[2] Arrhythmias Flashcards
1
Q
What are arryhthmias?
A
A group of conditions in which there is either a disturbance in pacemaker impulse formation, contraction impulse conduction, or a combination of the two, resulting in rate and/or timing of contracting being insufficient to maintain normal cardiac output
2
Q
What are the types of arrhythmias?
A
- Supraventricular tachycardia
- Heart block
- Ventricular fibrillation
3
Q
What is a supraventricular tachycardia?
A
An abnormally fast heart rate arising from inproper electrical activity in the upper part of the heart, starting from either the atria or the AV node
4
Q
What causes supraventricular tachycardias?
A
Generally due to either re-entry, or increase automaticity
5
Q
What are the main types of supraventricular tachycardias?
A
- Atrial fibrillation
- Paroxysmal supraventricular tachycardia
- Atrial flutter
- Wolff-Parkinson-White syndrome
6
Q
What is atrial fibrillation?
A
A heart condition that results in irregular and abnormally fast heart rate
7
Q
What is the pathophysiology of atrial fibrillation?
A
Multiple abnormal atrial pacemakers discharge randomly, resulting in chaotic atrial depolarisation and loss of normal atrial contraction. Because the firing of pacemakers is so fast, the myocardium can’t relax properly between contractions, reducing the hearts efficiency and performance.
The irregular impulses are contracted to the ventricles. Ventricular depolarisation occurs normally via the His-Purkinje system, so the ventricles do contract, but at an abnormal rhythm
8
Q
Describe the pulse and heart rate in atrial fibrillation
A
Irregularly irregular
9
Q
On what basis is atrial fibrillation classified?
A
Depending on the degree to which it affects the patient
10
Q
What are the classifications of atrial fibrillation?
A
- Paroxysmal atrial fibrillation
- Persistent atrial fibrillation
- Long-standing persistent atrial fibrillation
- Pernament atrial fibrillation
11
Q
What is paroxysmal atrial fibrillation?
A
Atrial fibrillation where episodes come and go, and usually stop within 48 hours without treatment
12
Q
What is persistent atrial fibrillation?
A
Atrial fibrillation where each episode lasts for longer than 7 days if untreated
13
Q
What is long-standing persistent atrial fibrillation?
A
Atrial fibrillation when the patient has had continuous atrial fibrillation for a year or longer
14
Q
What is pernament atrial fibrillation?
A
When atrial fibillation is present all the time
15
Q
What is the cause of atrial fibrillation?
A
Exact cause is unknown, however more common with age, and affects certain grops of people more than others
16
Q
What groups of people are at increased risk of atrial fibrillation?
A
- Those with other heart conditions, including high blood pressure, atherosclerosis, heart valve diseae, congenital heart disease, cardiomyopathy, and pericarditis
- Those with lung conditions, including pneumonia, asthma, COPD, lung cancer, diabetes, pulmonary embolism, and CO poisioning
17
Q
What is it called when atrial fibrillation arises in someone without a pre-existing condition?
A
Lone atrial fibrillation
18
Q
What are the triggers for an episode of atrial fibrillation?
A
- Excessive alcohol intake, particularly binge drinking
- Overweight
- Excessive caffeine intake
- Recreational drug misuse, particularly amphetamines or cocaine
- Smoking
19
Q
Does everyone with atrial fibrillation have symptoms?
A
No, some people, particularly older people, don’t have any symptoms, and the abnormality is only discovered during routine tests or investigations for another conditions
20
Q
What are the symptoms of atrial fibrillation?
A
- Heart palpitation
- Increased heart rate
- Tiredness
- Exercise intolerance
- Feeling faint
- Chest pain
- Hypotension
21
Q
What investigations into atrial fibrillation are performed?
A
- ECG
- Echocardiogram
- Chest x-ray
- Blood tests
22
Q
How does the ECG appear in atrial fibrillation?
A
- P wave absent, and replaced by irregular fibrillation waves
- QRS complexes are normal, however they are irregularly irregular
23
Q
Why is the P wave absent and replaced with irregular fibrillation waves in the ECG of atrial fibrillation?
A
Because the P wave is produced by normal generation of an impulse at the SA node, and the conduction of this impulse across the atria. In atrial fibrillation, this is not happening, and rather there is disorganised contraction of the atria
24
Q
Why are the QRS complexes normal in the ECG of atrial fibrillation?
A
Due to normal conduction of the ventricles
25
What does NICE recommend to do once ECG has established that the patient has atrial fibrillation?
Performing other tests to try and determine the underlying cause
26
What is the purpose of an echocardiogram in the investigation of atrial fibrillation?
Looks for heart-related problems, and assess the structure and function of valves
27
What is the purpose of a chest x-ray in the investigation of atrial fibrillation?
Looks for any lung problems causing atrial fibrillation
28
What is the purpose of blood tests in the investigations of atrial fibrillation?
Look for anaemia, reduced kidney function, or hyperthyroidism
29
What are the categories of treatment of atrial fibrillation?
* Medications to control heart rate
* Medications to reduce the risk of stroke
* Procedures to restore normal heart rhythm
30
How do anti-arrhythmics control atrial fibrillation?
Either by restoring a normal heart rhythm, or controlling the heart rate
31
What does choice of anti-arrhythmic in atrial fibrillation depend on?
Other medical conditions, side effects of the chosen medication, and how well the condition responds
32
What drugs are available to restore a normal heart rhythm in atrial fibrillation?
* Flecanide
* ß-blockers
* Amiodarone
33
What drugs are available to reduce the resting heartbeat in atrial fibrillation?
* ß-blockers, such as bispropolol or atenolol
* Calcium channel blockers, such as verapamil or diltiazem
* Digoxin
* Amiodarone
34
What factors have to be taken into consideration when deciding on the best treatment of atrial fibrillation?
* Age
* Overall health
* Type of atrial fibrillation
* Symptoms
* Underlying cause, if present
35
Why is it important for a patient with atrial fibrillation to be on medication to reduce the risk of stroke?
The rapid and irregular contraction of the heart in atrial fibrillation means that there is a high risk of the formation of blood clots in the heart chambers, which can consequently enter the blood stream, travel to the brain, and cause a stroke
36
What factors is the risk of stoke in atrial fibrillation based on?
* Age
* History of other medical conditions such as stroke, blood clots, valvular disease, heart failure, hypertension, diabetes, or heart disease
37
What medications might be given to prevent stroke in atrial fibrillation?
* Warfarin
* Rivaroxiban
* Apixiban
38
What is cardioversion?
Giving the heart a controlled electric shock in an attempt to restore normal rhythm
39
How is the cardioversion procedure performed?
Electrodes are connected to a defibrillator are placed on the chest. The defibrillator monitors the heart rhythm, and delivers one or multiple electric shocks to the heart through the chest wall. The procedure is done under general anaesthetic
40
What is the risk with cardioversion treatment?
Clot formation
41
When is there a risk of clot formation in cardioversion treatment of atrial fibrillation?
If the patient has atrial fibrillation for more than two days
42
How is the risk of clot formation with cardioversion treatment of atrial fibrillation minimised?
The patient is given anti-coagulation for 3-4 weeks before cardioversion, and for at least 3 weeks after
43
What is catheter ablation treatment for atrial fibrillation?
A procedure that destroys the diseased area of the myocardium, and therefore interrupts abnoormal electrical circuits
44
How is catheter ablation treatment of atrial fibrillation carried out?
Catheters are guided through a vein into the heart, where they record electrical activity to find the source of the abnormality. Once the abnormality is found, heat is generated by high frequency radiowaves, and transmitted through one of the catheters to destroy the tissue
45
When is catheter ablation treatment of atrial fibrillation used?
Only once medication has failed, either because it was ineffective or intolerable
46
What are the potential consequences of atrial fibrillation?
* Stroke
* Heart failure
47
How can atrial fibrillation cause heart failure?
It can weaken the heart
48
What is paroxysmal supraventricular tachycardia?
A supraventricular tachycardia of unknown cause
49
What does the underlying mechanism of disease in paroxysmal supraventricular tachycardia involve?
An accessory pathway that results in re-entry
50
What are the risk factors for paroxysmal supraventricular tachycardia?
* Alcohol
* Caffeine
* Nicotine
* Psychological stress
51
What are the symptoms of paroxysmal supraventricular tachycardia?
Often, people have no symptoms. When they do, episodes start and end suddenly, and symptoms include;
* Palpitations
* Feeling faint
* Sweating
* Shortness of breath
* Chest pain
52
What does the ECG show on paroxysmal supraventricular tachycardia?
* Narrow QRS complexes
* Heart rate typically between 150 and 240BPM
53
What are the treatments for paroxysmal supraventricular tachycardias?
* Vagal maneuvers, such as the Valsalva maneuver
* Medications
* Cardioversion
54
How is the Valsalva manuever performed?
The patient is asked to hold their breath whilst trying to exhale forcibly, as if straining a bowel movement. Alternatively, they can hold their nose and exhale against the obstruction.
55
How does the Valsalva maneuver work?
By increasing intra-thoracic pressure, and affecting baroreceptors in the arch of the aorta
56
Why should the carotid sinus massage not be performed?
Due to the risk of stroke in those with atherosclerotic plaques in the carotid arteries
57
What is the first line pharmacological treatment in paroxysmal supraventricular tachycardias?
Adenosine
58
What is adenosine?
An ultra-short acting AV nodal blocking agent
59
When is adenosine indicated in the treatment of paroxysmal supraventricular tachycardias?
If vagal manuevers are ineffective
60
How should paroxysmal supraventricular tachycardias be treated if adenosine is unsuccessful, or there is recurrence?
Dilitazem or verapamil
61
What is atrial flutter?
Atrial flutter as an abnormal heart rhythm that starts in the atrial chambers of the heart, and is characterised by a sudden onset, regular abnormal heart rhythm with fast heart rate
62
Why is there are risk of stroke in atrial flutter?
Atrial flutter leads to poor contraction of the atrium, which can lead to pooling of blood in the heart, and result in the formation of blood clots
63
How can atrial flutter progress?
It is not a stable rhythm, and often degenerates into atrial fibrillation
64
What are the classifications of atrial flutter?
* Type I, also known as common atrial flutter or typical atrial flutter
* Type II, or atypical atrial flutter
65
What is the atrial rate in type I atrial flutter?
240-340BPM
66
What causes type I atrial flutter?
A re-entrant loop that circules the atrium, passing through the cavo-tricuspid isthmus
67
What is the cavo-tricuspid isthmus?
A body of fibrous tissue in the lower atrium, between the vena cava and tricuspid valve
68
What can type I atrial flutter be further divided into?
Clockwise and counterclockwise
69
What is more common, clockwise or counterclockwise atrial flutter?
Counterclockwise
70
Describe the ECG in counterclockwise type I atrial flutter
Has inverted flutter waves in ECG leads II, III, and aVF
71
Describe the ECG in clockwise type I atrial flutter
Upright flutter waves in II, III, and aVF
72
What is the atrial rate in type II atrial flutter?
340-440BPM
73
In whom does type II atrial flutter occur in?
Almost always people who have undergone previous surgery or catheter ablation procedure
74
What are the signs and symptoms of atrial flutter?
* Palpitations
* Shortness of breath
* Chest pain
* Lightheadedness
* Nausea
* Nervousness
75
What might prolonged atrial flutter lead to?
Decompensation, with loss of normal heart function
76
How might decompensation in atrial flutter manifest?
* Exercise intolerance
* Oedema
* Noctural breathlessness
77
How does underlying heart disease affect the symptoms of atrial flutter?
May mean someone is affected by symptoms sooner
78
How is atrial flutter characterised on ECG?
The presence of flutter waves, at a regular rate of 200 to 300BPM
79
What do 'flutter waves' look like?
They may be symmetrical, resemble P waves, or be asymmetrical with saw tooth shape
80
How is adenosine used in the diagnosis of atrial flutter?
It can help differentiate between atrial flutter and other forms of SVT, because adenosine blocks the AV node, and so there is no QRS complex to block the appearance of flutter waves, and they therefore become obvious.
81
How is atrial flutter treated?
Same as atrial fibrillation
82
What are the potential complications of atrial flutter?
* Myocardial infarction
* Tachycardia-induced cardiomyopathy
* Stroke
83
Why can atrial flutter lead to myocardial infarction?
Because the rapid heart rate can lead to significant problems in those with existing heart disease, and can lead to inadequate blood flow to the myocardium
84
What is Wolff-Parkinson-White syndrome?
A disorder due to a specific problem with the electrical system of the heart
85
What % of people with WPW never develop symptoms?
About 40%
86
What causes WPW?
Unknown, however can be due to inherited gene mutation (PRKAG2)
87
What does the underlying mechanism of WPW involve?
An accessory electrical connection pathway between the atria and ventricles, for example the Bundle of Kent
88
What are the symptoms of WPW?
Patients usually asymptomatic when not having a fast heart rate. If symptoms are present, they include;
* Palpitations
* Dizziness
* Shortness of breath
* Syncope
89
What does the ECG show in WPW?
* A delta wave - a slurred upstroke in the QRS complex
* Short PR interval
* Wide QRS complex
90
What is treatment for WPW based on?
Risk stratification of the individual
91
What does risk stratification in WPW determine?
Risk of sudden cardiac death
92
What are the indications of high risk in WPW?
* Previous episodes of unexplained syncope, or palpitations
* Failure of delta waves to disappear with increases in heart rate
* Multiple pathways
* Septal location of pathway
* Ability to induce atrial fibrillation or AVRT
93
Why is failure of delta waves to disappear at higher heart rates an indicator of high risk in WPW?
Because it shows that the accessory pathway can still conduct electrical impulses at a high rate
94
How is WPW treated if deemed to be at high risk of sudden cardiac death?
Catheter ablation
95
How is WPW treated if experiencing tachycardia?
* If signs and symptoms are severe, cardioversion
* If relatively stable, medication may be sufficient
96
How can atrial fibrillation caused by WPW be treated?
With amiodarone or procainamide
97
What is heart block?
A form of bradycardia that results from delay or interruption of the impulse when travelling from the atria to the ventricles
98
Where in the impulse-conduction pathway can blockages occur?
SA node, AV node, at or below the bundle of His, left or right bundle branches, or fasicles of left bundle branch
99
What are the types of heart block?
* First degree heart block
* Second degree heart block
* Third degree heart block
100
What happens in first degree heart block?
Electical impulses are slowed as they pass through the conduction system, but do all successfully reach the ventricles
101
What happens in second degree heart block?
Impulses are further delayed with each subsequent heartbeat, until one fails to be conducted to the ventricles completely
102
What happens in third degree heart block?
Electical impulses from the atria do not reach the ventricles. The ventricles generate their own impulses, called ventricular ectopic beats, which are usually very slow, therefore causing significant bradycardia
103
What are the potential causes of heart block?
* Congenital heart block
* Heart surgery
* Coronary heart disease
* Heart attack
* Heart failure
* Diseases such as myocarditis, cardiomyopathy, Lyme disease, sarcoidosis, Lev's disease, diptheria, or rheumatic fever
* Toxin exposure
* Hypokalaemia or hypomagnesia
* Hypertension
* Metastatic cancer
* Penetrating chest trauma
* Medications
104
When does congential heart block occur?
Present from birth
105
In whom is congenital heart block more likely?
Babies who have congential heart disease, or if the mother has an autoimmune condition such as lupus
106
What medications can cause heart block?
* Medication for abnormal rhythm, such as disopyramide
* Medications for high BP, such as beta-blockers, calcium channel blockers, or clonidine
* Digoxin
* Fingolimoid
* Pentamidine
* Tricyclic antidepressants, such as amitripptyline
107
What are the symptoms of first degree heart block?
Doesn't usually cause any noticeable symptoms
108
What are the types of second degree heart block?
* Mobitz type 1
* Mobitz type 2
109
What are the symptoms of Mobitz type 1 heart block?
Most won't experience any symptoms, but some might get mild light-headedness or dizziness and fainting
110
What are the symptoms of Mobitz type 2 heart block?
* Mild light headedness or dizzness
* Fainting
* Chest pain
* Shortness of breath
* Hypotension
111
What are the symptoms of third degree heart block?
* Fainting
* Breathlessness
* Fatigue, sometimes with confusion
* Chest pain
* Bradycardia
* Palpitations
112
Describe the ECG in first degree heart block
* The PR interval is elongated
* All P waves are followed by a QRS complex
113
Describe the ECG in Mobitz type 1 second degree heart block?
The PR interval is erratic, and follows a pattern of PR interval elongating, until eventually a QRS complex. This means some, but not all, P waves are followed by a QRS complex
114
Describe the ECG in Mobitz type 2 heart block
There is usually a constant PR interval, but not all P waves are followed by a QRS complex - some are randomly dropped
115
Describe the ECG in third degree heart block
* P waves are normal, but no QRS complexes
* Ventricles generate their own signal, causing a spike, but beats are usually slow
116
When is heart block treated?
Usually only when it is causing symptoms
117
How is heart block treated?
The heartbeat may require stabilisation using transcutaneous pacing (TCP). Once the heartbeat is stabilised, a pernament pacemaker may need to be fitted
118
How is TCP performed?
Pads are attatched to the chest, and electrical pulses delivered through them to restore the heart rate to normal
119
What is ventricular fibrillation?
When the heart quivers instead of pumping blood, due to disorganised electrical activity in the ventricles
120
Why is ventricular fibrillation a very serious condition?
Because it can result in cardiac arrest and death if untreated
121
What is the underlying mechanism of ventricular fibrillation?
* Abnormal automaticity, as a product of a hypoxic myocardium becoming hyperirritable, and thus ectopic pacemaker sites arise, meaning the ventricles are being stimulated by more than one pacemaker
* Re-entry occuring in areas of ischaemic or infarcted myocardium, or underlying scar tissue
* Triggered activity due to the presence of after-depolarisations
122
What are after-depolarisations?
Depolarising oscillations in the membrane voltage, caused by a previous action potential.
123
What can happen if an after-depolarisation reaches threshold potential?
They can trigger another afterdepolarisation, and so self-propagate
124
What are the causes of ventricular fibrillation?
* Coronary heart disease
* Valvular heart disease
* Cardiomyopathy
* Bruguda syndrome
* Long QT syndrome
* Electric shock
* Intracranial haemorrhage
125
What is Bruguda syndrome?
A genetic condition that results in abnormal electrical activity within the heart, increasing the risk of sudden cardiac death
126
What mutation is present in about 20% of cases of Bruguda syndrome?
A mutation in a gene that encodes for a sodium ion channel in the myocytes
127
What is true of most people with Bruguda syndrome?
They are undiagnosed, as the condition often doesn't cause any symptoms
128
What are the symptoms of Bruguda syndrome, if present?
* Syncope
* Palpitations
* Sudden cardiac arrest
129
What is the purpose of genetic testing in Bruguda syndrome?
* Conformation of diagnosis
* Track risk in family members
130
Describe the potential ECG patterns of Bruguda syndrome
* Type I - coved type ST elevation, and a gradually descending ST segment, followed by a negative T wave
* Type 2 - saddle-back pattern
* Type 3 - coved or saddle back pattern, and less than 1mm ST elevation
131
What is long QT syndrome?
A condition which affects repolarisation of the heart folllowing contraction.
132
What is the pathophysiology of long QT syndrome?
It is a form of channelopathy, with the opening of L-type calcium channels during the plateau phase of the cardiac action potential causing early after-depolarisations
133
When does long QT syndrome develop?
May be present at birth, or might develop later in life
134
What might cause long QT syndrome to develop later in life?
* Medications
* Hypokalaemia
* Hypocalcaemia
* Heart failure
135
What medications can cause the development of long QT syndrome?
* Antiarrhythmics
* Antibiotics
* Antipsychotics
136
What are the risk factors for long QT syndrome?
* Female sex
* Increasing age
* Liver or renal impairment
* Family history
* Pre-existing cardiovascular disease
137
What are the signs and symptoms of long QT syndrome?
Most people have none, but those who do might experience;
* Syncope
* Seizures
* Sudden death
138
What might bring on an episode of symptomatic long QT syndrome?
* Stress
Exercise
139
How is long QT syndrome diagnosed?
ECG finding of QT interval greter than 440-500ms, together with clinical findings
140
How is long QT syndrome managed?
* Avoid strenous exercise
* Dietary prevention of hypokalaemia
* Use of beta-blockers
* Implantable cardiac defibrillator
141
What are the symptoms of ventricular fibrillation?
* Cardiac arrest
* Sudden cardiac death
142
What might cardiac arrest in ventricular fibrillation be precipitated by?
Patients sometimes complain of varying symptoms depending on the underlying cause, and may exhibit signs of gasping breathing
143
How is ventricular fibrillation treated?
* Defibrillation
* Implantation of cardioverter-defibrillator
144
What is defibrillation?
When an electrical current is applied to the ventriclar mass, either directly or externally through pads and paddles, with the aim of depolarising enoguh of the myocardium for coordinated contractions to occur again
145
What is the purpose of an implantable cardioverter-debrilliator?
It can quickly provide the same treatment as a defibrillator should another episode occur outside of the hospital
