AF is the most common cardiac arrhythmia. As an FY1 you will frequently review an ECG to discover new or fast AF after you may have requested one for a patient complaining of dizziness, lightheadedness, palpitations or shortness of breath.

From medical school you will be able to identify atrial fibrillation from the irregularly irregular pattern (using the RR intervals), narrow QRS complexes & the lack of P waves. Reviewing old ECGs & the notes can help identify if it is new. Note that atrial fibrillation can be persistent or paroxysmal.

Causes
  • PE
  • Infection
  • Acute alcohol intake/withdrawal
  • MI
  • Thyrotoxicosis
  • Post-surgery
Other Risk factors:
  • Hypertension
  • IHD; Cardiomyopathies; Valvular diseases; HF
  • Obesity
Most important point when assessing a fast AF
As with all supraventricular tachycardias, if the patient has any adverse features: shock, syncope, new heart failure, chest pain/myocardial ischaemia or if you're worried then place a peri-arrest call & ask a nurse to bring the crash trolley! For more details see the resus council's tachyarrythmia protocol.

Otherwise the assessment is as follows:

History
  • Ask if they have any cardiorespiratory symptoms (above) which will help inform when it may have started & the impact it has on the patient (e.g. falls in the elderly)
  • Screen through all the causes. It is better to treat the underlying cause.
Investigations:
  • Bloods: FBC, U&Es, Calcium (bone profile), Magnesium, LFT, TFT, CRP. Consider blood cultures if there's features of underlying infection
  • Echo for structural disease, valvular disease & regional wall motion abnormalities which help identify the underlying cause(s)
Management:
There are two broad areas to manage: rate/rhythm & anti-coagulation. Senior input is advised as this isn't something you should manage on your own.

Usually we aim to achieve rate control as reversing the rhythm might throw off a clot and cause the patient to have a stroke. Only if there's definite evidence that the onset was <48 hours and ideally with an echo confirming that there's no atrial thrombus would we aim for rhythm control. Imaging can also help identify if there are features of structural or ischaemic disease which can guide the use of fleicanide or amiodarone. You should consult your cardiology registrar if you feel it would be necessary to head down this route.

Rate control
Rate control aims to reduce the HR to <100. Not all patients need medication to control this as some have rate controlled AF or it will settle with treating their underlying condition causing tachycardia e.g. dehydration, infection or anaemia. They should be on a cardiac monitor for you to be able to judge the response to therapy (& to monitor for bradycardia).

However if the rate is very high and/or they are symptomatic then intravenous agents are often used. Oral agents also work such as atenolol or bisoprolol. Monitoring their blood pressure & checking for contraindications (e.g. bronchospasm in asthma) is important. Use local guidelines & your senior's advice to initiate the correct therapy but some examples are below.

1st line: Metoprolol IV 2.5 mg every 20 min. Frequently check patient’s BP as metoprolol can cause a drop.

2nd line: Digoxin 500 mcg IV as a loading dose. For elderly patients start with a lower dose 250 mcg IV loading dose.

Anticoagulation
Work out the CHA2DS2VASC  & HASBLED scores to work out their risk of a stroke & their risk of major bleeding. Usually those with a CHADVASC of >2 are anticoagulated & for a score of 1 people vary in their approach as long as they're at low risk of major bleeds. Discuss with your seniors. DOACs (a.k.a NOACs) are preferred but renal function & other contraindications may make warfarin preferable. Some people prefer starting on LMWH before converting to other agents but for DOACs this isn't necessary. These options vary from person to person & can also depend on local policies.

Written by Dr Elsa Barbosa (Registrar)
Additions by Dr Akash Doshi CT2