Confusable diagnoses · PANCE / PANRE

Atrial Flutter vs Supraventricular Tachycardia

Written & clinically reviewed by Ryan Busch, PA-C · Updated August 2026 · Report an error

Atrial Flutter and Supraventricular Tachycardia are easy to mix up on the boards. Here's a side-by-side comparison — presentation, workup, imaging, and first-line treatment — drawn from our full outlines.

Atrial Flutter vs Supraventricular Tachycardia at a glance

  • Atrial Flutter: Macro-reentrant atrial tachycardia with sawtooth flutter waves; treated like AFib for stroke risk.
  • Supraventricular Tachycardia: Regular narrow-complex tachycardia from reentry involving AV node ± accessory pathway — vagal maneuvers, adenosine, ablation.

Try two board-style questions on Atrial Flutter vs Supraventricular Tachycardia

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Question 1CardiovascularMedium
A 78-year-old woman is found unresponsive. EMS obtains an ECG showing a sawtooth flutter pattern at an atrial rate of 300 bpm with a ventricular rate of 150 bpm. Her BP is 78/50. What is the immediate treatment?
  • AIV diltiazem infusion
  • BIV amiodarone infusion
  • CIV adenosine 6 mg push
  • DSynchronized cardioversion
Reveal answer & full explanation
Correct answer: D — Synchronized cardioversion
  • AIV diltiazem infusion
  • BIV amiodarone infusion
  • CIV adenosine 6 mg push
  • DSynchronized cardioversion✓

Why synchronized cardioversion is correct

  • Atrial flutter with hemodynamic instability (BP 78/50) requires immediate synchronized cardioversion.
  • The classic sawtooth pattern at a 300 bpm atrial rate with 2:1 conduction gives a ventricular rate of approximately 150 bpm, which is typical of atrial flutter.
  • Cardioversion is highly effective for atrial flutter, often requiring only 50–100 J.

Why the others are wrong

  • A) IV diltiazem infusion — rate-control agents act too slowly in an unstable patient and risk further hypotension.
  • B) IV amiodarone infusion — also acts too slowly and risks further hypotension in hemodynamic instability.
  • C) IV adenosine 6 mg push — transient AV nodal blockade may unmask flutter waves diagnostically, but adenosine does not terminate atrial flutter and wastes time in a peri-arrest patient.
Question 2CardiovascularEasy
A 25-year-old woman presents with palpitations that began abruptly 30 minutes ago while she was seated at her desk. She has no chest pain, dyspnea, or syncope and takes no medications. ECG shows a regular, narrow-complex tachycardia at 155 beats/min without discernible P waves. The rhythm abruptly converts to normal sinus rhythm during a Valsalva maneuver. Which of the following is the most likely diagnosis?
  • AAtrioventricular nodal reentrant tachycardia
  • BEctopic (focal) atrial tachycardia
  • CInappropriate sinus tachycardia
  • DAtrial flutter with 2:1 atrioventricular conduction
Reveal answer & full explanation
Correct answer: A — Atrioventricular nodal reentrant tachycardia
  • AAtrioventricular nodal reentrant tachycardia✓
  • BEctopic (focal) atrial tachycardia
  • CInappropriate sinus tachycardia
  • DAtrial flutter with 2:1 atrioventricular conduction

Why Atrioventricular nodal reentrant tachycardia is correct

  • AVNRT is the most common paroxysmal supraventricular tachycardia, classically in young adults with structurally normal hearts
  • Abrupt onset and abrupt termination with a vagal maneuver are characteristic: increased vagal tone blocks conduction in the AV node and breaks the reentrant circuit
  • Absent discernible P waves fit AVNRT — the retrograde P wave is buried within the QRS complex
  • Acute management is vagal maneuvers, then adenosine; catheter ablation is definitive, with a >95% cure rate

Why the others are wrong

  • Ectopic (focal) atrial tachycardia — an automatic atrial focus warms up and slows gradually rather than starting and stopping abruptly, and vagal maneuvers increase AV block to expose the atrial rate rather than restore sinus rhythm (trap: assuming any regular narrow-complex tachycardia is atrial in origin)
  • Inappropriate sinus tachycardia — sinus mechanisms accelerate and decelerate gradually and only transiently slow with vagal maneuvers; they do not abruptly convert (trap: ignoring the abrupt on-off behavior)
  • Atrial flutter with 2:1 atrioventricular conduction — flutter near 150/min mimics SVT, but vagal maneuvers merely increase AV block and unmask flutter waves; they do not convert flutter to sinus rhythm (trap: buzzword-matching the rate near 150)
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Side-by-side comparison

FeatureAtrial FlutterSupraventricular Tachycardia
At a glanceMacro-reentrant atrial tachycardia with sawtooth flutter waves; treated like AFib for stroke risk.Regular narrow-complex tachycardia from reentry involving AV node ± accessory pathway — vagal maneuvers, adenosine, ablation.
Classic presentationECG: 'sawtooth' flutter waves (negative deflections in II, III, aVF and positive in V1) in typical counterclockwise flutter.; Often more symptomatic than AFib due to faster, regular ventricular rates; Palpitations, dyspnea, exercise intolerance; Lightheadedness, chest discomfort; May present as new HF or with embolic stroke; Regular…Sudden-onset palpitations with abrupt termination; Lightheadedness, dyspnea, anxiety; Chest pressure, near-syncope or syncope; Polyuria after episode (atrial natriuretic peptide release); Pre-existing WPW: may present with palpitations or rarely sudden death from pre-excited atrial fibrillation degenerating to VF; Regular rapid pulse…
Workup / key labsTSH, CBC, BMP, magnesium; Coagulation studies; Troponin if ischemia in differentialTypical AVNRT: rate 150-250, narrow QRS, retrograde P waves not visible or just after QRS as pseudo-R' in V1 / pseudo-S in inferior leads. Orthodromic AVRT: retrograde P visible after QRS in ST segment. Manifest WPW on resting ECG: PR <120 ms + delta wave + wide QRS + secondary ST-T changes.; Electrolytes, magnesium, TSH; CBC if anemia…
Imaging12-lead ECG — diagnostic when flutter waves visible; 2:1 conduction can hide them (rate 150 should prompt vagal maneuvers or adenosine to unmask); TTE for LA size, LV function, valve disease; TEE prior to cardioversion if duration unknown/>48 h and not adequately anticoagulated12-lead ECG during tachycardia and in sinus rhythm; Echocardiogram to assess for structural disease, especially before ablation; Holter or event monitor for diagnosis if episodes are infrequent; Electrophysiology study — diagnostic and therapeutic (ablation)
First-line treatmentHemodynamically unstable (hypotension, altered mental status, shock, pulmonary edema, ischemia) → immediate synchronized cardioversion. If stable, acute rate control: same as AFib — IV beta-blocker or non-DHP CCB; Anticoagulation: same CHA2DS2-VASc-based decision as AFib (flutter carries equivalent stroke risk). Before elective…Stable narrow-complex SVT: vagal maneuvers first — Valsalva (modified REVERT maneuver — supine with leg lift improves success), carotid sinus massage (avoid bilateral or in patients with carotid bruits or recent TIA); Adenosine 6 mg rapid IV push followed by saline flush; if no conversion in 1-2 min, give 12 mg, then repeat 12 mg — warn…

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Full outlines

Atrial Flutter Supraventricular Tachycardia (AVNRT / AVRT) All 514 diagnoses

Educational use only. This outline is a study aid for PA students and is not medical advice or a substitute for clinical judgment. FirstPassPA is an independent study tool and is not affiliated with, endorsed by, or sponsored by NCCPA or PAEA. PANCE® and PANRE® are registered trademarks of the National Commission on Certification of Physician Assistants; End of Rotation™ is a program of the Physician Assistant Education Association.