Certified Rhythm Analysis Technician (CRAT) Practice Exam 2025 - Free CRAT Practice Questions and Study Guide

In the context of an ECG (electrocardiogram), the measurement in millivolts (mV) is used to quantify the electrical activity of the heart. The ECG captures the electrical impulses that trigger each heartbeat, and these impulses generate voltages that can be detected and recorded by the ECG machine.

These electrical signals fluctuate based on the activity of the heart, such as depolarization and repolarization of the cardiac muscle, which correlates with the contraction and relaxation of the heart chambers. Each wave and segment of the ECG corresponds to specific phases of the heartbeat cycle, and their amplitudes are expressed in millivolts. Understanding this measurement is crucial for interpreting heart health and diagnosing various cardiac conditions.

The other options refer to different aspects of cardiac function that do not involve direct measurement in millivolts. The duration of each heartbeat and the time interval between heartbeats refer to timing measurements, while the amount of blood pumped by the heart pertains to hemodynamics rather than electrical activity.