Which of the following arrhythmias is classified as a narrow-complex tachyarrhythmia?

A narrow-complex tachyarrhythmia is characterized by a rapid heart rate (more than 100 beats per minute) with a QRS complex duration of less than 120 milliseconds. In this case, all of the listed arrhythmias fall under the category of narrow-complex tachyarrhythmias.

Atrial flutter is a type of supraventricular tachycardia with a characteristic "sawtooth" pattern of P-waves. The ventricular response can be rapid, and the QRS complexes typically remain narrow.

Atrial fibrillation involves disorganized electrical activity in the atria, leading to an irregularly irregular heart rate. Despite the irregularity, the QRS complexes are usually narrow as long as there is normal conduction through the ventricles.

Sinus tachycardia, which originates from the sinoatrial node, entails an increase in heart rate due to various physiological or pathological stimuli. Here, the QRS complexes also remain narrow.

Because each of these arrhythmias has a narrow QRS complex despite differences in their electrical activity and origins, the correct classification includes all of them as narrow-complex tachyarrhythmias. This understanding is crucial in recognizing and managing these conditions effectively during advanced life support