Background: Human oscillator is observed in and outside the nervous system. Cardiac rhythm is generated by heart itself but can be modulated by brain. Using the technique of transcranial magnetic stimulation (TMS) and resetting index, we studied if single-pulse TMS could reset the cardiac rhythm and help differentiate oscillator of neurogenic or non-neurogenic origin.
Methods: In addition to the study of 4 patients with essential tremor, cardiac rhythm was studied in 6 normal subjects. The magnetic intensity was initiated from motor threshold of hand muscle, and then with an increment of 10% up to the maximal output of magnetic stimulator. We used the resetting index (RI) to quantify the influence of the TMS.
Results: The resetting phenomenon was observed in essential tremor (RI = 0.92) but not in cardiac rhythm (RI = 0.02).
Conclusions: Single-pulse TMS is able to reset the rhythm of essential tremor but not heart beat. The pacing mechanism is different between essential tremor and heart beat. The cardiac rhythm is regulated and modulated chiefly by heart itself. Essential tremor should not share the same mechanism with heart beat.