For patients with large vessel occlusion (LVO) a direct to angiography (DTA) treatment approach without repeated imaging leads to reduced time to endovascular thrombectomy (EVT) and better functional and safety outcomes compared to patients who underwent repeat imaging on transfer, a US study shows.
The approach saved around 26 minutes overall from EVT centre arrival to groin puncture, which investigators say may have contributed to the roughly 15% absolute increase in the rate of 3-month functional independence in the DTA group.
While the findings have prompted US neurologists to advocate bypassing repeat imaging once patients have been transferred to an EVT-capable centre from a referring hospital, the study has re-affirmed the long-standing approach used in Australia.
In the cohort of 1140 patients, 327 (29%) were managed with the DTA approach, whereas 813 (71%) had repeated imaging before EVT.
Investigators report that every 10-minute increase in the time from arrival at the EVT centre to EVT initiation in the repeated imaging group resulted in a 5% reduction in the likelihood of achieving functional independence.
According to the study, the rate of 3-month functional independence was higher (52.6% vs 37.0%) and mortality trended lower (17.0% vs 24.4%) with DTA compared to repeat imagining.
The results were consistent in patients arriving in both the early (0-6 hours) and late (>6 to 24 hours) windows and during both regular work hours and on-call hours, which supported implementation of the DTA approach at any time, the authors said.
But the the potential efficacy and safety of DTA did decrease as transfer time increased with transfer times of three or more hours resulting in similar functional independence rates compared with repeated imaging.
US neurologists said that while repeated imaging may be reasonable with prolonged transfer times, their findings supported a DTA approach leading to faster treatment and better functional outcomes during all hours and treatment windows.
Standard of care
Speaking to the limbic neurologist at Royal Melbourne Hospital, Professor Bruce Campbell, said DTA is already widely taken up in Australia, as more advanced imaging upfront was considered standard care.
“I think Australia does pretty well where this is concerned. Our philosophy in general has been to get all the imaging done at the referring hospital, which is quite different to the US.”
Typically in the US patients will receive a non contrast CT, while some may or may not also receive a CT angiogram to prove a blocked vessel, Professor Campbell explained.
“Once patients are transferred to an EVT-capable centre they’ll be back in the CT scanner getting imaged to see if they actually have a target and brain to save for the procedure.”
It’s an approach he described as ‘wasteful’ in terms of time.
“You really want to get the imaging right the first time and that’s kind of the way we’ve always done it for a good amount of patients – you do the imaging, establish eligibility (for EVT) at the referring hospital and only transfer if patients need the procedure, which means they go to angiography directly when they arrive.”
Professor Campbell said imaging won’t need to be repeated unless something has ‘majorly’ changed or where there has been an exceedingly long transfer.
“In that case you can’t rely on what you saw more than three hours ago still reflecting the status of the brain on arrival,” he said.
Clinicians might also consider repeat imaging if a patient has got considerably better, he added.
“Particularly if the angiography suites are not quite ready but most of those patients still have some sort of target so unless we get infinitely better intravenous thrombolysis strategies most people, even when they’ve improved, have something the interventionist can pull out.”
For those patients who have deteriorated Professor Campbell said most angiography equipment would be able to exclude haemorrhage.
“So people who have got worse can go straight to an angiography suite and on CT people who’ve got better, if they’re almost entirely back to normal, fair enough you might not want to do an angiogram for no good reason but there are also non invasive angiography options, like intravenous DSA, that you could be performed in an angio-suite.”
Australia doing the ‘impossible’
Professor Campbell, who also penned an editorial linked to the US paper, said most Australian hospitals outside metropolitan areas areequipped with CT scanners capable of identifying a blocked vessel and salvageable brain, which was not just important for transferring the right patient to EVT-capable hospitals.
“There are treatments that can be done at the initial hospital with standard thrombolysis. We now have evidence to say that you can give thrombolysis beyond 4.5 hours if you’ve got the right imaging profile. So being able to do that CT perfusion scan (in the referring hospital) means that if they’ve got someone who has woken up with a stroke, rather than their only option being to ship them up to a metropolitan centre, they’ve got the option of giving thrombolysis and then transferring if the imaging is favourable.”
For Professor Campbell, who co-led the the well-known EXTEND-IA and EXTEND-IA TNK trials that looked at stent thrombectomy with standard clot-dissolving therapy, Australia has led the stroke imaging field.
“We have put a lot of effort into getting those sort of advanced sequences done at small hospitals. In America I’m asked how we do it – they say it’s impossible.”
In part it comes down to the health care system – one that allows relatively easy transfer of imaging between hospitals, he said.
“We’re generally working in public hospitals that are part of the same network that work together a bit more cohesively than the very siloed, more commercial approach in the US”.
But it was also a matter of having ‘a legacy of more advanced stroke imaging as standard care’, he emphasised.
“For us a stroke patient gets a non-contrast CT, a CT perfusion, a CT angiogram, which tells you everything you could possibly want to know about the stroke. It means you can make sensible decisions, you know whats caused the stroke in many cases and whether there’s salvageable brain and that means you can treat at any time not just in the first few hours.”
The study was published in JAMA Neurology