Introduction: For patients with suspected large vessel occlusion (LVO) stroke should we bypass alteplase treatment at Primary Stroke Centres (PSC) in favor of endovascular therapy (EVT) at Comprehensive Stroke Centres (CSC) (mothership) or transport the patient to the PSC for alteplase and then transfer to the CSC for EVT (drip and ship)? This is complicated by the inability to definitively diagnose LVO stroke without imaging.
Methods: The efficacy decay of alteplase and EVT over time and the accuracy of the Los Angeles Motor Scale (LAMS) LVO screening tool were combined with various treatment times to predict the probability of good outcome (mRS 0 - 1 at 90 days) for both transport strategies for patients with LAMS ≥4.
Results: The results are shown in the Figure. If the patient is closest to the CSC mothership is always superior. If treatment is fast at both centres drip and ship is superior if the centres are far apart and the patient must travel past a PSC to get to a CSC, otherwise the strategies are equivalent (Panel A). Slow treatment at the PSC increases the area where mothership is superior and eliminates drip and ship unless the time from onset to alteplase administration exceeds 4.5 hours in the mothership scenario (Panel B). Slow treatment at both centres decreases the mothership area and expands the drip and ship area (Panel C).
Conclusions: Due to the uncertainty in patient diagnosis both transport options are equivalent in most scenarios. A triaging tool with greater positive predictive value would increase the size of the mothership areas. However, even with diagnosis uncertainty the importance of fast treatment times is illustrated.