Cardiovascular · Topic 16 of 48

Atrial Flutter

Cardiovascular · arrhythmia

Atrial Flutter

A sawtooth right-atrial circuit at about 300 per minute, usually conducted 2:1 at 150 — cardiovert, anticoagulate like AF, and ablate the isthmus.

Key numbers

Sawtooth flutter waves in II, III, aVFatrial ~300/min

2:1 block: regular rate of 150ventricular ~150/min

Synchronized cardioversion, starting at 200 J200 J

Isthmus ablation cures typical fluttercure > 95%

01 · Look for2:1 block: regular rate of 150

The AV node usually conducts every second flutter wave (2:1 block), giving a regular ventricular rate of about 150/min; suspect flutter in any regular narrow-complex tachycardia at 150.

02 · DoSynchronized cardioversion, starting at 200 J

Synchronized cardioversion is the treatment of choice for most initial episodes and is mandatory with 1:1 conduction or hemodynamic compromise; the 2025 AHA initial energy is 200 J, escalating if it fails.

03 · DoIsthmus ablation cures typical flutter

Catheter ablation across the cavotricuspid isthmus cures typical flutter in more than 95% of patients and prevents recurrence more effectively than antiarrhythmic drugs.

What it is

Core idea

Typical flutter: right atrial isthmus macroreentryTypical flutter is a right atrial macroreentrant circuit around the tricuspid annulus through the cavotricuspid isthmus; counterclockwise rotation gives the classic negative sawtooth in the inferior leads.

Causes & risk factors

Why it happens

Flutter and AF travel togetherMost patients with flutter have or develop AF (69% already had AF at first flutter diagnosis); AF often appears after isthmus ablation, so continue anticoagulation if AF was ever documented.

Presentation

What you'll see

Adenosine or vagal maneuvers unmask flutter wavesCarotid sinus massage or adenosine briefly increases AV block and exposes hidden flutter waves, but does not usually terminate flutter — a diagnostic, not therapeutic, response.

Variable block makes flutter irregularBlock can vary beat to beat, making the ventricular rhythm irregular and mimicking AF, or be fixed at 3:1 or 4:1, giving slower regular rates.

Diagnosis & monitoring

Work-up

Sawtooth flutter waves in II, III, aVF must knowTypical flutter shows continuous, regular sawtooth flutter waves, most obvious in the inferior leads II, III and aVF, at an atrial rate of 250–350/min (typically 300).

Do right now

In this order

First moves

Synchronized cardioversion, starting at 200 J200 J

→

Rate control: beta-blocker or diltiazem

→

Anticoagulate flutter exactly like AF

Why each step

Synchronized cardioversion, starting at 200 JSynchronized cardioversion is the treatment of choice for most initial episodes and is mandatory with 1:1 conduction or hemodynamic compromise; the 2025 AHA initial energy is 200 J, escalating if it fails.

Rate control: beta-blocker or diltiazemControl the rate with a beta-blocker or nondihydropyridine CCB (diltiazem, verapamil), as in AF; rate control is harder to achieve in flutter, which is why cardioversion is often preferred.

Anticoagulate flutter exactly like AFAnticoagulation for atrial flutter follows the same CHA₂DS₂-VASc risk rules as AF, including 3 weeks of anticoagulation (or TEE) before elective cardioversion and at least 4 weeks after cardioversion or ablation.

Management

Orders

Ibutilide converts flutter better than AFIV ibutilide (1 mg over 10 minutes if ≥ 60 kg) converts flutter more often than AF; it prolongs QT, so monitor the ECG for 4 hours after the infusion for torsades.

Red flags & don'ts

Avoid harm

Block the AV node before class IC/IA drugs avoidClass IA and IC drugs (procainamide, flecainide, propafenone) can slow the flutter rate and speed AV conduction enough to cause 1:1 conduction and a paradoxical rate surge; give an AV-nodal blocker first.

Atrial flutter or atrial fibrillation?

Commonly confused

Atrial activity	Regular sawtooth flutter waves, 250–350/min
Ventricular rhythm	Usually regular, often 150 with 2:1 block
Ablation	Cavotricuspid isthmus line cures > 95%
Anticoagulation	Same CHA₂DS₂-VASc rules as AF

More detail

Reference

Show 6 reference facts

After isthmus ablation, about a third of patients develop AF within 14 months (53% with prior AF vs 23% without at 16–18 months), and 60–70% by 5 years.

Thromboembolic risk with isolated flutter is thought to be about half that of AF, but guidelines do not distinguish them for anticoagulation because AF so often coexists.

Atypical (non-isthmus-dependent) flutter uses another circuit, often scar after cardiac surgery or AF ablation, and is managed like AF; the old type I/II flutter terminology is no longer used.

Regular flutter below 120/min may cause few symptoms; faster or variable conduction causes palpitations, and the jugular venous pulse may show flutter a waves.

Atrial fibrillation, by contrast, has no P waves, chaotic fibrillatory waves and an irregularly irregular rhythm; elective cardioversion starts at ≥ 200 J biphasic and pulmonary vein isolation succeeds in 60–80%.

Overdrive (rapid atrial) pacing can terminate flutter as an alternative to shock, and antitachycardia pacing is a rare long-term option in patients who also need a pacemaker.

Pearl

A regular narrow tachycardia at exactly 150 is atrial flutter with 2:1 block until proven otherwise.

Sources · Merck Manual Professional — Atrial Flutter · Joglar JA et al. 2023 ACC/AHA/ACCP/HRS Guideline for the Diagnosis and Management of Atrial Fibrillation (includes typical atrial flutter). Circulation 2024;149:e1–e156 · Merck Manual Professional — Atrial Fibrillation · Corvert (ibutilide fumarate) injection prescribing information — DailyMed · 2025 AHA Guidelines for CPR and ECC — Part 9: Adult Advanced Life Support (Circulation 2025; doi 10.1161/CIR.0000000000001376), cpr.heart.org text · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).