What is a key feature of reviewing ECG tracings?

A key feature of reviewing ECG tracings is identifying deviations from normal heart rhythm. The electrocardiogram (ECG) is primarily used to evaluate the electrical activity of the heart, and it allows for the detection of arrhythmias, conduction abnormalities, and other significant deviations in heart rhythm. By analyzing the waveform characteristics, intervals, and overall pattern of the heartbeat, healthcare professionals can pinpoint various heart rhythm irregularities, which may indicate underlying cardiac issues or diseases.

The other options relate to different aspects of cardiovascular health but do not fall within the primary scope of an ECG. For instance, determining electrolyte levels requires blood tests rather than ECG interpretation. Assessing heart valve function is typically conducted through imaging studies like echocardiograms rather than through an electrocardiogram. Similarly, measuring blood pressure is a separate assessment and not a function of the ECG itself. Thus, option C stands out as the accurate representation of the main purpose of reviewing ECG tracings.