Is increasing the pulse width from 0.5 to 1 ms an effective strategy to optimize clinical and electrical outcomes in bilateral <scp>ECT</scp> treatment?

Different approaches have been implemented in electroconvulsive therapy (ECT) to optimize the treatment and to individualize it to every patient's needs. Recently, there has been an increased interest in considering changes within the technique in order to reduce cognitive side effects while maintaining clinical efficacy. There is evidence that ultra-brief pulses (UBPs) have a better effect at preserving cognition1 but need higher suprathreshold dosages2 and number of treatment sessions to maintain efficacy3, 4 compared to longer pulse widths (PW). However, some case reports have suggested that lengthening the PW might result in improvement in some patients who have an inappropriate seizure or insufficient response with a shorter PW.5, 6 Thus, is PW reduction appropriate for everyone? Could patients who do not respond to shorter pulse widths benefit from a shift to longer pulses in the brief pulses (BPs) range? In our daily practice we also observed that some patients who responded inappropriately to 0.5 milliseconds (ms) PW, did better with 1.0 ms PW. So, we aimed to study the individual clinical evolution of patients who underwent a change from 0.5 to 1 ms PW during the same acute ECT course. We collected retrospectively 12 patients with a diagnosis of major depressive episode, either bipolar or unipolar, according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) and analyzed their individual evolution after shifting the PW from 0.5 to 1 ms during the same course of acute treatment with bilateral ECT (details in Appendix S1). The concurrent psychiatric treatment remained unchanged when performing ECT. Clinical status was measured at baseline and after the last session of ECT using the Hamilton Depression Rating Scale (HDRS) and by clinical evaluation before every session by the patients' treating psychiatrist. The seizure adequacy markers index7 that summarizes five ictal parameters was used to evaluate the seizure quality (Table S1 and Fig. S1). The Montreal Cognitive Assessment (MOCA) was used to evaluate any cognitive side effects of ECT. All the patients included in the study signed a written informed consent. All the patients included in the study were administered minimum but safe anesthesia dosage, individualized stimulus energy and hyperventilation during the sessions to facilitate outcomes; nevertheless, they still showed difficulties maintaining adequate seizure elicitation or responding clinically. Based on the criteria of the patient's treating psychiatrist, the patients received a change in PW from 0.5 to 1 ms in order to improve seizure quality parameters and optimize clinical response. Study population characteristics are found in Table S2. Table S3 reports all the patient's data on ECT parameters, treatment clinical and tolerance outcomes during the acute ECT course with both PW. All cases responded positively to the change in the PW from 0.5 to 1 ms, achieving an improvement in the electroencephalographic parameters (based on the seizure adequacy markers index)7 as well as clinical outcome. Eight patients achieved remission (75%) after switching to 1 ms PW, and three patients achieved partial clinical response (25%). During the sessions following the change to 1 ms PW, half of the patients needed to have their stimulus intensity raised. In just one case, a confusional syndrome appeared after the first 1 ms session. No other complications associated with the treatment were recorded. Even though there is a general trend to shorten PW, there is a lack of consensus in this field8 and most of the available studies used unilateral ECT, while in our study patients underwent bilateral (BL) ECT. In BL ECT, a study that found relatively lower efficacy of UBP raised controversy,9 but this finding was not replicated in subsequent studies.1, 3, 4, 10 The present study findings are in concordance with some case reports that have suggested that lengthening the PW might result in improvement in some patients who have an inappropriate seizure or insufficient response with shorter PW (UBP).5, 6 A prolonged chronaxie and the effect of wider PW to activate broader regions of brain tissue6 have been proposed as explanatory hypotheses for these findings. In conclusion, these observations lead us to hypothesize that lengthening the PW from 0.5 to 1 ms in patients undergoing bilateral ECT for a depressive episode could be a useful strategy to consider in certain groups of patients with poor-quality electroencephalographic parameters and scarce clinical improvement. However, further research with larger samples and randomized clinical trials are warranted to demonstrate this clinical observation. Such research ought to identify if lengthening the PW should be considered an optimization strategy in ECT. We thank all the patients and staff from the ECT Unit of Bellvitge University Hospital. We thank the CERCA Programme/Generalitat de Catalunya for institutional support. This research did not receive any grants/support from funding agencies in the public, commercial, or not-for-profit sectors for the submitted work. The authors declare no conflict of interest. Appendix S1. Supporting information (detailed methods, results and limitations). Figure S1. EEG representative waveform according to the seizure parameters evaluated by Seizure adequacy Score. Table S1. Seizure adequacy markers index according to the proposal of Minelli et al. Table S2. Characteristics of the sample. Table S3. Clinical characteristics, ECT parameters used and treatment outcome, including clinical response and tolerance, for each case in the sample. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

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