Which term describes rapid heart rate of 100-180 beats per minute?

• A. Sinus tachycardia
• B. Somatic tremor
• C. ST segment
• D. Standard limb lead

Answer: (A)

Sinus tachycardia describes a rapid heart rate in the 100–180 beats per minute range while the rhythm remains a normal sinus rhythm. That means the heartbeat is fast but still originates in the Sinoatrial (SA) node, with normal-looking P waves before each QRS complex and a regular pattern. This set of features distinguishes it from other ECG terms that don’t describe a true increase in heart rate: somatic tremor is an artifact from muscle activity distorting the tracing, the ST segment is simply the part of the ECG between the S wave and T wave used to assess ischemia, and a standard limb lead refers to electrode placement for recording the ECG. So the best match for a rapid heart rate in that range, with a normal rhythm origin, is sinus tachycardia.