Where is the most common origin of a narrow complex tachycardia?

The most common origin of a narrow complex tachycardia is indeed from the atria. This is primarily due to the fact that narrow complex tachycardias are typically associated with rapid electrical activity originating above the ventricles, specifically in the atria or the atrioventricular junction.

In such cases, the electrical impulses travel through the conduction system and to the ventricles in a normal, efficient manner, resulting in narrow QRS complexes on the electrocardiogram (ECG). Common forms of narrow complex tachycardias include atrial flutter, atrial fibrillation with a rapid ventricular response, and paroxysmal supraventricular tachycardia (SVT), which often involves reentrant circuits originating in or near the atria.

While the term "supraventricular" encompasses a similar range of mechanisms as those originating in the atria, the specific mention of atrial as the most common source of these rhythms indicates a focus on the origin of the tachycardia rather than its classification. The sinus node, while an important pacemaker of the heart, is less frequently the originating site of tachycardic rhythms compared to atrial reentrant mechanisms or ectopic atrial foci. This