Minor recorder imperfections can cause artifacts in the RR interval spectrum derived from Holter recordings

Spectral analysis of the heartbeat (RR) interval is a powerful tool for noninvasively assessing the autonomic nervous system. In addition, it may prove to be valuable in stratifying patients at risk for cardiac death. The authors report on a case in which spectral analysis of the RR interval exhibited harmonically related peaks within the physiological range that defied physiological explanation. Analysis showed that these peaks resulted from a subtle abnormality of the Holter recorder that was not apparent in the observed electrocardiogram. Since this type of abnormality can be produced by either minor damage or a manufacturing error in any brand of Holter recorder, the RR interval spectrum derived form a Holter electrocardiogram should always be critically examined for this particular artifact.