1
Q
What is the standard ECG paper speed?
A
25 mm per second (25 mm/s).
2
Q
What does the horizontal axis on ECG paper represent
A
Time.
3
Q
What does the vertical axis on ECG paper represent?
A
Amplitude (voltage)
4
Q
How much time does one small square represent on ECG paper?
A
40 milliseconds (0.04 seconds).
5
Q
How much time does one large square represent?
A
200 milliseconds (0.2 seconds).
6
Q
How many small squares make up one large square?
A
5 small squares.
7
Q
How many large squares represent one second on ECG paper?
A
5 large squares.
8
Q
How many large squares represent one minute on ECG paper?
A
300 large squares.
9
Q
What voltage does one small square represent vertically?
A
0.1 mV.
10
Q
What voltage does one large square represent vertically?
A
0.5 mV.
11
Q
What is the standard ECG calibration signal?
A
1 mV produces a 10 mm (10 small squares) vertical deflection.
12
Q
Why is the 1 mV calibration pulse important?
A
It confirms that the ECG is correctly calibrated.
13
Q
How would you calculate the duration of a waveform spanning 3 small squares?
A
3 × 40 ms = 120 ms.
14
Q
How long is a QRS complex that spans 2 large squares?
A
400 ms (0.4 seconds).
15
Q
How would you calculate heart rate using large squares?
A
300 ÷ number of large squares between R waves.
16
Q
How would you calculate heart rate using small squares?
A
1500 ÷ number of small squares between R waves.
17
Q
Why must ECG paper speed and calibration always be checked before interpretation?
A
Incorrect settings can lead to misinterpretation of intervals, rate, and voltage.
18
Q
What are the two ECG-related meanings of the word “lead”?
A
- The physical wires connecting electrodes to the ECG machine
- An imaginary line of sight along which electrical activity is measured
19
Q
When told to “connect the leads to the patient,” what does this refer to?
A
The physical cables attached to the electrodes.
20
Q
In ECG interpretation, what does the term “lead” mean?
A
An imaginary line drawn between electrodes used to view cardiac electrical activity.
21
Q
How many “views” of the heart does a 12-lead ECG provide?
A
12 different views, each from a different angle.
22
Q
Why are ECG leads described as “lines of sight”?
A
Each lead views electrical activity from a specific direction.
23
Q
What does each ECG lead represent in simple terms?
A
A snapshot of cardiac electrical activity from a particular angle.
24
Q
How many ECG lead systems are there?
A
Three lead systems.
25
Which leads are known as bipolar or limb leads?
Leads I, II, and III.
26
Why are Leads I, II, and III called “bipolar”?
Because they measure current between two electrodes.
27
Where are the electrodes for bipolar limb leads placed?
On the right arm, left arm, and left leg (or abdomen)
28
What does the viewer “look at” in bipolar limb leads?
Electrical current flowing between two limb electrodes.
29
Which leads are called augmented or unipolar leads?
aVR, aVL, and aVF.
30
Why are aVR, aVL, and aVF called “unipolar”?
They measure current between one electrode and a central reference point.
31
What is the “central reference point” in augmented leads?
An imaginary electrode located at the center of the limb lead triangle.
32
What does the viewer “look at” in augmented limb leads?
Electrical activity flowing between one limb electrode and the center of the triangle.
33
Why are lead angles important in ECG interpretation?
Because they determine how electrical activity is viewed by each lead.
34
What does the arrow associated with a lead represent?
The direction of the viewer’s eye or line of sight.
35
What should arrows representing augmented leads point toward?
Toward the center of the limb lead triangle.
36
Why can lead arrows sometimes be misleading in diagrams?
Because they may not accurately point to the true central reference point
37
Why is understanding leads and angles essential for ECG interpretation?
It explains why the same electrical event looks different in different leads.
38
What does overlaying Einthoven’s triangle onto the ECG leads demonstrate?
The degree values (angles) associated with each ECG lead
39
Why is the naming convention of ECG lead angles often confusing?
Because angles are expressed as positive and negative values, which can seem arbitrary.
40
What analogy helps explain positive and negative ECG angles?
Two protractors placed on the chest facing each other.
41
What do the “minus” degree values represent?
Angles measured on the more proximal protractor (e.g. −150°).
42
What do the “plus” degree values represent?
Angles measured on the more distal protractor (e.g. +30°).
43
Do the plus and minus signs have special physiological meaning?
No — they are simply labels, and could just as well be called A and B.
44
What is the most important requirement regarding lead angles?
To memorise the angle assigned to each lead and its opposite angle.
45
In lead diagrams, how are the primary and opposite angles usually shown?
Solid line → primary lead angle
Stippled line → opposite direction
46
What is the angle of Lead I?
0°
47
What is the angle of Lead II?
+60°
48
What is the angle of Lead III?
+120°.
49
What is the angle of lead aVL?
−30°.
50
What is the angle of lead aVR?
−150°.
51
What is the angle of lead aVF?
+90°
52
Why is knowing the opposite angle of each lead useful?
Because it helps determine whether electrical activity is moving towards or away from the lead.
53
What are leads V1–V6 called?
Precordial leads or chest leads.
54
How do precordial leads differ from limb leads?
They view the heart in the horizontal plane rather than the frontal plane.
55
What does each precordial lead measure?
Current flowing between one chest electrode and the imaginary central electrode.
56
Why is the imaginary central electrode important for chest leads?
It provides a reference point for measuring electrical activity.
57
From which planes can a standard 12-lead ECG view the heart?
Frontal plane → limb & augmented leads
Horizontal plane → precordial (V1–V6) leads
58
What is the key takeaway when learning ECG lead angles?
You do not need to deeply understand the geometry, but you must memorise the lead angles.
59
Why do ECG beginners struggle with “squiggles”?
Because it is difficult to relate the ECG waveform to underlying electrical activity
60
What is the first step when interpreting an ECG waveform?
Check which lead you are looking at.
61
Why is identifying the lead important?
Because each lead views the heart from a specific angle
62
What is the iso-electric line on an ECG?
The baseline where there is no net electrical activity toward or away from the lead.
63
Where is the iso-electric line usually identified?
Along the T–P segment
64
How can you best identify the iso-electric line?
By mentally drawing a line through the T–P intervals of several cycles.
65
What does a predominantly upright waveform represent?
A positive deflection.
66
What does a positive deflection indicate about wave movement?
The electrical wave is moving towards the lead/viewer.
67
What does a predominantly downward waveform represent?
A negative deflection.
68
What does a negative deflection indicate?
The electrical wave is moving away from the lead/viewer.
69
What is an equipolar deflection?
A waveform that deflects equally above and below the iso-electric line.
70
What does an equipolar deflection indicate about wave direction?
The wave is moving at 90° to the lead.
71
Why is the concept of equipolar deflection useful?
It helps determine the direction (axis) of electrical activity.
72
What are the key steps to interpret ECG squiggles?
Identify the lead
Find the iso-electric line
Determine if the deflection is positive, negative, or equipolar
Infer the direction of electrical activity
73
What is meant by the “combined ECG tracing”?
The complete ECG waveform formed by all waves, segments, and intervals together.
74
Which components combine to form an ECG tracing?
Waves, segments, and intervals.
75
What does one full ECG cycle represent?
One complete depolarization–repolarization cycle of the heart.
76
What does the QRS complex represent?
The vector sum of all electrical activity during ventricular depolarization.
77
Why is the QRS described as a “vector”?
Because it represents the overall direction and magnitude of ventricular electrical activity.
78
Does the QRS complex always contain a Q, R, and S wave?
No — not all components must be present.
79
When is a waveform still called a QRS complex?
Whenever it represents ventricular depolarization, regardless of its shape.
80
How can the QRS complex be written in ECG interpretation?
Simply as “QRS”, or with letters indicating its predominant form.
81
What do capital letters in QRS naming indicate?
A large deflection.
82
What do small (lowercase) letters in QRS naming indicate?
A small deflection.
83
Give examples of acceptable QRS naming.
R, rS, QS, qRS, RS.
84
What is a Q wave?
The first negative deflection before any positive wave.
85
What is an R wave?
The first positive deflection of the QRS complex.
86
What is an S wave?
A negative deflection following an R wave.
87
Why is understanding the QRS complex essential in ECG interpretation?
Because it reflects ventricular activation, conduction pathways, and axis direction.
88
What is the purpose of practising ECG interpretation using individual leads from the same ECG?
To understand how the same electrical event appears differently when viewed from different angles.
89
Why can three leads from one ECG look very different?
Because each lead views electrical activity from a different direction (angle)
90
From which direction does lead II view the heart?
From the left foot, looking upward toward the heart.
91
Why is the P-wave positive in lead II?
Because atrial depolarization spreads from right to left and downward, towards the viewer.
92
What does the flat portion of the PR interval in lead II represent?
Slowing of conduction in the AV node.
93
Why is the QRS complex positive in lead II?
Ventricular depolarization spreads downwards and to the left, toward the lead II viewpoint.
94
Why may there be no visible Q or S wave in lead II?
Because left ventricular mass dominates, overpowering electrical forces moving away from the viewer.
95
Why is the T-wave positive in lead II?
Ventricular repolarization also results in a net vector toward the viewer in lead II.
96
From which direction does lead aVR view the heart?
From the right shoulder.
97
Why is the P-wave negative in lead aVR?
Atrial depolarization moves away from the viewer.
98
Why is the PR interval still flat in lead aVR?
Because it still represents AV nodal delay, regardless of lead angle.
99
Why is the QRS complex negative in lead aVR?
Ventricular depolarization moves downwards and to the left, away from the aVR viewpoint.
100
Why is the T-wave negative in lead aVR?
Ventricular repolarization also results in a net vector away from the viewer.
101
From which direction does lead aVL view the heart?
From the left shoulder.
102
Why does the P-wave appear almost flat in lead aVL?
The atrial depolarization vector is nearly perpendicular (≈90°) to the lead.
103
Why is the QRS complex small and equipolar in lead aVL?
Because ventricular depolarization is viewed at approximately 90°, producing equal positive and negative deflections.
104
Why does the T-wave also appear flat in lead aVL?
Repolarization is viewed from a non-optimal (perpendicular) angle.
105
What key ECG principle is demonstrated by comparing leads II, aVR, and aVL?
Wave polarity depends on lead orientation, not on different electrical events.
106
Why does lead II often give the clearest ECG waveform?
Because its angle closely aligns with the main cardiac depolarization vector
107
Which leads are generally best for detecting rhythm abnormalities?
Lead II and V1.
108
Which leads are best for assessing P-waves?
Lead II and V1, sometimes aVR.
109
What is the key learning outcome from this ECG practice exercise?
ECG interpretation becomes logical when automaticity, conductivity, vectors, and lead orientation are considered together.
110
Which leads are best for assessing QRS abnormalities?
Chest leads V1–V6.
111
What are contiguous leads on an ECG?
Leads that view the same anatomical area of the heart from similar angles.
112
Why is understanding contiguous leads essential?
It allows localisation of myocardial infarction (MI) and identification of the affected coronary artery.
113
What must be present in contiguous leads to diagnose an MI?
Changes (e.g. ST elevation) in two or more contiguous leads.
114
Which leads view the inferior wall of the heart?
Leads II, III, and aVF.
115
Which coronary artery most commonly supplies the inferior wall?
The Right Coronary Artery (RCA)
(occasionally the left circumflex)
116
What ECG finding suggests an inferior MI?
ST elevation in II, III, and aVF.
117
Which leads view the lateral wall of the left ventricle?
Leads I, aVL, V5, and V6.
118
Which coronary artery supplies the lateral wall?
The Left Circumflex artery (LCx).
119
What ECG changes suggest a lateral MI?
ST elevation in I, aVL, V5, and V6.
120
Which leads view the interventricular septum?
Leads V1 and V2.
121
Which coronary artery supplies the septum?
The Left Anterior Descending artery (LAD).
122
What ECG finding suggests a septal MI?
ST elevation in V1 and V2.
123
Which leads view the anterior wall of the heart?
Leads V3 and V4.
124
Which coronary artery supplies the anterior wall?
The Left Anterior Descending artery (LAD).
125
What ECG finding suggests an anterior MI?
ST elevation in V3 and V4.
126
Which leads indicate an extensive anterior MI?
Leads V1–V6, I, and aVL.
127
Which artery is involved in an extensive anterior MI?
A proximal LAD occlusion.
128
Why is the posterior wall not directly seen on a standard ECG?
Because there are no posterior leads in a standard 12-lead ECG.
129
Which leads show reciprocal changes in posterior MI?
V1–V3.
130
What ECG changes suggest a posterior MI?
ST depression and tall R waves in V1–V3.
131
Which lead is especially useful for right ventricular infarction?
V1 (and right-sided leads such as V4R).
132
Which artery is usually responsible for right ventricular infarction?
The Right Coronary Artery (RCA).
133
How should contiguous leads be memorised for exams?
Inferior: II, III, aVF → RCA
Lateral: I, aVL, V5–V6 → LCx
Septal: V1–V2 → LAD
Anterior: V3–V4 → LAD
134
Where does the normal cardiac impulse originate?
The SA node.
135
In which directions does atrial depolarization normally spread?
Right to left and superior to inferior
136
What is meant by the cardiac “axis”?
The overall direction of electrical depolarization through the heart.
137
Why does the SA node normally control heart rhythm?
It has the fastest intrinsic rate of depolarization.
138
What happens to other pacemaker cells when the SA node fires normally?
They are suppressed by the SA node’s depolarization wave.
139
What occurs if the SA node is slow or fails?
Backup pacemakers (AV node or Purkinje fibres) take over → bradycardia.
140
What causes pathological tachycardias?
Abnormal pacemakers firing faster than the SA node, suppressing it.
141
What does the horizontal axis of the ECG represent?
Time (duration of electrical activity).
142
Why is atrial conduction slower than ventricular conduction?
Atria rely on cell-to-cell spread, ventricles use fast conduction pathways
143
What does widening of a wave or interval indicate?
Slower-than-normal conduction, usually due to pathology.
144
What is the normal duration of the QRS complex?
< 120 ms.
145
What does a narrow QRS (<120 ms) imply about impulse origin?
Supraventricular origin (SA node or atria).
146
Why does a supraventricular impulse produce a narrow QRS?
It enters the His–Purkinje “highway”, allowing rapid ventricular depolarization.
147
What does a wide QRS (>120 ms) indicate?
Abnormally slow ventricular conduction.
148
Name the two main causes of a wide QRS complex.
Ventricular origin (cell-to-cell spread)
Conduction block (e.g. bundle branch block)
149
What does the vertical axis of the ECG represent?
Amplitude (voltage).
150
What determines the size of a waveform?
The muscle mass through which the impulse travels.
151
Why is the P-wave smaller than the QRS complex?
The atria have less muscle mass than the ventricles.
152
What causes abnormally large QRS amplitudes?
Ventricular hypertrophy.
153
What single ECG measurement helps determine pacemaker origin?
QRS duration
Narrow = supraventricular
Wide = ventricular or conduction block
General Medicine
flashcards
Decks in class (37)
# Cards
-
EOB Exams659
-
ECG Module 196
-
ECG Module 2153
-
ECG Module 3: normal sinus rhythm284
-
ECG Module 4: Wave abnormalities324
-
ECG Module 5: Rhythm abnormalities243
-
Chest X- ray165
-
Hypertension52
-
Advanced Airway Management341
-
CPR48
-
Post Cardiac Arrest Care35
-
CardioPulmonary Resuscitation532
-
Basic Airway Management122
-
Capnography41
-
Ventilator Settings27
-
Ventilation15
-
Anaphylaxis130
-
Cardiac Infections75
-
Benzodiazepine Overdose112
-
Iron Overdose92
-
Opioid Overdose122
-
Paracetamol Overdose107
-
TCA Overdose80
-
Bradycardia198
-
Tachycardia251
-
Hyponatremia121
-
Hyperthermia27
-
Hypothermia71
-
Hypertensive Emergency146
-
Delirium127
-
Sepsis105
-
Status Epilepticus108
-
Snack bites155
-
Acute Kidney Injury101
-
Pneumonia22
-
Bronchiectasis23
-
COPD40
