AtrialFlutter

Symptomatic atrial flutter · complete reference · all trials · full doses + brand names · Full Card

Symptoms / Associated Sx

• Regular rapid palpitations; dyspnea; fatigue; reduced exercise tolerance; chest discomfort; presyncope; visible rapid regular neck vein pulsations at 300/min

• Typical ventricular rate ~150 bpm (2:1 AV block) — any regular tachycardia at exactly 150 bpm should trigger flutter on the differential until adenosine challenge; 3:1 block = 100 bpm; 4:1 block = 75 bpm; variable block mimics AF with irregular rhythm

• Hemodynamic compromise if rapid rate + underlying HF, severe valvular disease, or RV dysfunction (pulmonary HTN/COPD); hemodynamic instability = cardioversion indication

• Post-cardiac surgery flutter (POAF): peaks Days 2–5 post-CABG or valve surgery; often self-limited but requires anticoag; CTI-dependent flutter common; incisional reentry also possible

Neg

• Pt denies irregularly irregular pulse with absent P waves and fibrillatory ECG baseline — argues against AF (AF has variable ventricular rate; flutter has regular ventricular rate from fixed AV block ratio; both carry same stroke risk and require same anticoag algorithm)

• Pt denies regular narrow tachycardia that terminates completely and abruptly with adenosine 6 mg IV — argues against SVT/AVNRT (adenosine terminates SVT by blocking AV node; adenosine in flutter → transient AV block → flutter waves visible for 3–5 seconds → flutter immediately resumes at same rate; adenosine is diagnostic in flutter, NOT therapeutic)

• Pt denies regular rate-appropriate tachycardia with upright P waves in I+aVF and P:QRS 1:1 — argues against sinus tachycardia (sinus tachy = physiologic response; treat the cause; never rate-control sinus tachycardia with AV nodal blockers)

• Pt denies wide complex irregular tachycardia at rates >200 bpm with delta wave on baseline ECG — argues against WPW with any tachyarrhythmia (WPW: NEVER adenosine/BB/CCB/digoxin → AV block → accessory pathway conduction → VF; procainamide [Pronestyl] or cardioversion only)

• Pt denies rapid junctional rhythm (100–150 bpm) with retrograde P or absent P, in post-cardiac surgery or digoxin toxicity context — argues against junctional tachycardia (digoxin toxicity: check digoxin [Lanoxin] level; post-surgery: observe — usually self-limited)

Social History (SHx)

• Prior flutter episodes and prior ablation (CTI ablation: >90% cure; if ablation failed or recurred → EP re-evaluation; left atrial flutter post-AF ablation requires different ablation approach); prior cardioversions

• Prior cardiac surgery (CABG/valve/ASD closure/Fontan/TGA repair — scar-based reentry circuits; standard CTI ablation will NOT cure); prior AF ablation (left atrial flutter from PV isolation gap — most common 1–6 months post-ablation); COPD/pulmonary HTN (↑RA pressure → RA dilation → flutter substrate)

• CHA2DS2-VASc score; current anticoagulation and adherence; family history

Main Etiology

• Typical CTI-dependent counterclockwise macroreentry (~90% of flutter): reentry circuit travels counterclockwise around the tricuspid annulus through the cavotricuspid isthmus (CTI); ECG: negative sawtooth waves in II/III/aVF, positive in V1/aVR; CTI ablation is curative >90%

• Typical CTI-dependent clockwise macroreentry (~10%): reentry travels clockwise; ECG: positive waves in II/III/aVF; same CTI ablation approach

• Atypical/non-CTI flutter: post-surgical scar circuits (mitral valve repair, CABG, ASD closure, Maze procedure — right or left atrial scar); left atrial flutter (post-AF ablation gap reentry at pulmonary vein isolation scar — presents 1–6 months post-ablation; requires 3D mapping and targeted gap ablation, NOT CTI ablation); IART in repaired congenital heart disease (Fontan: reentry around Fontan baffle; TGA: baffle reentry — EP specialist required)

RF

• Same as AF: HTN (most important modifiable), obesity, DM, OSA, ETOH, older age, family history

• Additional flutter-specific: prior cardiac surgery (POAF flutter in 20–40% post-CABG/valve; scar reentry in complex congenital repair); COPD/pulmonary HTN (↑RA pressure → RA dilation → flutter substrate); repaired congenital heart disease (Fontan, TGA, ASD repair — all create right atrial scar); prior AF ablation (left atrial flutter via gap reentry at PVI scar)

Data

• ECG — 12-lead + long rhythm strip (sawtooth flutter waves at 300 bpm: negative in II/III/aVF + positive in V1/aVR = typical counterclockwise flutter; waves often hidden within QRS or T wave — use long rhythm strip; measure flutter cycle length to confirm 300 bpm; adenosine 6 mg IV rapid IV push → transiently increases AV block → flutter waves unmasked for 3–5 seconds → flutter resumes — diagnostic ONLY, never therapeutic; have crash cart available — brief sinus arrest possible)

• BMP (K+ — target ≥4.0 mEq/L before any antiarrhythmic drug; hypokalemia ↑torsades risk with ibutilide [Corvert]/sotalol [Betapace]/dofetilide [Tikosyn]; Mg2+ — target ≥2.0 mEq/L; replete before antiarrhythmic; Cr — affects DOAC dosing and sotalol/dofetilide dosing)

• TSH (hyperthyroidism — same trigger as AF; obtain in new-onset flutter)

• Troponin I/T (ACS as trigger; demand ischemia from tachycardia; elevated = worse prognosis)

• Echo (TTE) (EF — critical for rate agent selection; same rules as AF: ↓EF = metoprolol [Lopressor], NOT diltiazem [Cardizem]/verapamil [Calan]; LA size; RV size and function — ↑RV = COPD/pulmonary HTN substrate; valvular disease; structural heart disease)

• Coagulation studies (baseline INR; anti-Xa if on DOAC; same anticoag algorithm as AF — flutter carries same thromboembolic risk but is frequently undertreated)

• CHA2DS2-VASc score (same calculation as AF; ≥2 M / ≥3 F → Class I anticoag; flutter commonly undertreated for stroke prevention — a dangerous pattern)

• TEE (LAA thrombus: same 5–15% prevalence as AF if flutter ≥48h or unknown duration; required before elective cardioversion if ≥3 weeks anticoag not confirmed)

DDx

AF (irregularly irregular, fibrillatory baseline, variable ventricular rate — same anticoag algorithm; same stroke risk; both require cardioversion if unstable) · SVT/AVNRT (regular; terminates COMPLETELY with adenosine [Adenocard] — not just slows; retrograde P waves visible post-termination) · Sinus tachycardia (regular P:QRS 1:1; upright P in I+aVF; rate-appropriate for clinical context; treat underlying cause) · Junctional tachycardia (100–150 bpm; P absent or retrograde; post-cardiac surgery or digoxin [Lanoxin] toxicity — check level) · VT with 2:1 retrograde block (wide complex, AV dissociation, fusion/capture beats; ~150 bpm; treat as VT) · Left atrial flutter post-ablation (different morphology; sawtooth less classic; standard CTI ablation will NOT cure; EP referral)

Home Meds

• Continue: anticoagulants (flutter carries same stroke risk as AF — NEVER hold; most dangerous anticoag error = treating flutter as lower stroke risk than AF); BB (carvedilol [Coreg]/metoprolol succinate [Toprol-XL]) for rate control; amiodarone (Pacerone) if prescribed

• Hold: flecainide (Tambocor) and propafenone (Rythmol) if flutter is the presenting rhythm without a concurrent AV nodal blocker (slows flutter cycle → 1:1 AV conduction → ventricular rate 200+ bpm → hemodynamic collapse — Class III contraindication); sotalol (Betapace) and dofetilide (Tikosyn) if QTc >500 ms or K+ <4.0 or Mg2+ <2.0; dronedarone (Multaq) if decompensated HF; NSAIDs

• Adjust: diltiazem (Cardizem) for rate control — use only if EF ≥50% confirmed

Plan

• Hemodynamic stability — assess first: Unstable (SBP <90, AMS, APE, active ischemia) → synchronized DC cardioversion 50–100 J biphasic (flutter cardioverts at lower energy than AF; start at 50 J; escalate to 100 J then 200 J if unsuccessful; higher energy for atypical/LA flutter) | 50 J is usually sufficient for typical CTI flutter — overdosing at 200 J risks post-shock arrhythmia; overdrive pacing via temporary pacemaker wire is an alternative for hemodynamically stable patients with permanent pacing already in place

• Electrolyte correction (before any antiarrhythmic): KCl IV to K+ ≥4.0 mEq/L; MgSO4 2 g IV over 15–30 min; check QTc on ECG (if QTc >500 ms → defer ibutilide [Corvert]/sotalol [Betapace]/dofetilide [Tikosyn])

• Rate control: flutter is notoriously difficult to rate-control (AV nodal agents often produce step-wise rate changes rather than gradual ↓; 2:1 block at 150 → 3:1 at 100 bpm → consider cardioversion instead); diltiazem (Cardizem) 0.25 mg/kg IV over 2 min → 0.35 mg/kg in 15 min if needed → 5–15 mg/hr infusion → ER 120–360 mg PO daily (HFpEF, no structural disease); metoprolol tartrate (Lopressor) 2.5–5 mg IV q5 min ×3 (any patient; preferred if EF unknown or reduced); amiodarone (Pacerone) 150 mg IV over 10 min → 1 mg/min ×6h → 0.5 mg/min ×18h if BB/CCB insufficient; NEVER flecainide (Tambocor) or propafenone (Rythmol) for rate control of flutter — 1:1 conduction risk

• Chemical cardioversion (stable patients): ibutilide (Corvert) 1 mg IV over 10 min → may repeat ×1 in 10 min if no conversion (60–70% conversion rate for flutter; 40–50% for AF; QTc monitoring 4–6h post-infusion; MgSO4 2 g IV bolus at bedside for immediate torsades rescue; avoid if QTc >500 ms, EF <30%, severe hypokalemia/hypomagnesemia); alternatively DC cardioversion 50–100 J synchronized is more reliable and often preferred

• Anticoagulation — identical to AF:

  • Flutter ≥48h or unknown duration before cardioversion → anticoag ≥3 weeks (warfarin [Coumadin] INR 2–3 OR DOAC with verified adherence) OR TEE to exclude LAA thrombus → cardioversion → anticoag ≥4 weeks post-cardioversion mandatory (atrial stunning — same risk as AF)

  • CHA2DS2-VASc ≥2 M / ≥3 F → long-term anticoag: apixaban (Eliquis) 5 mg PO BID preferred (ARISTOTLE data); rivaroxaban (Xarelto) 20 mg PO daily with meal; dabigatran (Pradaxa) 150 mg PO BID; warfarin (Coumadin) INR 2–3 for mechanical valves/moderate-severe MS only

  • Flutter anticoag commonly undertreated: clinicians often (incorrectly) consider flutter lower risk than AF; same CHA2DS2-VASc algorithm; same thromboembolic risk; do not rationalize omitting anticoag

• CTI ablation — refer to EP at every admission for symptomatic typical flutter (Class I, 2023 ACC/AHA): cure rate >90%; annual recurrence <5% post-ablation vs 50–60% on antiarrhythmic drugs; radiofrequency or cryoablation of cavotricuspid isthmus; procedure time 1–2h; same-day discharge in many centers; counsel every patient — ablation is the preferred treatment for typical flutter; not a last resort; no lifelong antiarrhythmic drug needed post-ablation

• Antiarrhythmic drugs (bridge while awaiting ablation or if ablation declined): amiodarone (Pacerone) 400 mg PO TID ×7 days → 200 mg PO daily (most effective for maintenance; annual PFT/TFT/LFT/ophthalmology monitoring; iodine-containing compound); sotalol (Betapace) 80→160 mg PO BID (inpatient initiation required for QTc monitoring ×3 days; reduce dose if CrCl <60; avoid CrCl <40; avoid QTc >500 ms); dofetilide (Tikosyn) 500 mcg PO BID adjusted for CrCl (inpatient initiation mandatory — in-hospital QTc monitoring required; Class I contraindication with verapamil [Calan], ketoconazole, hydrochlorothiazide, trimethoprim); AVOID flecainide (Tambocor)/propafenone (Rythmol) without concurrent BB/CCB

• Left atrial flutter (post-AF ablation): presents 1–6 months post-PVI ablation; different circuit from CTI flutter; standard CTI ablation will NOT cure; requires repeat EP study + 3D electroanatomic mapping + targeted gap ablation at prior PVI scar; refer back to original EP center or experienced AF ablation center

• Congenital heart disease flutter (Fontan/TGA/ASD repair): highly complex circuit; non-CTI macroreentry around surgical scars; EP specialist with congenital heart disease expertise required; standard ablation approaches often insufficient; rhythm control often preferred over rate control for hemodynamic reasons

• PT/OT eval and treat — early ambulation once rate controlled or post-cardioversion; fall precautions while anticoagulated; functional assessment

• Trend daily: BMP (K+ ≥4.0 and Mg2+ ≥2.0; QTc if on antiarrhythmic — hold sotalol [Betapace]/dofetilide [Tikosyn] if QTc >500 ms); ECG (rate + rhythm; spontaneous conversion to SR?); coags (INR if warfarin); telemetry; fever curve

• Escalation triggers: hemodynamic instability at any time → cardioversion 50–100 J · 1:1 AV conduction (ventricular rate 200–300 bpm — after IC antiarrhythmic or spontaneous) → immediate synchronized cardioversion · ibutilide (Corvert)-induced torsades → MgSO4 2 g IV rapid bolus + unsynchronized cardioversion/defibrillation if sustained · QTc >500 ms on antiarrhythmic → hold drug + replete electrolytes + EP consult · refractory rate control despite BB + CCB + amiodarone (Pacerone) → cardioversion is preferred over escalating pharmacologic rate control · post-AF ablation left atrial flutter identified → refer to original EP center (not CTI ablation)

• Discharge: anticoag per CHA2DS2-VASc (apixaban [Eliquis] 5 mg PO BID preferred — flutter carries same stroke risk as AF; this is commonly undertreated); rate control agent at effective dose; EP referral for CTI ablation (Class I — counsel: >90% cure, avoid lifelong antiarrhythmic drugs, preferred treatment for typical flutter); antiarrhythmic bridge only if ablation delayed (amiodarone [Pacerone] 200 mg daily preferred); cardiology/EP f/u 4–6 weeks; anticoag education; return precautions: palpitations + presyncope + syncope + stroke symptoms

⚠ Red Flags

• 1:1 AV conduction (ventricular rate 250–300 bpm) — spontaneous or after flecainide (Tambocor)/propafenone (Rythmol) → immediate synchronized DC cardioversion; IC antiarrhythmics can slow flutter cycle → 1:1 conduction → extreme tachycardia → hemodynamic collapse

• Flecainide (Tambocor) or propafenone (Rythmol) administered for flutter without a concurrent AV nodal blocker → 1:1 conduction → ventricular rates 200+ bpm → cardiogenic shock → Class III contraindication in flutter without AV nodal blocker

• Ibutilide (Corvert)-induced torsades de pointes (2–4% risk) → MgSO4 2 g IV bolus rapidly; sustained VT/VF → defibrillation; always monitor QTc for 4–6h post-ibutilide and have MgSO4 at bedside before infusion

• Left atrial flutter post-AF ablation — standard CTI ablation will NOT cure; must identify the correct circuit with 3D mapping; referring to wrong ablation approach = procedure failure + recurrence + unnecessary radiation exposure

• Atrial flutter in Fontan/repaired congenital heart disease → hemodynamic instability can be rapid due to loss of atrial kick in single-ventricle physiology; EP specialist referral urgently; standard management approaches often insufficient

• Undertreating anticoag in flutter (treating it as lower stroke risk than AF) → same thromboembolic risk; same CHA2DS2-VASc algorithm applies; flutter stroke risk = AF stroke risk

• Cardioverting flutter of unknown duration without TEE or ≥3 weeks anticoag → LAA thrombus risk same as AF (5–15%) → cardioembolic stroke

Senior IM Resident Pearls

• "Regular tachycardia at exactly 150 bpm = atrial flutter until proven otherwise": any regular narrow tachycardia at ~150 bpm → inspect II/III/aVF for sawtooth waves; perform adenosine 6 mg IV (with crash cart) → transient AV block unmasks flutter waves; adenosine terminates SVT but flutter RESUMES after transient slowing; this distinction is diagnostic gold standard at bedside

• Adenosine in flutter — diagnostic only, never therapeutic: adenosine 6 mg IV → transiently increases AV block → flutter waves visible for 3–5 seconds → flutter immediately resumes; adenosine TERMINATES SVT but NOT flutter; distinguish: if tachycardia terminates completely → SVT; if it slows then resumes → flutter; always have crash cart available — brief sinus arrest is possible

• CTI ablation — Class I indication, not last resort: >90% long-term cure; annual recurrence <5% vs 50–60% on antiarrhythmics; many EP centers perform at index hospitalization; procedure time 1–2h; counsel proactively — ablation is the definitive preferred treatment; no lifelong antiarrhythmic drug needed; most patients who remain on antiarrhythmics for flutter are undertreated

• Flutter anticoag = AF anticoag (commonly undertreated): same stroke risk; same CHA2DS2-VASc threshold; same pre-cardioversion anticoag requirements (≥48h or unknown → 3 weeks anticoag or TEE); same post-cardioversion atrial stunning (4 weeks mandatory); do not rationalize omitting anticoag in flutter — pattern of undertreatment is a well-documented clinical error

• Flecainide/propafenone + flutter without AV nodal blocker = 1:1 conduction danger: IC antiarrhythmics slow atrial flutter rate from ~300 to ~200 bpm → AV node can now conduct 1:1 → ventricular rate 200 bpm → hemodynamic collapse; always co-prescribe BB or CCB if IC agent is used; cleaner strategy = amiodarone (Pacerone) + ablation referral

• Left atrial flutter post-AF ablation (gap reentry): presents 1–6 months post-PVI ablation; appears similar to typical flutter on surface ECG but different morphology; standard CTI ablation will definitively NOT cure; requires 3D electroanatomic mapping to identify gap in PVI scar; refer to original EP center; increasing in prevalence as AF ablation volume increases

• Common mistake — flutter in Fontan and repaired congenital heart disease: standard CTI ablation approach may not address the reentry circuit; hemodynamic compromise can be rapid due to AV synchrony dependence; these patients require adult congenital heart disease + EP expertise; never manage complex congenital flutter as routine flutter

• Common mistake — stopping anticoag after flutter cardioversion: atrial stunning persists up to 4 weeks post-cardioversion; mandatory anticoag ≥4 weeks regardless of maintained SR; the same error seen in AF post-cardioversion management