CORRESPONDENCE: LETTER TO THE EDITOR
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Rohit Mehta, MD*,
Amit A. Doshi, MD,
Marg Pizzuto, RN,
Chittoor Sai-Sudhakar, MD,
Ayesha K. Hasan, MD and
David P. Chan, MD
* The Sanger Clinic, Carolinas Heart and Vascular Institute, Medical Center Plaza, 1001 Blythe Boulevard, Suite 300, Charlotte, North Carolina 28203 (Email: rohitmehta{at}alumni.duke.edu).
Dr. Le Poland de Waroux and colleagues have described an interaction of the Heartmate II left ventricular assist device (LVAD) (Thoratec Heartmate II, Thoratec, Pleasanton, California) and the St. Jude Medical (SJM) implantable cardioverter-defibrillator (ICD) (Atlas II + HF, model V-367, St. Jude Medical, Sunnyvale, California) that is unique and not explained by the previously published report from our group (1).
We commend Dr. Le Poland de Waroux and colleagues for deciphering this new interaction; however, the nomenclature of the interaction is incorrect in their description. The interaction in question is based upon the need for the device programmer to serve both older and newer generation devices.
The programmer (SJM-Merlin) utilizes an 8-kHz "test" pulse of inductive telemetry (direct link to a programmer head) to determine whether a newer generation (64-kHz operating frequency) or older generation (8-kHz operating frequency) is in place (A. Dianaty, written communication, May 2008). This test or "handshake" pulse lasts 2 to 5 s, and it is the transient nature of this pulse that explains the ability of shielding to overcome the interaction with the Atlas II (A. Dianaty, written communication, May 2008).
While the 8-kHz inductive "handshake" is responsible for the interaction in question, it is not a function of the listen-before-talking (LBT) protocol. The LBT protocol is a guideline issued by the Federal Communication Commission to regulate utilization of wireless telemetry devices in the Medical Implant Communications Service (MICS) band (2). The Federal Communication Commission mandates that all devices in the MICS band scan the bandwidth for current "traffic" before transmitting on this frequency. All current ICD wireless telemetry must utilize LBT to function in the MICS band to minimize the potential for interactions. Boston Scientific devices operate in the Industrial, Scientific, and Medical band and thus are not subject to the LBT requirement (3).
The difficulties with device interactions will only become more prevalent over time as higher storage and more complex devices necessitate faster download speeds and more remote access options. As we encounter these complexities, it will take a collaborative effort from physicians, engineers, and industry to navigate these problems. We thank Dr. Le Poland de Waroux and colleagues for becoming an integral part of this collaboration.
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Footnotes
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Please note: The authors would like to thank the following individuals for their help in delineating the interactions in question: Ali Dianaty, Al Schwartz, and Rick Turek (St. Jude Medical).
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References
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1. Mehta R, Hasan AK, Pizzuto M, Love CJ, Sai-Sudhakar C, Chan D. Device interactions in patients with advanced cardiomyopathy J Am Coll Cardiol 2008;51:1613-1614.[Free Full Text]2. Medtronic Technical Support. Radiofrequency considerations for the use of wireless telemetry with the Medtronic CareLink programmer and implanted medical devices. 3. Von Arx J, Gaskill R, Mass W, et al. Boston Scientific Cardiac Rhythm Management White Paper. 2006. Order number C3-277-0806.
Related Article
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Device Interactions and Cardiomyopathy
- Jean-Benoît le Polain de Waroux, Sebastien Marchandise, and Christophe Scavee
J. Am. Coll. Cardiol. 2008 52: 1887.
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