Q: How do you document QTc intervals?

A: David Pickham, RN, PhD, replies:

Developed more than 100 years ago, the electrocardiogram (ECG) records the electrical activity that underlies the heart’s mechanical activity. Standardized recording settings of the ECG allow direct measurement and interpretation of 2 main electrical signal characteristics (Figure 1): (1) signal magnitude (strength), measured in millivolts (mV), and (2) signal duration, measured in milliseconds (ms).

During the ECG’s development, Willem Einthoven, the 1924 Nobel prize recipient, standardized ECG waveform nomenclature. It is thought that in choosing the PQRST standard, Einthoven was both respecting Descartes’ established curve labeling system and allowing “room” for future discovered waves to be appropriately labeled (intentionally chosen from the middle of the alphabet).1 

Each wave deflection on the ECG represents a portion of the heart’s electrical activity and is labeled in the same way it has been labeled for the past...

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