Atrial Fibrillation (Acute) Flashcards
What is atrial fibrillation (AF)?
Atrial fibrillation (AF) is a supraventricular tachyarrhythmia.
Electrocardiographic characteristics include:
- Irregularly irregular R-R intervals (where atrioventricular conduction is not impaired)
- Absence of distinct repeating P waves
- Irregular atrial activations
What is new-onset AF?
New-onset AF is defined as a new onset or a first detectable episode of AF, whether symptomatic or not.
What are the most common causes of AF?
- Sepsis
- Mitral Valve Pathology (stenosis or regurgitation)
- Ischemic Heart Disease
- Thyrotoxicosis
- Hypertension
What are the risk factors for new-onset AF?
- Coronary artery disease (CAD)
- Hyperthyroidism
- Valvular disease
- Hypertension
- Heart failure
- Diabetes
- Thyroid disorders
- COPD
- Obstructive sleep apnoea
- Advanced age
Damage to which heart valve is most commonly the cause of AF?
Mitral valve
What are the signs of AF?
- Tachycardia with irregularly irregular pulse
- Hypotension
- Signs of valvular heart disease (e.g. added heart sounds)
- Signs of hyperthyroidism
- Signs of heart failure (e.g. elevated JVP)
- Signs of infection
What are the symptoms of AF?
- Palpitations
- Dizziness
- Sycope
- Fatigue
- Dyspnoea
- Chest pain/ tightness or discomfort
- Anxiety
What investigations should be ordered for AF?
- ECG
- FBC
- Clotting profile
- Electrolyes, urea and creatinine
- Thyroid function
- CXR
- Echocardiogram
- Cardiac biomarkers
What ECG changes are seen in AF?
- Absent P waves
- Presence of fibrillatory waves that vary in size, shape and timing
- Irregularly irregular QRS complexes
- Variable QRS heights
Why investigate using FBC?
Use to detect non-cardiac factors precipitating AF (e.g., anaemia and infection).
Normal range but can be elevated or reduced.
Why investigate clotting profile?
Take as a baseline to identify any patient with an underlying coagulation defect and inform management with anticoagulants.
Baseline values.
Why investigate electrolytes, urea and creatinine?
Request in all patients to exclude renal impairment, hypokalaemia, hyperkalaemia, and hypomagnesaemia. Chronic kidney disease is a general cardiac risk factor and a specific risk factor for AF.
May show electrolyte abnormalities; high or low potassium, or low magnesium; baseline values.
Why investigate thyroid function?
Thyrotoxicosis may present with AF.
Suppressed thyroid-stimulating hormone (TSH) with elevated free T4 and/or T3.
Why investigate CXR?
CXR in patients who are otherwise healthy and presenting with new-onset AF (e.g., secondary to alcohol ingestion) may be normal. Pneumonia, pericarditis, or heart failure may precipitate new-onset AF.
May show cardiomegaly, in particular left atrial enlargement; signs of heart failure; other precipitating pathology, such as pneumonia
Why investigate using echocardiogram?
Echocardiogram in patients who are otherwise healthy and presenting with new-onset AF (e.g. secondary to alcohol ingestion) may be normal.
May show abnormalities, such as left ventricular hypertrophy, left atrial enlargement, segmental or global wall motion abnormalities, valvular stenotic or regurgitation abnormalities, cardiomyopathy with low left ventricular ejection fraction (LVEF) or pericardial disease.
Can use TEE or TOE.
Why investigate cardiac biomarkers?
Myocardial ischaemia may be a cause or consequence of AF.
Elevated creatine kinase-MB or troponin with myocardial ischaemia.
What criteria scoring systems are used to assessment of AF? And why?
CHAD-VASc: risk of thromboembolism
HAS-BLED: risk of bleeding
Briefly describe the CHA2DS2-VASc score
CHA2DS2-VASc score result:
- 0: no anticoagulation
- 1: consider anticoagulation
- >1: offer anticoagulation
C – Congestive heart failure
H – Hypertension
A2 – Age >75 (scores 2)
D – Diabetes
S2 – Stroke or TIA previously (scores 2)
V – Vascular disease
A – Age 65-74
S – Sex (female)
Briefly describe HAS-BLED score
Estimate the 1-year risk for major bleeding in patients with atrial fibrillation (1 point for each):
H – Hypertension
A – Abnormal renal and liver function
S – Stroke
B – Bleeding
L – Labile INRs (whilst on warfarin)
E – Elderly
D – Drugs or alcohol
What are the 3 elements in the management of AF?
- Rate control
- Rhythm control
- Prevention of thromboembolic events
When is direct current (DC) cardioversion indicated?
Used immediately if the patient is haemodynamically unstable with chest pain, shortness of breath, dizziness or sycope, hypotension and rapid heart rate.
Briefly describe DC cardioversion
DC cardioversion is performed under adequate short-acting general anaesthesia and involves delivery of an electrical shock synchronised with the intrinsic activity of the heart by sensing the R wave of the ECG.
When is rate control used?
NICE guidelines suggest all patients with AF should have rate control as first line unless:
- There is reversible cause for their AF
- Their AF is of new onset (within the last 48 hours)
- Their AF is causing heart failure
- They remain symptomatic despite being effectively rate controlled
What drugs are used in rate control of AF?
Rate control with beta-blocker and/ or calcium-channel blocker:
- Beta-blocker: esmolol, metoprolol, propanolol or bisprolol
- Calcium-channel blocker: diltiazem or verapamil
Why are beta-blockers and calcium-channel blockers used for rate control in AF?
Beta-blockers and calcium-channel blockers slow atrioventricular nodal conduction of cardiac impulses and subsequently reduce ventricular rate.
When is rhythm control used?
Rhythm control can be offered to patients where:
- There is a reversible cause for their AF
- Their AF is of new onset (<48 hours)
- Their AF is causing heart failure
- They remain symptomatic despite being effectively rate controlled
What are the 2 options for cardioversion?
Pharmacological or electrical
Differentiate between immediate or delayed cardioversion
Immediate cardioversion if the AF has been present for less than 48 hours or they are severely haemodynamically unstable.
Delayed cardioversion if the AF has been present for more than 48 hours and they are stable.
What drugs are used in pharmacologial cardioversion?
Flecainide, propafenone, amiodarone or dronedarone
Which drugs cannot be used for rhythm control in AF patients with coronary artery disease (CAD)?
Class IC agents (flecainide and propafenone) have a higher mortality in patients with coronary artery disease (CAD) and are contraindicated in patients with CAD and cardiac dysfunction.
Briefly describe the longer-term rhythm control strategy in AF
Long Term Medical Rhythm Control:
- Beta blockers are first line for rhythm control
- Dronedarone is second line for maintaining normal rhythm where patients have had successful cardioversion
- Amiodarone is useful in patients with heart failure or left ventricular dysfunction
What anticoagulants are used for pre-cardioversion in new onset AF?
Offer heparin initally; continue heparin until a full assessment has been made and appropriate antithrombotic therapy has been started, based on risk stratification.
Once sinus rhythm has been restored, direct oral anticoagulants should be started (DOACs). Anticoagulation may be with apixaban, dabigatran, rivaroxaban or a vitamin K antagonist.
Briefly describe the longer-term anticoagulation strategy of AF
Use the CHA2DS2-VASc score to calculate stroke risk in all patients presenting with AF.
If you are considering anticoagulation, use the HAS-BLED score to:
- Assess the risk of a major bleed
- Identify modifiable risk factors for bleeding
Use a direct oral anticoagulant (DOAC) or a well-managed vitamin K antagonist (e.g. warfarin)
What drugs can be used for anti-coagulation in long term management of AF?
If using a DOAC, choose one of apixaban, edoxaban, rivaroxaban, or dabigatran.
If using warfarin, start the patient on a parenteral anticoagulant (if they aren’t on one already as part of the pre-cardioversion anticoagulation), such as unfractionated heparin or a low molecular weight heparin, at the same time.
Why is anticoagulation used in patients with new-onset AF?
Prevention of stroke
How does AF lead to ischemic stroke?
The uncontrolled and unorganised movement of the atria leads to blood stagnating in the left atrium, particularly in the atrial appendage. Eventually this stagnated blood leads to a thrombus (clot). This clot then mobilises (becomes an embolus) and travels with the blood. It travels from the atria, to the ventricle, to the aorta then up in the carotid arteries to the brain. It can then lodge in the cerebral arteries and cause an ischaemic stroke.
What are the complications of new-onset AF?
- Acute stroke
- Myocardial infarction
- Congestive heart failure
What differentials should be considered in AF?
- Atrial flutter
- Wolff Parkinson-White syndrome
- Atrial tachycardia
How does AF and atrial flutter differ?
Differentiating signs and symptoms:
- Clinical history and physical examination may not be useful in differentiating from AF
Differentiating investigations:
- ECG shows absence of P waves, presence of characteristic flutter waves that give typical saw tooth appearance in the inferior limb leads, and QRS complexes that are regularly irregular
How does AF and Wolff-Parkinson-White syndrome differ?
Differentiating signs and symptoms:
- Usually present at younger age and often precipiated by exercise
Differentiating investigations:
- Classic ECG has shortened PR interval and delta waves on the QRS complex, which may degenerate into AF
How does AF and atrial tachycardia differ?
Differentiating signs and symptoms:
- Clinical history and physical examination may not be useful to differentiate from AF
- Atrial tachycardia is more common in patients with COPD.
Differentiating investigations:
- ECG shows abnormal P waves
- In multifocal atrial tachycardia, there are at least 3 different morphologies of P waves
