Journal: Brain Stimulation (2022)
Authors: Stultz DJ, Pitch R, Tuttle C, Miller S, Osburn S, Shafer C, Burns T.
Background:
With respect to TMS coils used in TMS, the strength of a magnetic field decreases as it travels from its source at a rate of R-3 or 1/R3, where R is the distance from the center of the coil. For a typical figure-8 TMS coil, the peak source field is about 15,000 gauss (1.5 Tesla); this diminishes to about 0.55 gauss at 30 cm from the center of the coil. The H-1 coil produces a much broader magnetic field that is less uniform but still results in an acceptably low field level at 30 cm. The location of an implanted device in the anterior chest wall is more than 30 cm for most patients. Thus, TMS coil magnetic field level is sufficiently low enough not to induce meaningful currents in conductors exposed to it when used correctly.
Objective:
This paper describes two patients with cardiac pacemakers treated in two independent clinics with two different coil types. In each case, the patient was made aware of the potential risks related to the use of TMS with pacemakers, and the procedure was coordinated with the patient’s cardiologist.
Methods:
Patient 1 was treated using an H-1 coil over the left DLPFC at 18Hz, 120% MT, 55 trains for 2 seconds with a 20-s intertrain interval for 1980 pulses per session. He received 28 sessions. Patient 2 was treated with a figure-8 coil stimulating the left DLPFC at 10Hz, 120% of SMT, 4 seconds with an 11-s intertrain interval, 3000 pulses/session for 36 sessions. Both patients had a donut magnet placed over the pacemaker, which converts the pacemaker into an asynchronized mode, which means it no longer senses the intrinsic heart rhythm. Thus, the implanted pacemaker will now discharge at a fixed rate. Once the magnet is removed, the pacemaker reverts to its original pacing programming.
Results:
Patient 1’s post-treatment Beck Depression and PHQ-9 scales demonstrated remission (5 and 4, respectively), with the patient stating, “I have not felt this good in 16 years”. Patient 2 achieved full remission for the first time in 30 years. The pre-and post-treatment BDI-II scores were 35 and 5, respectively.
Conclusions:
With the simple procedure described above, we delivered TMS therapy to two patients with cardiac pacemakers who were refractory to numerous other treatments. Based on safety recommendations by Rossi et al., 2021 and the four previously mentioned cases, it appears pacemaker use in TMS is well tolerated.
