EP Staff Education Clinical Staff Ilyas Colombowala, MD, FACC, FHRS →
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Procedure

Atrial Flutter Ablation (CTI)

Catheter ablation of the cavotricuspid isthmus to interrupt the typical right atrial flutter circuit. High success, short procedure, low complication rate.

Typical duration
1.5–2 h
Sedation
Moderate sedation

Equipment & setup

  • ▸Femoral venous access kit, single or dual right groin
  • ▸Long sheath (SR0 or Mobile) for catheter stability across the isthmus
  • ▸Decapolar catheter for coronary sinus and right atrial activation reference
  • ▸Duodecapolar or Halo catheter for tricuspid annular mapping (optional)
  • ▸Ablation catheter — irrigated tip RF (ThermoCool, FlexAbility) or contact-force
  • ▸3D electroanatomic mapping system (often used selectively, not always required)
  • ▸Activated clotting time monitor and heparin
  • ▸Fluoroscopy with right anterior oblique and left anterior oblique views

Common pitfalls

  • ▸Pouches and recesses in the isthmus producing skip lesions and gaps
  • ▸Failure to achieve bidirectional block — must confirm with differential pacing
  • ▸Eustachian ridge prominence blocking catheter reach to the IVC
  • ▸Inadvertent right coronary artery injury (rare, usually with deep grooves)
  • ▸AV nodal damage from catheter migration superiorly during ablation
  • ▸Missing left atrial atypical flutter when CTI ablation fails to terminate the arrhythmia

Indications

  • Symptomatic typical (CTI-dependent) atrial flutter — first-line, often preferred over chronic antiarrhythmics
  • Recurrent flutter despite rate or rhythm control
  • Flutter induced by class IC or amiodarone therapy for AF — common in patients on rhythm control
  • Tachycardia-mediated cardiomyopathy from persistent flutter
  • Combined PVI + CTI in patients with both AF and documented typical flutter

Less straightforward:

  • Atypical flutter — requires 3D mapping and is a different (longer, harder) procedure
  • Asymptomatic flutter with good rate control and tolerated anticoagulation

Pre-procedure prep

  • Anticoagulation for at least 3 weeks at therapeutic levels, or TEE within 24 hours if duration uncertain
  • Anticoagulation rules for flutter mirror AF — do not skip this
  • NPO after midnight, baseline ECG, electrolytes, INR if on warfarin
  • Antiarrhythmics: typically continued through the procedure; useful for inducing the arrhythmia if not present
  • Sedation plan: most CTI ablations are well tolerated under moderate sedation; general anesthesia rarely needed unless patient factors dictate

Setup & equipment

  • Single right femoral vein access is often sufficient; dual access for cases requiring mapping catheter
  • Decapolar catheter to the coronary sinus through the os, proximal poles in the RA
  • Ablation catheter via a long sheath to improve stability across the isthmus
  • Heparin to ACT 250–300 once catheters are in
  • 3D mapping optional for routine typical flutter; mandatory for atypical

Technique

Confirming the diagnosis

  • In flutter at the start: activation mapping shows counterclockwise (or clockwise) rotation around the tricuspid annulus
  • In sinus rhythm: induce with burst pacing from the CS or RA, then confirm circuit with entrainment
  • Entrainment from the isthmus: post-pacing interval equals tachycardia cycle length within 30 ms confirms CTI dependence

Ablation strategy

  • Linear lesion from the tricuspid annulus to the IVC across the cavotricuspid isthmus
  • Start at the ventricular edge — large A and small V signals — and drag toward the IVC
  • 30–50 W irrigated RF, contact force 10–30 g
  • Watch for impedance drop and signal attenuation along the line
  • Anatomic challenges: pouches, ridges, and the Eustachian ridge can require catheter reshaping or switching to a steerable sheath

Confirming bidirectional block

This is the procedural endpoint and easy to falsify if you don’t test rigorously.

  • Pace from CS proximal, observe activation sequence along the lateral RA — should travel up the septum, across the roof, down the lateral wall (counterclockwise around the annulus). No conduction across the isthmus.
  • Pace from lateral RA, observe activation along the CS — should travel up and over the roof to reach CS proximal. No conduction across the isthmus.
  • Differential pacing: pace from sites progressively closer to the line; the local electrogram should appear after the activation has traveled around the annulus
  • Wait 20–30 minutes after the final lesion and reconfirm

If block isn’t durable, look for gaps along the line (often near the Eustachian ridge or ventricular insertion) and touch up.

Atypical flutter notes

  • Build a high-density 3D activation map covering the full tachycardia cycle length
  • Identify the circuit and the critical isthmus
  • Target the narrowest, slowest segment of the circuit
  • Common left atrial circuits: perimitral (requires line to mitral annulus), roof-dependent (line across the roof), septal

Complications

  • Vascular access complications (~1%)
  • AV block (<1%) — from catheter migration superiorly; constant fluoroscopic and electrogram monitoring
  • Right coronary artery injury (rare) — the RCA runs in the AV groove near the isthmus
  • Tamponade (rare with CTI ablation specifically)
  • Recurrence — typical flutter recurrence after documented bidirectional block is 5–10%, usually from line reconnection

Post-procedure care

  • Bed rest 2–3 hours with groin pressure, then ambulate
  • Same-day discharge is standard for uncomplicated cases
  • Anticoagulation continues for at least 4 weeks; long-term anticoagulation per CHA2DS2-VASc
  • Counseling on AF risk: 25–35% of patients develop AF within 2 years even after successful flutter ablation. Set this expectation up front; monitor for it.
  • Follow-up at 4–6 weeks with rhythm assessment

Watch

Short videos to help illustrate this topic. Embedded from the original channels — content belongs to them.

Video pending Add a youtube video ID to display: CTI ablation: anatomy and lesion strategy
CTI ablation: anatomy and lesion strategy · EP teaching channel · Fluoroscopic views and isthmus mapping.

Last reviewed by Dr. Colombowala on May 22, 2026.

Not medical advice. This page is educational. Your situation may differ — discuss it with Dr. Colombowala or your treating physician before making decisions.