Chapter 12/13 Flashcards
1
Q
ECG/ EKG abbreviation
A
ElectroCardioGram
2
Q
EKG
A
A recording of the electrical currents of the heart
3
Q
How many EKG leads
A
12 because they are more detailed and accurate. 3-5 for continuous monitoring of rhythm
4
Q
Value of EKG
A
To detect damaged heart disease, from direct heart disease or other organ failure affecting the heart, serial ECGs are valuable in checking response to treatment, does not defects in the pumping ability of the heart
5
Q
When to order ECG
A
Signs and symptoms of acute cardiac disorder, Pre-op screening, Hx of heart disease, Hx of Cardiac surgery, physical exam findings that would indicate the need for ECG
6
Q
ECG leads
A
View from several different angles, electrical activity of heart at different angles. Has + and - components (12 leads- 6 limb leads, 6 chest leads, 10 wires- one on each limb, 6 on chest)
7
Q
Chest leads (precordial leads)
A
Looking at specific areas of the heart
8
Q
Primary electrolytes responsible for electrical difference across the RMP are
A
potassium, sodium, and calcium
9
Q
Which has the greatest concentration inside the cardiac cell
A
potassium about 151 meq/l inside cell, 4 outside
10
Q
Concentration of K outside the cardiac cell is
A
4 meq/l
11
Q
Concentration of k inside the cardiac cell is
A
151 meq/l
12
Q
Na outside the cardiac cell is
A
144 meq/l
13
Q
Na inside the cardiac cell is
A
7 meq.l
14
Q
Concentration of Ca is about what outside the cell
A
5 meq/l
15
Q
Concentration of Ca inside cell
A
less than 1 meq/l
16
Q
When the cardiac cell is in its resting or polarized state, the inside of the cell is ___Charged with what cation
A
Negatively charged with K cation
17
Q
When the cardiac cell is in its resting or polarized state the outside of the cell is ___ charged with what cation
A
Positively charged with Na cation
18
Q
Na+/K+ pump establishes
A
- an increased Na+ concentration outside the cell 2. an increased K concentration inside of the cell. both ions then diffuse along their concentration gradients. K diffuses out, Na diffuses in at the same time.
19
Q
For every 50 to 75 K ion that diffuse out of the cell only
A
1 Na diffuses into the cell, exchange ration results in a deficiency of positive cations inside the cell
20
Q
RMP of the mycardial cells is about
A
-90 mV
21
Q
Cornerstone to the understanding of the electrophysiology of the heart is the five electrophysiologic phases of the action potential
A
ECG
22
Q
ECG
A
is used to record the five phases of the action potential
23
Q
Phase 0 name
A
Rapid Depolarization (early phase)
24
Q
Depolarization
A
trigger for myocardial contraction
25
Rapid Depolarization (early phase) activate
ventricle muscle fibers initiated by the SA node
26
ventricular muscle fibers are activated between
60-100 times/min by an electrical impulse initiated by the SA node
27
This action changes the RMP and allows a rapid inward flow of Na into the cell through specific Na channels
Phase 0: Rapid Depolarization, causing the cell to become positively charged
28
The voltage inside the cell at the end of depolarization is about
+30 mV, producing a rapid up stroke in the action potential
29
Repolarization
process by which the cells of the heart return to their resting state
30
Other name for Phase 1
Initial Repolarization
31
Immediately after Phase 0
Phase 1: Initial Repolarization
32
Initial Repolarization
The channels for K open and permit K to flow out of the cell, an action that produces an early but incomplete repolarization
33
Illustrated as a short downward stroke in the action potential curve just before the plateau
Phase 1: Repolarization
34
Name for Phase 2
Plateau state
35
Plateau state
Slow inward flow of Ca which in turn significantly slows the outward flow of K
36
Prolongs the contraction of the myocardial cells
phase 2 : Plateau state
37
Name for Phase 3
Final Rapid Repolarization
38
Final Rapid Repolarization
Inward flow of Ca stops, the outward flow of K is again accelerated and the rate of repolarization accelerates
39
Phase 4 name
Resting or polarized state
40
Resting or polarized state
the voltage sensitive ion channels return to their pre-depolarization permeability. the excess Na inside the cell and the loss of K are returned to normal by the Na and K ion pumps. an Additional Na and Ca pump removes the excess Ca from the cell
41
The heart is composed of how many cardiac cells
2
42
the 2 cardiac cells are
Contractile muscle fibers, and specialized "pacemaker cells" called autorythmic cells
43
Myocardial contractile fiber cells make up
the bulk of the musculature of the myocardium and are responsible for the pumping activity of the heart.
44
Approx how much of the heart is composed of the autorhythmic cells
1 %, majority of which are located in the SA node
45
SA Node
Have the unique ability to initiate an action potential spontaneously, which in turn triggers the myocardial fibers to contract.
46
Automaticity
ability of the cells in the SA node (pace maker cells) to generate an action potential without being stimulated.
47
Excitability (irritability)
is the ability of a cell to reach its threshold potential and respond to a stimulus or irritation
48
The lower the stimulus needed to activate a cell, the more
excitable the cell
49
Conductivity
is the unique ability of the heart cells to transmit electrical current from cell to cell throughout the entire conductive system
50
Contractility
the ability of cardiac muscle fibers to shorten and contract in response to an electrical stimulus
51
additional properties of the myocardial contractile fibers and autorythmic cells are
refractory periods
52
Refractory periods entail
1. the ionic composition of the cells during different phases of the action potential and 2. the ability of the cells to accept a stimulus
53
Absolute Refractory Period
is the time in which the cells cannot respond to a stimulus. The ionic composition of the cells isnt in place to receive a stimulus.
54
Phases 0,1,2, and about half of phase 3 represent the
absolute refractory period
55
Relative refractory period
is the time in which repolarization is almost complete and where a strong stimulus may cause depolariation of some of the cells. Some cells may respond normally, some in abnormal way, and some not at all.
56
The second half of phase 3 represents
the relative refractory period of the action potential
57
the Nonrefractory period
occurs when all the cells are in their resting or polarized state. The cells are ready to respond to a stimulus in a normal fashion
58
Phase 4 represents what period
Nonrefractory period
59
Duration of each refractory period may vary in response to use of
medications or recreational drugs, presence of disease, electrolyte imbalance, myocardial ischemia, or myocardial injury
60
components of the conductive system include
Sinoatrial node (sa node), atrioventricular junction (AV node), bundle of His, the right and left budle branches, and the purkinje fibers.
61
SA node
initiates the cardiac contraction by producing an electrical impulse that travels through the right and left atria.
62
In the right atrium, the electrical impulse that travels through the
anterior internodal tract, middle internodal tract, and posterior internodal tract
63
All three internodal pathways become one at the
AV junction
64
Bachmanns bundle
Conducts electrical impulses by the SA node directly to the left atrium
65
The electrical impulse generated by the SA node cause the right and left atria to
Contract simultaneously, in turn causing the blood in the atria to move into the ventricles
66
Where is the AV junction located
just behind the tricuspid in the lower portion of the right interatrial septum
67
AV junction
relays the electrical impulse from the atria to the ventricles via the bundle of his
68
Bundle of His location
enters the intraventricular septum and divides into the left and right bundle branches
69
Normal heart, total time required for an electrical impulse to travel from the SA node to the end of the Purkinje fibers is about
0.22 seconds (entire heart depolarize time)
70
What plays an important role in the rate of impulse formation, conduction, and contraction strength
autonomic nervous system
71
Regulation of the heart is controlled by
neural fibers from both the sympathetic and parasympathetic nervous systems
72
Sympathetic neural fibers
innervate the atria and ventricles of the heart. When stimulated, the sympathetic fibers cause an INCREASE in the heart rate, AV conduction, cardiac, contractility, and excitability
73
Parasympathetic neural fibers, via the vagus nerve, innervate
the SA node, atrial muscle fibers, and the AV junction. It has little or no influence on the ventricular musculature.
74
Stimulation of the parasympathetic system causes the heart rate, AV conduction, contractility, and excitability to do what
DECREASE
75
Which phase is the rapid upstroke in the action potential
Phase 0
76
When does the inward flow of CA into the heart stop
Phase 3
77
Which phase is the plateau stage of the action potential
Phase 2
78
The SA node is also called the
Pacemaker
79
Which of the following slows the HR and AV conduction
Parasympathetic nervous system
80
When can a strong stimulus cause an unwanted depolarization of the heart
Relative refractory period
81
which phase is called the resting state
Phase 4
82
Which of the following means the ability to transmit electrical current from one cell to another
Conductivity
83
An electrical difference across the fibers of the heart is called the
Resting membrane potential
84
The entire sequence of electrical changes during depolarization and repolarization is called
Action Potential
85
What are the unipolar leads
aVL, V6, aVR
86
The imaginary line that can be drawn between the positive and negative electrodes in leads I, II, and III is called
Axis
87
Which leads monitor the electrical activity of the heart in the frontal space
aVL, Lead II, aVR, Lead III, and aVF
88
Which leads monitor the left ventricle
V5 and V6
89
The small squares on the standard ECG paper represent
0.04 second
90
The normal duration of the P wave is no longer than
0.11 second
91
The normal duration of the PR interval is no longer than
0.20 second
92
The normal duration of the QRS complex is less than
0.12 second
93
The normal duration of the ST segment is
0.12 second or less
94
The normal duration of the T Wave is
0.20 second
95
Electrocardiogram (ECG)
is a graphic representation of the electrical activity of the hearts conductive system recorded over a period of time. Also used to monitor the hearts response to therapeutic interventions.
96
Standard 12-ECG system consists of
4 limb electrodes and 6 chest electrodes.
97
Collectively the electrodes (or leads) view
the electrical activity of the heart from 12 different positions - 6 standard limb leads and 6 precordial (chest) leads
98
Each lead
1. views the electrical activity of the heart from a different angle 2. has a positive and negative component 3. monitors specific portions of the heart from the point of view of the positive electrode in that lead
99
Standard limb leads
Leads I, II, III, aVR, aVL, and aVF.
100
They are called limb leads because
they are derived from electrodes attached to the arms and legs.
101
Bipolar leads
Leads I, II, and III. Which means they use two electrodes to monitor the heart, one positive and one negative.
102
Axis
Imaginary line that can be drawn between the positive and negative electrodes for leads I, II, and III
103
Eithovens Triangle
The triangle formed around the heart by the three axes
104
Unipoar Leads
aVR, aVL, and aVF. They monitor the electrical activity of the heart between the positive electrode and the zero electrical reference point at the center of the heart
105
letter a stands for, v stands for
augmentation, voltage
106
Collectively, the limb leads monitor the electrical activity of the heart in the
frontal plane
107
frontal plane
which is the electrical activity that flows over the anterior surface of the heart; from the base to the apex of the heart, in a right to left direction
108
Left Lateral Leads
Leads I and aVL, monitor the left lateral side of the hear
109
Inferior Leads
Leads II, III, and aVF. view the lower surface of the heart
110
which lead is usually ignored
aVR since it does not contribute much info
111
Precordial leads monitor the heart from the
horizontal plane
112
Horizontal plane
which means they record electrical activity that transverses the heart.
113
Leads V1 and V2 monitor the
right ventricle
114
V3 and V4 monitor
the ventricular septum
115
V5 and V6 view the
left ventricle
116
Leads V1, V2, V3 and V4 are also called the
anterior leads
117
V5 and V6 are also called
Lateral Leads
118
Modified chest lead (MCL)
is a bipolar chest lead similar to the precordial lead V1. The positive electrode is placed on the chest (in the same position as V1 and the negative electrode is placed on the left arm or left shoulder area.
119
MCL may be helpful in
visualizing some waveforms
120
ECG run at what speed
25 mm/ sec
121
Each small square has a duration of
0.04 sec
122
Each large square delineated by the darker lines has how many small boxes and a duration of what
5 small squares, and a duration of 0.20 seconds
123
The paper on all ECG monitors runs at a speed of what
5 large squares per second, or 300 large squares per minute
124
The verticle portion of each small square represents
amplitude (or voltage) of 0.1 mV and 1 mm in distance
125
1 mv =
10mm (10 small verticle squares)
126
ECG configurations are composed of
waves, complexes, segments, and intervals recorded as voltage (on vertical axis) against time (on horizontal axis)
127
A single waveform begins and ends at the
baseline
128
when the waveform continues past the baseline, it changes into another
waveform
129
Two or more waveforms together are a
complex
130
a flat, straight, or isoelectric line is called a
segment
131
Interval
a waveform, complex, connected to a segment
132
Positive Deflections
all ECG tracings above the baseline
133
Waveforms below baseline
Negative Deflections
134
Normal cycle of electrical activity in the heart begins with what and is recorded as what
begins with atrial depolarization and is recorded as the P wave
135
Shape of P wave
Symmetrical and upright
136
P wave is followed by
a short pause while the electrical current passes through the AV node, this is seen on the ECG tracing as a flat or isoelectric line after the P wave
137
Normal duration of the P wave is
0.08 to 0.11 second
138
The normal amplitude of the P wave
is 0.2 and 0.3 mV
139
An increased duration or amplitude of the P wave indicates the presence of what such as
presence of atrial abnormalities, such as hypertension, valvular disease, or congenital heart defect
140
Repolarization of the atria is usually not recorded on an ECG tracing because
atrial repolarization normally occurs when the ventricles are depolarizing, which is a greater electrical activity
141
P prime (P') wave
atria depolarize in response to a stimulus outside the SA node
142
Starts at the beginning of the P wave and ends at the beginning of the QRS complex
PR interval
143
Normal duration of the PR interval is
0.12 to 0.20 second
144
The PR interval represents the
total atrial (supraventricular) electrical activity prior to the activation of the bundle of His, ventricular branches, and Purkinje fiber system
145
Represents ventricular depolarization
QRS complex
146
why is the QRS complex higher than the P wave
because the muscle mass of the ventricles is greater than that of the atria
147
Under normal conditions, the duration of the QRS complex is
less than 0.12 second
148
abnormal ventricular induced QRS complex waves are
longer than 0.12 second
149
Other abnormal QRS complex include
premature ventricular contractions (PVCs), increased amplitude, and T waves of opposite polarity
150
Represents the time between ventricular depolarization and repolarization
ST segment
151
normally ST segment measures
0.12 second or less
152
ST segment may be elevated or depressed due to
myocardial injury, ischemia, and certain cardiac medications.
153
A flat, horizontal ST segment above or below the baseline is highly suggestive of
ischemia
154
Represents Ventricular Repolarization, rest, and recovery
T wave
155
Normally the T Wave has a what deflection of about what mV
Positive deflection of about 0.5 mV, although it may have a negative delfection
156
The duration of the T wave normally measures
0.20 second or less
157
At the beginning of the T wave, the ventricles are in their
effective refractory period
158
at about the peak of the T wave, the ventricles are in their
relative refractory period and thus, are vulnerable to stimulation
159
T waves are sensitive indicators for the presence of a number of abnormalities, including
acid-base imbalance, hyperventilation, hyperkalemia, ischemia, and the use of various drugs
160
Follows the T wave and has the same polarity (deflection) as the T wave
U wave, origin not known, because of its low voltage the U wave usually is flat and not seen
161
when does the U wave become prominent
in the presence of certain electolyte disturbance, certain medications, and heart disease
162
Represents total ventricular activity
QT interval
163
QT interval
Ventricular depolarization (QRS) and repolarization (ST segment and the T wave).
164
Normally the QT measures about
0.38 second, and varies in males and females and with age
165
General Rule of QT interval
should be about 40% of the measured RR interval
166
P wave heart activity
Atrial depolarization
167
PR interval heart activity
Total atrial electrical activity prior to activation of the bundle of His, ventricular branches, and Purkinje fiber system
168
QRS complex heart activity
Ventricular depolarization
169
ST segment heart activity
Time between ventricular depolarization and repolarization
170
T wave heart activity
Ventricular Repolarization
171
U wave heart activity
usually is a flat or not seen
172
QT interval heart activity
Total ventricular activity
