Narrow complex tachycardia is defined by which criteria?

Narrow complex tachycardia is defined by which criteria?

• A. Heart Rate > 100 BPM and QRS < 120 ms
• B. Heart Rate > 60 BPM and QRS < 100 ms
• C. Heart Rate < 100 BPM and QRS < 120 ms
• D. Heart Rate > 100 BPM and QRS > 120 ms

Answer: (A)

Narrow complex tachycardia means a fast heart rhythm that still uses the normal conduction pathways to activate the ventricles, so the QRS complex stays narrow. The rate part is what defines tachycardia in general—over 100 beats per minute—while the QRS width indicates how the ventricles are being activated. A QRS duration less than 120 milliseconds shows the impulses are conducted through the usual His-Purkinje system, producing a narrow QRS. So the defining combination is a heart rate above 100 BPM with a QRS duration under 120 ms. If the QRS is wider than 120 ms, that suggests a wide complex tachycardia, which often points to a ventricular origin or aberrant conduction rather than a true narrow complex tachycardia. If the rate criterion isn’t met, or the QRS is not narrow, it doesn’t fit this category.

Narrow complex tachycardia means a fast heart rhythm that still uses the normal conduction pathways to activate the ventricles, so the QRS complex stays narrow. The rate part is what defines tachycardia in general—over 100 beats per minute—while the QRS width indicates how the ventricles are being activated. A QRS duration less than 120 milliseconds shows the impulses are conducted through the usual His-Purkinje system, producing a narrow QRS.

So the defining combination is a heart rate above 100 BPM with a QRS duration under 120 ms. If the QRS is wider than 120 ms, that suggests a wide complex tachycardia, which often points to a ventricular origin or aberrant conduction rather than a true narrow complex tachycardia. If the rate criterion isn’t met, or the QRS is not narrow, it doesn’t fit this category.