“Time is brain”: assessing how Prehospital Video Triage (PVT) is improving the speed, cost-efficiency and effectiveness of London’s acute stroke pathways

Strokes are responsible for causing more deaths and disabilities than almost any other condition in London. Mitigating their devastating impact has been a priority across our capital for some years; we’ve made a real difference to outcomes through pioneering new models of care like the London Stroke Model and trialling innovations like Point of Care testing for biomarkers related to clotting and brain bleeds. The good news is that thanks to these coordinated and concerted efforts, if you have a stroke today, your risk of death or disability is about 25% lower than it was in the year 2000 – but there’s much more to do.

At the heart of continuing to drive progress through innovation is our “need for speed”. Act FAST is what we ask the public to do if they suspect stroke; acting fast is also our own mantra for delivering high-quality stroke care. But speed alone is not everything – particularly if the ambulance carrying a patient with a suspected stroke is headed towards a service that doesn’t offer the right care for their individual needs. Making the best possible initial decision about what treatment pathway the patient needs is also critically important.

Our philosophy of making the right pathway decision first time and then getting to the right treatment as quickly as possible is especially true for mechanical thrombectomy.  This procedure – where blood clots in the brain are physically removed using a catheter device – is one of the most effective tools we have to restore blood flow and end a stroke event. Every year about 1,200 Londoners will have a stroke where the best treatment option is a mechanical thrombectomy.

The challenge of optimising access to mechanical thrombectomy is threefold. Firstly, deciding on whether a mechanical thrombectomy is likely to be a safe and effective treatment is a decision that can only be taken by a specialist stroke clinician, traditionally requiring transportation to a treatment centre for assessment. Secondly, performing the procedure requires highly specialist equipment and training, meaning that not all urgent stroke treatment centres (called Hyper Acute Stroke Units; HASUs) are able to offer them. Thirdly, effectiveness is highly time-dependent – for every hour saved between the onset of the stroke and the procedure taking place, the chance of a positive long-term prognosis increases by about 25%.

Combined, these factors have historically made stroke care in London a lot more of a lottery than it should be. Too many patients have had their mechanical thrombectomy procedures delayed because of what amounts to bad luck in where they were physically located when the stroke took place, or initially being taken to the wrong HASU or emergency department because of a lack of accuracy in current stroke triage approaches.

The price of those delays is stark: avoidable life-changing disabilities or even death.

Prehospital Video Triage (PVT): using video technology to put stroke specialists “in the ambulance”

Originally piloted during the Covid-19 pandemic in North Central London, PVT provides a digital link between ambulance services assessing patients with a possible stroke and expert stroke specialists.

Using video technology, specialist clinicians can deliver a remote assessment of the patient, allowing for more accurate triage and direction towards the most appropriate service for treatment or further investigation. As well as rapidly identifying patients for whom mechanical thrombectomy is the best option, this assessment provides for differential triage of those presenting with symptoms that can mimic stroke – such as Bell’s Palsy, some infections or seizures, those with rapidly resolving symptoms known as Transient Ischaemic Attacks (TIAs), and those requiring stroke unit care but who are unlikely to require thrombectomy. This rapid remote assessment ensures that each person can receive tailored care led by the most appropriate service.

A major evaluation of more than 6,500 patients triaged via North Central London’s stroke pathway between 2020 and 2024 highlighted some of the potential benefits. Based on results shared at 2026’s European Stroke Organisation Conference by Dr Jonathan Best:

• PVT demonstrated a similar sensitivity to current assessment approaches, with substantially better specificity. In simple terms this means it correctly identified strokes at least as well as the current assessments used, while significantly reducing the number of instances where a “false positive” was recorded (i.e. a stroke was indicated after the initial assessment, but further examination finds this to be incorrect).
• Using PVT, around 30% fewer non-stroke HASU admissions occurred than would have been expected using the previous usual stroke screening tool (FAST) alone.
• Patients treated following PVT had an 18% shorter time between hospital arrival and beginning thrombectomy treatment, likely due to improved intelligence about inbound patients.

Combined, these results show the role PVT could play in improving how services care for people with suspected strokes – helping to ensure that limited resources are deployed effectively to treat the most urgent stroke cases as quickly as possible.

This evaluation was focused on a pathway based around a single HASU. If a pan-London implementation including all eight HASUs achieved similar results, benefit at an even greater scale would be expected, given how treatment centres are distributed across the capital.

Health economics and the return on investment for Prehospital Video Triage (PVT)

Recently, the Health Innovation Network South London also conducted a return on investment analysis to help understand the financial implications of adopting PVT at a pan-London level.

This analysis weighed the costs of implementing and running a pan-London PVT service over five years (such as providing specialist clinicians to run a 24/7 service, software costs and training for London Ambulance Service clinicians) against the direct NHS benefits accrued during the same time period (such as reduced inappropriate HASU admissions, cost savings from improved outcomes following earlier access to thrombectomy, reduced urgent care attendances, recurrent stroke cases prevented and reduced inter-facility transfers).

The results were compelling: for every £1 spent on delivering PVT, the NHS in London should expect to realise £2.25 in benefits.

These benefits were distributed evenly across three major components: reduction in inappropriate HASU admissions (approximately 30% of total benefits), earlier access to mechanical thrombectomy (26%), and avoidance of inter-facility transfer costs for non-stroke cases (29%). The remaining 15% of benefits arose from reduced ED attendances, avoided GP appointments for suspected TIA cases, and the prevention of recurrent strokes following TIA through earlier treatment.

What comes next: ensuring Prehospital Video Triage (PVT) becomes a sustainable platform for further innovation

All the data we have suggests embedding PVT across London should be a foregone conclusion. It improves outcomes, it saves money and it doesn’t harm the patient or staff experience. Indeed, the findings from London are being used to guide PVT roll-outs in other parts of the country.

However, the reality is that the scale and complexity of London brings some unique challenges. Although the London Ambulance Service covers the entire capital, treatment for suspected and confirmed strokes is split between eight HASUs, six thrombectomy centres and 21 TIA clinics and emergency departments, as well as hundreds of primary care services. For PVT to work for London’s nine million residents, each of these services must be able to act together seamlessly and at lightning speed.

With significant changes currently taking place to how the NHS in London is organised at a city and regional level, coordinating a shift towards PVT as “business as usual” is particularly tricky. We’ll need to demonstrate some of the same sense of ambition and perseverance as the originators of the London Stroke Model did, nearly twenty years ago.

Excitingly, PVT isn’t the only innovation we’re harnessing to improve stroke care. In fact, it is part of our vision for the “London Stroke Model 2.0” – intended to make London the world’s leading city for stroke treatment and post-acute care. Building on the existing London Stroke Model, PVT will be combined with rapid Point of Care blood testing to allow for definitive pre-hospital decision making and direct to mechanical thrombectomy transfers; greater coordination with TIA centres will enable next-day clinic bookings. The transformation won’t stop there: further integration with frailty and neurology services and patient data platforms including the Universal Care Plan will allow for more joined-up and person-centred treatment; and technologies such as Ambient Voice Technology will significantly reduce the time clinicians spend documenting cases during triage, improving efficiency and enabling more effective call handling.

It won’t be easy, but if there’s any city in the world with the innovative capabilities to transform stroke care – it’s London.