Atrial Fibrillation

AF is super common in the elderly. If an older person is on long-term Warfarin, it is very likely that they have AF. This past week, I felt the pulses of two older patients with AF. The pulse is meant to be irregularly irregular (different to regularly irregular, let’s be particular about this) but to be honest, if I hadn’t been told beforehand that they had AF, I would not have tried to convince myself it was irregular. I guess I need to feel more pulses.


Atrial Fibrillation (AF)

Definition: an irregular heart rhythm originating in the atrium

Aetiology/ risk factors:

-a chaotic irregular atrial rhythm at 300-600 bpm with the AV node responding intermittently, hence an irregular ventricular rate. Cardiac output drops by 10-20% as the ventricles aren’t primed reliably be the atria.

Causes:

-Heart failure/ ischaemia, Hypertension, Myocardial infarction (seen in 22%)

-Mitral valve disease

-Pulmonary embolism, Pneumonia

-Hyperthyroidism

-Caffeine, alcohol

-Post-op

-Hypokalaemia, hypomagnesaemia

Rare causes:

-Cardiomyopathy, Constrictive pericarditis, Atrial Myxoma, Endocarditis, sick skins syndrome

-Lung cancer

-Haemochromatosis, sarcoidosis

Lone AF = no cause found

Epidemiology: common in the elderly (≤9%)

Symptoms:

-may be asymptomatic

-palpitations

-chest pain

-dyspnoea

-faintness, dizziness

Signs:

irregularly irregular pulse

-apical pulse rate (usually in the 5th intercostal space, mid-clavicular line) > radial rate

-1st heart sound of variable intensity (as blood flow from atria varies between beats)

-Other signs as AF often associate with non-cardiac disease (e.g. thyroid or valvular disease)

-signs of left ventricular failure (pulmonary oedema- fine crackles, pink froth sputum etc.)

Investigations:

ECG: irregularly irregular narrow QRS complexes, absent P waves, fibrillatory baseline

Image result for ecg af

24 hr ECG (24h tape): if paroxysmal AF suspected

Bloods: cardiac enzymes (troponin- ischaemic heart disease?), thyroid function tests (hyperthyroidism?)

U&Es (↓K? ↓Mg?)- there is increased Digoxin toxicity risk with hypokalaemia, hypomagnesaemia and hypercalcaemia

-Echo: consider echo to look for left atrial enlargement, mitral valve disease, poor LV function and other structural abnormalities

Management:

Acute AF: Presents < 48h from onset– cardioversion

(Cardioversion: can be electrical- therapeutic dose of electric current applied to the heart at a specific moment in the cardiac cycle to restore sinus rhythm- or pharmacological- using anti-arrhythmics)

If very ill or haemodynamically unstable:

-O2    -Check U&Es (for reversible causes)

EMERGENCY electrical cardioversion (IV amiodarone if unavailable) without delaying in order to start anticoagulation.

-Treat associated illness e.g. MI, pneumonia)

Acute AF without life‑threatening haemodynamic instability:

-Offer rate (1st  line: Verapamil or Bisoprolol. 2nd : Digoxin or Amiodarone) or rhythm (Amiodarone or Flecainide) control if the onset of the arrhythmia is less than 48 hours, and start rate control if it is more than 48 hours or is uncertain.

– Consider either pharmacological or electrical cardioversion in those who will be treated with a rhythm control strategy.

Cardioversion regimen:

-Give O2 if needed, place win ITU or CCU (Coronary Care Unit), GA or IV sedation, monitor ECG

Electrical Cardioversion usually monophasic (200J –> 360J –> 360J), may be biphasic (200J)

Pharmacological Cardioversion:

Flecainide or IV Amiodarone- if no evidence of structural or ischaemic heart disease

– IV Amiodarone- if evidence of structural heart disease

-In acute AF, start full anticoagulation with Low Molecular Weight Heparin (LMWH) to keep options open for cardioversion even if 48h time limit running out. If 48h period has elapsed, cardioversion is ok if transoesophageal echo is thrombus free.

 

Chronic AF: Presents > 48h from onset- rate control and anticoagulation

Rate control is as good as rhythm control and is 1st line in long-term management, but rhythm control may be appropriate if: symptomatic or Congestive Cardiac Failure, younger, presenting for 1st time with lone AF, AF from a corrected precipitant (e.g. electrolyte disturbance)

Anti-coagulation:

-If AF started > 48h ago or uncertain and elective cardioversion is planned, ensure ≥3 weeks of anticoagulation before cardioversion (followed by long-term rhythm control). During this period offer rate control as appropriate.

-Warfarin– aim for INR of 2-3

Alternatively:

Dabigatran– direct thrombin inhibitor, may be as good as warfarin

-Apixaban, Rivaroxaban

CHA2DS2-VASc Score: quantifies risk of stroke and helps with decision making regarding anticoagulation

Each scores 1 point except >75 and prior stroke/TIA/Thromboembolism

Congestive heart failure (or Left ventricular systolic dysfunction)

Hypertension

Age ≥75 years (2)

Diabetes mellitus

S(2)– Prior Stroke or TIA or Thromboembolism

Vascular disease (e.g. peripheral artery disease, myocardial infarction, aortic plaque)

Age 65–74 years

Sc– Sex category (i.e. female sex)

Score of 2 = annual stroke risk of ~2.2%.

-If score 1 or more (2 or more if older) consider oral anticoagulation.

Rate Control: 1st line management

Beta-blocker or rate limiting Calcium Channel Blocker (diltiazem or verapamil) = first choice

-Try Digoxin monotherapy only for non-paroxysmal AF if sedentary lifestyle

-If symptoms persisting- combine 2 of: beta blocker, diltiazem, digoxin

(Don’t give beta-blockers with diltiazem or verapamil without expert advice due to bradycardia risk. Do not offer amiodarone for long-term rate control).

Rhythm Control:

Consider pharmacological and/or electrical rhythm control for AF if symptoms continue after heart rate has been controlled or rate‑control strategy has not been successful.

Offer electrical (rather than pharmacological) cardioversion (> 48h) if cardioversion is elected.

-Consider amiodarone therapy starting 4 weeks before and continuing for up to 12 months after electrical cardioversion to maintain sinus rhythm.

-Do echo first (make sure no emboli in heart that are going to fly off when you cardiovert them)

-After electric cardioversion = long term drug treatment to maintain rhythm control:

-1st line: Beta blocker

Other options to consider if cardioversion and drug treatment is unsuitable or unsuccessful:

-left atrial catheter ablation

-AV node ablation

-Pacing

 

Paroxysmal AF:

Sotalol or Flecainide PRN may be tried (i.e. when symptomatic) if: infrequent AF, BP > 100 mmHg systolic, no past LV dysfunction.

-Anti-coagulate:  Warfarin (Dabigatran or aspirin)

-left atrial catheter ablation, AV node ablation or pacing may be suitable

 

Complications:

-Embolic stroke- main complication, risk reduced by warfarin, from 4% to 1%/yr

-Worsens any existing heart failure

Prognosis:

-Chronic AF in a diseased heart does not usually return to sinus rhythm

References: Cheese & Onion, NICE guidelines
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