2 Basics: Waves, Complexes, Intervals, and HR Flashcards
1
Q
The vertical axis of the ECG paper represents ______ and the horizontal axis represents ______
A
Voltage
Time
2
Q
One large box on the ECG paper represent…
A
- 2 seconds of time
0. 5 mV
3
Q
One small box on the ECG paper represents …
A
- 04 seconds
0. 1 mV
4
Q
What is the isoelectric line?
A
Flat line that occurs when no electrical activity is occurring or impulses are too weak to be detected
Used as a baseline to identify changing electrical movement
5
Q
The P wave is produced by…
A
Initiation of impulse in SA node
Depolarization of RA and LA
Impulse passing through AV junction
6
Q
Normal P waves are…
A
Upright and round
- 06-0.10 s (60-100 ms)
- 5-2.5 mm high
7
Q
The PR interval begins at _________ and ends at _________
A
The start of the P wave
The beginning of the QRS complex
8
Q
Normal PR interval
A
0.12 - 0.20 s (120-200 ms)
9
Q
The beginning of the P wave to the beginning of the QRS complex
A
PR interval
10
Q
What is the PR segment?
A
Flat (isoelectric) line between the end of the P wave and the start of the QRS complex
11
Q
What are the components of the QRS complex?
A
Q wave - first negative deflection following PR segment
R wave - any positive deflection following Q wave or PR segment
S wave - any negative deflection that extends below the baseline following the R wave
12
Q
Normal QRS duration is…
A
0.06 to 0.12 s (60-120 ms)
13
Q
Flat line that follows QRS complex
A
ST segment
14
Q
Larger, slightly asymmetrical waveform that follows ST segment
A
T wave
15
Q
Point were the QRS complex meets the ST segment
A
J-point
16
Q
What is the QT interval?
A
Beginning of the QRS complex to the end of the T wave
Represents time of ventricular depolarization and repolarization
17
Q
Normal duration of QT interval
A
0.36 - 0.44 s (360-440 ms)
Varies depending on the HR - as HR slows, the QT increases
18
Q
What does a normal ECG rhythm look like (Limb Lead II)?
A
Upright, round P waves occurring at regular intervals at ~60-100 bpm
PR interval of normal duration (0.12-0.20 s) followed by a QRS complex of normal upright contour and duration (0.06-0.12s)
Flat ST segment followed by an upright, slightly asymmetrical T wave
19
Q
What is the calibration mark and why is it there?
A
Helps ensure ECG machine is properly calibrated
Serves as reference point on ECG tracing
Standard signal is 1.0 mV in amplitude (2 large boxes)
20
Q
Markings on ECG tracing that are not a product of heart’s electrical activity
A
Artifact
Many causes (ie patient movement)
Can mimic life-threatening dysrhythmias
21
Q
These leads record difference in electrical potential between a positive and negative electrode using a third electrode called a ground
A
Bipolar leads (limb leads I, II, III)
22
Q
What are the poles for Lead I?
A
Right arm is negative
Left arm is positive
23
Q
What are the poles for Lead II?
A
Right area is negative
Left leg is positive
24
Q
What are the poles for Lead III?
A
Left arm is negative
Left leg is positive
25
Which leads are bipolar?
Leads I, II, III
All the rest are unipolar
26
______ use one positive electrode and a reference point calculated by the ECG machine (center of the heart)
Unipolar leads
27
Which leads are unipolar?
Augmented Limb Leads
• aVr - augmented vector Right
• aVl - augmented vector Left
• aVf - augmented vector foot
```
Precordial leads (“chest” or “V” leads)
• V1-6
```
28
What are the three augmented limb leads?
aVr, aVL, aVf
All unipolar
Enhanced by ECG machine b/c waveforms produced by these leads are normally small
29
Augmented limb leads use the same electrodes as limb leads but ...
One is positive, the other two have no charge and serve as a common ground
30
Which direction is positive for aVr?
Right arm - views base of the heart (atria and great vessels)
31
Which direction is positive for aVL?
Left arm - views lateral wall of left ventricle
32
Which direction is positive for aVf?
Left leg - view inferior wall of left ventricle
33
The precordial leads are all...
Positive electrodes
34
Lead placement:
V1
4th ICS on the right side of the sternum
35
Lead placement:
V2
4th ICS on the left side of the sternum
36
Lead placement:
V3
Halfway between V2 and V4 🙄
37
Lead placement:
V4
5th ICS in MCL (Septum)
38
Lead placement:
V5
Anterior auxiliary line, same horizontal plane as V4
39
Lead placement:
V6
Midaxillary line, same horizontal plane as V4
40
Leads _________ should be on the same horizontal plane
V4-V6
41
What views are provided by the precordial leads?
Anterior and lateral views of the heart in a horizontal plane
42
When are Modified Chest Leads (MCL) used?
For patient monitoring in ED, telemetry, and ICU
MCL1 and MCL6 provide continuous cardiac monitoring
43
When using Modified Chest Leads, where do you place the positive electrode?
In the same position as precordial leads V1 or V6
44
Different combinations of leads will tell you about...
Different surfaces of the heart
45
Which are considered the Anterior Leads?
V1-4
46
Which are considered the Lateral Leads?
Lead I, aVL, and V5-6
47
Which are considered the Inferior Leads
II, III, aVf
48
Why do we use so many god damn leads?
Help to distinguish focal problems from more widespread problems (Ischemia/infarct vs drug/electrolyte effects)
49
What are the five steps in analyzing an ECG?
Determine regularity
Calculate rate
Evaluate P waves
Evaluate QRS complexes
Evaluate PR intervals
50
Characteristics of Normal Sinus Rhythm
Rhythm: Regular
Rate: 60-100 bpm
P waves: Upright and rounded (in most leads), one preceding each QRS complex
QRS complexes: Narrow, 0.06 - 0.12 seconds
PR interval: 0.12 - 0.20 seconds
T waves: Upright and slightly asymmetrical
51
How do you describe a regular rhythm?
The distance of the R-R intervals and P-P intervals is the same
52
How do you describe an irregular rhythm?
The distance of the R-R intervals and P-P intervals differs
Irregular rhythms are considered ABNORMAL
53
What are the three methods of determining rhythm regularity?
Caliper Method
Pen and Paper Method
Counting the Small Squares Method
54
What are the different types of rhythm irregularity?
Occasional or very
Slightly
Sudden acceleration in HR (or slowing)
Patterned
Totally
Variable Conduction Ratio
55
What type of rhythm is this:
Pacemaker changes location from site to site
Slightly irregular
Referred to as “wandering atrial pacemaker”
56
Sudden HR acceleration is also referred to as...
Paroxysmal tachycardia
A normal rate that suddenly accelerates to a rapid rate producing an irregularity in the rhythm
57
Irregularity repeating itself in a cyclic fashion is referred to as...
Patterned irregularity
Examples:
Sinus Dysrhythmia (ie - respiration)
2nd-degree AV heart block
Type I
58
Totally Irregular (or Irregularly Irregular) rhythms are typically seen in ....
Atrial fibrillation
Ectopic sites in the atria fire at a rate of more than 350 bpm
Only some of the atrial impulses are conducted through the AV node
59
What are the different methods for calculating HR?
6-second interval x 10 method
Large-Box Estimate (count-down method)
1500 method
Rate Calculator
60
How does the 6-second interval x 10 method work?
Count the number of QRS complexes found in a 6-second portion of the ECG and multiply by 10
Quick and easy (no tools) but not as accurate as other methods
61
How does the Large-Box countdown method work?
Find an R wave located on or near a bold line
Count down along each bold line until the next consecutive R wave (300, 150, 100, 75, 60, 50, 43)
The bold line it falls on or is closest to represents the HR
62
What is the downside of the countdown method?
Less accurate with irregular rhythms
63
What’s the best way to interpolate the rate when use the countdown method and the R-R interval falls between the large boxes?
If rate is between 100-75, there are 25 numbers between them, so each small box can represent 5 bpm (25/5) - so 95, 90, 85, 80
64
Most accurate method for calculating HR
1500 method - count the number of small squares between two consecutive R waves and divide 1500 by that number
Requires no special tools but math is required (boo)
CANNOT be used with irregular rhythms
65
What is a normal HR in adults?
60-100 bpm
66
Heart rate < 60
Bradycardia
67
Heart rate > 100
Tachycardia
68
First deflection from baseline at the beginning of cardiac cycle
Sinus P wave
69
How does a normal p wave appear on lead II?
Upright and rounded
Precedes each QRS complex
Duration 0.06 - 0.10 seconds
Amplitude 0.5 - 2.5 mm
70
Tall, rounded or peaked, P waves may be seen with ...
Increased right atrial pressure and right atrial dilation
Amplitude > 2.5 mm suggests RAE
Aka P pulmonale
71
Wide (enlarged), notched or biphasic P waves may be seen in ...
Increased left atrial pressure and left atrial dilation
Width > 10.s (2.5 small boxes) suggests LAE
Aka P mitrale
72
What is P pulmonale?
Right Atrial Enlargement (RAE)
P wave > 2.5 mm TALL
73
What is P mitrale?
Left Atrial Enlargement (LAE)
P wave > 0.10s (2.5 small boxes)
74
What can cause different looking P waves?
Impulses arising from the atria but NOT the SA node
Seen with:
• Premature atrial complexes (PACs)
• Wandering atrial pacemaker
• Atrial tachycardia
75
P wave of early beat that differs in appearance from underlying rhythm
Premature atrial complex (PAC)
76
What happens to the P wave during atrial tachycardia?
With the rapid rate, the P wave is likely buried in the T wave of the preceding beat
When this occurs, the T waves are often peaked, notched, or larger than normal
77
What are “F” waves?
Flutter waves - produced when an ectopic site in the atria fires rapidly at a rate of 250-350 bpm
Often described as a “saw-toothed” pattern - more P waves than QRS complexes
78
What are ”f” waves?
Fibrillatory waves - Produced when the atria fire rapidly from many sites at a rate >350pm
Absence of discernible P waves, instead there is a chaotic looking baseline preceding the QRS complexes
79
What produces inverted P waves?
Retrograde depolarization of the atria
Associated with dysrhythmias that originate from the AV junction
80
Inverted P waves occur when...
Depolarization arises from the:
• Lower right atrium near the AV node
• Left atrium
• AV junction
May immediately precede, occur during, or follow the QRS complex
81
What does more P waves than QRS complexes indicate?
The impulse was initiated in the SA node or atria but was blocked and did not reach the ventricles
82
What are the different components of the QRS complex?
Q wave - first negative deflection following he PR segment
R wave - any positive deflection following Q wave or PR segment
S wave - any negative deflection that extends below the baseline following the R wave
83
Normal QRS duration is ....
0.06 to 0.12s
84
When looking at the QRS complex, there is only one _______ but there can be more than ________
Q wave
R or S wave
In that case, the second R or S wave is called R’ or S’
If the R or S wave is small, use the lower case “r” or “s”
85
How to measure the QRS complex
Starting point is where the first wave of complex starts to move away from baseline
Ending point is where the last wave of the complex begins to level out (flatten) at, above, or below the baseline
86
Measurement of the QRS complex should include _______ but it shouldn’t __________
Entire S wave
Overlap into the ST segment or the T wave
87
QRS complexes should appear normal (upright and narrow) if...
Rhythm is initiated from a site above the ventricles (SA node, atria, AV junction)
Conduction has progressed normally from the bundle of His, through the right and left bundle branches, and through the purkinje fibers
Normal depolarization of the ventricles has occurred
88
Normal QRS can be seen in dysrhythmias that...
Arise from above the ventricles, unless there is a conduction delay through the ventricles or other type of abnormality
89
When do you see abnormal QRS complexes?
When there is abnormal depolarization of the ventricles
Pacemaker site in these abnormal QRS complexes can be...
• SA node
• Ectopic pacemaker in the atria, AV junction, bundle branches, purkinje network, or ventricular myocardium
90
What are some examples of causes for abnormal QRS complexes?
```
Ventricular hypertrophy
Intraventricular conduction disturbance
Aberrant ventricular conduction
Ventricular pre-excitation
Ventricular ectopic or escape pacemaker
Ventricular pacing by cardiac pacemaker
```
91
TALL QRS complexes are usually caused by...
Hypertrophy of one or both ventricles
An abnormal pacemaker
Aberrantly conducted beat
92
Low-voltage QRS complexes are more commonly seen in...
Obese patients
Pericardial effusion
Hypothyroidism
93
Wide-Bizarre QRS complexes are often the result of...
Intraventricular conduction defect - right or left bundle branch block
They are of supraventricular origin
94
Aberrant conduction occurs when ...
Electrical impulses reach the bundle branch while it is still refractory after conducting a previous electrical impulse
The impulse travels down the unaffected bundle branch first, followed by the other —> wider than normal QRS complex
95
_______ denotes depolarization of the heart from the SA node through the atria, AV node, and His-Purkinje system
PR interval
Measured from the beginning of the P wave to the beginning of the Q wave (or R wave if Q is absent)
96
PR intervals are considered abnormal if they are...
Shorter than 0.12 s
Longer than 0.20 s
Absent
Vary in duration
97
Shorter PR intervals (< 0.12 s) occur when...
The impulse originates in the atria close to the AV junction or in the AV junction
An impulse arises from a supraventricular site but travels through abnormal accessory pathways to the ventricles
98
Shorter PR intervals lead to ...
Premature ventricular depolarization (PRE-EXCITATION)
99
Longer PR intervals occur when...
There is a delay in impulse conduction through the AV node
Ex: 1st-degree AV heart block
100
In __________, the pacemaker site moves from beat to beat causing the P waves to appear different and the PR intervals to vary
Wandering atrial pacemaker
101
2nd degree AV heart block Type I has PR intervals that are...
Progressively longer until a QRS complex is dropped, then the cycle repeats
102
Absent PR intervals occur in...
Atrial flutter and fibrillation and in ventricular dysrhythmias
103
In 3rd degree AV heart blocks, what happens to the PR interval
It is not measurable
All of the impulses are blocked as they travel through the AV node
Essentially, the atria and ventricles are beating independently of each other
