
58
right axis deviation
- QRS negative in lead I
| - QRS positive in aVF
59
left axis deviation
- QRS positive in lead I
| - QRS negative in aVF
60
extreme right axis deviation
- QRS negative in lead I
| - WRS negative in aVF
61
characteristics of right axis deviation
- poor R wave progression
62
characteristics of left ventricular hypertrophy
- left axis deviation (sometimes)
- increased R wave amplitude in leads over L ventricle
- increased S wave amplitude in leads over R ventricle
- down sloping ST segment
- T wave inversion
63
criteria for dx of L ventricular hypertrophy
R wave amplitude in V5 or V6 plus S wave amplitude in V1 or V2 exceeds 35 mm/7 boxes
