Atrial Flutter

Atrial flutter is a supraventricular tachyarrhythmia driven by a single, highly organized macro-reentrant electrical circuit — a fundamentally different mechanism from atrial fibrillation's chaotic, disorganized atrial activation. The most common form, typical (cavotricuspid-isthmus-dependent) flutter, circles a fixed anatomical loop in the right atrium at a very stable rate of roughly 250-350 times per minute (classically about 300/min), producing the characteristic "sawtooth" flutter-wave pattern on ECG. This chapter assumes familiarity with the Atrial Fibrillation chapter and deliberately does not repeat it: the Canadian Cardiovascular Society's 2020 guideline explicitly directs that atrial flutter be stratified and anticoagulated using the identical CHADS-65 algorithm as atrial fibrillation^[1][2] — the full stroke-risk algorithm, DOAC dosing tables, and HAS-BLED bleeding-risk assessment live in that chapter and are not duplicated here. What genuinely differs, and is this chapter's focus, is the electrophysiology (a single organized circuit rather than chaotic multiple wavelets), the distinctive ECG signature, ventricular rate control that is often harder to achieve pharmacologically than in AF, and catheter ablation of the cavotricuspid isthmus being a first-line, curative option for typical flutter with a success rate exceeding 90% — a materially different treatment philosophy from AF, where ablation is an important option but is not uniformly positioned as first-line for every patient.^[3]

A classic "sawtooth" atrial flutter rhythm strip with variable atrioventricular conduction (alternating roughly between 4:1 and 5:1 block) — the flutter waves themselves stay perfectly regular even though the resulting ventricular rate does not. (Original tracing: James Heilman, MD; SVG derivative: Mysid, CC BY-SA 3.0/GFDL, Wikimedia Commons)

Typical presentation

Palpitations, fatigue, dyspnea, and reduced exercise tolerance are typical, similar to atrial fibrillation. Because typical flutter most often conducts to the ventricle at a fixed 2:1 ratio, the ventricular rate frequently sits at almost exactly 150 beats per minute — a strikingly regular narrow-complex tachycardia that can be mistaken for other regular SVTs (AVNRT/AVRT) or for sinus tachycardia. A persistently regular rate of approximately 150 bpm should raise suspicion for flutter with 2:1 block until proven otherwise. As with AF, a substantial share of flutter is identified incidentally or presents only with reduced exercise tolerance rather than palpitations, and symptom burden does not track with stroke risk.

• Structural or valvular heart disease, prior myocardial infarction, and heart failure — shared with atrial fibrillation.
• Prior cardiac surgery involving an atriotomy — a leading, flutter-specific cause of atypical, scar-related circuits.
• Prior catheter ablation, including a prior AF ablation — a recognized cause of later scar/"gap"-related atypical flutter.
• Chronic obstructive pulmonary disease and other chronic pulmonary disease — a particularly strong, classically taught association with atrial flutter specifically.
• Hypertension, obesity, obstructive sleep apnea, diabetes mellitus, and chronic kidney disease — the same general cardiometabolic risk factors as atrial fibrillation.
• Hyperthyroidism.
• Digoxin toxicity — flutter with high-grade or unusually regular atrioventricular block is a classic toxic presentation.
• Congenital heart disease repaired in childhood with an atriotomy (for example, after a Fontan procedure) — a lifelong flutter risk from the surgical scar.
• Advancing age and male sex.
• Coexistence with atrial fibrillation — many patients with flutter also have, or go on to develop, AF from the same diseased atrial substrate; the two arrhythmias are closely linked, not separate diseases with independent risk profiles.

Confirming the diagnosis

• 12-lead ECG showing regular atrial activity at approximately 250-350 beats per minute (classically about 300/min) with no isoelectric baseline between flutter waves — the "sawtooth" pattern. Typical counterclockwise flutter shows negative sawtooth waves in the inferior leads (II, III, aVF) and a positive deflection in V1; the clockwise variant shows the mirror image. Atypical flutter often lacks this classic morphology.^[3]
• The ventricular rate is a fixed fraction of the atrial rate — most often 2:1 (giving a rate near 150 bpm), less often 3:1 or 4:1 — though the conduction ratio can vary (including a Wenckebach-type pattern), producing an irregular ventricular rate that can superficially resemble atrial fibrillation. Look specifically for the organized, regular flutter-wave baseline to distinguish the two.
• When flutter waves are not clearly visible — for example, buried in a fast baseline — a vagal maneuver or IV adenosine given during continuous ECG recording can transiently increase AV block and unmask the flutter waves without terminating the rhythm; this is diagnostically useful even though it is not curative.^[3]
• Echocardiography to assess left atrial size, left ventricular ejection fraction, and structural or valvular heart disease — the same rationale as atrial fibrillation, and LVEF still governs which rate-control and rhythm-control drugs are appropriate.
• TSH, to identify hyperthyroidism as a reversible contributor.
• A digoxin level if the patient is taking digoxin and presents with new or worsening high-grade AV block.
• Electrolytes and renal function, both as a general baseline and because they are required inputs for anticoagulant dosing.

Stroke-risk and bleeding-risk assessment — identical to atrial fibrillation

Apply the CHADS-65 algorithm exactly as described in the Atrial Fibrillation chapter: age 65 or older, or any CHADS2 risk factor at any age, warrants anticoagulation, with a DOAC preferred over warfarin for nonvalvular disease.^[1][2] Bleeding risk is assessed with HAS-BLED, also exactly as in that chapter. Neither algorithm is repeated here — atrial flutter is not treated as a lower-risk arrhythmia for stroke-prevention purposes, so the full tables, DOAC renal/age/weight dosing, and bleeding-risk stratification in the Atrial Fibrillation chapter apply without modification.

• Prevent stroke and systemic embolism, using the identical priority and CHADS-65-based decision as atrial fibrillation.
• Achieve adequate ventricular rate control — recognizing this is frequently harder to titrate reliably than in atrial fibrillation.
• Restore and maintain sinus rhythm, actively considering catheter ablation of the cavotricuspid isthmus as a first-line strategy for typical flutter rather than only after drug therapy has failed.
• Identify and correct reversible contributors: thyrotoxicosis, digoxin toxicity, an uncontrolled pulmonary exacerbation, or a recent cardiac surgery-related scar circuit.
• Recognize that flutter and AF frequently coexist or that one follows the other from the same diseased atrial substrate, and monitor accordingly even after apparently successful flutter treatment.

• Catheter ablation of the cavotricuspid isthmus — a first-line, curative option for typical flutter, with success exceeding 90%.^[3]
• Ablation of atypical flutter — more complex, requiring 3D electroanatomic mapping of the specific non-cavotricuspid-isthmus circuit; lower success rate and more frequent recurrence than typical flutter, but still worthwhile for symptomatic or drug-refractory disease.
• Electrical cardioversion — highly effective given flutter's organized rhythm, often at a lower energy than typically required for AF; the same pre- and post-cardioversion anticoagulation requirements as AF apply.
• Overdrive atrial or transesophageal pacing — a distinctive option for organized flutter, able to terminate typical flutter without a shock when an existing pacemaker/ICD atrial lead or temporary epicardial wires are available.
• AV-node ablation with permanent pacemaker implantation — a last-resort rate-control option when pharmacologic rate control fails, as in AF, though reached less often for typical flutter given how effective and safe cavotricuspid isthmus ablation is.
• Treat reversible contributors directly: thyrotoxicosis, an uncontrolled pulmonary disease exacerbation, or digoxin toxicity.
• Left atrial appendage occlusion — the same alternative stroke-prevention strategy as AF, for patients at high stroke risk with a genuine contraindication to long-term oral anticoagulation; not repeated here beyond this cross-reference.

Anticoagulant selection and dosing (DOACs and warfarin) are identical to atrial fibrillation and are not repeated in this table — see the Atrial Fibrillation chapter's Pharmacologic Treatment Options and Drug Tables sections. The rows below cover only what is genuinely different for flutter: rate control and pharmacologic cardioversion.

Pregnancy

Rate control with a beta-blocker (e.g., metoprolol) is preferred, as in AF. Electrical cardioversion is considered safe at any stage of pregnancy, given the low energy reaching the fetus, and is often favoured over pharmacologic cardioversion; data on ibutilide and procainamide in pregnancy are limited, so reserve them for situations where cardioversion cannot be delayed. Anticoagulation follows the identical approach to AF in pregnancy (low-molecular-weight or unfractionated heparin preferred over DOACs and warfarin) — see the Atrial Fibrillation chapter.

Breastfeeding

Beta-blockers used for rate control are generally considered compatible with breastfeeding, as in AF; anticoagulant selection in lactation follows the same approach described in that chapter.

Chronic obstructive pulmonary disease and other pulmonary disease

Flutter has a particularly strong, classic association with COPD and other chronic pulmonary disease. Avoid nonselective beta-blockers given the bronchospasm risk; a cardioselective agent (metoprolol, bisoprolol) or a non-dihydropyridine calcium channel blocker is preferred. Treating the underlying pulmonary exacerbation often substantially eases rate control, and sometimes resolves the flutter altogether.

Recent cardiac surgery

Flutter — often atypical, scar-related to the surgical atriotomy — is common in the early postoperative period and is frequently self-limited. When temporary epicardial pacing wires are present, overdrive atrial pacing can terminate it without cardioversion or additional drug therapy.

Digoxin toxicity

New or worsening flutter with high-grade or unusually regular AV block in a patient taking digoxin should prompt a digoxin level and toxicity workup — not simply the addition of more AV-nodal-blocking therapy.

Patients with a prior AF or flutter ablation

New flutter after a prior ablation — including a prior AF ablation — is a recognized presentation of scar/"gap"-related atypical flutter; refer back to electrophysiology rather than assuming the original procedure has simply failed outright.

Renal impairment and elderly patients

Ibutilide and procainamide carry a higher proarrhythmic/torsades risk in elderly patients and in significant structural heart disease — use with caution and continuous ECG monitoring. Renal-function-based anticoagulant dosing principles are identical to AF and are not repeated here.

• Renal function and anticoagulation monitoring follow the identical cadence as atrial fibrillation — not repeated here; see that chapter.
• Reassess ventricular rate control and symptom burden at routine follow-up, and escalate toward ablation referral rather than simply re-reassuring if targets are not being met.
• After cavotricuspid isthmus ablation, confirm the treating electrophysiologist has documented procedural success (bidirectional isthmus block), and monitor for symptomatic recurrence.
• Actively monitor for the development of atrial fibrillation even after a technically successful flutter ablation. Because the same diseased atrial substrate that produced the flutter often also predisposes to AF, a substantial proportion of patients develop AF after CTI ablation. Continue anticoagulation based on the ongoing CHADS-65 result and current risk factors — not on the flutter having been "cured."
• Continuous ECG/QTc monitoring during and for several hours after ibutilide or procainamide administration, given their torsades de pointes risk.
• Periodic TSH follow-up if hyperthyroidism was identified as a contributing, reversible factor.

1. Inadequate rate control despite an optimized beta-blocker or non-dihydropyridine CCB, with or without digoxin: refer promptly for cavotricuspid isthmus ablation for typical flutter, rather than continuing to escalate rate-control drug doses — ablation's high success rate makes this a preferred next step sooner than the equivalent point in AF management.
2. Recurrent flutter after electrical or pharmacologic cardioversion: refer for cavotricuspid isthmus ablation.
3. Recurrent typical flutter after a prior cavotricuspid isthmus ablation (isthmus gap reconduction): repeat ablation — still associated with a high success rate.
4. Atypical flutter refractory to rate or rhythm control: refer for specialist electrophysiology assessment and 3D electroanatomic mapping-guided ablation.
5. New atrial fibrillation identified after a successful flutter ablation: manage as AF per that chapter, including reassessing and continuing or resuming anticoagulation based on CHADS-65 — a "cured" flutter does not mean stroke risk has resolved.
6. Stroke or TIA despite therapeutic anticoagulation, or bleeding on anticoagulation: manage identically to AF — see that chapter; not repeated here.

• Treating flutter's stroke risk as lower than AF's, or withholding anticoagulation because it is "just flutter" — the CHADS-65 algorithm and its recommendation are identical.
• Using flecainide or propafenone for flutter without a concurrent AV-nodal-blocking agent — this risks a rate-slowed 1:1 conduction and a dangerous, rapid ventricular response.
• Missing flutter with 2:1 block because the ventricular rate looks like an unremarkable, perfectly regular tachycardia near 150 bpm.
• Escalating rate-control drug doses indefinitely rather than referring for cavotricuspid isthmus ablation once first-line therapy proves inadequate for typical flutter.
• Treating a technically successful cavotricuspid isthmus ablation as having eliminated all future arrhythmia or stroke risk — atrial fibrillation frequently develops afterward from the same diseased atrial substrate.
• Missing digoxin toxicity as a cause of new-onset flutter with high-grade AV block, and responding by adding more AV-nodal-blocking therapy instead of checking a level and holding the drug.
• Giving ibutilide without first correcting potassium and magnesium, or without the required continuous ECG monitoring for at least 4 hours afterward, given its real torsades de pointes risk.
• Assuming atypical flutter will respond to cavotricuspid isthmus ablation the same way typical flutter does — it requires a different, more complex mapping-guided procedure and carries a lower success rate.

How to use this table: Anticoagulants (DOACs and warfarin) for stroke prevention are identical to atrial fibrillation and are covered in full in the Atrial Fibrillation chapter's drug tables — they are not repeated here. This table covers only the drug classes genuinely specific to, or genuinely different in, atrial flutter: rate control and pharmacologic cardioversion. Doses are adult doses and require patient-specific confirmation, including renal/hepatic adjustment. Select any drug name to open its complete Pharmasist Drug Database page.

Rate control — beta-blockers

Preferred class for rate control at any left ventricular ejection fraction. Flutter's single, fixed-rate reentrant circuit is frequently harder to control than AF's more chaotic conduction, so higher or combination dosing is common.

Rate control — non-dihydropyridine calcium channel blockers

Use only if LVEF is greater than 40% — negative inotropy can worsen heart failure with reduced ejection fraction.

Rate control — cardiac glycoside

Add-on when first-line therapy is insufficient. Notably less useful as monotherapy in flutter than in AF, since it does not blunt the fixed, rapid atrial rate driving conduction.

Pharmacologic cardioversion — Class III antiarrhythmic

Ibutilide is generally preferred over other pharmacologic cardioversion agents specifically because its efficacy in flutter meaningfully exceeds its efficacy in AF — a genuine point of difference from atrial fibrillation management.

Pharmacologic cardioversion — Class Ia antiarrhythmic

An alternative to ibutilide, and the preferred agent specifically when pre-excitation (Wolff-Parkinson-White) is suspected, since it slows accessory-pathway conduction directly.

Rhythm control — special situation

Reserved, as in AF, for reduced ejection fraction or refractory disease given its toxicity burden.