Certified Rhythm Analysis Technician (CRAT) Practice Exam 2026 – All-in-One Study Guide for Exam Success!

The ST segment in an ECG waveform represents the period between ventricular depolarization and repolarization. During this segment, the ventricles are in a plateau phase of the myocardial action potential, which is crucial for maintaining a coordinated contraction. It is a critical part of the cardiac cycle, as it shows the heart muscle after it has contracted but before it begins to relax, essentially reflecting a time when the heart is preparing for the next cardiac cycle.

This segment is particularly important in diagnosing certain cardiac conditions, such as myocardial ischemia or infarction, where deviations from the normal ST segment can indicate underlying heart issues. Understanding this aspect of the ECG helps in evaluating the heart's electrical activity and overall health, providing significant information for patient assessments.