Atrial Fibrillation Flashcards
1
Q
What type of rhythm abnormality is AF?
What is more likely to cause it in acutely unwell patients and older patients?
A
- AF is a common tachycardia
- in an acutely unwell patient is can be caused by underlying illness, such as sepsis, pneumonia and hyperthyroidism
- it may be reversible by treating the underlying cause
- in older patients it tends to be found without an obvious precipitating factor
- this may be asymptomatic and found incidentally, or it may present with palpitations
2
Q
Why is atrial fibrillation significant in the long term?
A
it increases the risk of stroke
3
Q
What are the 2 main areas of management in AF?
A
- managing the AF itself through either rate or rhythm control
- assessing and managing the stroke risk with anticoagulation
4
Q
What is the typical progressive disease pattern associated with chronic AF?
A
- episodes of paroxysmal AF that are < 1 week in duration
- often multiple episodes of this that may resolve before progressing
- persistent AF where episodes are > 1 week in duration
- long-term persistent where episodes > 12 months
- permanent AF
5
Q
What is AF associated with an increased risk of?
A
it is associated with an increased risk of stroke and heart failure
6
Q
How does the prevalence of AF change with age?
What % of stroke patients have AF?
A
- incidence increases with age
- present in 2-4% of the general population
- present in 5% of over 65s and 10% of over 70s
- present in 15% of all stroke patients
7
Q
What are the risk factors associated with AF?
A
- obesity
- hypertension
- type 2 diabetes mellitus
- obstructive sleep apnoea
- smoking
- coronary artery disease
- valvular heart disease
- heart failure
- chronic kidney disease
8
Q
What are the potentially reversible causes of AF?
A
- excess alcohol consumption
- hyperthyroidism
- electrolyte abnormalities
- sepsis
9
Q
What are potential cardiac and pulmonary causes associated with acute presentation of AF?
A
Cardiac:
- heart failure
- heart ischaemia (MI)
- hypertension
- mitral valve disease
- congenital heart disease (rare)
Pulmonary:
- PE
- pneumonia
- bronchocarcinoma
10
Q
What are other causes associated with acute presentation of AF?
A
- hyperthyroidism (fast AF)
- sometimes hypothyroidism can cause slow AF
- alcohol
- post-operatively
- sepsis
- high caffeine intake
- antiarrhythmic drugs
- hypokalaemia
- hypermagnesemia
11
Q
What is meant by the term “lone AF”?
A
- this refers to cases of AF where no cause can be found
- many cases initially labelled as lone AF have a cause discovered upon further investigation
12
Q
How does AF usually present?
What type of pulse is present and what should be done in this scenario?
A
- AF is usually asymptomatic, particularly in chronic AF
- acutely it can present with:
- palpitations
- chest pain
- dyspnoea
- dizziness / syncope
- it is associated with an irregularly irregular pulse
- an ECG should be performed on everyone with an irregular pulse
13
Q
What findings might be present on examination of someone with AF?
A
- irregularly irregular pulse
- apical pulse rate > radial pulse rate
- 1st heart sound of varying intensity
- signs of LV dysfunction
14
Q
What are the indications for someone presenting with AF to be referred to the emergency department?
A
- hypotension
- “fast AF” with a ventricular rate > 110
- significant symptoms
- syncope or pre-syncope
- chest pain
- ECG showing ischaemic changes
15
Q
What is involved in the pathology of AF?
What are the consequences of this condition on cardiac output?
A
- AF causes an irregular atrial rhythm between 300 - 600 bpm
- the AV node is unable to transmit beats as quickly as this, so it does so intermittently, resulting in an irregular ventricular rhythm
- irregular stimulation of the ventricles reduces cardiac output by up to 20%, as well as allowing stasis of blood in the heart chambers
16
Q
What ECG findings are typical in atrial fibrillation?
A
- there are absent P waves with an irregular baseline
- irregular ventricular rate (QRS complexes)
- the QRS complex is normal shape as conduction through the AV node is normal
- T waves are normal
- In V1 the trace resembles atrial flutter
17
Q
What blood tests are performed in atrial fibrillation and why?
A
- U&Es to check for renal dysfunction
- TFTs as AF can occur secondary to hyperthyroidism
- cardiac enzymes
-
CMP - calcium, magnesium & phosphate
- aim for magnesium > 1 in patients with AF (normal is 0.7 - 1.1)
18
Q
What other investigations may be conducted in suspected AF?
A
Echocardiogram:
- this is used to assess for structural heart disease
- mitral valve disease
- left ventricular dysfunction
- left atrial enlargement
Polysomnography:
- used to assess for sleep apnoea, which is an important risk factor
19
Q
What are the 4 steps involved in management of a newly diagnosed AF patient?
A
- identify any risk factors and reversible causes
- characterise any structural heart disease that may be associated with AF
- this typically involves sending a patient for an echocardiogram
- assess and manage ventricular rate
- consider anticoagulation
20
Q
What is meant by “acute atrial fibrillation”?
Who does this tend to affect?
A
- this is AF that is < 48 hours in duration
- tends to affect younger patients
- patients are likely to have an identifiable and reversible cause
21
Q
What is involved in the treatment of acute atrial fibrillation?
A
- treat the underlying condition (e.g. pneumonia, MI)
- control the ventricular rate
- consider anticoagulation
- consider DC or drug cardioversion
22
Q
What type of anticoagulation is recommended in acute AF?
Why is this performed?
What should be done if anticoagulants are contraindicated?
A
- typically, heparin (5,000 - 10,000 U IV) is used in the acute setting
- this is important as it prevents thrombus formation and thrombi are a contraindication for cardioversion
- if anticoagulants are contraindicated, then a trans-oesophageal ultrasound (TOE) needs to be performed prior to mechanical cardioversion to rule out the presence of a thrombus
23
Q
What should be done in an acutely ill patient with acute AF?
A
DC cardioversion
- do not delay treatment to give anticoagulants
- cardioversion should be performed in ITU with sedation
- patient is shocked at 200J initially, and then 2 further attempts at 360J if this is unsuccessful
24
Q
What are the stages in management of a patient with chronic atrial fibrillation?
A
- Identify and treat any reversible causes
- send the patient for an echo to rule out any structural heart disease
- control the ventricular rate and/or rhythm
- assess the need for anticoagulation
25
For most patients with chronic AF, rate control is considered as effective as rhythm control
What are the exceptions to this?
* for most patients with chronic AF, rate control is considered as effective as rhythm control except for...
* **young patients**
* **1st episode of AF**
* **significant heart failure**
* **physically active patients**
* a **rhythm control option** should be considered in these patients
* rate vs. rhythm control has **no difference in long-term mortality**, but **rhythm control** tends to result in **fewer symptoms**
26
What are the 2 possible first line rate control treatments for chronic AF?
Can they be used together?
**_B-blocker_ or _Ca2+ blocker_**
* using both together is contraindicated as it can cause **heart block**
* B-blockers are generally preferred
27
Which beta-blockers are suitable for use in AF?
Which ones are preferred in heart failure?
* atenolol
* metoprolol
* bisoprolol
* carvedilol
* nebivolol
* bisoprolol, carvedilol and nebivolol are preferred in heart failure
28
What calcium channel blockers are appropriate for use in chronic AF?
**non-dihydropyridine** calcium channel blockers
these are **_diltiazem_** and **_verapamil_**
29
What is the second line rate control option in chronic AF?
beta-blocker or calcium channel blocker WITH **_digoxin_** or **_amiodarone_**
* digoxin and amiodarone are **antiarrhyhtmic medications** used to treat an irregular heartbeat
* digoxin as a sole treatment for AF is not widely acceptable and may only be suitable for some **very sedentary elderly patients**
30
Which medication should B-blockers not be given with and why?
* they should NOT be given with **_verapamil_** or **_diltiazem_** (L-type calcium channel blockers)
* there is a risk of **bradycardia** and **heart block**
31
What are the 4 different rhythm control options for chronic AF?
* **flecanide**
* only recommended for use in those with dangerous arrhythmias or when significant symptoms cannot be managed with other treatments
* used to treat ventricular & supraventricular tachycardias
* **amiodarone**
* **electrical cardioversion**
* **catheter ablation**
* a catheter is passed through the blood vessels into the heart to stop abnormal electrical signals in the heart
32
When is flecanide contraindicated?
* left ventricular dysfunction
* known coronary artery disease
* left ventricular hypertrophy
33
What are the possible risks associated with amiodarone?
* it can cause **thyrotoxicosis**
* it interacts with many other medications
* it can cause **liver impairment**
* long-term use increases risk of **lung fibrosis**
34
When is catheter ablation most commonly used?
it is most commonly used in younger patients who have failed rhythm control with other options
35
What score is used to assess the need for anticoagulation?
the **_CHA2DS2-VASc score_**
(Chads-Vasc)
after this, you then need to calculate the **_HAS-BLED score_** to determine the patient's risk of bleeding
36
What are the components involved in the CHADSVASc score?
How many points are awarded for each component?
* C - **congestive heart failure** or LVEF \< 40%
* H - **hypertension**
* A2 - **_age 75 or more_**
* **__**scores 2 points
* **D - diabetes**
* S2 - **_previous stroke, TIA or thromboembolism_**
* **__**scores 2 points
* V - **vascular disease**
* A - **age 65-74**
* Sc - **female gender**
37
How is the CHADS VASc score interpreted?
Which patients should be offered anticoagulation?
* most patients with a **_score of 1 or more_** should be offered anticoagulation
* anticoagulation is **strongly recommended** in patients scoring **_2 or more_**
* you then need to use the **_HASBLED score_** to calculate the **risk of bleeding**, as the risks of anticoagulation may outweigh the benefits
38
39
What are the different components involved in the HASBLED score?
* H - **hypertension**
* A - abnormal **renal** or **liver function**
* S - previous history of **stroke**
* B - previous history of **major bleeding**
* L - **labile INR** (\<60% of time in therapeutic range)
* E - **IV drug use**
* D - **drug and alcohol use**
* NSAIDs, anti-platelet agents and alcohol \>8 units / week
40
How is the HASBLED score interpreted?
When does the risk of anticoagulation outweigh the benefit?
* an answer of "yes" to each item is worth **1 point**
* a score of **_3 or more_** indicates a **_high risk of bleeding_**
* if patient is a high risk of bleeding then **anticoagulation is not advisable** as the risks outweigh the benefits
41
What anticoagulants are generally preferred to be used instead of warfarin?
Why is this the case?
**_direct oral anticoagulants (DOACs)_**
* this includes **rivaroxaban**, **apixaban** and **dabigatran**
* they do not require monitoring of INR
* they are less likely to interact with other drugs
* they have standardised dosing
42
How does rivaroxaban work?
* it is an anticoagulant used to prevent blood clots
* specifically used to treat DVT, PE and prevention of clots in AF
* it **_inhibits factor Xa_**
* this interrupts the intrinsic and extrinsic pathway of the blood coagulation cascade, which **inhibits the formation of _thrombin_** and **development of thrombi**
43
How does apixaban work?
* it is also a **_direct inhibitor of factor Xa_**
* factor Xa catalyses the conversion of prothrombin to thrombin, which is responsible for fibrin clot formation
* inhibiting factor Xa indirectly **decreases clot formation induced by thrombin**
44
How does dabigatran work?
* it reversibly binds to the active site on the **_thrombin molecule_**
* this prevents thrombin-mediated activation of coagulation factors
* it can inactivate thrombin even when it is fibrin-bound, meaning that it may **enhance fibrinolysis**
45
When are DOACs not recommended?
What is the one downside of using this medication?
* they are not recommended for use when **structural heart disease** is present
* DOACs are **less easily reversible** than warfarin
46
What is paroxysmal AF?
What method is used for treatment of this condition and what 2 criteria must be present in order for this to be suitable?
* this is a condition in which **short spells of AF come and go**
* upon investigations, the patient may often be in sinus rhythm
* the **_"pill in the pocket"_** treatment method is used
* this involves **_flecainide_** or **_solatol PRN_** - which are drugs that control the **rhythm**
* this is only suitable if **_systolic BP \> 100_** and there is **_no underlying LV dysfunction_**
47
What is the 1st line treatment for paroxysmal AF in older and younger patients?
* first line treatment involves **_sotolol / bisoprolol_** (beta-blockers)
* in **young patients**, first line treatment involves **_flecainide / verapamil_**
* ^ should be avoided in older patients as they are **negatively inotropic** (and cause vasodilatation)
48
What are the 2nd and 3rd line treatments for paroxysmal AF?
When do these tend to be used?
* 2nd line is **_amiodarone_** which tends to be used in those with **some LV dysfunction**
* 3rd line is **_digoxin_**, which is used in those with **severe LV dysfunction** as it is positively inotropic
* this tends to have a weak effect and takes several weeks to become effective
49
When is cardioversion used for rhythm control in acute AF?
* when the symptoms have been ongoing for **_\< 48 hours_**
* often **amiodarone** will also have been given to these patients
50
When might cardioversion be used for rhythm control in chronic AF?
What is a good marker of outcome from this?
What treatment needs to be stopped prior to the treatment?
* when patient has had **_\> 3 weeks of anticoagulant therapy_** AND **TOE** has proven **_no thrombus_**
* **_LV dilation_** is a good predictor of outcome
* those with a **LV diameter \> 5.5cm** are unlikely to have a successful cardioversion
* if the patient is on **_digoxin_**, this needs to be stopped a few days before treatment
51
Which drugs are typically used for drug cardioversion?
* **_amiodarone_** is the drug of choice, which can be given IV or PO
* **_flecainide_** may be used in patients with **no known IHD or WPW syndrome**
* this is negatively inotropic (reduces the strength of contractions)
52
If paroxysmal AF is reversed, when should anticoagulation therapy be continued?
* it may be continued even if normal sinus rhythm has been restored if other **risk factors are still present**
* the **CHADS VASc score** should be used to determine this
* anticoagulation should only be discontinued if sinus rhythm is present and there are no risk factors for emboli (CHADS = 0)
53
What is the major complication associated with AF?
How can this be prevented?
**_thrombo-embolic stroke_**
* the degree of anticoagulant therapy required in AF can be assessed using **CHADS VASc score**
* any score **_above 2_** requires anticoagulation with **_warfarin_**
54
Why should warfarin not be given to patients at low risk of stroke (CHADS \< 2)?
* warfarin in itself can be a stroke risk as it can cause a bleed
* it should only be given to high-risk patients with a CHADs score \> 2
55
What other group of patients may the risk of giving warfarin outweigh the benefits?
* patients at **_high risk of falls_** (typically elderly with many co-morbidities)
* the risk from fall, and subsequent bleed, may be greater than the risk of stroke
56
Why do many patients undergo TOE?
What is this an attempt to visualise?
* thrombus formation most commonly occurs in the **_left atrial appendage_**
* this is very difficult to view on transthoracic echo
* many AF patients undergo TOE as the echo transducer is right next to the left atrium, so this gets a good view
57
