Author + information
- Jean-Benoît le Polain de Waroux, MD⁎ (, )
- Sebastien Marchandise, MD and
- Christophe Scavee, MD
- ↵⁎Division of Cardiology, Cliniques Universitaires St-Luc, Avenue Hippocrate, 10-2881, B-1200 Brussels, Belgium
We read with much interest the Research Correspondence by Mehta et al. (1) of 2 cases of device interactions in patients with advanced cardiomyopathy. We experienced the same problem with a patient equipped with a St. Jude Medical (SJM) implantable cardioverter-defibrillator (Atlas II + HF, model V-367, St. Jude Medical, Sunnyvale, California) who was implanted with a Heartmate II left ventricular assist device (LVAD) (Thoratec Heartmate II, Thoratec, Pleasanton, California). Similar to the 2 cases reported by the group of Mehta et al. (1), our case demonstrated no possible telemetry after the implantation of the LVAD pump, and the replacement of the implantable cardioverter-defibrillator (ICD) was the only clinical solution. Mehta et al. (1) partially clarified the nature of the interaction. We also found that it was specifically produced by the Heartmate II pulse-width modulator, which operates at a constant frequency of 7.2 kHz. However, in our case, the patient was implanted with a new generation of SJM CRT-D (which uses an operating frequency of 64 kHz). According to the explanation given in the correspondence from Mehta et al. (1), no interaction would have been expected. In fact, the Federal Communications Commission who regulates the operating frequencies of all implantable devices has mandated device operating in UHF bands to use a “listen-before-talking” (LBT) accessing protocol for safety reasons (2). All ICDs, even the last Current and Promote generation from SJM, use an LBT assessing protocol operating at a frequency of 8 kHz (communication from SJM Belgium, St. Jude Medical, Zaventem, Belgium, April 2008) (Table 1). Interactions could thus occur either between the pulse-width modulator and the LBT protocol (newest generation) and/or the data transmission per se (oldest generation). This was clearly demonstrated by clinical tests that we performed with demonstration devices: the initial interrogation of all SJM ICDs is always impossible if the distance between the ICD and the LVAD pump is shorter than 6 inches. However, the communication to the device is possible close to the Heartmate for the newest generation of SJM ICDs (LBT: 8 kHz; operating frequency: 64 kHz) if the initial recognition of the ICD is established far away from the LVAD pump. By contrast, with the oldest generation of SJM devices (LBT and operating frequency: 8 kHz), communication in proximity of the Heartmate remained unavailable even if the initial recognition is performed far away from the LVAD pump. The operating frequency of an ICD is thus not the only mechanism that explains the inability to interrogate the SJM ICDs in proximity of the Heartmate II LVAD pump. Other potential sources of interactions (such as the LBT frequency used) should be taken into account before choosing a replacement device. In our opinion, device interactions are important factors that should be recognized by manufacturers who are required to provide safety information about this specific risk.
- American College of Cardiology Foundation