Identify the condition characterized by narrow QRS complexes and a regular rhythm.

The condition characterized by narrow QRS complexes and a regular rhythm is atrial tachycardia. In this dysrhythmia, the reentrant circuit or enhanced automaticity in the atria leads to a rapid heart rate typically exceeding 100 beats per minute. The QRS complexes remain narrow because the ventricular depolarization occurs through the normal conduction system, without any interruption or blockage, allowing for efficient conduction from atria to ventricles.

In atrial tachycardia, the rhythm is regular, which means that the intervals between consecutive QRS complexes are consistent. This is a key characteristic that differentiates atrial tachycardia from other conditions that may present with irregular rhythms, such as atrial fibrillation, which features an irregularly irregular rhythm and is characterized by uncoordinated electrical activity in the atria.

In contrast, conditions like ventricular tachycardia feature wide QRS complexes due to the abnormal impulse generation and conduction originating from the ventricles, and sinus bradycardia is identified by a slower heart rate with a normal ventricular conduction pattern, but it does not fit the criteria of having a regular rhythm at a rapid rate. Therefore, the presence of narrow QRS complexes along with a regular rhythm points