Wide-complex QRS complexes may be seen in which of the following conditions?

Wide-complex QRS complexes are characteristic of conditions where the electrical impulse is originating from the ventricles rather than being appropriately conducted through the normal conduction pathways of the heart. Ventricular tachycardia is a situation where the ventricles are not only depolarizing rapidly but are also doing so in a manner that produces a wide QRS complex. This is due to the fact that the impulse is not conducted through the bundle branches, causing it to spread through the ventricular myocardium in a slower manner.

In contrast, sinus tachycardia and atrial fibrillation typically produce normal-width QRS complexes because they involve the atria and have conduction that follows the normal pathway into the ventricles. First-degree AV block may also present normal QRS complexes, as the delay only occurs in the atrioventricular node without affecting the duration of the QRS complex. Therefore, the interpretation of wide-complex QRS complexes being observed most prominently in ventricular tachycardia signifies a critical distinction in understanding cardiac rhythms and identifying potentially life-threatening arrhythmias.