Q&A: The benefits and technology behind mechanical thrombectomy

Michael Gilvarry, general manager at the Neuro Technology Centre in Galway for Cerenovus, part of Johnson & Johnson Medical Devices Companies, spoke to Med-Tech Innovation News about mechanical thrombectomy procedure for ischemic stroke, the technology behind it, as well as its benefits.  

Tell us about the mechanical thrombectomy procedure for treating ischemic stroke?

Mechanical thrombectomy is a minimally invasive procedure that offers a strong benefit to ischemic stroke patients over standard medical therapy (i.e. intravenous thrombolysis) in the first six hours after stroke onset, but also in a subset of patients in the 6-24 hour window. 

With stroke, time is brain - every second counts. The quicker and more completely a clot can be removed to restore blood flow to the brain the better it is for the patient. The greatest benefits to a patient is when mechanical thrombectomy retrieves (or catches) the stroke causing clot entirely at the first pass or attempt. When the first pass is successful, it avoids repeated clot retrievals attempts, therefore reducing the risk of complications and procedure time. 

The European Stroke Organisation (ESO) recommends mechanical thrombectomy as a gold standard treatment option for ischemic stroke; however, it is drastically underused as a first line treatment for stroke. It is estimated that annually 13.7 million people globally will have a stroke, and 85% of those will be ischemic. Although stroke survival has improved, stroke is still a leading cause of disability worldwide and has social and economic impact, and   the burden of stroke is likely to increase substantially in the next 10 years. 

What technology is used in such surgery?

During a mechanical thrombectomy procedure, catheters are inserted into an artery in the groin and threaded all the way through the arteries in the neck, and into the brain until it reaches the blood clot which has caused the stroke using fluoroscopy guided imaging. A stent-like clot retriever is inserted through catheter, deployed, and is then ‘retrieved’ or pulled backwards to remove the clot. 

Innovating and improving existing devices is one of the ways we can improve treatment in stroke and large vessel occlusion. Key to the success of any mechanical thrombectomy procedure is achieving first pass success (substantial reperfusion of a thrombolysis Cerebral Infarction (mTICI)) by removing the clot in one attempt. In the ARISE II study, over 90% of patients achieved substantial reperfusion, and the Cerenovus Embotrap Revascularisation Device accounted for over 50% of successful first pass reperfusions.

Interventional devices have transformed first-line stroke treatment and will continue to do so over the next 20 years, however more hospitals and clinics may need to look beyond short-term cost to long term savings and could benefit from implementing the procedure in the stroke pathway. With COVID-19 that may be hard to consider at the moment. 

In the UK there are approximately 100,000 strokes a year and 1.2 million stroke survivors. Before COVID-19, the NHS set out The National Stroke Programme to deliver better treatment and care to stroke patients. In light of the changes forced upon health services by the COVID-19 pandemic, the need to deploy resources efficiently is even more pressing. This certainly applies in stroke medicine where mechanical thrombectomy plus best medical management is recommended in national guidelines. 

A study has revealed the economic impacts of the practice – can you give us specifics for the UK and Ireland?

Data from a U.K. study published in the Journal of NeuroInterventional Surgery (JNIS) show that the improved clinical outcomes associated with the first pass effect (FPE) led to lower healthcare resource use and lower estimated costs in the first year after stroke. 

Achieving FPE led to potential per-patient per case acute (i.e. procedural/hospitalisation-related costs) cost savings of £1,751; and a per-patient annual care cost savings in the first year after stroke of £2,132. 

When looking at mechanical thrombectomy, it is essential to consider the long-term consequences of stroke, and therefore look at the long-term costs benefits rather than short-term expenditures. Other studies show mechanical thrombectomy is more cost effective when viewed in terms of the incremental cost per quality-adjusted life year (QALY) gained. It is associated with an incremental cost per QALY gained of £7,061 (over 20 years). That is significantly lower than many other standard medical therapies deployed in the NHS. 

As well as offering better clinical outcomes, mechanical thrombectomy reduces in-hospital time. In the ARISE II study, successful first pass reperfusion through mechanical thrombectomy with the EmboTrap II device led to a reduction in length of stay in hospitals to 6.1 days from 9.5 days, when compared to patients who did not achieve first pass effect. When we consider the potential capacity which could be made available through increased use of this this procedure, treating stroke with mechanical thrombectomy and achieving first pass may have a real impact on finite resources.

What further innovation can we expect from Cerenovus in the future?

We are continuing to better our understanding of clot science, through our Neuro Thromboembolic Initiative (NTI). This is a commitment to advance the treatment of stroke through interdisciplinary collaboration and investment in clot and stroke research. How we understand clots and their behaviour enhances our opportunity to design devices that improve patient outcomes and, overall, advance the treatment of acute ischemic stroke.

We know that nearly a quarter of mechanical thrombectomies fail after three attempts, and we also know that each attempt changes the composition of the clot, increasing the difficulty of retrieval. We are committed to ensuring that as many patients as possible benefit from this effective therapy, and this year we added the Cerenovus Nimbus device to our Stroke Solutions suite, specifically designed to facilitate tough and resistant clot removal.

Only by furthering our understanding of clot composition and behaviour will we be able to develop innovative therapies to effectively treat ischemic stroke, giving patients the best chance at a positive outcome.

Our vision is that neurointerventionists will have the tools and the understanding to achieve first pass with as many patients as possible, thereby potentially avoiding or reducing the devastating impact of stroke on patients, their loved ones and society as a whole.