Which of the following is a sign of symptomatic tachycardia?

Symptomatic tachycardia is characterized by a heart rate typically exceeding 100 beats per minute and associated symptoms that may include palpitations, dizziness, shortness of breath, or chest pain. The definition is important in clinical settings as it helps to determine the urgency and method of treatment.

In this situation, a narrow QRS complex with a heart rate exceeding 150 indicates a specific form of tachycardia, often associated with symptoms due to the elevation in heart rate. The significance of a narrow QRS complex is that it suggests a supraventricular origin of the tachycardia, which can lead to reduced cardiac output and resultant symptoms, confirming the diagnosis of symptomatic tachycardia.

A heart rate over 100 is also indicative of tachycardia in general, but it does not specify whether the individual is symptomatic or asymptomatic. Normal blood pressure can be present in many conditions that might not warrant the designation of symptomatic tachycardia. A slow heart rate, on the other hand, directly contradicts the notion of tachycardia, as it indicates bradycardia rather than an elevated heart rate.

Thus, the selection that includes a narrow QRS with a heart rate over 150 is accurate