http://content.nejm.org/cgi/reprint/352/13/1389.pdf

A Holter Hazard

To the editor: A 52-year-old woman underwent
Holter monitoring to evaluate palpitations. She did
not report any other symptoms. Physical examination
was unremarkable. An electrocardiogram obtained
with the patient at rest was normal, with a
rate of 90 beats per minute. The Holter monitor
showed marked bradycardia throughout the period
of monitoring (Fig. 1). In the hospital, cardiac
monitoring showed a normal rhythm, with the rate
between 70 and 100 beats per minute and no paus-
es or bradycardia. An electrocardiogram obtained
by changing the speed of the paper to 100 mm per
second reproduced the Holter findings. The patient's
apparent bradyarrhythmia reflected mechanical
problems with the Holter tape that somehow
changed the speed of recording. Repeated
Holter monitoring a week later was unremarkable.
This case illustrates that when test results do not
represent the patient's symptoms, mechanical or
nonclinical factors should be considered in the differential
diagnosis.

Malvinder S. Parmar, M.D.
Northern Ontario School of Medicine
Timmins, ON P4N 8P2, Canada
parmar@vianet.on.ca