Abstract
BACKGROUND: In anaesthesiology, time domain parameters of the ECG are frequently used for long QT diagnosis, determination of branch blocks and for identifying atrioventricular blocks. However, this analysis depends on several factors and therefore the time domain parameters are prone to variability. OBJECTIVE: To determine the variability of expert assessments of ECG time domain parameters in daily clinical practice. DESIGN: In an observational study 18 physicians labelled the onset, peak and end of the waves (P-QRS-T) for 26 preselected, distinctive beats. Based on this, clinically important durations and intervals were derived: the duration of the P wave, T wave and QRS complex, as well as the length of the PQ and QT interval. These parameters were subsequently analysed with respect to inter-expert variability (for all experts and discipline-based subgroups) and, additionally, were compared with computer-aided analysis. SETTING: ECG recordings from participating patients were recorded in March 2015 during standard examination in the hospital and stored in the local ECG database. PATIENTS: We did not define inclusion or exclusion criteria for the patients themselves; the ECG beats were selected by a medical expert with respect to their shapes and abnormalities. MAIN OUTCOME MEASURES: Variability of clinically relevant ECG wave durations and intervals quantified were expressed as the interquartile range and the Q(2)/Q(98) span for 18 investigators. RESULTS: The resulting wave durations (P(dur), QRS(dur) and T(dur)) and intervals (PQ and QT) showed high variability, for instance, captured by the Q(2)/Q(98) span ranging from 39 to 99 ms. CONCLUSION: The observed, inter-investigator variability of assessing the PQ and QT intervals, as well as the wave durations, might result in important variance regarding ECG-associated diagnoses. Whether these variances play a major role in typical clinical situations would have to be demonstrated with further clinical observational studies.