Atrial Fibrillation Flashcards
What is Atrial fibrillation?
- Contraction of the atria is uncoordinated, rapid and irregular
- Due to disorganised electrical activity which overrides normal, organised activity of SAN
- disorganised activity in atria also leads to irregular conduction of electrical impulses in the ventricles
What will disorganised electrical activity in ventricles cause?
- irregular irregular ventricular contractions
- tachycardia
- HF due to poor filling during diastole
- Inc risk of stroke
How can an ischaemic stoke occur from atrial fibrillation?
tendency for blood to collect in the atria and from blood clots (stasis), clots can become emboli and travel to brain to block cerebral arteries
How does atrial fibrillation present?
- usually asymptomatic but can have:
- palpitations
- breathlessness
- syncope
- symptoms of associated conditions e.g. stroke, sepsis or thyrotoxicosis
What are the two possible diagnosis from irregularly irregular pulse?
1) atrial fibrillation
2) Ventricular ectopics
How should irregularly irregular pulse diagnosis be differentiated?
- ECG
- Ventricular ectopics disappear when heart rate is high e.g. during exercise
How would AF show on ECG?
- absent P wave
- narrow QRS
- irregularly irregular ventricular rhythm
What are the two types of AF?
Valvular - AF when patients have moderate or severe mitral stenosis or mechanical heart valve (which is likely to have lead to the atrial fibrillation)
Non-valvular - AF without valve pathology or with mitral regurgitation or aortic stenosis
What are the common causes of AF?
- Sepsis
- Mitral Valve Pathology
- Ischaemic Heart disease
- Thyrotoxicosis
- Hypertension
What are the two aspects of AF that need to be treated?
1) Rate and rhythm control
2) Anticoagulation to prevent stroke
What are the medications used for rate control in AF?
1) Beta blocker
2) CCB
3) Digoxin (only in sedentary people)
when should rate control not be the first line treatment for AF?
- there is reversible cause of AF
- AF is new onset
- AF is causing HF
- they remain symptomatic even after effective rate control
Why is slowing heart rate good for patients with AF?
- The higher the heart the less time is available for ventricles to fill with blood so reducing the CO
- Slower heart rate extends diastole so ventricles have more time to fill
When is rhythm control offered to patients?
(when not using rate control):
- there is reversible cause of AF
- AF is new onset
- AF is causing HF
- remain symptomatic despite effective rate control
What are the two ways normal sinus rhythm can return?
1) single ‘cardioversion’ event that returns normal rhythm
2) long term medical rhythm control that sustains normal rhythm
When should you use delayed cardioversion and when should you use immediate cardioversion?
immediate - if AF onset is shorter than 48 hours ago severely haemodynamically unstable
delayed - AF present for more than 48 hours and stable
Why is anticoagulation medication essential before delayed cardioversion?
- anticoagulants prevent blood clot forming
- if blood clot formed, reverting back to the normal sinus rhythm has high risk of mobilising clot and causing stroke
What are the two options for cardioversion?
1) pharmacological
2) Electrical
What is the first line pharmacological cardioversion?
Flecanide amiodarone (used in patients with structural heart disease)
What does electrical cardioversion involve?
patient put under general anaesthetic and cardiac defibrillator used to shock patient
What are the three medications used for long term rhythm control?
1) Beta blockers
2) Dronedarone (used when already have had successful cardioversion)
3) Amiodarone (used in patients with HF or LV dysfunction)
What is Paroxysmal AF?
- AF comes and goes in episodes
- episodes not lasting more than 48 hours
How is Paroxysmal AF treated>
- Can still be anti coagulated depending on CHADSVASc score
- Can also use ‘pill in pocket’ approach where take flecanide is given to take whenever symptoms appear
- ‘pill in pocket’ only used when no structural heart disease and infrequent episodes
When should flecanide be avoided?
patients with atrial flutter as can cause 1:1 AV conduction and significant tachycardia
Why is anticoagulant medication important for AF?
- atrial blood is often stagnant in left atrium particularly in atria appendage
- leads to thrombus formation
- embolus can travel up carotid arteries to brain
- casting ischaemic stroke
What is the major risk of anticoagulants?
- higher risk of serious bleed
- usually risk of stroke significantly outweighs risk of bleeding (bleed easier to treat)
What scoring system is used to assess risk of serious bleed?
HASBLED
- Hypertension
- Abnormal renal/liver function
- Stroke
- Bleeding
- Labile INRs (whilst on Warfarin)
- Elderly
- Drugs/alcohol
What is used to assess wether a patient with AF should be started on anticoagulants?
CHA2DS2-VASc (if have one or more risk factors of these shouldn’t take ACs, some are worth 2 points so shouldn’t take if worth 2)
- Congestive HF
- Hypertension
- Age >75 (worth 2)
- Diabetes
- Stroke or TIA previously (2)
- Vascular disease
- Age 65-74
- Sex female
What is the MoA of warfarin?
- antagonises Vitamin K
- Vitamin K essential for functioning of several clotting factors
- prolongs prothrombin time (time it take for blood to clot)
How is the extent of anti-coagulation by Warfarin measured?
- INR (international normalised ratio)
- compares prothrombin time of patient to prothrombin time of normal healthy adult
- INR 1 = normal
- INR 2 = Prothrombin time double normal
What is the target INR for AF?
2-3 i.e. blood should be clotting 2 to 3 times slower than the normal person
What common things will affect INR outside warfarin?
- antibiotics as affect activity of P450 enzymes which metabolise Warfarin
- Leafy green vegetables (contain Vit K)
- Cranberry juice and alcohol (affect P450)
What is the half life of Warfarin
1-3 days
How can Warfarin be reversed in an emergency?
Give Vitamin K
Give two examples of anticoagulants?
- Warfarin
- NOACS/DOACS (novel anticoagulants) (now called Direct Oral anticoagulants)
Name a DOAC?
Apixaban
Dabigatran
Rivaroxaban
Why are DOACs currently used less?
- still on patent so very expensive compared to warfarin
- coming off patent soon so will be far cheaper
What is the half life of apixaban?
12hours
How can DOACs be reversed?
- apixaban and rivaroxaban = Andexanet alfa
- dabigatran = Idarucizumab
What are the advantages of DOACs compared to warfarin?
- No monitoring required
- No major interactions
- equal if not slightly better at preventing stroke in AF
- equal if not slightly lower risk of bleeding than warfarin
