Most patients with electronic medical devices undergo CT scans without any adverse consequences. However, FDA has received a small number of reports of adverse events in which CT scans may have interfered with electronic medical devices, including pacemakers, defibrillators, neurostimulators, and implanted or externally worn drug infusion pumps. There have been similar reports in the literature.Specifically, for pacemakers, the effect has been described only as "transient changes in pacemaker output pulse rate."
It is possible that this interference is being reported more frequently now because of the increased utilization of CT, the higher dose-rate capability of newer CT machines, an increase in the number of patients with implanted and externally worn electronic medical devices, and better reporting systems.
We are continuing to investigate this issue while working with device manufacturers and raising awareness in the healthcare community. To date, no patient deaths have been reported from CT scanning of implanted or externally worn electronic medical devices.
Recall that pacemakers must sense existing heartbeats and respond with pacing when no signals are detected. If the pacemaker or defibrillator senses outside signals, it might interpret that "noise" as a biologic signal and respond accordingly. So, if a pacemaker senses outside "noise" and interprets it as a biologic signal, it might briefly inhibit pacing. If a defibrillator senses such "noise" as a biologic signal, it might either inhibit pacing or, if the noise detected is of a sufficiently high frequency for long enough, it might respond with an attempt to correct the rhythm by rapid pacing or a shock (depending on how the defibrillator was programmed).
From the FDA's announcement, it appears the problem primarily occurs when a high radiation dose is emitted from the scanner directly over the device - and this is usually only a brief phenomenon. Whether is is a new finding, or just better reported, remains to be seen (I suspect the latter).
The biggest impact of this announcement will be for device companies and EP nurses, doctors, and technicians - since the implication from this disastrous "early notification" is that we might have to check every pacemaker or defibrillator after every CT scan performed (you've got to be kidding me!).
The lack of guidance for heart rhythm specialists by the FDA and the Heart Rhythm Society in this regard is stunning and warrants review. It seems the Heart Rhythm Society just parrots the FDA's announcement. Perhaps it was because maybe it's not such a big deal after all:
MedSun is the FDA's Medical Product Safety Network of 350 hospitals spread throughout the United States. Information from 132 of these facilities indicated that they have not experienced any CT medical device interference, while 3 have had from 1 to 3 events that may have been CT scan induced. Fifteen MedSun facilities indicated they take some precautionary steps when CT scanning patients who have electronic medical devices.In short, this seems like a "cover your ass" move by the FDA that threatens to potentially scaremonger our patients.
I guess thanks to the Congressional oversight these days, when it comes to such notifications, the FDA is damned if they do and damned if they don't.