When might a patient develop wide QRS complexes in arrhythmias?

A patient develops wide QRS complexes primarily during ventricular tachycardia (VT), which is characterized by a rapid heart rate originating from the ventricles. In this condition, the electrical impulses are conducted through the ventricles in an abnormal manner, which leads to a prolonged duration of the ventricular depolarization. This results in the appearance of wide QRS complexes on an electrocardiogram (ECG).

In contrast, supraventricular tachycardia (SVT) typically shows narrow QRS complexes because the originating rhythm comes from above the ventricles, where the conduction remains normal and does not affect the width of the QRS complex. Asystole indicates a complete absence of electrical activity in the heart and does not produce any QRS complexes. Atrial fibrillation may exhibit varying QRS widths, but it usually presents with narrow complexes as well, given that the impulses are still conducted through the ventricles without any delay.

Thus, the presence of wide QRS complexes is most notably associated with ventricular tachycardia, marking it as a critical distinguishing feature of this arrhythmia.