Narrow complex tachycardia (NCT) is often due to supraventricular tachycardia (SVT). SVT with aberrancy, preexcitation, paced rhythm, rate-dependent bundle branch block, preexisting conduction defects or SVT due to drugs, and electrolyte abnormality can also be wide complex. Wide-complex tachycardia (WCT) is often ventricular tachycardia (VT), but fascicular VT (fVT) can present as NCT. Thus, WCT can be either VT or SVT. This has been a perplexing problem for the emergency physician for ages. Here, in this case series, we describe the novel use of point-of-care ultrasound to differentiate SVT from VT. © 2022 Elsevier B.V., All rights reserved.