Case 5: Atrial Fibrillation

Question 1

Risk factors for AF

- CHA2-DS2-VASC Score

Answer 1

• Rate of ischaemic stroke increases with increasing CHA2-DS2-VASc score
• Benefits of warfarin/dabigatran use = greater for patients with higher score
• Patients with no risk factors: should not use anticoagulant - if stroke risk low

(refer to notes)

Question 2

Pathophys of AF

Answer 2

○ Atria beat irregularly instead of beating effectively to move blood into ventricles

→ Most common type of irregular heart beat, arrhythmia

→ Normal conditions: upper and lower chambers of heart work together to pump blood throughout the body

• blood pumps from atria - ventricles in regular and coordinated way
• Regular heart: regular steady rhythm, evenly and uniformly beat
• Electrical signals travel through heart in regular pattern –> originate in SA node
• Each signal causes heart to beat

→ Afib: Atria beat very fast, irregular pattern, out of rhythm

• Atria: quiver and uncoordinated
• Irregular pattern –> atria don’t coordinate with ventricles
• Heart is out of rhythm
• Afib: occurs when electrical signals start in the wrong place and misfire
• Faulty signals: cause atria to quiver –> not contract completely
• Electrical signal spreads in rapid disorganised way

Question 3

Describe the classification of patients with AF based on symptoms.

Answer 3

Paroxysmal AFIb

• Periods of Afib that come and go
• Momentary, last for days but go away on their own

Persistent Afib
- Doesn’t go away on its own

Permanent AFIb
- Those who have had Afib for long time
Heart cant return to normal rhythm at all

Symptoms: subtle or severe, may come and go, may not experience symptoms at all

• Palpitations
• Chest pain
• Feeling light headed, dizzy
• Shortness of breath
• Chest discomfort
• Reduced capacity for exertion/ sleeping problems
• Fatigue

Question 4

Outline place of rate control therapy in AF

- medication options

Answer 4

Rate control therapy: aims to improve symptoms by reducing heart rate

Preferred first line treatment:
○ Beta blocker
- Bisoprolol (1.25-20mg od), Metoprolol succinate (23.75-190mg od), Carvedilol (unapproved indication - 3.125-50mg bd)
- Sotalol: should not be prescribed for rate control in patients with AF –> potential to cause arrhythmias
○ Alternative: rate limiting calcium channel blocker

OR CCB - only in patients w left ventricular ejection fraction > 40%

• Diltiazem (120-360mg od modified release)
• Verapamil (120-480mg od modified release)

Can use BB + diltiazem - if patients dont benefit from either alone - caution in left ventricular dysfunction or cardiac conduction abnormalities (effects difficult to predict)
- Combined use of verapamil with beta-blockers is not recommended due to the risk of hypotension and systole

Most benefit obtained if resting heart rate = < 110 beats per minute (bpm)

Second line rate control treatment - amiodarone

Question 5

Describe the role of electrical and pharmacological cardioversion in the management of atrial fibrillation (AF)

Answer 5

Rhythm Control - restore sinus rhythm

Initiated in Secondary care

First line for some patients:

• E.g symptomatic paroxysmal attacks, heart failure associated with AF, acute cardioversion in new onset AF of less than 48 hrs duration
• For patients who have ongoing symptoms despite optimal use of medicines to control heart rate

○ Acute cardioversion: may be appropriate in patients w new onset of AF

• Electrical current: used to restore normal heart rhythm
• Consider referral for patients: presenting within 48 hours of symptom onset
• Urgent: haemodynamic instability

○ Medicines for rhythm control:
Amiodarone, flecainide, propafenone, disopyramide, sotalol

Question 6

Compare and contrast the drugs (amiodarone and flecainide) used for sinus rhythm control in patients with AF.

Answer 6

(see notes)

Question 7

Assessing the risk of stroke in AF

• choices available to reduce stroke risk
• importance of anticoagulation in patients with AF.

Answer 7

Assessing stroke risk in AF

• Using CHA2-DS2 VASc score
• Re-evaluate patients yearly who are low at risk
• For non-valvular AF

During Afib - blood can collect or pool in heart + cause clot to form
Clot can travel from heart –> brain = cause stroke

Choices available to reduce stroke risk

○ Oral anticoagulation therapy - prevent stroke and systemic embolism
○ Dabigatran - superior to warfarin
- 150mg BD for most
- 110 mg bd (elderly or impaired renal function)
- Cant take: renal impairment, prosthetic heart valves
- Can be reversed
- Cant be blister packed
- Compared to Warfarin:
150mg BD - similar rate of major bleeding as dabigatran , less rate of stroke and SE
110mg - similar rate of S and SE, decreased rate of major bleeding

○ Rivaroxaban

• 20mg od
• Can blister pack
• Good with renal impairment (CrCl >15 mL/min)

Importance of anticoagulation in AF

○ Decrease risk of stroke: using anticoagulants

• CHA2DS2-VASc score: Females > 2 and Males > 1 = likely to benefit from anticoagulant
• Patients with AF = increased risk of thromboembolism (stroke or systemic embolism)
• Experience more severe strokes than others
• Antiplatelet medications not recommended for reducing stroke risk
• OACs are superior to aspirin and/or clopidogrel
• Risk of bleeding increased w concurrent use of antiplatelets + anticoagulants

Subsidised anticoagulants: Warfarin, dabigatran, rivaroxaban

Question 8

Explain how you would counsel a patient who was taking an oral anticoagulant (NOAC i.e. dabigatran, rivaroxaban or VKA i.e. warfarin)

Answer 8

(See notes)

Question 9

Rate control vs rhythm control (managing AF symptoms)

Answer 9

Rate control: improve symptoms by reducing heart rate

Rhythm control: restore sinus rhythm using electrical cardioversion OR pharmacological cardioversion - antiarrhythmic medicines

Rate control preferred bc medicine regimens more simple