Case 13 Flashcards
1
Q
How long is the PR interval normally?
A
120-200 ms
2
Q
Which area of the heart has the fastest firing rate?
A
SAN normally 60-100bpm
Fastest intrinsic rate - pacemaker
3
Q
When are palpitations more common?
A
Puberty
Pregnancy
Menopause
4
Q
What may exacerbate palpitations?
A
Stress, alcohol, caffeine
5
Q
Breathlessness can present in both tachy and bradyarrhythmias, what causes the breathlessness and how many tachy/bradyarrhythmias lead to this?
A
Breathlessness = reduced cardiac output
CO = SV x HR
Bradyarrhythmias reduce heart rate
Tachyarrhythmias reduce stroke volume (insufficient time to fill/ empty)
6
Q
Chest pain can present in both tachy and bradyarrhythmias, what causes the chest pain and how many tachy/bradyarrhythmias lead to this?
A
Myocardial oxygen demand exceeds supply
Increased demand from increased hear rate - tachyarrhythmia
Decreased demand from decreased cardiac output - brady/ tachyarrhythmia
7
Q
What is the equation for blood pressure?
A
BP = CO x total peripheral resistance
8
Q
How do the arrhythmias that lead to sudden cardiac death arise?
A
1/3 - primary arrhythmias, structurally normal heart
2/3 - structurally abnormal heart, 80% with CAD, 20% cardiomyopathy
9
Q
How do the arrhythmias that lead to sudden cardiac death arise?
A
1/3 - primary arrhythmias, structurally normal heart
2/3 - structurally abnormal heart, 80% with CAD, 20% cardiomyopathy
So most fatal arrhythmias are secondary to coronary artery disease
10
Q
What is a primary arrhythmia?
A
Hear rhythm abnormality that develops out of the blue, not secondary to anything
11
Q
What does the ECG look like in atrial fibrillation?
A
No p waves - chaotic baseline of fibrillation waves
Irregularly irregular rhythm
12
Q
What is the most common sustained arrhythmia?
A
Atrial fibrillation
13
Q
What are the risks of atrial fibrillation?
A
Cerebral thromboembolic event - stroke, transient ischaemic attack
Ventricular tachycardia if accessory pathway present - death
14
Q
What differentiates paroxysmal, persistent and permanent atrial fibrillation?
A
Paroxysmal - episode lasts less than 48 hours
Persistent - episode lasts more than 48 hours but less than a week
Permanent (fewer symptoms observed by patient as get used to it)
15
Q
Which rhythm control drugs can be given for atrial fibrillation?
A
VW class Ic - flecainide, propafenone VW class III - amiodarone, dronedarone
16
Q
How useful is aspirin in stroke prevention in atrial fibrillation?
A
No role
17
Q
What happens in 1st degree heart block?
A
Pathological slowing of conduction from atria to ventricles
Long PR interval >200ms on ECG
18
Q
What usually causes 1st degree heart block?
A
Slow conduction within the AVN
Often caused by AVN blocking drugs
19
Q
What are the consequences of 1st degree heart block?
A
Doesn’t usually cause symptoms or need drugs
20
Q
What may be the symptoms of 2nd degree or complete heart block?
A
Dyspnoea, T-LOC, chest pain from reduced CO
21
Q
What happens in complete heart block?
A
Conduction from atria to ventricles fail
Heart continues to beat due to escape rhythm e.g. from ventricles if AVN blocked from them
22
Q
What happens in complete heart block?
A
Conduction from atria to ventricles fail
Heart continues to beat due to escape rhythm e.g. from ventricles if AVN blocked from them
23
Q
What is the most life threatening regular broad complex tachycardia?
A
Ventricular tachycardia
24
Q
What is the most life threatening regular broad complex tachycardia?
A
Ventricular tachycardia
25
What kind of patient has ventricular tachycardia?
History of structural heart disease e.g. ischaemic heart disease
Inherited heart problems - cardiomyopathies, long QT syndrome
26
What family history might be alarming to VT?
Young ischaemic heart disease
Death younger than 40
Known heritable heart disease
27
What family history might be alarming to VT?
Young ischaemic heart disease
Death younger than 40
Known heritable heart disease
28
What past medical history might be alarming to VT?
MI
Heart failure
Ischaemic, congenital, valvular heart disease
Cardiac surgery
29
What clinical findings might be alarming to VT?
Abnormal ECG
Heart murmur
Signs of heart failure
30
Which inherited conditions can predispose to primary arrhythmias?
Long QT syndrome
Brugada syndrome
Wolff-Parkinson-White syndrome
31
What are the inherited cardiomyopathies that can predispose to arrhythmias?
Hypertrophic
Dilated
Arrhythmogenic RV
32
What helps the spread of excitation from SAN to LA?
Bachmann's bundle
33
What electrically separates the atria from ventricles?
Anulus fibrosus
34
What causes depolarisation in a normal cell and cardiac pacemaker cell?
Normal cell - Sodium influx causes depolarisation
| Cardiac pacemaker cell - Calcium influx causes depolarisation
35
Which phase of cardiac pacemaker cells does sympathetic/ parasympathetic stimulation effect?
Phase 4 - altering the rate of funny current (slow inward current of sodium)
36
What are the unipolar limb leads?
aVR/ Augmented vector right - lead on R wrist
aVL/ Augmented vector left - lead on L wrist
aVF/ Augmented vector foot - lead on L foot
37
What's the PR interval?
Start of p wave to start of QRS
| 0.12-0.20 seconds
38
How do you convert seconds to milliseconds (ms)?
x1000
39
Which part of the ECG represents atrial systole?
P wave
40
Which part of the ECG represents electrical conduction through the AVN?
PR segment
41
Which part of the ECG represents ventricular systole and atrial repolarisation?
QRS complex
42
Which part of the ECG represents a time where the ventricles are entirely depolarised?
ST segment
43
Which part of the ECG represents ventricular repolarisation?
T wave
44
Which part of the ECG represents ventricular depolarisation and repolarisation?
QT interval
45
What is the sequence of the ECG?
P wave, PR segment, QRS complex, ST segment, T wave
or
PR interval, QT interval
46
How long is the QRS complex in order to be classed as:
A) Normal?
B) A broad complex?
A) Normal is less than 120ms
| B) QRS duration >120ms
47
What is the QT interval?
Start of the QRS complex to the end of the T wave
| Normal: less than 450ms
48
Which part of the ECG represents atrial depolarisation and the time take to pass through the AVN?
PR interval
49
How is an ECG recording calibrated?
Set to 1mV that is 1cm (10 small squares high)
| Paper feeding in at 25mm/s
50
If paper is fed in at a rate of 25mm/s what does one large square represent?
0.2 seconds
51
If paper is fed in at a rate of 25mm/s what does one small square represent?
0.04 seconds
52
How do you calculate the heart rate on an ECG?
300/ no. of large squares in R-R interval
53
What is a tachycardic heart rate?
>100bpm
54
What is a bradycardic heart rate?
Less than 60 bpm
55
Work out the heart rate for the following R-R intervals:
A) 4 large squares
B) 5 large squares
C) 6 large squares
A) 75
B) 60
C) 50
56
What 2 things should be considered on assessing rhythm of the ECG trace?
R-R interval: regular, regularly irregular or irregularly irregular
Is every P wave followed by a QRS complex: sinus
57
Which leads will be positive and negative in right axis deviation?
Positive: III and aVF
Negative: I and aVL
58
What causes right axis deviation?
```
Average depolarisation moves to the right
Right ventricular hypertrophy
COPD
PE
lateral MI
Wolff-Parkinson-White syndrome (WPW)
```
59
Which leads will be positive and negative in left axis deviation?
Positive: aVL and I
Negative: II, III and aVF
Only significant when II is negative
60
What causes left axis deviation?
LVH
Inferior MI
WPW syndrome Left anterior hemiblock
61
What should the INR of patients with atrial fibrillation be?
INR of 2 to 3
62
What is the mechanism of atrial flutter?
Macro re-entry circuit in right atrium - area of slow conduction near the IVC
The AV node cannot conduct impulses at this rate leading to AV block - ventricles only beat once for every 2/3/4 atrial beats
The most common is a 2:1 block producing a ventricular rate of 150bpm
63
What is typically the atrial rate in atrial flutter?
Atrial rate of around 300bpm
64
What can cure atrial flutter?
Radiofrequency catheter ablation - burn the area between the inferior vena cava and the tricuspid annulus so that it can no longer conduct impulses
65
What does atrial flutter look like on ECG?
Saw-tooth appearance - regular flutter waves
66
How would you describe a sequence of 3 flutter waves before every QRS complex?
3:1 AV block
67
What would show left atrial enlargement on an ECG?
Bifid p wave called P mitrale
| RA depolarises before the LA
68
What may cause a bundle branch block, causing the QRS complex to be >120ms?
Conduction system fibrosis
Ischaemic/ Hypertensive/ Valvular heart disease (especially aortic stenosis)
Cardiac surgery
Cardiomyopathies
69
Which type of bundle branch is always pathological?
Left
| right can be present in normal hearts
70
What can cause right bundle branch blocks?
MI
PE
Cor pulmonale
Normal variant
71
What can cause left bundle branch blocks?
IHD, MI
Hypertension
Aortic Stenosis
Dilated cardiomyopathy
72
What are the ECG changes in a STEMI?
ST elevation: >2mm in chest leads, >1mm in limb leads
ST elevation must be in at least 2 contiguous leads
First change: Tall peaked T waves
T wave inversion (immediate or delayed)
73
ST elevation in which leads suggest an anterior infarction?
V2-5
74
ST elevation in which leads suggest an inferior infarction?
III and aVF
75
ST elevation in which leads suggest a lateral infarction?
I, aVL and V5-6
76
What could happen do the ECG with an NSTEMI?
T wave flattening/ inversion
ST segment depression >0.5mm (up-sloping/ horizontal/ down-sloping)
ECG may be normal
77
If an NSTEMI is suspected from ECG recording, what is required for confirmation?
Troponin rise
78
What ECG changes are seen in pericarditis?
Widespread concave upwards ST elevation (saddle-shaped)
Widespread PR depression
Reciprocal ST depression and PR elevation in aVR
Later T wave inversion
79
What are examples of broad complex tachyarrhythmias/ wide QRS complexes?
Ventricular tachycardia, torsades de pointes
Ventricular fibrillation
Supraventricular tachycardia with bundle branch block
80
What are examples of narrow complex tachyarrhythmias/ narrow QRS complexes?
```
Sinus tachycardia
Atrial fibrillation
Atrial flutter
AV node re-entry tachycardia (AVNRT)
AV re-entry tachycardia (AVRT)
Atrial tachycardia
```
81
Which causes pre-excitation; AVNRT or AVRT?
AVRT
82
Which leads would have inverted T waves in a left sided accessory pathway?
V1-3
83
Which leads would have inverted T waves in a right sided accessory pathway?
V4-6
84
What are the differences in QRS complex between AVRT causing orthodromic tachycardia compared to antidromic tachycardia?
```
Orthodromic tachycardia (retrograde passage through accessory pathway, more common) - narrow QRS
Antidromic tachycardia (anterograde passage through accessory pathway, less common) - wide QRS
```
85
What ECG changes are observed in AVNRT?
In sinus rhythm looks like a normal ECG
Supra-ventricular tachycardia with narrow QRS complexes
May have inverted P waves
86
What ECG changes are observed in AVRT?
In sinus rhythm there is a delta wave
Short PR interval
Orthodromic tachycardia – looks like a SVT
Antidromic tachycardia – looks like VT
87
How are ANVRT and AVRT treated?
Vagal manoeuvres
If this fails then adenosine
In haemodynamically compromised patients, DC cardioversion is indicated
88
What are the reversible causes of cardiac arrest?
```
(4 H's)
Hypoxia
Hypovolaemia
Hyper/ hypo kalaemia/ hypocalcaemia/ hypoglycaemia
Hypothermia
(4 T's)
Thromboembolic
Tamponade (cardiac)
Tension pneumothorax
Toxins
```
89
What's the antidote for heparin?
Protamine sulphate
90
What's the antidote for warfarin?
Vitamin K
91
What's the antidote for novel oral anticoagulants?
Idarucizumab
92
What is the name of the accessory pathway in Wolf-Parkinson-White syndrome?
Bundle of Kent
93
What is the difference between Mobitz type 1 and 2 2nd degree heart block?
Mobitz type 1: progressive lengthening of PR interval until failure of conduction of an atrial beat
Mobitz type 2: Mostly constant PR interval, occasional atrial depolarisation whiteout subsequent ventricular depolarisation
94
What happens in 2nd degree heart block?
Conduction from atria to ventricles is intermittent
ECG shows non-conducted p waves (not followed by QRS complex)
PR interval progressively lengthens in type 1
PR interval is constant in type 2
95
Which direction does the septum normally depolarise ?
Left to right
96
How can left bundle branch blocks be differentiated from right on ECG?
```
(William Marrow)
LBBB: W in V1, M in V6
RBBB: M in V1, W in V6
W is a QRS complex
M is an RSR pattern
```
97
Which leads would have tall, peaked P waves in P pulmonale? How tall?
Which leads must have a positive p wave? How tall?
Inferior - II, III and aVF >2.5mm
| V1 and V2 >1.5mm
98
What causes P pulmonale?
Right atrial enlargement from pulmonary hypertension (chronic lung disease/ PE) or tricuspid regurgitation
99
Do regular narrow complex tachyarrhythmias increase the risk of sudden cardiac death?
No
100
What is the valsalva manoeure and when should it be used?
Moderately forceful attempted exhalation against closed airway
For symptoms of tachycardia
101
What does adenosine do to the conducting system of the heart?
Injected short acting AVN blocker
102
What are beta 1 receptors coupled to?
Gs proteins
103
What can encourage delayed after depolarisations?
Digoxin
Adrenaline (via GPCR)
through increasing intracellular calcium
104
What happens in delayed after depolarisations?
Calcium is super threshold
| Asynchronous action potentials are fired until the calcium runs out
105
What is the threshold for action potential roughly?
-40mV
106
What is an example of a Na+ channel blocker used for SVT?
Flecainide
107
How do sodium channel blockers stop SVT?
They block fast path channels
108
Give an example of a beta blocker used to treat SVT and state how beta blockers are effective
Bisoprolol
| Block B1 adrenoceptors, reducing the slope of phase 4 potential
109
Which phase of the action potential do potassium channel blockers affect?
Phase 3
110
Example of a potassium channel blocker
| and how do they work in treating VT, AF, atrial flutter and WPW?
Amiodarone
Blocking K+ channels slow repolarisation
Prolonging refractory period of cardiac action potential
111
Name a calcium channel blocker used in treating arrhythmias and state the arrhythmias it is used to treat
Diltiazem
| Paroxysmal SVT and reducing ventricular rate in atrial fibrillation
112
How does adenosine stop AVNRT?
Activates alpha 1 receptors
Inhibiting adenylyl cyclase - decreasing cAMP
Triggers K+ efflux & inhibiting Ca2+ entry to SAN - cell hyperpolarisation
113
How is heparin administered?
IV
114
How would you monitor anticoagulation in a patient given heparin?
Measure prothrombin time compared against activated partial thromboplastin time (aPTT)
115
What is the MOA of warfarin?
Vitamin K carboxylase inhibitor
| Prevents formation of gamma-carboxylated blood clotting factors
116
What is the MOA of heparin?
Activates anti-thrombin III
| Inactivating thrombin and factor Xa
117
What do low molecular weight heparin inhibit?
Factor Xa
118
What does the NOAC dabigatran inhibit?
Thrombin
119
What does the NOACs rivaroxaban and apixaban inhibit?
Factor Xa
120
What are the phases of a normal action potential?
```
0 Rapid depolarisation
1 Early repolarisation
2 Plateau
3 Rapid repolarisation
4 Resting potential
```
121
During phase 0 what does Ina occur through?
Ina (inward Na+ current)
| Nav1.5 channels
122
During phase 1 what does Ito occur through?
Ito (transiently outward K+ current)
| Kv1.4
123
During phase 2 what does Ikr occur through?
Ikr (Rapidly delayed rectifier K+ channel)
| Kv11.1
124
During phase 2 what does Iks occur through?
Iks (slowly delayed rectifier K+ channel)
| Kv7.1
125
During phase 2 what does Ica,L occur through?
Ica, L (SR Ca2+ release via L-type channels)
| Cav1.2
126
What's the normal length of the QT interval?
0.35-0.43 seconds
