Week 10 - Atrial Fibrillation Flashcards
What is atrial fibrillation (AF)
- Is a type of arrhythmia (irregularly irregular heart rhythm)
- AF tends to be fast + irregular (100-180 bpm)
- is common + prevalence increases with age
- seen on ECG, absent P waves - Caused by ectopic foci
= another place in heart (NOT SAN or AVN) is causing electrical excitations (pre mature heartbeats)
= no organised atrial depolarisation + chaotic atrial activity
What is the Mechanism of AF
Caused by ectopic foci / changes in atrial tissue causing abnormal impulse formation
- Atrial structure abnormalities e.g. ischaemia, fibrosis, hypertrophy
- Inflammation / oxidative stress
- Atrial remodelling
- Atrial excitation abnormalities
- inc. ↑ conduction, ↓ AP duration, ↓ refractory period, ↑ depolarisation, abnormal intracellular Ca2+ - Genetic variants
Risk factors for AF
- hypertension
- obesity
- old age
- diabetes
- MI
- heart disease or coronary artery disease
- alcohol (binge drinking)
- smoking
- family history
↑ risk of: STROKE, heart failure and death
Signs and Symptoms of AF
- palpitations
- fatigue
- shortness of breath
- dizzy / light headed / loss of consciousness
- hypotension
- can be asymptomatic
What are the goals of therapy
- Prevent stroke + systemic embolism
- 1st thing to asses is STROKE risk (AF ↑ risk massively)
- use anti-coagulants NOT anti-platelets (they don’t treat AF) - Control symptoms + improve QoL
- achieved by ventricular rate control, conversion to sinus rhythm (= depolarisation begins at SAN) + maintaining rhythm
Prevent complication (managing disease is straightforward but complications are harder = need to monitor)
What treatment is used to prevent stroke & systemic embolism
ANTI-COAGULANTS are used (= antithrombotic therapy)
- TARGET = factor 10a and factor 2a (thrombin)
- e.g. Warfarin (most recommended) and Heparin
- target INR (time take for blood to clot) = 3 (2.5 to 3.5)
- CONSIDER: risk of bleeding
- DONT give to <65 with no risks / score 1 for women
- Score ≥ 2 = DOAC (direct oral anti-coagulation) e.g. apixaban
- Score 1 / 2 (in women) = consider DOAC
DOAC = 1st line- If DOAC contraindicated use vit K antagonist e.g. warfarin
- If patient is on warfarin consider changing to a DOAC
- stop warfarin, measure INR
- if INR < 2 = apixaban or dabigatran
- if INR < 2.5 = edoxaban
- if INR <3 = rivaroxaban
How is stroke risk assessed
CHADSVAS Score
- used to asses stroke risk + decide if patient needs anti-coagulant
- has a max of 9 points
Conditions + Points:
- Congestive HF = 1 point
- Hypertension = 1 point
- Age (> 75) = 2 points
- Diabetes = 1 point
- Stroke / iscahemic attack / thromboembolism history = 2 points
- Vascular disease = 1 points
- Age (65-74) = 1 point
- Sex (female) = 1 point
What treatments are used to improve symptoms + QoL
- Rate Control (controls heart rate)
- use drugs that slow conduction through AVN
- - Rhythm Control (controls conduction in heart)
- anti-arrhythmic drugs
- Cather ablation (destruction of tissues causing electrical impulses) of left atrium to maintain sinus rhythm
= all impulses from SAN
- cardioversion (returns heartbeat to sinus rhythm)
For both treatment need to have thromboembolic risk assessed
If on rhythm control NEED rate control to prevent recurrence of AF
How does rate control improve symptoms
- 1st line treatment due to better outcomes in AF patients
- easy, less complication, less monitoring, less side effects - Preferred in elderly (>65) patients as they’re more prone to proarrhythmia, AF is often permeant + asymptomatic
What 4 drugs are used for rate control
- B-blockers
- 1st line (monotherapy initially)
- offer any B-blocker EXCEPT sotalol
- e.g. propranolol, metoprolol, esmolol (oral or IV) - Calcium channel blockers (CCB)
- 1st line (if b-blocker contraindicated) ~ monotherapy initially
- don’t use if AF patient also has HF
- e.g. diltiazem or verapamil
- in LOW BP patients use IV diltiazem - Digoxin
- not 1st line as it ↑ mortality risk
- used if patient has non-paroxysmal AF, does little physical activity, other rate-limiting drugs are contraindicated
- can’t use if high activity as it doesn’t slow down ventricular rate during exercise (just slows resting rate)
- can be oral or IV - Amiodarone (NOT long-term treatment)
- used in patients who don’t respond to CCB, B-blocker OR critically ill AF patients
If monotheraphy fails use 2 of the following:
- B-blocker
- CCB (Diltiazem)
- Digoxin
Target:
- Asymptomatic patients = < 110bpm
- Symptomatic AF patients / HF = < 80 bpm
How does rhythm control improve symptoms
Preferred in patients:
- with HIGH CV risk = improved survival
- (inc. >75, had stoke, ischaemic attack OR >65, female, HF, diabetes, CKD, hypertension, etc.)
- rate control treatment failed
- have HF (preferred in symptoms,ptpomatic patients)
- young patients (<65)
- Use anti-arrhythmic drugs
- SIDE EFFECTS: proarrhythmia (development of new arrhythmia / aggravation of pre-existing arrhythmia)
What 3 treatments are used for rhythm control
- Cardioversion
- returns / converts heartbeat to normal sinus rhythm (normal ECG)
- CANT use if clot present as may cause clot to move, if moves to brain can cause stroke, transient ischaemic attack (blood supply to brain is disrupted)
Can be electrical or pharmacological
1. Electrical Cardiovesrion
- Done using a DCC (direct current cardioversion)
- if AF persisted > 48 hours
- if had AF for < 48 hours anti-coagulant drugs are NOT needed before conversion (SAFE)
- if had AF > 48 hours conversion is UNSAFE (due to risk of thrombus) = need to us anticoagulant for 3 WEEKS (unless TEE scan shows no presence of thrombus)
2. Pharmacological Cardioversion
- NOT preferred due to side effects, loading dose + maintenance dose, if patient impairments
- e.g. Amiodrone, Diofetilide
- Anti-arrhythmic drugs
- maintain sinus rhythm
- use B-blocker (1st line) unless contraindicated
- Dronedarone (2nd line - used after successful cardioversion - K+ channel blocker)
- Amiodrone (used if have left ventricle impairment or HF)
- if infrequent + have few symptom OR have no history of left ventricle failure use drug when episode starts (a.k.a “pill-in-the-pocket”)
- Cather ablation
- USED if all drugs / other methods have failed
- Destroys the foci generating irregular electrical signals
- cather is guided through heart veins + finds the abnormality source
- source is destroyed via burning / heat = tissue death
