| Paper authors: | Tabitha Iseger, Martijn Arns, Jonathan Downar, Daniel Blumberger, Zafiris Daskalakis, Fidel Vila-Rodriguez |
| Year of paper publication: | 2020 |
| Post authors: | Alice Erchov, Lisa Ridgway, Fidel Vila-Rodriguez |
| Download the research article: | Iseger (2020) Cardiovascular differences between sham and active iTBS related to treatment response in MDD |
Introduction
It is no question that neurostimulation treatments like rTMS change your brain for the better. Because of this, rTMS is capable of treating depression even when people did not benefit from antidepressants. However, less is known about how rTMS affects other parts of the body: primarily, the heart.
Research has shown that people with depression have changes in their heart function. Overall, heart rate is found to be higher and heart rate variability is lower. This means that the heart tends to beat faster, and there is more consistency in the timing of these beats. However, high heart rate variability is a good thing: it means that your body can flexibly adapt to stress, rest, and changing demands.
Past studies have shown that rTMS treatment for depression has the ability to reverse illness-related changes in heart rate and heart rate variability. In fact, decelerations (slowing) of heart rate in response to treatment could help clinicians make sure they are targeting the region of the brain that would lead to the best improvement in depression symptoms.
However, it was unclear whether the accelerated version of rTMS, called iTBS, would have the same effects on heart function. It is possible that heart rate could be used to help pinpoint the target of iTBS for a more precise, effective treatment.
Methods
Fifteen people with depression (average age of 32 years) participated in this study. Everyone in this study had to have tried at least one antidepressant in the past, without seeing an improvement in their symptoms. This meant that their depression was treatment-resistant.
Participants got daily iTBS treatment every weekday, for 6 weeks. This means everyone had a total of 30 treatment days. Each treatment day had 2 sessions of iTBS.
In order to determine changes in heart function that were not due to iTBS (e.g., placebo), participants also received 2 sessions of sham (fake) iTBS every treatment day. Then, researchers could compare the changes in heart function between a sham and real iTBS treatment for every person and day.
Results
- iTBS significantly lowered heart rate during stimulation, and this was detectable from the first 30 seconds of treatment.
- Heart rate variability was higher during iTBS, meaning that heart tended to beat in less consistent intervals. This is more similar to what we would see in a person without depression.
- iTBS significantly lowered blood pressure during stimulation.
- These differences were found consistently during iTBS for the whole 30 days, but none of them stayed after treatment was no longer being delivered. This means that the stimulation itself appeared to be driving these changes, and these did not appear to persist long-term.
The researchers theorize that this could be because iTBS is stimulating the “rest and relax” part of our nervous system. This parasympathetic system is what our bodies use to
Conclusion
Heart rate appears to play a significant role in how someone reacts to rTMS/iTBS. During treatment, the heart tended to beat slower and at more sporadic intervals – both things that indicate a healthy individual. Specifically, someone without depression. These changes appear to be specific to while treatment is delivered and is not sustained over time, meaning that changes in heart function could be used to determine where the iTBS coil should be placed in order to maximize results. This line of research has the ability to improve our ability to treat depression. More studies are needed in order to further understand how iTBS can be used to treat both our hearts and our brains.