Discussion
To date, there is a paucity of reported cases of EMI interaction between
ICDs and LVADs, with the first case reported in 2006.2Six cases have reported an interaction between ICDs and the HeartMate
II, resulting in the inability to interrogate and program the ICD,
inappropriate shocks, and pacing inhibition (St. Jude Medical and Sorin
being the most commonly affected ICDs).2-7 Five other
case reports show interactions between HeartWare and ICDs presenting as
pacing inhibition or inappropriate shocks.8-12 With
HeartMate III, 7 cases of ICD EMI have been reported, resulting in
communication failure in 6 cases and over-sensing LVAD noise signal in
one case. 13-15
Several strategies have been proposed to enable successful
communication, interrogation, and reprogramming of an ICD in the setting
of EMI with an LVAD:
- The HeartMate III user’s manual recommends that prior to implanting an
ICD or pacemaker into a HeartMate III patient, the device to be
implanted be placed in close proximity to the LVAD pump (approximately
10 cm) and assure that telemetry communication is established. This
approach may be the easiest to confirm the safe distance between the
ICD and the LVAD without requiring special equipment and can be
performed in office settings. However, this is only a screening
technique and its effectiveness may be limited after device implant.
If a patient receives a HeartMate III pump and has a previously
implanted device that is found to be susceptible to electromagnetic
interference, the ICD or pacemaker device should be replaced with one
that is not prone to programming interference.
- A Faraday cage is an enclosure used to block electromagnetic fields
that can be created temporarily with conductive material such as metal
sheets, mesh or more conveniently, a cast iron pan/sheet externally
positioned to isolate the ICD device from the field created by the
LVAD motor. Creating a Faraday cage has been shown to be useful in
isolating both devices and thus eliminating potential communication
interference.3
- Altering the operating frequency of the LVAD or ICD may theoretically
eliminate EMI between the two devices. The operating frequency of an
ICD is fixed and only altered by changing to another manufacture’s
pulse generator. This comes with procedural risks, most notably pocket
infection. LVAD generated EMI, determined by motor speed, can be
adjusted to below 1300 rpm or above 11,000 rpm to establish ICD
communication.4 However, extreme alterations to the
LVAD motor may cause hemodynamic compromise and therefore, is not a
viable option, in general.
Currently, there are no optimal solutions eliminating EMI interactions
between LVADs and ICDs after device implantation. Therefore, selection
of the combination of available LVAD and ICD devices must be carefully
considered before implantation of either device. Further research is
needed to assess, interpret and prevent EMI interaction between ICDs and
third-generation, magnetically driven LVADs.