ECGs and Arrhythmias Flashcards
1
Q
What are the different parts of an ECG?
A
P wave
PR interval
QRS complex: Q wave, R wave, S wave
ST Segment
T wave
QT interval
2
Q
What does the P wave represent?
A
Atrial Depolarisation
3
Q
What does the PR interval represent?
A
Time between atrial depolarisation and ventricular depolarisation
AVN delay
4
Q
What does the Q wave of a normal QRS complex represent?
A
Depolarisation of the intraventricular septum
5
Q
What does the R wave of a normal QRS complex represent?
A
Depolarisation of the ventricle
6
Q
What does the S wave of a normal QRS complex represent?
A
Final depolarisation of the ventricles at the base of the heart
7
Q
What does the ST segment represent?
A
Time between ventricular depolarisation and Repolarisation?
8
Q
What does the T wave represent?
A
Ventricular Repolarisation
9
Q
What does the QT interval represent?
A
Time for both ventricular depolarisation and repolarisation.
10
Q
What is the standard calibration of an ECG?
A
25 mm/s
0.1 mV/mm
11
Q
What do the boxes on ECG paper represent?
A
1mm box - 40 msec (0.04 sec)
5mm box - 200 msec (0.2 sec)
25mm box - 1 sec
12
Q
What are the normal interval times of each wave?
A
PR: 120 - 200
ST: 270 - 330
QT: 350 - 420
QRS: 80 - 110
13
Q
How many leads does an ECG have?
A
A 12-lead ECG records 12 leads, producing 12 separate graphs on a piece of ECG paper.
14
Q
What are the bipolar leads?
A
Lead I, II, III
15
Q
What are the unipolar leads?
A
Precordial leads (V1 - V6)
aVR, aVL, aVF
16
Q
Which are the three pacemakers of the heart?
A
- SA Node: dominant; intrinsic rate of 60-100bpm
- AV Node: back-up pacemaker; intrinsic rate of 40-60bpm
- Ventricular cells: back-up pacemaker; intrinsic rate of 20-45bpm
17
Q
What is “situs inversus” and how must we adapt an ECG for it?
A
Situs inversus is a genetic condition in which the organs in the chest and abdomen are positioned in a mirror image from their normal positions
Therefore perform ECG for RHS
18
Q
What is Rule 1 of the ECG?
A
PR interval should be 120-200 milliseconds, or, 3-5 little squares
19
Q
What is Rule 2 of the ECG?
A
Width of the QRS complex should not exceed 120ms (3 small squares)
20
Q
What is Rule 3 of the ECG?
A
QRS complex should be dominantly upright (positive) in Leads I and II
21
Q
What is Rule 4 of the ECG?
A
QRS Complex and T wave tend to have the same general direction in the limb leads
i.e. if you have a negative QRS you should get a negative T wave
22
Q
What is Rule 5 of the ECG?
A
All waves are negative in aVR
23
Q
What is Rule 6 of the ECG?
A
R wave: grows from V1 to V4
S wave: grows from V1 to V3, disappears in V6
24
Q
What is Rule 7 of the ECG?
A
ST segment should start isoelectric,
Except in V1 and V2 where it may be elevated
25
What is Rule 8 of the ECG?
P wave should be upright (positive) in I, II and V2-V6
26
What is Rule 9 of the ECG?
Should be no Q wave, or only a small Q wave less than 0.04 seconds (1 small square) in I, II and V2-V6
27
What is Rule 10 of the ECG?
T waves must be upright in I, II and V2-V6
28
What might tall, pointed P waves indicate?
Right atrial enlargement (P pulmonale)
29
What might notched/bifid (M shaped) P waves in limb leads indicate?
Left atrial enlargement (P mitrale)
30
What might a short PR interval with a delta wave indicate?
Wolf-Parkinson White pattern
31
What might a long PR interval indicate?
First degree heart block
32
What will the QRS complex look like in LVH vs. RVH?
LVH:
Elongated R wave in V1
inverted T wave in V6
RVH:
Absent S wave in V1
Flat T in V6
33
What criteria do we use to diagnose LVH?
S wave in V1 + R wave in V5 or V6 (which ever is tallest) > 35mm
34
What is the 'J' point?
Point between the QRS complex and ST segment
35
What is a STEMI?
ST segment elevation myocardial infarction
36
What is the morphology of an abnormal T wave?
Symmetrical; tall; peaked; biphasic or inverted
37
What happens to the QT interval when heart rate increases?
QT interval shortens
38
What is the U wave?
U waves are thought to represent repolarization of the Purkinje fibers. However, the exact source of the U wave remains unclear.
39
Regular rhythm: how can we calculate HR?
The 300 method: count the number of "big boxes" between two QRS complexes and then divide 300 by this number
40
Irregular rhythm: how can we calculate HR?
ECG records 10 seconds of rhythm per page. Count the number of beats during these 10 seconds and multiply by 6.
41
What is axis deviation?
The normal QRS axis should be between -30 and +90 degrees.
Left axis deviation is defined as the major QRS vector, falling between -30 and -90 degrees.
Right axis deviation occurs with the QRS axis and is between +90 and +180 degrees
42
What pattern would you see in RBBB vs LBBB?
RBBB
V1 - m pattern
V6 - w pattern
LBBB
V1 - w pattern
V2 - m pattern
43
What view of the heart does the Lead I give rise to?
Lateral view
44
What view of the heart does the Lead II give rise to?
Inferior view
45
What view of the heart does the Lead III give rise to?
Inferior view
46
What view of the heart does aVR give rise to?
Lateral view
47
What view of the heart does aVL give rise to?
Lateral view
48
What view of the heart does aVF give rise to?
Inferior view
49
What view of the heart does the V1 lead give rise to?
Septal view
50
What view of the heart does the V2 lead give rise to?
Anterior /Septal
51
What view of the heart does the V3 lead give rise to?
Anterior view of the heart
52
What view of the heart does the V4 lead give rise to?
Anterior view of the heart
53
What view of the heart does the V5 lead give rise to?
Lateral view of the heart
54
What view of the heart does the V6 lead give rise to?
Lateral view of the heart
55
Which of the leads form the high lateral ECG territory?
Lead I
aVL
56
Which of the leads form the inferior ECG territory?
Lead II
Lead III
aVF
57
Which of the leads form the septal ECG territory?
V1
V2
58
Which of the leads form the anterior ECG territory?
V2
V3
V4
59
Which of the leads form the lateral ECG territory?
V5
V6
60
What can cause left axis deviation?
Left anterior fascicular block
Left bundle branch block
Left ventricular hypertrophy
61
What causes right axis deviation?
Left posterior fascicular block
Right heart hypertrophy/strain
62
Normality: what should the normal P wave look like?
- Positive in inferior leads + lead I
- Negative in aVR
- Biphasic in V1
- <120ms wide
- <0/3mV (3 small squares) tall
63
What do low amplitude/flat P waves suggest?
- AF
- Obesity
- Hyperkalaemia
64
What do high amplitude (tall) P waves suggest?
R atrial enlargement
65
What do broad notched (bifid) P waves suggest?
L atrial enlargement
66
What would P waves that changed morphology beat-to-beat suggest?
- Focal atrial tachycardias
- "Wandering pacemaker"
67
What causes a shorter PR interval?
- younger patients
- pre-excitation conditions e.g. Wolf Parkinson White - an accessory pathway between atria and ventricles
68
Normality: what a normal QRS complex?
Negative S waves in V1 transitioning to positive R wave by V6
69
What does a broad QRS complex suggest?
- ventricular conduction delay/ bundle branch block
- pre-excitation
70
What does a small QRS complex suggest?
- obese patient
- pericardial effusion
- infiltrative cardiac disease
71
What does a tall QRS complex suggest?
LVH (diagnostic criteria: S wave in V1 and R wave in V5 or V6 >35mm
thin patient
72
What can be a cause of "long QT" or "short QT" syndromes?
- congenital
- drugs - Class I and III antiarrhythmic Drugs
- electrolyte imbalances - Calcium
73
Normality: what are the characteristics of a normal ST segment?
*measured from J point to start of T wave*
- isoelectric
74
What conditions distort the ST segment?
- elevated in early repolarisation
- MI
- pericarditis
- myocarditis
75
Normality: what is the morphology of a normal T wave?
- positive in leads I, II, V2 to V6
- negative in aVR (and sometimes III)
- asymmetrical
76
What are features of abnormal T waves?
1. Symmetrical
2. Tall and peaked
3. Biphasic
4. Inverted
77
In what conditions would you see T wave changes?
- ischaemia/ infarction
- myocardial hypertrophy
- cardiomyopathy
78
What might ST elevation in leads 2, 3 and aVF suggest?
RCA blockage.
These leads show the activity of the inferior aspect of the heart and the RCA supplies the inferior aspect of the heart with blood.
79
Give 3 effects of hyperkalaemia on an ECG.
1. Tall 'tented' T waves.
2. Flat P waves.
3. Broad QRS.
80
Give 2 effects of hypokalaemia on an ECG.
1. Flat T waves.
2. QT prolongation.
3. ST depression.
4. Prominent U waves.
81
Give an effect of hypocalcaemia on an ECG.
1. QT prolongation.
2. T wave flattening.
3. Narrowed QRS.
4. Prominent U waves.
82
Give an effect of hypercalcaemia on an ECG.
1. QT shortening.
2. Tall T waves.
3. No P waves.
83
Give 3 potential consequences of arrhythmia.
1. Sudden death.
2. Syncope.
3. Dizziness.
4. Palpitations.
5. Can also be asymptomatic.
84
Define bradycardia.
< 60 bpm.
85
Define tachycardia.
> 100 bpm.
86
Give the two broad categories of tachycardia.
1. Supra-ventricular tachycardia's.
2. Ventricular tachycardia's.
87
Where do supra-ventricular tachycardia's arise from?
They arise from the atria or atrio-ventricular junction.
88
Do supra-ventricular tachycardia's have narrow or broad QRS complexes?
Supraventricular tachycardias are often associated with narrow complexes.
89
Where do ventricular tachycardia's arise from?
The ventricles.
90
Do ventricular tachycardia's have narrow or broad QRS complexes?
Ventricular tachycardias are often associated with broad complexes.
91
Name 5 supra-ventricular tachycardia's.
1. Atrial fibrillation.
2. Atrial flutter.
3. AV node re-entry tachycardia (AVNRT).
4. Accessory pathway.
5. Focal atrial tachycardia.
92
Give 4 causes of sinus tachycardia.
1. Physiological response to exercise.
2. Fever,
3. Anaemia.
4. Heart failure.
5. Hypovolemia.
93
Describe characteristics of an ECG taken from someone with atrial fibrillation.
1. Absent P Waves
2. QRS complex does not follow every P wave.
3. Fine oscillation of the baseline.
4. Irregularly Irregular Rhythm
94
The ECG taken from someone with atrial fibrillation shows a fine oscillation of the baseline and absent QRS waves. Why?
The atria fire a lot, it is chaotic. The AV node and ventricles can't keep up -> irregularly irregular pulse.
95
What are some risks in a patient with AF?
Artial activity is chaotic and mechanically ineffective.
Stagnation of blood in the atria -> thrombus formation and a risk of embolism -> stroke.
Reduction in cardiac output -> Heart failure
96
What are some causes of Atrial Fibrillation?
Hypertension,
Coronary artery disease,
Valvular heart disease (particularly mitral valve stenosis),
Cardiac surgery
97
Give 4 symptoms of atrial fibrillation.
1. Palpitations.
2. Shortness of breath.
3. Fatigue.
4. Chest pain.
5. Increased risk of thromboembolism and therefore stroke.
98
What score can be used to calculate the risk of stroke in someone with atrial fibrillation?
CHADS2 VASc.
99
What does the CHADS2 VASc score take into account?
1. Age.
2. Hypertension.
3. Previous stroke/TIA.
4. Diabetes.
5. Female.
A score >2 indicates the need for anticoagulation.
100
Describe the treatment for atrial fibrillation.
1. Rate control - beta blockers, CCB and digoxin.
2. Rhythm control - electrical cardioversion or pharmacological cardioversion using flecainide.
3. Flecainide can be taken on a PRN basis in people with infrequent symptomatic paroxysms of AF.
4. Long term - catheter ablation and a pacemaker.
101
Atrial fibrillation treatment: what might you give someone to help with rate control?
Beta blockers, CCB and digoxin.
102
Atrial fibrillation treatment: what might you give someone to help restore sinus rhythm (rhythm control)?
Electrical cardioversion or pharmacological cardioversion using flecainide.
103
What is the long term treatment of atrial fibrillation?
Catheter ablation - it targets the triggers of AF.
104
Describe the ECG pattern taken from someone with atrial flutter.
1. Narrow QRS.
2. 'sawtooth' flutter waves.
105
The ECG shows a continuous undulating pattern and sawtooth flutter waves. What arrhythmia is this describing?
Atrial flutter.
106
What pathophysiological mechanism can cause atrial flutter?
The re-entry mechanism - there is blockage of the normal circuit. Another pathway forms, takes a different course and re-enters the circuit -> tachycardia.
107
What is the commonest supra-ventricular tachycardia?
AV node re-entry tachycardia (AVNRT).
108
Do you see P waves in AVNRT?
No - the P waves are within the QRS complex.
109
Give 4 symptoms of AVNRT.
1. Sudden onset/offset palpitations.
2. Neck pulsation.
3. Chest pain.
4. Shortness of breath.
110
Describe the acute treatment of AVNRT.
Acute treatment: vagal manoeuvre and adenosine.
111
What drugs might you give to someone to suppress future episodes of AVNRT?
Beta blockers, CCB, flecainide.
112
What does sinus (or atrial) tachycardia look like on an ECG?
QRS complex follows every P wave
Very fast heart rate
113
Describe the pathophysiology of accessory pathway arrhythmias.
Congenital muscle strands connect the atria and ventricles - accessory pathway. This can result in pre-excitation of ventricles.
114
Describe 3 characteristics of an ECG taken from someone with accessory pathway arrhythmia.
1. Delta wave.
2. Short PR interval.
3. Slurred QRS complex.
115
Give an example of an accessory pathway arrhythmia.
Wolff-Parkinson-White syndrome.
116
Describe the pathophysiology of focal atrial tachycardia.
Another area of the atrium becomes more autonomic than the sinus node and so sinus node function is taken over -> focal atrial tachycardia.
117
What are narrow complex tachycardias?
Rapid cardiac rhythm > 100bpm, QRS complex <120ms:
Supraventricular tachycardia
Atrial fibrillation/flutter
118
What do broad complex tachycardias denote?
Rapid cardiac rhythm >100bpm, QRS complex >120ms
Ventricular tachycardia
Supraventicular tachycardia with bundle branch block/pre-excitation
119
What is the treatment for ventricular tachycardia in an urgent situation?
DC cardioversion.
120
What is the long term treatment for ventricular tachycardia in high risk patients?
Implantable defibrillator.
121
What are ectopic beats?
Very common, generally benign arrhythmias caused by premature discharge. The patient may complain of symptoms of 'skipped beats'.
122
Give 3 causes of long QT syndrome.
1. Congenital.
2. Electrolyte disturbances e.g. hypokalaemia and hypocalcaemia.
3. A variety of drugs.
123
Give 2 signs of long QT syndrome.
1. Palpitations.
2. Syncope.
124
Give 4 causes of sinus bradycardia.
1. Ischaemia.
2. Fibrosis of the atrium.
3. Inflammation.
4. Drugs.
125
Give 3 causes of heart block.
1. CAD.
2. Cardiomyopathy.
3. Fibrosis.
126
What are the 3 types of AV block?
First degree
Second degree
Third degree
127
What does first degree AV block look like on an ECG?
1:1 conduction but with prolonged PR interval >200ms
128
What does second degree AV block look like on an ECG?
occasional failure of impulse passing through the AVN
2:1 conduction (i.e. every other P wave is not followed by a QRS complex)
129
What does third degree AV block look like on an ECG?
P waves independent to the ventricles
Complete absence of AVN conduction
The ventricles have set their own rhythm (which is much slower) as they are no longer governed by the action of the SAN and atria
130
What are the 2 sub-types of second degree heart block?
Mobitz type I
Mobitz type II
131
What is Mobitz type I heart block?
PR interval gradually increases until AV node fails and no QRS is seen.
This then Repeats
132
What is Mobitz type 2 Heart Block.
There is a sudden unpredictable loss of AV conduction and so loss of QRS.
PR interval is constant but every nth QRS complex is missing.
133
Describe third degree AV block.
Atrial activity fails to conduct to the ventricles. P waves and QRS complexes therefore occur independently.
134
What is the Pathogenesis of Bundle Branch Block?
Where electrical conduction down the left/right bundle branch in the bundle of HIS/septum is blocked/delayed often by fibrosis.
This causes the impulse conduction to the ventricles to occur at different times creating a second R wave in the leads associated with the right/left ventricles on an ECG.
135
Give the Acute and Chronic Causes of Bundle Branch Block?
Acute - IHD, myocarditis
Chronic - HTN, Coronary artery disease, cardiomyopathy.
136
LBBB: what would you see in lead V1 and V6?
A 'W' shape would be seen in the QRS complex of lead V1 and a 'M' shape in V6.
WiLLiaM.
137
RBBB: what would you see in lead V1 and V6?
A 'M' shape would be seen in the QRS complex of lead V1 and a 'W' shape in V6.
MaRRoW.
138
What ECG changes are you likely to see in ischaemia and infarction?
T wave flattening and inversion
ST segment depression first → progresses to ST elevation
Q waves (old infarction)
139
Infarction involving the left anterior descending coronary artery will give rise to changes in which ECG leads?
Anterior leads: V2, V3, V4
140
Infarction involving the L circumflex coronary artery will give rise to changes in which ECG leads?
Lateral: V5, V6
141
Infarction involving the R coronary artery will give rise to changes in which ECG leads?
Inferior: II, III, aVF
