Cardiac arrhythmias - atrial fibrillation
Description
- Supraventricular tachyarrhythmia - irregularly irregular, no organised P waves
| Pattern | Duration |
|---|---|
| Paroxysmal | <7 d, self-terminating |
| Persistent | >7 d |
| Long-standing persistent | >1 yr |
| Permanent | Rhythm control abandoned |
- Pattern sets management intent, not stroke risk - risk is identical across patterns
- "Valvular AF" = moderate-severe MS or mechanical valve only
- The only group in which DOACs are contraindicated
Epidemiology
- ~2-5% adults; >10% if age >75
- Lifetime risk ~1 in 3
- M>F incidence; F higher absolute stroke risk
- Prevalence rising - ageing, obesity, wearable-driven detection
- Aboriginal and Torres Strait Islander Australians: earlier onset, RHD contribution
Aetiopathogenesis
Mechanism
- Pulmonary vein sleeve ectopy triggers; atrial substrate sustains
- Substrate
- Atrial stretch, fibrosis, inflammation
- -> dec conduction velocity, dec refractory period
- -> multiple reentrant wavelets
- "AF begets AF" - electrical remodelling within hours, structural within weeks
Drivers - all modifiable
- Cardiac - HTN, HF, mitral valve disease, IHD
- Metabolic - obesity, diabetes, CKD
- Behavioural - alcohol, endurance exercise
- Respiratory - OSA
- Endocrine - thyrotoxicosis
Secondary / acute
- Sepsis, PE, post-operative (esp. cardiac surgery), electrolytes
- Secondary AF still carries long-term recurrence and stroke risk - do not dismiss it
Stroke mechanism
- LA appendage stasis -> thrombus -> cardioembolism
Diagnosis
Documentation
- >=30 s on any single-lead recording is sufficient
- Wearable-detected AF still needs ECG confirmation
- Ambulatory monitor or implantable loop recorder if paroxysmal suspected
Presentation
- Palpitations, dyspnoea, fatigue, presyncope
- Often asymptomatic - may present as stroke
Workup - every new AF
- TTE: LA size, valves, EF
- TFTs, FBE, UEC, LFTs, HbA1c
- Screen for OSA and alcohol
Stroke risk - CHA2DS2-VA (Australian score, sex excluded)
| Factor | Points |
|---|---|
| Congestive HF (HFrEF or HFpEF) | 1 |
| Hypertension | 1 |
| Age >=75 | 2 |
| Diabetes | 1 |
| Stroke / TIA / systemic embolism | 2 |
| Vascular disease (MI, PAD, aortic plaque) | 1 |
| Age 65-74 | 1 |
- Australia dropped sex from the score before ESC did - female sex is a risk modifier, not a criterion
Bleeding risk
- HAS-BLED identifies modifiable factors
- Never a reason to withhold anticoagulation - fall risk essentially never outweighs stroke benefit
Management
Three parallel problems - Anticoagulate, Better symptom control, Comorbidities.
A. Anticoagulation
Decided independently of rhythm strategy and of AF pattern
- Anticoagulate if:
- CHA2DS2-VA >=2 -> yes
- CHA2DS2-VA =1 -> consider
- CHA2DS2-VA 0 -> none
- DOAC preferred over warfarin - dose-reduce for renal function, weight, age
- Warfarin INR 2-3 mandatory if moderate-severe MS or mechanical valve
- Aspirin has no role in stroke prevention in AF
- LAA occlusion only if genuine long-term contraindication to anticoagulation
- Post-PCI: DOAC + clopidogrel, drop aspirin early - less bleeding than triple therapy
B. Better symptom control
- Rate control
- Beta blocker or non-DHP CCB first line (CCB avoided if EF <40%)
- Digoxin as add-on; amiodarone not first line - toxicity
- Lenient target (resting <110) acceptable if asymptomatic with preserved LV
- AV node ablation + pacing if drugs fail
- Rhythm control - favour if symptomatic, young/active, HF, or diagnosed within 12 months (EAST-AFNET 4)
- Unstable -> immediate DC cardioversion
- AF >48 h or unknown duration: 3 weeks anticoagulation or TOE first, then 4 weeks after
- Flecainide only in structurally normal hearts, always with an AV nodal blocker
- Otherwise 1:1 conducted flutter
- Amiodarone if structural heart disease; sotalol needs QT monitoring
- Catheter ablation (PVI)
- First-line option in symptomatic paroxysmal AF; superior to drugs after failure
- In HFrEF reduces mortality + HF hospitalisation (CASTLE-AF)
- Less successful with LA dilatation, obesity, OSA, persistent AF
- Continue anticoagulation after successful ablation if stroke risk persists
C. Comorbidity and risk factor management
Treatment, not advice
- >=10% weight loss, alcohol reduction, BP control, CPAP for OSA, exercise
- Each reduces AF burden and recurrence after ablation
Associations
- HTN, obesity, OSA, alcohol - the modifiable quartet
- HF - bidirectional, each worsens the other
- Mitral valve disease (esp. MS), RHD
- Thyrotoxicosis
- IHD and cardiac surgery
- Sick sinus / tachy-brady - AF alternating with pauses, often needs pacing before rate control
- CKD, diabetes, endurance athletes
Natural history & complications
- Progressive: paroxysmal -> persistent -> permanent as substrate accrues
- Earlier rhythm intervention preserves more atrium
- ~5x stroke risk - AF strokes larger, more disabling, higher mortality
- Tachycardia-mediated cardiomyopathy - fully reversible with rate or rhythm control
- Also: HF, cognitive decline and dementia, reduced QoL, increased mortality
Monitor
- Symptoms and rate control
- Anticoagulation adherence
- Renal function - DOAC dose depends on it
- LV function
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