Which term corresponds to the time interval between the ventricular contraction and the beginning of ventricular relaxation?

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

Answer: (C)

The ST segment is the period on an ECG between ventricular depolarization and ventricular repolarization. It occurs after the QRS complex, which represents ventricular contraction, and before the T wave, which marks ventricular relaxation. So the interval between the end of contraction and the start of relaxation corresponds to the ST segment. The other terms aren’t about timing in the heart’s electrical cycle: a standard limb lead refers to electrode placement, standardization is machine calibration, and somatic tremor is muscle-related noise.