Mechanical Thrombectomy – Faster Than Ever
Hildegard Kaulen | 2016-02-17
Professor Martin Bendszus and his team are reducing the transfer time between stroke diagnosis and mechanical thrombectomy. By combining a CT scanner with a mobile C-arm in a single room, they cut picture-to-puncture times to just 35 minutes for the first three patients.
Photos: Carsten Buell
Mechanical Thrombectomy Now Crucial
The stroke world has changed. For a long time, the only proven effective treatment for acute ischemic stroke was intravenously administered thrombolysis with recombinant tissue-type plasminogen activator (r-tPA). Now, mechanical thrombectomy has advanced to become an important option. Clinical studies with names such as MR CLEAN, ESCAPE, EXTEND-IA, and SWIFT-PRIME have demonstrated that interventional clot retrieval improves outcomes for certain stroke patients. The evidence was so convincing that the American Heart Association / American Stroke Association updated its guidelines in June 2015 to give the strongest recommendation possible for patients who meet certain criteria: class 1, level of evidence A.
“Since the studies were published, we have received many more referrals from hospitals in the area, and we doubled our numbers in 2015,” says Professor Martin Bendszus, MD, Head of Neuroradiology at Heidelberg University Hospital in Germany. His department is a key component in one of Germany’s leading stroke centers, treating hundreds of stroke patients every year. Bendszus estimates that, with strict eligibility criteria, around 15 percent of the 270,000 strokes that occur annually in Germany could potentially be considered candidates for mechanical thrombectomy. He estimates that this number could increase to 20 percent with broader criteria.
Time is Brain
In addition to the patient’s age and the National Institutes of Health Stroke Scale (NIHSS), the crucial factor in a stroke is the time it takes to restore perfusion. “Recent trials have shown that if the blocked artery can be recanalized 20 minutes faster, it will increase the chances of a better clinical outcome by between 10 and 15 percent,” says Bendszus. Unfortunately, most hospitals lose critical time transferring patients between the emergency room, diagnostic imaging, and the interventional suite, as well as during the negotiations that precede each transfer.
In Heidelberg, the CT and biplane angiography systems are located in adjacent rooms, yet it still takes 15 to 20 minutes to move a patient. When the brain is not perfused, approximately two million brain cells die every minute. This is why, when planning his second thrombectomy suite, Bendszus wanted the diagnostic imaging and the mechanical opening of the artery to take place on one table in one room. In a combined system, the technical personnel can begin preparing for the intervention as soon as the patient has been scanned. This is the best way to minimize picture-to-puncture times.
Three Requirements for the New Suite
The suite had to not restrict normal CT operation. Bendszus’ team performs over 15,000 CT examinations annually, so it had to be able to use the room for normal daily routine, too. The system also had to be similar to a standard angio system in terms of usability so that everyone performing a mechanical thrombectomy would be immediately familiar with the system – and it had to provide good enough image quality for the procedure to be performed safely. Finally, the setup had to allow for very rapid switching from CT to intervention if there was an acute indication for a thrombectomy.
The new suite is equipped with a 64-slice CT system for diagnostic imaging. The adjacent room houses a mobile C-arm with flat detector technology for the mechanical thrombectomy. It takes five minutes to set up. The CT table is positioned 95 cm from the gantry so that the C-arm can slot into this space during the intervention. The standard CT table is made of carbon and is longer than usual to make it suitable for the thrombectomy. Controls for everything are mounted at the side of the table or on a trolley. The two monitors are mounted on the ceiling, and there is a radiation protection wall. “What makes it so special is its simplicity,” explains Bendszus. “We’re using the systems without any expensive reconstruction costs, and are achieving a high level of flexibility and accessibility.”
In a Siemens-supported study1, Bendszus and colleagues showed that diagnosing and treating patients with the combined system is feasible. “The combination is just as suited to this procedure as conventional angiography systems are,” says Johannes Pfaff, MD, the physician in charge of the study. He and Bendszus treated three patients (aged between 51 and 84) for the study. “The average time between diagnostic scan and puncture of the femoral artery was 35 minutes,” says Pfaff. “The time between high-quality CT stroke imaging and groin puncture could fall to just 28 minutes. We have never been so fast.”
Crucially, time was saved by keeping the patient in one place. In previous studies, moving a patient from the CT room to the neighboring angio suite led to picture-to-puncture times of 57 minutes, and picture-to-recanalization times of 250 minutes. “The problem now is we’re so fast that the logistics have to be adjusted,” says Bendszus. “The anesthetist should theoretically already be in the room for the diagnostic CT scan.” Following the feasibility study, a larger study will now be conducted with 50 patients in order to confirm the impressive times. “We have already included 34 patients,” says Pfaff. “We hope to publish the results this year.”
Who is Eligible for Mechanical Thrombectomy?
“We decide on the basis of the infarct core and the size of penumbra – not just on the basis of the time elapsed after symptom onset,” says Bendszus. The infarct core is the amount of irreversibly damaged tissue. The penumbra is malperfused tissue that may still be saved through fast recanalization. Core and penumbra are both measured using CT perfusion imaging. In published studies, mechanical thrombectomy was performed within 12 hours from symptom onset. “If the infarct core is small and the penumbra is large, the time elapsed is less relevant,” says Bendszus.
Bendszus also considers a wider range of indications. The published studies report on the treatment of patients with occlusions in the internal carotid artery and the proximal middle cerebral artery. In Heidelberg, more distally located thrombi are also removed using stent retrievers. The primary risk is that part of the thrombus is lost during retrieval, causing a new embolization elsewhere. “We can perform a diagnostic CT scan at any point during the intervention, which allows us to react immediately to any complications,” says Pfaff. “This is a significant safety factor.”
Structured Training is Key
So which hospitals should offer mechanical thrombectomy? “Maximum care hospitals with a department of neurology must offer this procedure,” says Bendszus. “However, proper training for the intervention is essential. You have to understand the approach and learn how to probe the vessels. You also have to understand the diagnostic images.” Bendszus is therefore calling for structured training. He stresses that it is now up to professional medical associations to ensure that high-quality care is available across Germany in the near future.
Bendszus also has a new trauma room concept in mind. Following the diagnostic CT scan, various vascular interventions could be performed on the same table. The effectiveness of the treatment can then be checked as required during the intervention using CT imaging. “The amazing thing is that it’s so easy to implement and there is no need for additional construction work,” says Bendszus. “Here, the technology is driving the clinical applications forward.”
About the Author
Hildegard Kaulen, PhD, is a molecular biologist. After working at Rockefeller University in New York and Harvard Medical School in Boston, she became a freelance science journalist in the mid-1990s. Her work appears in many quality daily newspapers and scientific journals.
1published in May 2015 in the Journal of Neurointerventional Surgery (doi:10.1136/neurintsurg-2015-011744).
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