If a child has a heart rate of 200 and a rapid rhythm with narrow QRS complexes, what is the likely rhythm?

When encountering a child with a heart rate of 200 beats per minute and a rapid rhythm characterized by narrow QRS complexes, the most likely rhythm is supraventricular tachycardia (SVT). This is primarily due to the nature of SVT, which typically presents with a fast heart rate that originates above the ventricles, often at the atrial level or at the junction of the atria and ventricles.

The key indicators here are the rapid heart rate and the narrow QRS complexes. In SVT, the impulse follows a rapid conduction pathway, which keeps the QRS complexes narrow because the ventricles are depolarizing normally. In children, SVT is one of the more common tachyarrhythmias and can occur due to a reentrant circuit, often at the atrioventricular junction.

Other rhythms listed, such as atrial fibrillation and ventricular tachycardia, have different characteristics. Atrial fibrillation typically presents with an irregularly irregular rhythm and varying QRS complexes, while ventricular tachycardia often shows wide QRS complexes due to abnormal ventricular conduction. Sinus tachycardia, while it can also present with a rapid heart rate, usually occurs in response to physiological stressors and