LTE Exchange about Pulsewidth-Spaans and de Arriba-Arnau
The below exchange of letters recently appeared on PubMed:
The likeliness of 0.5 and 1.0 ms stimuli in BL ECT.Spaans HP.
Reply to the likeliness of 0.5 and 1.0 ms stimuli in bilateral electroconvulsive therapy (ECT).
All patients received bilateral ECT, but some patients
were treated with the “half age” dosing strategy and for the
others dose titration was used. In the case of dose titration,
treatment was done with “a stimulus intensity administered
1.5–2.5 times above patient’s seizure threshold”, which I
have interpreted as a treatment stimulus that is 1.5 to 2.5
times the seizure threshold stimulus, such as in studies like
Sackeim et al. [3 ]. Depending on the available sample size,
it would be very interesting to make a comparison between
the dose-titrated and “half-age” subgroups of the 0.5 ms and
1.0 ms sample. This is why:
The initial seizure threshold (IST) for 0.5 ms is probably
about half the IST for 1.0 ms (see for comparison the IST
for 0.3 ms vs. 1.5 ms in patients with depression in [4 ] and
IST for 0.5 ms vs. 1.5 ms in patients with schizophrenia in
[2 ]. Therefore, if we use 0.5 ms with the ‘half age” dosing
strategy instead of 1.0 ms with the same total energy setting
(e.g. 30% when the patient is 60 years old ≈ 151 mC), we
automatically treat the 0.5 ms patients with a higher stimulus
dose relative to seizure threshold. As we know this multiplier
is especially important in unilateral ECT, but also the
speed of response seems higher for high-dose than for lowdose
bilateral ECT [3 ].
From the reply:
"Based on Dr. Spaans’s comments, we worked on a post hoc analysis of the data in the titration group of the sample (n=43) comparing 0.5 ms (n=22/43) against 1.0 ms (n=21/43) and we observed that there were no statistically significant differences between the two pulse width subgroups in the percentage of patients that achieved response (90.9% in 0.5 ms vs 95.2% in 1.0 ms) and remission (77.3% in 0.5 ms vs 71.4% in 1.0 ms), nor in the number of ECT sessions needed in the acute treatment course (12.82±4.74 in 0.5 ms vs 11.19±2.99 in 1.0 ms). The number of sessions required using 0.5 ms was comparable to a previous research (13.7±4.7 in 0.50 ms) that used stimulus doses of 1.5 times the IST in bilateral ECT [2].
The initial seizure threshold was similar in both pulse widths and did not reach a statistical significant difference (92.78±35.96 mC in 0.5 ms vs 114±46.89 mC in 1.0 ms). We observed that 0.5 ms group in our sample had indeed lower IST although this mean difference did not reach the half of the IST for 1.0 as hypothesized from previous data, and was approximately 20 percent less than the IST observed for 1.0 ms. This fact might be because the pulse width difference in ms in this sample is less pronounced than in previous studies that compared pulses more separated between them according to pulse width, for instance, using the ultrabrief 0.3 ms against the extreme of brief pulse 1.5 ms (IST: 59±49 in 0.3 ms vs 162±151 in 1.5 ms) [3]. We also have to keep in mind that the mean age of this study sample is older (65.21±9.77 in the dose titration patients) than the Sackeim’s one (51±17 in 0.3 ms and 53±18 in 1.5 ms).
The stimulus dose at the last ECT session (272.62±139.90 mC in 0.5 ms vs 301.54±187.03 mC in 1.0 ms) was similar in both pulse widths in the dose titration group as well.
Regarding patients treated with the half-age dosing strategy (n=51) and comparing 0.5 ms (n=25/51) against 1.0 ms (n = 26/51), they had similar response (100% in both pulse widths) and remission rates (96% in 0.5 ms vs 88.46% in 1.0 ms) for both pulses. There was no difference in the total number of sessions required along the treatment course in this group (9.92±2.16 in 0.5 ms vs 11.46±3.69 in 1.0 ms), suggesting that both pulse widths had comparable speed of response.
Although stimulus dose at the first session (186.48 ± 44.25 mC in 0.5 ms vs 208.36± 59.82 mC in 1.0 ms) was higher than in the dose-titrated patients, as expected due to the use of half-age in a population of 69.14±9.85 years as mean age, the stimulus dose at the last ECT session (253.01±107.77 mC in 0.5 ms vs 300.44±116.44 mC in 1.0 ms) did not show differences between pulse widths and were similar to the ones reported in the dose titration group.. Further research is warranted to better understand the pulse width influence upon the effectiveness and tolerance of ECT, but these post hoc analyses of our study reinforce the initial findings that 0.5 ms and 0.1 ms might behave quite similar[ly] in bilateral ECT for major depression patients."
This is a highly technical discussion about fine
points in ECT technique. It will be boring to most, fascinating to some. The quest to refine ECT is most worthwhile; however, it should not come at the expense of clinical efficacy.
I have previously written about the remarkable near-universal acceptance of the seizure threshold dogma, despite very limited data.
I would also reiterate the point that the factory default setting for the Thymatron ECT device is 0.5 ms, so it is likely that very large numbers of patients have had successful bilateral and unilateral ECT at this pulsewidth.
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