PHANTOM-S: Mobile Stroke Unit Reduces Time to tPA

May 30, 2013

London, United Kingdom — Evaluation of stroke patients and administration of tissue plasminogen activator (tPA) in a special ambulance converted into a mobile stroke unit enabled more patients to be treated and reduced time to treatment in a German study.

The Pre-Hospital Acute Neurological Treatment and Optimization of Medical care in Stroke (PHANTOM-S) trial was reported today here at the XXII European Stroke Conference (ESC).

Presenting the study, Heinrich Audebert, MD, Charité-Universitätsmedizin Berlin, Germany, said: "We have shown that the use of mobile stroke units can be integrated into the emergency medical system, they are safe and they are superior to regular care for reducing time to tPA treatment."

Coauthor Martin Ebinger, MD, also from Charité-Universitätsmedizin, explained to journalists that the special stroke emergency mobile unit (STEMO) has a computed tomography (CT) scanner, a neurologist, and a radiology technician on board. "As soon as the patient is on board, they are given a CT scan, the results of which are transmitted to a neuroradiologist to read. The patient is clinically evaluated by the neurologist on board. If it is decided the patient fits the criteria, tPA is given in the ambulance."

"This is a radical new approach. It is well proven that reducing time to tPA treatment increase the chances of a good outcome. And we have shown that use of this mobile stroke unit can reduce time to treatment by about 25 minutes."

So far only 1 STEMO van is in use, serving an area defined by a 75% chance of reaching patients within 16 minutes, covering more than 1 million inhabitants.

The stroke emergency mobile unit (STEMO)

In his presentation, Dr. Audebert noted that despite efforts to streamline procedures in hospitals to provide treatment as soon as possible, the 4.5-hour time window from onset of symptoms means that most patients don't receive tPA. It is estimated that just 10% of stroke patients actually get such treatment, and this may increase to about 12% in specialized stroke centers.

The study compared randomly allocated periods with and without the mobile unit available. In total, 1804 evaluable patients were attended by the STEMO ambulance and were compared with 2965 patients who received regular emergency services.

Results showed that by using the STEMO van, more stroke patients received tPA, and the thrombolytic was administered 25 minutes faster.

Table. PHANTOM-S: Main Results

Endpoint Mobile Unit Control
Stroke patients given tPA (%) 33 21
Time to tPA (min) 52 77


Major bleeding rates and 7-day mortality did not differ between groups.

Dr. Ebinger commented to Medscape Medical News, "We increased the thrombolysis rate to 33%, a number hitherto unheard of, without any safety signal. The time reduction is also very impressive given that Berlin already has a very high level of stroke care."

Interesting Approach

Commenting to Medscape Medical News, Martin Brown, MD, University College London, who has applied for funding for a similar mobile stroke unit in London, said he thought it was an interesting approach.

"It certainly makes sense to try and get the treatment to the patient as soon as possible, and use of these mobile units is one way of doing this. The real question for me, however, is whether this is more efficient than trying to get patients to hospital more quickly. I would like to know how much difference 25 minutes makes and whether taking these experts away from the hospital is cost-effective."

The model is similar to that used for prehospital diagnosis of myocardial infarction, so that patients can be directed to the most appropriate hospital for interventional treatment, but Dr. Brown pointed out that the diagnosis of stroke is more complex than that of myocardial infarction.

"Paramedics can be trained relatively easily conduct an ECG [electrocardiogram], and this can be transmitted electronically to an expert to be read. But diagnosis of ischemic stroke requires a CT scan to rule out hemorrhagic stroke and an expert clinical examination. This could be done by camera but it is not the same as having an expert on board."

XXII European Stroke Conference. Large Clinical Trials 5. Presented May 30, 2013.


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