ECG Differentiation of SVT, PSVT, and Atrial Flutter

Introduction to SVT and Atrial Flutter

The American Heart Association recommends assessing rhythm regularity to differentiate between atrial fibrillation, multifocal atrial tachycardia, or atrial flutter with variable AV conduction, with irregular ventricular rate suggesting atrial fibrillation, and regular ventricular rate proceeding to next steps to differentiate between atrial flutter, AVNRT, AVRT, or atrial tachycardia 1

Atrial rate of 250-350 bpm, typically 300 bpm, with characteristic "sawtooth" flutter waves best seen in leads II, III, aVF, and V1, and atrial rate exceeds ventricular rate, with no isoelectric baseline between flutter waves, according to the European Society of Cardiology 1, 2
Variable AV block produces different ventricular rates, such as alternating 2:1 and 4:1 conduction, as stated by the American College of Cardiology 1

Rate typically 150-250 bpm with extreme regularity after first 10-20 beats, with P waves hidden within or at the terminal portion of QRS, and pseudo S-waves in inferior leads and pseudo R' in V1, as described by the European Heart Journal 1, 2, 3
"Short RP" pattern, with RP interval less than PR interval, and 1:1 AV relationship, with rare exceptions of 2:1 block, according to the American Heart Association 1, 3

Rate 150-250 bpm with regular rhythm, and P wave visible in early ST-T segment following QRS, with RP interval typically 70-100 msec or longer, and "Short RP" pattern in typical orthodromic AVRT, as stated by the American College of Cardiology 1, 3
May show pre-excitation, delta wave, on baseline sinus rhythm ECG if Wolff-Parkinson-White syndrome, according to the European Society of Cardiology 1

Rate typically 150-250 bpm, with P wave morphology differing from sinus and usually visible near end of or after T wave, and "Long RP" pattern, with RP interval greater than PR interval, because rhythm is driven by atrium with normal AV conduction, as described by the American Heart Association 1, 2
1:1 AV conduction in most cases, according to the European Heart Journal 1

Atrial fibrillation with prominent atrial activity is frequently misdiagnosed as atrial flutter, with only 31% of physicians correctly identifying AF with prominent atrial activity in multiple leads, and wide-complex tachycardia requires different approach, with QRS greater than 120 ms may representing ventricular tachycardia or SVT with aberrancy, as stated by the American College of Cardiology 1, 3
The presence of AV dissociation or fusion complexes confirms VT, according to the European Society of Cardiology 1, 3