The study by researchers from Royal Melbourne Hospital and their collaborators at Monash University and Monash Health was published in the New England Journal of Medicine.
Stroke is the second single greatest killer and one of the leading causes of disability amongst adults in Australia and worldwide. Eighty per cent of all strokes are caused by a blood clot blocking a blood vessel in the brain, known as an ischaemic stroke.
Adjunct Clinical Professor Thanh Phan, Department of Medicine at Monash University, said ischaemic stroke patients had improved outcomes when treated with a clot busting drug given intravenously within 4.5 hours of stroke onset.
“However, intravenous clot-busting drugs alone may not be effective enough if there is a very large clot blocking a major brain artery,” Professor Phan said.
“And bigger clots cause bigger damage. Our study has shown for the first time that an intervention known as stent-thrombectomy in addition to an intravenous clot-busting drug leads to significantly better outcomes for patients with large clot blockages.”
Stent-thrombectomy is a minimally invasive procedure performed via an angiogram (an x-ray procedure where dye is injected into the arteries to visualise the clot). A radiologist inserts a small tube (stent) via an artery in the groin and feeds it up into the brain to capture and remove the offending clot with a specialised retriever device.
Earlier randomised clinical trials using such devices were inconclusive. However, these studies used older devices, had longer times to treatment, as well as a lack of advanced imaging methods to identify the blockage and brain at risk.
“The success of this trial is likely due to better patient selection through the use of advanced imaging to detect salvageable brain tissue, blood vessel occlusion, as well as earlier time to treatment,” Professor Phan said.
This finding is in line with the Dutch MRCLEAN trial, published in the January issue of the same journal.
Lead researcher, Dr Bruce Campbell from the Royal Melbourne Hospital reported the significant findings of the Australian trial. Just 24 hours after suffering a stroke, the rate of re-opening of the blocked artery increased from 32 per cent in the group receiving the clot busting drug alone to 89 per cent in the group receiving both the clot busting drug and the intervention using the stent-retriever device. After three months, only 40 per cent of the group who received the clot busting drug alone had recovered their independence compared to 71 per cent in the group treated with the combined intervention.
Notably, there were no safety issues such as excessive bleeding in the brain with the device treatment.
“It is estimated from this trial that 10 per cent of patients undergoing clot busting therapy will also require this specialised treatment,” Professor Phan said.
In many countries, including Australia, there are a limited number of hospitals that can provide stent-thrombectomy and a limited number of specialists are trained to perform the procedure. Currently many patients have to be transferred between hospitals.
“An important implication from this trial is that patients with large clot blockages will need to be transferred to tertiary referral centres such as the Royal Melbourne Hospital and Monash Medical Centre,” Professor Phan said.
“This may have implications for health funding as selected hospitals will need to be designated as referral centres with appropriate resources in order to provide this type of therapy.”
The Monash team included members of the Stroke & Ageing Research Group at Monash University and the Stroke Unit, Monash Health (Professor Thanh Phan, Dr Henry Ma) and the Radiology Department at Monash Health (Associate Professor Winston Chong, Associate Professor Ronil Chandra).