How reliable and how comparable are Holter ECG evaluations from different devices and/or persons? A case study of 3 reevaluations of a small trial

Comparison between 3 different Holter ECG evaluations in a small clinical study with n=30 Holter recordings (25 usable ones) revealed different sources of incompatibility and incomparability. Increased attention should be given to comparable system definitions and to quality control of devices and operators. Due to vulnerability by technical artifacts, some parameters-like minimum heart rate-seem to be unsuitable for comparisons. Technical differences might account for a considerable extra amount of variability resulting from lack of technical standards and comparability of Holter devices.