Page 40 - Read Online

Zhao et al. Vessel Plus 2021;5:10 I http://dx.doi.org/10.20517/2574-1209.2020.77 Page 5 of 12

Benefits for endovascular thrombectomy
In contrast to published literature on the benefits of MSUs on intravenous thrombolysis, little has been
comparatively reported on endovascular thrombectomy. Although the procedure is performed in hospital,
the role of accurate triage and early notification of neuro-interventional services has been a proposed
[17]
advantage of MSUs . The lack of early data may be in part due to the unique organization of stroke
services in the bigger pioneering MSUs, such as in Berlin, Germany where the majority of stroke centers
[11]
have EVT capability, meaning MSUs are not able to provide a triage service locally .
The Melbourne MSU is therefore one of the very first services to report on the efficacy of MSU-enabled
triage in reducing time to EVT commencement . In the first 365 days of operation, the MSU had facilitated
[2]
endovascular thrombectomy for 42 patients. Using a comparator of all direct and metropolitan secondary
transfer patients to the largest EVT center in Victoria (Royal Melbourne Hospital), patients receiving
facilitated thrombectomy via the Melbourne MSU did so a median of 51 min (95%CI: 30-72) faster. On
further analysis, cases that bypassed of the local non-EVT hospital received the most time saving of 71 min
(95%CI: 46-96), whereas the equivalent time saving if the patient was located closest to a comprehensive
center was 6 min (95%CI: 19-31). This suggests that a large proportion of the time savings are due to
improved triage and avoidance of secondary transfers.

Further contributions to faster EVT were for time from hospital arrival to EVT commencement, which was
17 min (95%CI: 8-26) faster for MSU patients compared to in-hospital controls. This is likely attributed
partly to early pre-hospital notification of neuro-interventional services to prepare the angiography suite
for an impending case. Another factor was that one-third of MSU patients received EVT without need
for repeat in-hospital imaging. Generally, repeat imaging after arrival in hospital with the addition of CT-
perfusion is required if the onset time is > 6 h [18,19] or if the MSU CT-angiogram is not adequate to show the
relevant occlusion. However, at the start of the Melbourne MSU the conservative approach was to repeat
imaging for all potential EVT cases, although this policy was subsequently relaxed as the comprehensive
centers became more familiar with MSU. Therefore, the proportion of MSU EVT cases that need repeat
imaging will likely decrease with ongoing operation. In comparison, the time savings for hospital arrival to
EVT commencement for US-based MSUs were 10 min or less [20, 21] .

Despite the lack of statistically significant time saving for EVT patients that did not need bypass, the two-
thirds that were eligible for thrombolysis still received intravenous therapy substantially faster. Around 10%
of all large vessel occlusions managed by the Melbourne MSU did not proceed to the angiography suite due
to improving symptoms or recanalisation from thrombolysis. There are almost certainly further cases that
proceeded to angiography but did not require intervention due to recanalisation. Analysis of data from two
US-based MSUs showed that large vessel occlusion recanalisation solely with thrombolysis was greater than
[22]
with in-hospital controls (29.4% vs. 22%, P = 0.04) . This suggests that there is still benefit from MSUs
attending potential EVT cases even if the patient is located near a comprehensive center, especially if the
patient is thrombolysis-eligible. In addition, not all EVT centers in metropolitan Melbourne are able to run
multiple angiography laboratories simultaneously, or all laboratories may be engaged in active cases. This
means that MSU personnel can confirm angiography and neuro-intervention availability prior to hospital
arrival and, if necessary, divert to another EVT center.

Benefit on disability avoidance from reperfusion therapy
In addition to time savings, we also examined the possible disability avoidance of providing earlier
thrombolysis and EVT, given improved post-stroke outcomes are highly associated with faster reperfusion
[23]
therapy . This was based on previous literature that estimated the overall avoided disability-adjusted life
[25]
days for each minute of faster thrombolysis and EVT (in addition to thrombolysis) , as derived from
[24]
previous trial data. Using these estimates, it was calculated that in the first 365 operational days, the time