Problem 2: Management of Atrial Fibrillation Flashcards
Describe what AF is
Heart condition that causes irregular and abnormally fast heart rate. It is caused by abnormal electrical impulses fired randomly in the atria. Different types of AF:
Paroxysmal - episode come and go and typically last 48 hours.
Persistent - episode lasts longer than 7 days
Long standing persistent - continuous AF for a year or longer
Permanent - AF is present at all times
AF is a supra ventricular tachycardia characterised by disorganized atrial electrical activity. This electrical disorganisation results in the absence of substantial atrial depolarisation, which is characterised by the absence of P waves on the ECG.
Symptoms: palpitations, reduced ability to exercise, fatigue, dizziness, confusion, shortness of breath
Explain how AF is managed using pharmacological / non-pharmacological examples
Treatment is managed in two branches: rate control and rate-limiting.
Rate control offered as first-line strategy (unless reversible cause, heart failure etc)
Standard beta-blockers and CCBs for rate control as initial monotherapy.
Beta blockers include bisoprolol, atenolol, propanolol and metoprolol. Via B1 receptors, reduce force of contraction and speed of conduction in the heart. They slow ventricular rate in atrial fibrillation mainly by prolonging the refractory period of the atrioventricular node.
Calcium channel blockers include amlodipine, nifedipine, diltiazem and verapamil. They reduce Ca2+ entry into cardio and vascular cells, causing relaxation and vasodilatation in arterial smooth muscle. They suppress cardiac conduction, particularly across the AV node to slow cardiac rate.
If monotherapy not controlling symptoms consider combination therapy with a bet-blocker, diltiazem or digoxin.
Not amiodarone for long term rate control
Digoxin for rate limiting - consider for non-paroxysmal AF only if sedentary.
Digoxin is a cardiac glycoside that is negatively chronotropic (it reduces heartrate) and positively inotropic (increases the force of contraction). In AF its therapeutic effect arises mainly via reduction of conduction at the AV node, preventing some impulses being transmitted to the ventricles, thereby reducing ventricular rate.
Non-pharmacological examples:
Explain how the assessment of stroke and bleeding risk is calculated. What are Anna’s scores in each assessment
Stroke risk for patients with atrial fibrillation is calculated by CHA2DS2-VASc stroke score. Should be used for symptomatic or asymptomatic paroxysmal, persistent or permanent AF or atrial flutter.
Age, sex, CHF history, hypertension history, stroke/TIA/thromboembolism history, vascular disease history, diabetes history?
The HAS-BLED score assesses the risk of bleeding in people who are starting or have started anticoagulation.
Hypertension, renal disease, liver disease, stroke history, prior major bleeding, high or unstable INR, age >65, medication use predisposing bleeding (NSAIDS or antiplatelets), alcohol use
Give the rationale for why Anna needs to continue to take her warfarin
Do not offer stroke prevention therapy to people aged under 65 years with atrial fibrillation and no risk factors other than their sex (that is, very low risk of stroke equating to a CHA2DS2-VASc score of 0 for men or 1 for women
But in patients with a CHA2DS2-VASc score of 2 or above, offer anticoagulation.
Atrial fibrillation
To reduce blood clot formation, one of the following is normally prescribed; warfarin, dabigatran and apixaban.
Provide reasons as to why Anna has a ‘yellow book’. List the risks associated with warfarin.
Yellow booklet has three main functions: space to record dose of warfarin for patient to take and INR readings recorded from clinic. Information about dosing, tablets, side effects and warning symptoms of warfarin safety issues. Then carried around so that if Anna is involved in an accident or needs urgent medical help she has the record on her persons.
Risks include bleeding; serious side effects are prolonged nose bleeds (more than 10 minutes), blood in vomit, blood in sputum, passing blood in urine or faeces, black faeces, unusual headaches, heavy or increased periods / vaginal bleeding.
Describe the target INR for Anna
INR target is between 2 and 3; patients over 75 should aim for 2 as safer and reduced bleeding risk. Maintain 2.5
Discuss the alternative anticoagulant agents that are available for the management of AF
Direct Oral Anti Coagulants (DOACs)
Table for comparison on slides:
Rivaroxaban - direct inhibitor of factor Xa, 0.5 - 3 hours peak effect, 80% bioavailability, 20mg OD, no monitoring required.
Apixaban - direct inhibitor of factor Xa, 5mg BD, also doesn’t require monitoring. Interactions with potent CYP3A4 inhibitors (same as rivaroxaban). Not reversible
Dabigatran - direct inhibitor of of FIIa and thrombin, 150mg BD, 80% renal excretion (reversible by dialysis if needed), PPI and p-glycoprotein inhibitors interactions.
Warfarin: lots of clinical experience, cheap, effects are easily reversed with vitamin K, anticoagulant effect easily measured via INR.
DOACS: direct inhibition of proteins on the coagulation cascade, more predictable pharmacokinetics leading to fixed dose routine, no need for routine monitoring, rapid onset of action and no interaction with food/diet
Provide the rationale for the use of digoxin in this case
Consider digoxin monotherapy for people with non‑paroxysmal atrial fibrillation only if they are sedentary
