Variability of different methods for measurement of ECG intervals and ECG interval temporal variation

We found significant variation within each computer and cardiologist method for measurement of the ECG waveform intervals. Comparison between methods revealed that the HP system had a smaller variability than the MAC or the cardiologist, and that the MAC had a smaller variability than the cardiologist. No variability was found when a cardiologist used different paper trace speeds. Using HP measurements, we found a significant difference in ECG intervals over time, which was greater than the variability found within the method at baseline. The delineation of variability within and between ECG interval measurement methods may allow more reliable application of ECG interval changes in the therapeutic medical management of patients and prevention of side effects from drugs that affect ECG intervals. Computerized ECG waveform analysis is a widely available technology whose full role in therapeutic medical management may not be appreciated.