Cardiovascular

Atrial Flutter

Atrial flutter is a single organised re-entry circuit, usually running around the tricuspid valve, and the ventricular rate is whatever fraction of it the atrioventricular node lets through.

In a nutshell

Atrial flutter is one organised atrial re-entry circuit, usually through the cavotricuspid isthmus, with an atrial rate of 250 to 330 beats per minute. If flutter is causing a life-threatening feature, give a synchronised shock starting at 70 to 120 J.

Classic presentation

Palpitations and breathlessness with a regular narrow-complex tachycardia stuck at about 150 beats per minute, and continuous sawtooth atrial activity in leads II, III, aVF and V1.

Key points

Flutter with a fixed conduction ratio is a regular narrow-complex tachycardia. With a varying ratio it is irregular and looks exactly like AF at the bedside.
CHA2DS2-VASc estimates a person's yearly risk of stroke from AF. It decides one thing: whether to offer lifelong anticoagulation. NICE applies it to flutter unchanged.
CHA2DS2-VASc components: cardiac failure, hypertension, age 75 or over (doubled), diabetes, prior stroke (doubled), vascular disease, age 65 to 74, female sex. Maximum 9.
ORBIT estimates a person's yearly risk of major bleeding on an anticoagulant. It does not decide whether to anticoagulate; it decides which bleeding risks you correct first.
NICE's five exceptions to rate-control-first name flutter directly: flutter suitable for an ablation strategy. No other arrhythmia is singled out that way.
AF is present before flutter ablation in 24 to 62% of people and may follow it in 30 to 70%, so a successful ablation does not end anticoagulation.
A stable conduction ratio keeps the ventricular rate high, so rate control often fails and the rate falls in steps as the ratio changes.
Cardioversion energy is where flutter and AF genuinely part company: 70 to 120 J for flutter, an initial shock at maximum output for AF.

First-line investigation

A 12-lead ECG: measure the atrial rate, not just the ventricular rate, and state the atrioventricular conduction ratio. Look for flutter waves in leads II, III, aVF and V1.

Management

Unstable flutter

ABCDE (airway, breathing, circulation, disability, exposure). Monitor ECG, BP and oxygen saturations, record a 12-lead ECG, give oxygen if saturations are below 94%, obtain IV access.⁴
Life-threatening features: shock, syncope with severe or ongoing hypotension, myocardial ischaemia, severe heart failure with pulmonary oedema, or immediately after return of spontaneous circulation.⁴
If one is caused by the flutter, give a synchronised shock at 70 to 120 J, stepping the energy up if it fails, to a maximum of 3 attempts.^2,4
Synchronise every shock to the R wave. Sedate or anaesthetise a conscious patient if that is possible without delay. Do not wait to achieve anticoagulation.^2,3
If 3 shocks fail and instability persists, give amiodarone 300 mg IV over 10 to 20 minutes. The alternative is procainamide 10 to 15 mg/kg (maximum 1 g) over 20 minutes. Then shock again.^2,4
Amiodarone loading may be followed by 900 mg IV over 24 hours. Offer heparin at first presentation to anyone on no or subtherapeutic anticoagulation.^2,3

Stable flutter: prove it, then slow it

Vagal manoeuvres first. If they fail, adenosine 6 mg by rapid IV bolus, then 12 mg, then 18 mg, each into a large vein over 2 seconds with cardiac monitoring.^4,5
Adenosine exposes the flutter waves; it does not stop the circuit. Avoid it in asthma, chronic obstructive lung disease, long QT syndrome and pre-excitation.^5,1
Metoprolol up to 5 mg by IV injection at 1 to 2 mg/minute, repeatable after 5 minutes, to a total of 10 to 15 mg. Orally, 50 mg two or three times daily.⁹
Or verapamil 5 to 10 mg by slow IV injection over 2 minutes, 3 minutes in the elderly, with a further 5 mg after 5 to 10 minutes if needed.⁸
Never IV verapamil after an IV beta-blocker: a listed contraindication risking bradycardia, hypotension and asystole. Also barred below a rate of 50 or a systolic pressure of 90 mmHg.⁸
Digoxin is licensed for flutter: load 0.75 to 1.5 mg orally over 24 hours, then 125 to 250 micrograms daily. Halve it if amiodarone is co-prescribed.^7,3

Rhythm control and ablation

NICE makes rate control first line except in five situations, one of which is flutter suitable for an ablation strategy. Flutter is the only arrhythmia NICE names there.³
Flutter lasting over 48 hours or of uncertain duration: delay planned cardioversion until a minimum of 3 weeks of therapeutic anticoagulation, or use a transoesophageal echocardiography-guided strategy.³
Instability overrides that: cardiovert now. Beyond 48 hours NICE prefers electrical to pharmacological cardioversion. Anticoagulation continues afterwards whatever the pre-cardioversion score.³
Refer symptomatic, recurrent or persistent typical flutter for cavotricuspid isthmus ablation: one line across the isthmus breaks a circuit that is anatomically fixed.^3,1
Refer within 4 weeks of failed treatment, or of recurrence after cardioversion.³

Stroke prevention, exactly as in atrial fibrillation

Score CHA2DS2-VASc. NICE names atrial flutter in that population, alongside AF and continuing recurrence risk after cardioversion or ablation, with no separate threshold.³
Offer a direct oral anticoagulant at a score of 2 or more. Consider one for a man scoring 1. Withhold in under-65s whose only risk factor is their sex.³
If a direct oral anticoagulant is contraindicated, not tolerated or not suitable, offer a vitamin K antagonist. Drug choice and dosing are in the atrial fibrillation chapter.³
A high ORBIT score directs you to correct hypertension, poor INR control, antiplatelets, antidepressants, NSAIDs, alcohol and anaemia. It is not a reason to withhold treatment.³
Never aspirin monotherapy for stroke prevention, and never withhold anticoagulation for age or falls alone.³
If a disabling ischaemic stroke is the presentation, the stroke pathway governs: aspirin 300 mg for the first 2 weeks before anticoagulation is considered.^6,3

1:1 conduction and pre-excitation

A class 1c drug slows the circuit, so the atrioventricular node can suddenly conduct 1:1 and the ventricular rate rises. Do not start one without specialist review.^1,3
If the atrial arrhythmia is pre-excited, avoid adenosine, verapamil, diltiazem, beta-blockers, digoxin and IV amiodarone. Use procainamide or synchronised cardioversion with urgent expert help.^4,8

Driving and review

Group 1 licence: no driving for at least 4 weeks if the arrhythmia caused or is likely to cause incapacity, and the DVLA must be notified.¹⁰
Group 2: notify, licence refused or revoked. Relicensing needs the cause treated, 3 months free of incapacitating arrhythmia and an ejection fraction of at least 40%.¹⁰
After catheter ablation other than for ventricular tachycardia: Group 1 at least 2 days, Group 2 at least 2 weeks, and the DVLA need not be notified.¹⁰
Review the need for anticoagulation at least annually, and do not stop it merely because typical flutter has been ablated.^3,1

Exam traps

Flutter cardioverts at 70 to 120 J; AF gets an initial shock at maximum defibrillator output. Do not carry the AF energy across.
Adenosine unmasks flutter, it does not treat it. The circuit runs on behind the transient block, and that persistence is the diagnostic answer.
A ventricular rate near 150 suggests 2:1 flutter but is not diagnostic, and plenty of flutter is neither 150 nor regular.
Slowing the atrial circuit with a class 1c drug can raise the ventricular rate, because 1:1 conduction becomes possible.
Do not withhold anticoagulation because the rhythm is only flutter. NICE names atrial flutter in the CHA2DS2-VASc population with no separate threshold.
IV verapamil is contraindicated after an IV beta-blocker, and in flutter with an accessory pathway, where it can accelerate conduction down the pathway.
The BNF carries no arrhythmia dose for diltiazem, and NICE records its rate-control use as off-label, so do not quote a diltiazem dose from memory.

Illustrations

Atrial flutter on a 12-lead ECGECG showing regular flutter activity. Assess the inferior leads and V1, calculate the atrial rate and identify the atrioventricular conduction ratio rather than relying on a ventricular rate of 150 alone.James Heilman, MD, Wikimedia Commons · CC-BY-SA-3.0

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.