Atrial Fibrillation Flashcards
What is AF?
- Chaotic, irregularly irregular rythm
What is the px of AF?
Ageing
- Atrial myocardium has short refractory period - ageing reduces period > permits rapid contraction
Multiple wavelets
- wavefronts (spontaneous waves of excitation) become fragmented resulting in multiple daughter wavelets
Autonomic foci
- located primarily in the pulmonary veins, act to initiate AF
Explain the px of re-entry circuit
- Heart disease, HTN, age > changes to atrial morphology
- varying atrial myocardium has varying excitability and conductivity
- Eg; atrial myocardium with slower conducting area
- shorter refractory period
- can be re-excited again after normal heart activation of heart
- can re-excite normal myocardial tissue
- re-enrty circuit triggered
- AV node captures impulses in irregular intervals
What causes AF?
*remember SMITH
- Sepsis
- Mitral Valve disease
- Ischaemic Heart Disease
- Thyrotoxicosis
- HTN
Apart from SMITH, what are the other causes of AF?
Cardiac
- Hypertension
- IHD
- Valvular disease (RHD)
- Cardiomyopathy
Non-cardiac
Respiratory
- COPD
- Pneumonia
- Pulmonary embolism
- Pleural effusion
- Lung cancer
Endocrine
- Thyrotoxicosis
- Diabetes mellitus
Infection
Electrolyte disturbances
Drugs
- Bronchodilators
- Thyroxine
Lifestyle
- Alcohol
- Caffeine (contribution is debated, there is no evidence that at normal levels of consumption caffeine causes AF)
What are the sx for AF?
- Asymptomatic
- Chest pain
- Palpitations
- Dyspnoea
- Presyncope
What are the signs of AF?
- Irregularly irregular pulse
- Tachycardia
What Ix would you perform for AF?
- ECG
- absent p waves
- narrow QRS complexes
- irregularly irregular
- BP
- Obs
- Blood test
- FBC
- Cholesterol
- U&E
- cardiac enzyme
- thyroid function test
- Bone profile
- Mg
- Imaging
- CXR
- CT/MRI
- Echo
What are the two principles of treating AF?
- Rate & rhythm
- Anticoagulation
What is the reason to control the rate in AF?
- In AF, contractions are not coordinated > ventricles fill up by suction and gravity > less efficient
- Higher HR > less time for ventricles to fill up
- By decreasing HR > extend time during diastole > ventricles can fill up blood > increase CO
What medications can you use for rate control in AF?
First line
- Beta blocker (atenolol 50-100mg OD)
- Dont give with Verapamil
- CCB
- Diltiazem
- Verapamil
Other therapies
- Digoxin monotherapy - used in sedentary patients
- Sotalol - only prescribed by cardiologist
What is the reason to control rhythm in AF?
- Return pt to normal sinus rhythm
- Decrease risk of developing stroke, HF
What are the two types of cardioversion to control rhythm in AF?
- Pharmacological
- Amiodarone
- Sotalol
- Electrical
- AF that present >48hrs
- Must be anticoagulated for 4-6 weeks first before cardioversion
What are the examples of pharmacological cardioversion?
- Amiodarone
- Sotalol
What machine is used to deliver the electrical cardioversion in AF?
- DC Cardioversion
What is the main risk of AF?
- stroke
What is the reason to give anticoagulation for AF?
- Uncontrolled and unorganised atrial movement > blood stagnating in atrial appendages (LAA more common)
- Stagnated blood > thrombus
- Embolus travels with blood to carotid arteries and to the brain
- Lodge in cerebral arteries > ischaemic stroke
What medications would you consider for anticoagulation in AF?
- DOAC - apixaban, rivaroxaban
- Warfarin (target INR 2-3)
What tool is used to assess stroke risk for pts c AF?
CHA2DS2-VASc score
What does CHA2DS2-VASc stand for?
- Congestive HF
- HTN
- 75 and > = 2points
- Diabetes
- Stroke / TIA = 2 points
- Vascular disease
- 65-74
- Sex (female)
What tool is used for establishing a patient’s risk of major bleeding whilst on anticoagulation?
HAS-BLED score
What does HAS-BLED stand for?
- H – Hypertension
- A – Abnormal renal and liver function
- S – Stroke
- B – Bleeding
- L – Labile INRs (whilst on warfarin)
- E – Elderly
- D – Drugs or alcohol
What are the 3 mechanisms that cause cardiac arrhythmias?
- Enhanced automaticity
- exercise
- hypovolaemia
- ischaemia
- electrolyte imbalance
- Triggered activity
- Re-entry
What are the 3 types of AF? Briefly describe each of them
- Silent AF
- Paroxysmal - stop within 7 days w/o tx
- Persistent - > 7days
- Long standing AF
- Permanent - continous AF which has occured for more than 1 yr
What does the different CHADS VASC score indicate?
- Total score = 9
- 0 (truly low risk), 0% = Dont require anticoagulation
- 1 (intermediate risk), 1.3% = Consider Anticoagulation for men
- 2 (significant risk), 2.2% = Recommend Anticoagulation for both genders
*0&1 for women is considered low risk, anticoag not advised
What does HAS-BLED stand for?
- HTN
- Abnormal liver or kidney (1 point for each)
- Stroke
- Prior major bleeding
- Labile INR
- Elderly >65
- Drugs or alcohol (1 point for each)
*total 9 points
What is the HAS-BLED score for?
- Estimates risk of major bleeding for patients on anticoagulation to assess risk-benefit in atrial fibrillation care
What medication would you give if pt has high risk of cardioversion failure?
- Give amiodarone 4 weeks before procedure and 12 months after
What are the rules in managing acute AF for
1) If pt has adverse sign (shock, MI syncope, HF)
2) If pt stable and AF started <48 hrs ago
3) if pt stable and AF started >48h ago
- ABCDE > Cardioversion: amiodarone
- Rate or rythm control may be tried
- cardioversion: flecanide (normal heart) or amiodarone
- Start Heparin in case cardioversion delayed
- Rate control
- Bisoprolol or diltiazem
- DC cardioversion only if pt is anticoagulated for >3weeks
What are the risk of cardioversion?
- Dislodged blood clot
- HF
- Heart damage (temporary)
How would you manage AF with anticoagulation?
- Acute AF
- Heparin until full risk assessment for emboli is made
- DOAC or warfarin if high risk emboli
- Chronic AF
- Use CHADS VASc and balance with HAS BLED
How would you acutely Mx AF?
- O2 if sats <90%
- IV access & 12 lead ECG
- Vagal manouvers for SVT
- Control rate
- Adenosine
- B-blocker: metoprolol 1-10mg IV
- CCB: Verapamil 5-10mg IV
- Digoxin in HF
- 500mcg PO > 500mcg PO after 8hrs > 250mcg PO after 8h
- Control rythm
- Amiodarone, sotalol, flecanide, lidocaine
- Warfarin or DOAC
- If onset <48h or anticoagulated for >3wk, start cardioversion
- DC cardioversion under sedation
- flecanide 300mg PO (if no structural heart damage)
- Amiodarone 300mg IV over 20-60mins
- 900mg over 24hrs
What is lone AF?
- AF with no underlying heart disease
What are the classifications of AF?
Paroxysmal
- Recurrent (more than 1 episode ≥30 seconds in duration).
- Terminates spontaneously within 7 days (usually within 48 hours of presentation).
Persistent
- Lasts longer than 7 days or requires termination by pharmacological / electrical cardioversion.
Permanent
- Refractory to cardioversion.
- Sinus rhythm cannot be restored or maintained.
- AF is accepted as a final rhythm.
If Paroxysmal AF, further monitoring is required. What are the options for cardiac monitoring?
- 24hr Cardiac Monitor
- Holter monitor
- Implantable loop recorder
How would you mx rhythm control in AF?
- If Haemodynamically instable/AF onset <48hrs
- DC cardioversion
- If haemodynamically stable/AF onset >48hrs
- Anticoagulation 3 weeks before cardioversion or
- Pharmacological options
- IV amiodarone
