AF - definition
Atrial fibrillation (AF) is a supraventricular tachyarrhythmia. It is characterised by uncoordinated atrial activity on the surface ECG, with fibrillatory waves of varying shapes, amplitudes, and timing associated with an irregularly irregular ventricular response
AF - types
- Paroxysmal: recurrent AF that terminates spontaneously within 7 days
- Persistent: recurrent, > 1 week without self-terminating
- Long-standing persistent: > 12 months
- Permanent AF: decision to not stop the rhythm
- Non-valvular AF: absence of rheumatic mitral stenosis, a mechanical or bioprosthetic heart valve, or mitral valve repair
AF - causes
- Cardiac causes, such as hypertension, valvular heart disease, HF, ischaemic heart disease, rheumatic heart disease (MS), sick sinus syndrome, WPW.
- Respiratory causes, such as chest infections, pulmonary embolism, and lung cancer.
- Systemic causes, such as alcohol, thyrotoxicosis, electrolyte depletion, infections, DM, peri-operative.
- Focal AF: often younger, symptomatic people with repetitive, short atrial runs, and frequent short runs of paroxysmal AF.
- Post-operative: typically after cardiac surgery and self-limiting.
- Mitral stenosis or prosthetic heart valve-related.
- Athletes: usually paroxysmal; related to duration/intensity of exercise.
AF - risk factors
increasing age diabetes mellitus hypertension congestive heart failure (CHF) valvular heart disease coronary artery disease (CAD) other atrial arrhythmias cardiac or thoracic surgery hyperthyroidism
AF - presentation
- irregularly irregular pulse rate
- palpitations (fluttering in the chest or a feeling of the heart ‘racing’ or ‘galloping’)
- hypotension, dizziness, SOB
- elevated jugular venous pressure (in new-onset AF)
- added heart sounds (valvular disease eg mitral stenosis due to rheumatic heart disease; a gallop rhythm - S3 - may be heard in heart failure)
- HR could be 160-180 bpm
- severe: sings of CHF, syncope, chest pain, hypotension, tachycardia
AF - investigations
- TFTs (suppressed TSH if hyperthyroidism)
- FBC
- Blood urea and electrolytes, calcium, magnesium, and glucose measurements. (hypokalaemia?)
- 12-lead ECG = absent P waves; presence of fibrillatory waves that vary in size, shape, and timing; irregularly irregular QRS complexes
- Transthoracic echocardiogram if there is a high risk or a suspicion of underlying structural heart disease (such as a heart murmur) or functional heart disease (such as heart failure)
- Chest X-ray if lung pathology (such as lung cancer or pneumonia) is suspected
AF - first line management
RATE CONTROL
- beta-blocker (cardioselective*) or rate-limiting calcium-channel blocker (verapamil, diltiazem) (but never both)
- Consider digoxin monotherapy for people with non-paroxysmal AF only if they have a sedentary lifestyle
- follow up within 1 week
(beta-blockers are contraindicated in people with asthma, and rate-limiting calcium-channel blockers are contraindicated in people with co-existing heart failure)
*atenolol, bisoprolol, metoprolol, nebivolol
When do you refer for rhythm-control treatment (cardioversion)?
(haemodynamically stable patient)
Refer people:
- With new-onset AF.
- Whose AF has a reversible cause (eg chest infection)
- Who have heart failure thought to be primarily caused, or worsened, by AF.
- With atrial flutter who are considered suitable for an ablation strategy to restore sinus rhythm.
What are rhythm-control treatment?
Rhythm-control treatments used by specialists include:
- Electrical cardioversion
- Pharmacological cardioversion with antiarrhythmic drugs (such as amiodarone or sotalol)
For people having cardioversion for AF that has persisted for longer than 48 hours, electrical (rather than pharmacological) cardioversion is used
NICE: Amiodarone is commenced 4 weeks prior to the DC cardioversion and is to continue for 12 months after the cardioversion to maintain sinus rhythm
Amiodarone monitoring: LFTs and TFTs
- can cause thyroid dysfunction, and liver fibrosis and hepatitis
AF and haemodynamic instability - treatment
- onset of arrhythmia is within 48 hours: offer rate-control treatment or refer for cardioversion
- onset of arrhythmia is more than 48 hours: start rate-control treatment. If cardioversion is needed, it should be delayed until the person has been maintained on therapeutic anticoagulation for a minimum of 3 weeks.
What is electrical cardioversion?
Synchronized electrical cardioversion uses a therapeutic dose of electric current to the heart at a specific moment in the cardiac cycle, restoring the activity of the electrical conduction system of the heart. Two electrode pads are used (or, alternatively, the traditional hand-held “paddles”), placed on the chest of the patient, or one is placed on the chest and one on the back. A cardioverter delivers a reversion shock, by way of the pads, at the optimal moment in the cardiac cycle which corresponds to the R wave of the QRS complex on the ECG.
(defibrillation works at a random moment in the cardiac cycle as opposed to cardioversion)
When to offer anticoagulation treatment?
Assess stroke risk using the CHA2DS2VASc score tool. This defines ‘major’ and ‘clinically relevant non-major’ risk factors which increase the risk of stroke.
- Offer anticoagulation treatment to all people with a CHA2DS2VASc score of 2 or above, and consider offering it to men with a CHA2DS2VASc score of 1, after taking into account the person’s bleeding risk assessed using the HAS-BLED score tool
- If the person is willing to take an anticoagulant, prescribe warfarin or a novel oral anticoagulant drug (NOAC; dabigatran, rivaroxaban, or apixaban)
Warfarin vs DOACs
- DOACs are non-inferior to warfarin for the prevention of stroke in people with AF - however they are only licensed for use in non-valvular AF
- DOACs are associated with a reduced risk of haemorrhagic stroke and intracerebral haemorrhage
- DOACs have a relatively short half-life and their anticoagulant effect fades rapidly after 12 to 24 hours
- Warfarin, unlike DOACs, needs regular blood tests to monitor coagulation control
- unlike warfarin (antidote is vit K), there are, as yet, no specific antidotes for DOACs
(if on warfarin, monitor INR –> between 2 and 3)
What is The CHA2DS2VASc score tool?
Used to assess risk of stroke in AF patients
- Congestive heart failure/left ventricular dysfunction = 1
- Hypertension = 1
- Age older than or equal to 75 years = 2
- Diabetes mellitus = 1
- Stroke/TIA/thromboembolism = 2
- Vascular disease = 1
- Age 65–74 years = 1
- Sex category (female) = 1
What is the HAS-BLED score?
Assess 1-year risk of major bleeding in patients on anticoagulants with AF (each is 1 point)
Hypertension
Abnormal liver/renal function
Stroke
Bleeding (eg haematuria, haematemesis etc)
Labile INR
Elderly (aged over 65 years)
Drugs (antiplatelet agents or NSAIDs) or alcohol
0-2 = low bleeding risk
3 or > = high bleeding risk
Conservative treatment
- reduce alcohol, BMI
- glycaemic control, OSA control
- target HR for AF patients = 90 bpm at rest (unless symptomatic - individualised)
AF - 3rd line treatment
Radio-frequency ablation
- ablation around the pulmonary vein
- if AF + NO symptoms = do NOT ablate
- only ablate if symptomatic or have delta waves
WPW- which drugs to avoid?
ABCD
- Adenosine
- Beta blockers
- CCB
- Digoxin
they can cause an acceleration of the accessory pathway so risk of ventricular arrhythmias (VF)
instead use amiodarone or flecainide for WPW
Warfarin - side effects, CI, other facts
Side effects:
- bleeding
- hair loss, skin necrosis
- postural hypotension esp elderly
CI:
- 1st trimester of pregnancy (foetal cardiac + cranial malformations)
- 3rd trimester of pregnancy (bleeding risk at delivery)
- has low therapeutic index - TTR used to monitor
- interaction with CP450 inhibitors (toxicity - bleeding risk) and inducers (reduced effect - risk of clots)
- Broccoli, spinach, kale and sprouts are all high in vitamin K so should be avoided in excess by patients taking warfarin
