Lecture 7 - AF Flashcards
What is AF?
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
Causes of AF
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
Name the 4 types of AF
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
Symptoms of AF
May be asymptomatic (elderly)
Palpitations
Irregular pulse
Tachycardia
Breathlessness
Tiredness
Reduced exercise tolerance
Light-headedness/ fainting
ECG changes
What will an ECG show in AF?
Shows tiny, irregular ‘fibrillation’ waves between heartbeats
The rhythm is irregular and erratic
Name the investigations relevant to AF
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
Name the treatments of AF
Stroke prevention
Rhythm control
Rate control
Name a drug which controls rate
beta-adrenoceptor antagonists (beta-blockers)
What do beta-blockers do?
Block beta-adrenoceptors on cardiac myocytes to reduce HR
Name the cardioselective (beta1 selective drugs
atenolol, bisoprolol, metoprolol, nebivolol - fewer side effects and cautions
Name the non-cardioselective (active at beta1 and 2 adrenoceptors)
Carvedilol, propranolol, labetalol - more side effects and cautions
What monitoring is required with beta blockers?
HR and BP
State the beta-blocker side effects
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
What do rate limiting calcium channel blockers do?
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
What does diltiazem (benzothiazepine) act on?
Acts on vascular and cardiac tissue - routinely used off license in AF
What does verapamil (phenylalkylamine) act on?
Acts predominately on cardiac tissue
Side effects of rate-limiting calcium channel blocker
GI disturbances
Headache
Hypotension
Bradycardia
Flushing
Ankle swelling
Constipation
Dizziness
Oedema
What does digoxin do?
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
What monitoring does digoxin require?
HR
Drug interactions - amiodarone
Describe digoxin toxicity and potassium
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
Define hypokalaemia
Less K - more sites available for digoxin to bind on cardiomyocytes - enhanced cardiac effect and cardiac toxicity
Define hyperkalaemia
More K - fewer sites available for digoxin to bind enhanced plasma levels and systemic/ CNS toxicity
Symptoms of systemic/CNS toxicity:
Burred/ yellow vision
Confusion
Dizziness
GI disturbances
Fatigue
What does amiodarone do?
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
Side effects of amiodarone
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
What is the difference between amiodarone and dronedarone?
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
Define electronic cardio version
An electronic current is applied to the chest to ‘shock’ the heart back into sinus rhythm
No response to pharmacological treatment
Define ‘pill in the pocket’
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
When is ‘pill in the pocket suitable’ ?
Infrequent symptomatic episodes
Not hypertensive or bradycardic
No history of HF or IHD
No history of valvular heart disease
