B4-089 The Electrocardiogram Flashcards
1
Q
fast response cardiac action potential occurs in
A
- cardiomyocytes
- purkinje fibers
2
Q
slow response cardiac action potential occur in
A
- SA node
- AV node
3
Q
use 3 electrodes on both arms and left leg
A
limb leads
4
Q
configure Einthove’s triangle, with heart at center
A
limb leads
5
Q
- bipolar leads
- recording made between any two vertices of the triangle
A
limb leads
6
Q
use same 3 limb electrodes, but compare 2 leads vs. the third
A
augmented limb leads
7
Q
- unipolar leads
- called “aV”
A
augmented limb leads
8
Q
both limb and augmented limb leads are in the […] plane
A
coronal
9
Q
6 unipolar leads that lie on the perpendicular to others (transverse plane)
A
chest leads
10
Q
positioned as spokes of a wheel to intersect at a point
A
hexaxial system
limb/augmented limb
11
Q
movement of a depolarization wave toward the positive end of a lead produces a […] deflection
A
positive
12
Q
movement of a repolarization wave toward the positive end of a lead produces a […] deflection
A
negative
13
Q
the height of a wave relects the […] of the current
A
magnitude
14
Q
the length of a wave reflects its
A
duration
15
Q
the sum of segments and waves
A
intervals
16
Q
which interval shows the rate?
A
R-R
17
Q
atrial depolarization
A
p wave
18
Q
P wave + PR segment
A
PR interval
19
Q
ventricular depolarization
A
QRS complex
20
Q
corresponds to phase 2 of ventricular action potential
A
ST segment
21
Q
ventricular repolarization
A
T wave
22
Q
QRS complex + ST segment + T wave
A
QT interval
23
Q
firing of the SA node intiates
A
atrial depolarization
24
Q
specialized conduction paths to rapidly conduct the impuls from the SA node to the AV node and left atrium
A
internodal pathways
25
atrial depolarization is dependent on [...] current
sodium
26
if the sodium current is reduced, the P wave will be
wider and have lower amplitude
27
the impulse is delayed in the AV node which allows the atria to
contract before the ventricles depolarize
28
highest conduction velocity in heart
purkinje fibers
29
the conduction impulse spreads between myocytes via
gap junctions
30
why will the QRS complex appear different on each lead?
as depolarization spreads through the ventricles, it changes magnitude and direction
31
sequence of ventricular depolarization
1. depolarize atria
2. depolarize septum from left to right
3. depolarize anteroseptal region of myocardium toward apex
4. depolarize bukl of ventricle myocardium, from endocardium to percardium
5. depolarize posterior portion of the base of the left ventricle
32
* corresponds to phase 2 of the ventricular action potential
* recorded along isoelectric line of the ECG
ST segment
33
represents ventricular repolarization
T wave
34
represents the entire time required from the onset of ventricular depolarization to repolarization
QT interval
35
Ca+ current and K+ current
ST segment
36
average orientation and magnitude of a dipole representing the most intense phase of ventricular depolarization
mean electrical axis MEA
37
if the QRS is positive in both leads I and aVF, the MEA is
normal
38
conditions that change MEA
* pregnancy
* ventricular hypertrophy
* infarct
39
ECG is used to
1. measure cardiac function
2. detect electrolyte imbalance
3. evaluate effective treatment
40
parasympathetic system [...] heart rate
decreases
41
sympathetic system [...] heart rate
increases
42
mediated by adrenergic receptors
sympathetic
43
increases heart rate, conduction, and contractility
sympathetic
44
mediated via cholinergic receptors
parasympathetic
45
decreases heart rate, conduction, contractility
parasympathetic
46
increased sympathetic nerve firing to the heart increases
* funny sodium current
* calcium current
* potassium current
| norepinephrine
47
sympathetic activity makes MDP more [...] and phase 4 [...]
positive
steeper
48
increased sodium current will cause
contractions to be stronger and briefer
49
increased potassium current will cause
repolarization to be increased and occur faster
50
does sympathetic nerve activation change the P wave or QRS complex?
no
51
effect of increased funny sodium current
increased heart rate
52
effect of increased L-type calcium current
* increased depolarization
* increased conduction velocity through AV node
* increased contraction strength
53
effect of increased delayed rectifier potassium current
decreased action potential duration
54
effect of decreased funny sodium current
slowed depolarization and heart rate
55
effect of decreased calcium current
reduced depolarization and heart rate
56
effect of decreased postassium current
extends phase 3 repolarization
slows heart rate
57
* increased HR
* MDP less negative
* faster phase 4 depolarization
* decreased action potential duration
sympathetic effects (NE) on SA Node
58
* decreased heart rate
* MDP more negative
* slower phase 4 depolarization
* increased action potential duration
parasympathetic effects (ACh) on SA node
59
* increased conduction velocity
* faster phase 0 depolarization
sympathetic effects (NE) on AV node
60
* decreased conduction velocity
* slower phase 0 depolarization
parasympathetic effects (ACh) on AV node
61
* phase 2 becomes more positive
* action potential duration increases
* contraction strength increases
sympathetic effects (NE) on ventricles
62
heart rate > 100 bpm
tachycardia
63
heart rate slower than 60 bpm
bradycardia
64
group of conditions in which heartbeat is irregular
arrhythmia
65
limits time of filling between beats
tachycardia
66
inadequate to support proper cardiac output
bradycardia
67
causes of arrythmias
* disorders of impulse formation
* disorders of impulse conduction
* both
68
symptoms of arrhythmias
* palpitations
* lightheadness
* syncope
* SOB
* chest pain
69
normal sinus rhythm
* rate of 60-100 bpm
* each QRS preceded by P wave
* normal shape of QRS, duration < 120 ms
* no additional waves
* PR < 200 ms
* QT interval less than half the R-R
70
* originates in SA node
* more bpm than normal
* regular rhythm
* P waves similar
* QRS normal
sinus tachycardia
71
rapid regular tachycardia that occurs with reentrant activity
paroxysmal tachycardia
72
* heart rate in 200-350 bpm range
* sinus tachycardia
atrial flutter
73
* suppression of sinus node
* normal P waves
* normal PR
* normal QRS
* rate <60 bpm
sinus bradycardia
74
occurs in:
* well conditioned athletes
* during sleep
* hypothyroidism
* vagal stimulation
* medications
sinus bradycardia
75
signal originates from group of cells outside the SA node
ectopic focus
76
abnormal action potentials are triggered by a preceding action potential and can result in tachycardia
triggered activity
77
* "afterdepolarizations"
* occur during phase 2, 3, or 4
triggered activity
78
* occur during late phase 2/early phase 3
* associated with slow rates of phase 3 repolarization (long QT syndrome)
early afterdepolarizations
| EAD
79
* occur in phase 4 of ventricular myocytes
* high heart rates
* high Ca+ concentrations
delayed afterdepolarizations
| DAD
80
EADs and DADs are secondary to high [...]
calcium levels
81
abnormal depolarization triggers an action potential to spread through myocytes repeatedly
reentrant loop
82
single depolarization triggered by abnormal depolarizations
premature ventricular depolarization
83
three requirements for reentry:
1. abnormal electical circuit
2. slow conduction
3. unidirectional block
84
reentrant loops are more likely when
1. conduction velocity is decreased
2. duration of action potential is increased
85
results from the development of multiple reentry loops
fibrillation
86
* no p waves on ECG
* ventricular rate irregular
* 300-500 bpm
* "bag of worms"
atrial fibrillation
87
sawtooth baseline
atrial flutter
88
* prolonged PR interval
* every P waves causes QRS
* caused by reduced conduction velocity
first degree AV block
89
* multiple P waves precede each QRS
* QRS looks normal
* PR interval progressively lengthens
2nd degree heart block
90
* P waves not causing QRS complex
* QRS looks normal, indicates ectopic focus
* atrial and ventricular rate completely independent
third degree AV block
91
AV block
a-fib
atrial flutter
classified as
supraventricular
92
v tach
branch block
prolonged QT
v fib
classified as
ventricular
