Differentiating AFIB vs SVT vs VT on EKG Rhythm Strips

Key Distinguishing Features by Rhythm Type

The American College of Cardiology suggests that irregularly irregular R-R intervals with no discernible pattern of variation are indicative of Atrial Fibrillation (AFIB) 2
The European Heart Journal recommends that extremely regular R-R intervals after the first 10-20 beats are characteristic of Supraventricular Tachycardia (SVT) 3, 4, 5
The American Heart Association notes that wide QRS complexes (>120 ms in adults) and QRS morphology different from baseline sinus morphology are hallmarks of Ventricular Tachycardia (VT) 1, 6

The American College of Cardiology advises that irregularly irregular rhythms should be treated as AFIB, while regular or nearly regular rhythms should proceed to further evaluation 2, 3
The European Heart Journal suggests that narrow QRS (<120 ms) is almost always SVT, while wide QRS (>120 ms) should be treated as VT until proven otherwise 1, 3, 4

The American Heart Association warns that hemodynamic stability should not be used to rule out VT, as stable vital signs do not distinguish SVT from VT 1
The American College of Cardiology recommends that uncertain diagnoses with wide QRS tachycardia should always be treated as VT, given the higher mortality risk 1

The European Heart Journal suggests that vagal maneuvers or adenosine administration can help differentiate between sinus tachycardia, SVT, and VT, as sinus tachycardia will gradually slow, SVT will either abruptly terminate or transiently slow, and VT will typically not respond 2, 1