Lecture 7 - AF

Question 1

What is AF?

Answer 1

A chaotic rhythm from multiple foci within the atria
Disorganised atrial depolarisation and fast, ineffective atrial contraction
The AV node receives more electrical impulses that it can conduct, resulting in a fast, irregular ventricular rhythm
Stroke risk

Question 2

Causes of AF

Answer 2

Infection
Hypertension
CAD
ACS
Cardiac surgery
Abnormality in heart valves
Congenital heart defects
Hyperthyroidism
Stimulants - e.g. caffeine, tobacco, alcohol
Sleep apnoea
Sick Sinus Syndrome
Lung disease

Question 3

Name the 4 types of AF

Answer 3

Persistent - episodes > 7 days
Permanent - longstanding - may be resistant to cardio version
Lone - not associated with any other medical condition
Paroxysmal - short-recurrent bursts <7 days

Question 4

Symptoms of AF

Answer 4

May be asymptomatic (elderly)
Palpitations
Irregular pulse
Tachycardia
Breathlessness
Tiredness
Reduced exercise tolerance
Light-headedness/ fainting
ECG changes

Question 5

What will an ECG show in AF?

Answer 5

Shows tiny, irregular ‘fibrillation’ waves between heartbeats
The rhythm is irregular and erratic

Question 6

Name the investigations relevant to AF

Answer 6

Chest X-ray - identifies any pulmonary diseases e.g. COPD. emphysema and lung cancer that can cause AF
Blood tests - identify any abnormalities e.g. hyperthyroidism, anaemia - that can cause AF

Question 7

Name the treatments of AF

Answer 7

Stroke prevention
Rhythm control
Rate control

Question 8

Name a drug which controls rate

Answer 8

beta-adrenoceptor antagonists (beta-blockers)

Question 9

What do beta-blockers do?

Answer 9

Block beta-adrenoceptors on cardiac myocytes to reduce HR

Question 10

Name the cardioselective (beta1 selective drugs

Answer 10

atenolol, bisoprolol, metoprolol, nebivolol - fewer side effects and cautions

Question 11

Name the non-cardioselective (active at beta1 and 2 adrenoceptors)

Answer 11

Carvedilol, propranolol, labetalol - more side effects and cautions

Question 12

What monitoring is required with beta blockers?

Answer 12

HR and BP

Question 13

State the beta-blocker side effects

Answer 13

More associated with beta1 repctor blockage/crossing BBB:
Erectile dysfunction
Bradycardia
Reduced exercise tolerance
Hypotension
Fatigue
Nightmares and sleep disturbances (lipid soluble agents )
More associated with beta2 mediated effects:
Cold hand and feet
Masked symptoms of hypoglycaemia
Bronchoconstriction
Elevated blood and lipid cholesterol
Hypo/hyperglycaemia

Question 14

What do rate limiting calcium channel blockers do?

Answer 14

Reduce HR
Block voltage gated-dependent calcium channels and slow down conduction through the AVN
Can reduce cardiac contractility blocking calcium entry into cardiac myosotes

Question 15

What does diltiazem (benzothiazepine) act on?

Answer 15

Acts on vascular and cardiac tissue - routinely used off license in AF

Question 16

What does verapamil (phenylalkylamine) act on?

Answer 16

Acts predominately on cardiac tissue

Question 17

Side effects of rate-limiting calcium channel blocker

Answer 17

GI disturbances
Headache
Hypotension
Bradycardia
Flushing
Ankle swelling
Constipation
Dizziness
Oedema

Question 18

What does digoxin do?

Answer 18

Slows down conduction through the AVN by increasing the parasympathetic vagal tone
Can be used on combination with a beta-blocker or rate limiting calcium channel blocker
Not good for active people
Requires loading
Renally eliminated
Narrow therapeutic index

Question 19

What monitoring does digoxin require?

Answer 19

HR
Drug interactions - amiodarone

Question 20

Describe digoxin toxicity and potassium

Answer 20

Digoxin blocks the Na/K/ATPase pump that usually transports K into cells and Na out of the cells
Digoxin binds competitively at the same external site as K

Question 21

Define hypokalaemia

Answer 21

Less K - more sites available for digoxin to bind on cardiomyocytes - enhanced cardiac effect and cardiac toxicity

Question 22

Define hyperkalaemia

Answer 22

More K - fewer sites available for digoxin to bind enhanced plasma levels and systemic/ CNS toxicity

Question 23

Symptoms of systemic/CNS toxicity:

Answer 23

Burred/ yellow vision
Confusion
Dizziness
GI disturbances
Fatigue

Question 24

What does amiodarone do?

Answer 24

Slowing conduction through the AV and prolonging the cardiac action potential
Long half-life - slow onset of action and prolonged duration of side effects after discontinuation

Question 25

Side effects of amiodarone

Answer 25

Photosensitivity
GI disturbances
Corneal Microdeposits (reversible on discontinuation)
Blue/ grey skin
Hepato-biliary disorders - LFT monitoring required
Pneumonitis - chest X-ray monitoring required
Thyroid dysfunction
Taste disturbance
Headache

Question 26

What is the difference between amiodarone and dronedarone?

Answer 26

Less toxic
Less efficacious and some association with HF
Indicated for maintenance of sinus rhythm after successful cardio version in paroxysmal or persistent AF if not controlled by 1st line therapy in patients more than one of:
- diabetes
- hypertension requiring drugs more than 2 different classes
- previous TIA, stroke, systemic embolism
- left atrial diameter >50mm or >70 yrs without LVSD and no current NF

Question 27

Define electronic cardio version

Answer 27

An electronic current is applied to the chest to ‘shock’ the heart back into sinus rhythm
No response to pharmacological treatment

Question 28

Define ‘pill in the pocket’

Answer 28

Used to suppress paroxysmal AF with or without a known precipitant (caffeine or alcohol)
Patient has own supply of flecainide or propafenone and takes a single dose when symptoms develop

Question 29

When is ‘pill in the pocket suitable’ ?

Answer 29

Infrequent symptomatic episodes
Not hypertensive or bradycardic
No history of HF or IHD
No history of valvular heart disease