Atrial Flutter: What It Is, Why It Matters, and How Ablation Can Cure It

A highly curable arrhythmia — if properly diagnosed and treated

Atrial flutter is one of my favourite conditions to discuss with patients — not because the diagnosis is welcome news, but because the treatment story is genuinely one of the most satisfying in cardiology. For the most common form of atrial flutter, catheter ablation offers cure rates of 90–95%, with a remarkably elegant and technically straightforward procedure. Patients who have lived with months or years of debilitating symptoms can often walk away after a day-case procedure with a completely normal heart rhythm.

But atrial flutter is also one of the most misunderstood and undertreated arrhythmias in general medicine. So let me explain what it is, why it matters, and what can be done about it.

What Exactly is Atrial Flutter?

Atrial flutter is a rapid but organised heart rhythm that arises in the upper chambers of the heart — the atria. Unlike atrial fibrillation, where electrical activity is chaotic and random, atrial flutter involves a very specific, predictable electrical circuit. The most common form — known as typical or CTI-dependent (cavotricuspid isthmus-dependent) flutter — involves a large re-entrant circuit in the right atrium that travels around the tricuspid valve. The atria fire at approximately 300 beats per minute in this circuit.

Because the human AV node cannot conduct 300 beats per minute to the ventricles, it acts as a filter. Most commonly, every second atrial beat is conducted — producing a ventricular rate of approximately 150 beats per minute (2:1 block). This typically produces a rapid but regular pulse of precisely 150 bpm — a pattern that should always prompt an ECG, as it is a classic presentation of flutter.

On the ECG, typical flutter produces a characteristic ‘sawtooth’ pattern in the inferior leads — regular flutter waves at 300 per minute with the hallmark negative-positive morphology. Recognising this pattern is straightforward once you know what to look for, and it is one of the reasons that a 12-lead ECG is so valuable in assessing palpitations.

How is Atrial Flutter Different from AF?

This is the question I am asked most often when a patient receives a flutter diagnosis. The key differences are:

• Rhythm regularity: Flutter produces a regular pulse (at 150 bpm with 2:1 block, or 100 bpm with 3:1 block). AF produces an irregularly irregular pulse.
• Mechanism: Flutter involves a defined, predictable re-entrant circuit. AF involves chaotic, disorganised electrical activity from multiple sites.
• Treatability: Typical flutter is more predictably curable than AF with a single catheter ablation procedure.

Despite these differences, the two conditions share the same stroke risk profile. Atrial flutter increases the risk of stroke by a similar mechanism to AF — the atria do not contract effectively during flutter (particularly at high rates), blood stagnates in the left atrial appendage, and clots can form. The CHA₂DS₂-VA stroke risk scoring system applies to flutter in exactly the same way as AF, and anticoagulation decisions are made on the same basis.

Can Atrial Flutter Be Cured?

For typical CTI-dependent flutter, yes — and this is the message I most want patients to take from this article. Catheter ablation of the cavotricuspid isthmus (CTI) — a narrow strip of tissue in the right atrium that forms the critical isthmus of the re-entrant circuit — interrupts the flutter permanently. Creating a line of scar tissue across this isthmus renders the circuit non-conductive, and the flutter cannot occur. The procedure is technically straightforward compared with AF ablation, can usually be performed under conscious sedation, and takes approximately 45–90 minutes. Success rates are 90–95%, with low recurrence rates.

I perform CTI ablation for atrial flutter at OneWelbeck Heart Health as a day-case procedure. Patients typically go home the same day and return to normal activity within a few days.

The Relationship Between Flutter and AF

One important caveat to discuss with patients before flutter ablation is that approximately 25–30% of patients who undergo successful flutter ablation will subsequently develop AF, often within two to three years. This is because flutter and AF frequently share the same underlying atrial substrate — enlargement, hypertension, sleep apnoea — and eliminating flutter does not address that substrate. This risk does not change the recommendation for flutter ablation, but it does mean that ongoing monitoring is important, and that optimisation of the AF risk factors discussed elsewhere on this site remains relevant.

To discuss SVT or palpitations with Dr Boon Lim, book a consultation at OneWelbeck Heart Health — drboonlim.co.uk or call 0208 187 9888