Which component is NOT used to distinguish sinus tachycardia from reentry supraventricular tachycardia?

Which component is NOT used to distinguish sinus tachycardia from reentry supraventricular tachycardia?

• A. P waves
• B. QRS complex width
• C. PR interval
• D. Heart rate

Answer: (B)

Distinguishing sinus tachycardia from reentry SVT relies on atrial activity and rate more than how wide the ventricular complex is. The QRS width is not a reliable discriminator because both conditions can have a normal, narrow QRS when there’s no aberrant conduction. In sinus tachycardia you typically see visible P waves preceding each QRS with a normal PR interval and a rate that rises in response to physiologic stress. In reentry SVT, P waves may be hidden or appear abnormally related to the QRS, and the rhythm is usually very rapid and regular, with a PR interval that can be normal or difficult to measure. So the QRS width doesn’t help differentiate these two tachycardias, while the presence and timing of P waves, PR interval, and overall rate do.

Distinguishing sinus tachycardia from reentry SVT relies on atrial activity and rate more than how wide the ventricular complex is. The QRS width is not a reliable discriminator because both conditions can have a normal, narrow QRS when there’s no aberrant conduction. In sinus tachycardia you typically see visible P waves preceding each QRS with a normal PR interval and a rate that rises in response to physiologic stress. In reentry SVT, P waves may be hidden or appear abnormally related to the QRS, and the rhythm is usually very rapid and regular, with a PR interval that can be normal or difficult to measure. So the QRS width doesn’t help differentiate these two tachycardias, while the presence and timing of P waves, PR interval, and overall rate do.