Sinus Tachycardia:

Sinus tachycardia - emergency medicine approach

Overview

Sinus tachycardia is a physiological increase in sinus node firing that produces a regular, narrow‑complex tachycardia with P waves of sinus morphology.

In the emergency department the priority is recognising the rhythm, identifying and treating underlying causes, assessing for physiological instability, and ensuring safe disposition rather than routine pharmacological rate suppression.

Unexplained or unresolved sinus tachycardia should not be discharged without appropriate investigation, evidence of treatment response and senior review (RCEM).

Electrocardiographic recognition

Recognising sinus tachycardia on a 12‑lead ECG helps differentiate it from other narrow‑complex tachycardias.

• Key features: regular rhythm, one P wave before each QRS with sinus morphology (classically upright in lead II and aVF), normal PR interval and a narrow QRS unless baseline conduction disease is present.
• Rate: sinus tachycardia is usually >100 beats per minute; a practical upper estimate is roughly 220 - age, so very high rates in older adults should prompt reconsideration of diagnosis.
• Behaviour: sinus tachycardia typically has gradual onset and offset rather than abrupt starts or stops.
• Pitfalls: at high rates P waves may be small or obscured by T waves or baseline noise. If P waves are not clearly visible, use rhythm strips and different leads (II, V1), and interpret ECG together with the clinical context-do not reflexively label as supraventricular tachycardia (SVT).
• Management...