Doc Alert: Diagnostic Findings of iPhone Interference onECG

the following is an e-mail i received from my epocrates doc alerts. while interesting, i wonder how the patient managed to bring the charging iphone with him to get the ecg. usually there are cords hanging about when charging a phone. how do you just happen to not see that?

short post today only because i'm about to drop dead. i will have plenty to complain about tomorrow after working 23 hours in 2 days with 3 incompetent techs and a mostly competent intern. (different intern, not talking about myself - i, of course, am completely competent)

Information sourced from BMJ:

Emerg Med J doi:10.1136/emermed-2011-200078
[Link to free full-text Emerg Medicine article PDF] [PubMed® abstract]

Images in emergency medicine

ECG Interference From the iPhone

Accepted 24 March 2011
Published Online First 27 May 2011



Figure 1 ECG acquired before (A) and after (B) removal of charging iPhone.

A 44-year-old man presented to the emergency department with cocaine-induced chest pain. There was no previous cardiac history. His initial ECG was abnormal (figure 1A). On examination, he appeared well and a charging iPhone 4 was found beneath his forearm. The device was removed and another ECG was recorded (figure 1B).

ECG interference can arise from numerous potential sources.AC interference is minimised using physical shielding and electrical filters, essential given that ECG voltages are in the order of millivolts compared with the mains supply (230 V). Direct contact with the device may have bypassed these measures, and figure 1A shows AC interference as the characteristic 'thickened baseline' with 2 sinusoidal waves every 1 small square (50 Hz).

Electromagnetic interference from mobile communication devices is common, hence restrictions on use in certain settings The GSM receiver has been shown to cause high-voltage spike at regular intervals.¹ Figure 1A demonstrates such activity that resembles a pacing spike every 2 small squares caused by abnormal interpretation as genuine pacemaker pulses that are automatically expanded to allow better visualisation. These two forms of interference need to be recognised given how often ECGs are recorded within the emergency department.

Footnotes
Competing interests: None.
Patient consent: Obtained.
Provenance and peer review: Not commissioned; internally peer reviewed.

Reference
1. Baranchuk A, Kang J, Shaw C, et al. Electromagnetic interference of communication devices on ECG machines. Clin Cardiol 2009;32:588–92. [PubMed® abstract]

Copyright © 2011 BMJ Publishing Group Ltd and the College of Emergency Medicine. All rights reserved.
The above message comes from BMJ, who is solely responsible for its content.
You have received this email because you requested follow-up information to an Epocrates DocAlert® Message. For more information about DocAlert® Messages, please click here.
Best wishes,
The Epocrates Team
1100 Park Place, #300
San Mateo, CA 94403