[Image courtesy of Stanford University]
Stanford researchers have developed a new mechanical thrombectomy device that could improve how doctors treat stroke and other clot-related diseases.
The “milli-spinner” is a catheter-delivered tool that uses rotation and suction to compress and remove blood clots without breaking them apart. In preclinical studies, it restored blood flow on the first attempt in up to 90% of tough-to-treat clots, compared to 11% with current devices, potentially offering a safer and faster alternative for patients, according to the researchers.
“With existing technology, there’s no way to reduce the size of the clot. They rely on deforming and rupturing the clot to remove it,” said Renee Zhao, an assistant professor of mechanical engineering and senior author on the paper. “What’s unique about the milli-spinner is that it applies compression and shear forces to shrink the entire clot, dramatically reducing the volume without causing rupture.”
A new approach to an old challenge
During an ischemic stroke, a clot blocks blood flow to part of the brain. Existing thrombectomy devices, which vacuum or snare the clot, succeed on the first try only about half the time. Roughly 15% of attempts fail altogether.
The milli-spinner targets this problem using a different mechanical approach. Rather than pulling clots out intact or trying to break them up, the device compresses and compacts them.
It consists of a hollow, catheter-compatible tube that spins rapidly. A system of fins and slits near the tip creates localized suction that draws the clot against the spinning end. That combination of compression and shear forces compacts the fibrin into a tight ball.
In doing so, the device allows red blood cells trapped in the fibrin to escape and flow freely again. The remaining compact clot core is then suctioned out through the device.
“It works so well, for a wide range of clot compositions and sizes,” Zhao said. “Even for tough, fibrin-rich clots, which are impossible to treat with current technologies, our milli-spinner can treat them using this simple yet powerful mechanics concept to densify the fibrin network and shrink the clot.”
From propulsion to clot removal
The technology originated as an offshoot of Zhao’s work on millirobots, which are tiny machines designed to navigate the body and deliver targeted treatments. Initially conceived as a propulsion device, the milli-spinner’s ability to generate suction turned out to be critical.
“At first, we simply wondered whether this suction could help remove a blood clot,“ Zhao said. “But when we tested the spinner on a clot, we observed a striking clot color change, from red to white, along with a dramatic reduction in volume. Honestly, it felt like magic. We didn’t fully understand the mechanism at the time.“
That early success led to hundreds of design iterations, culminating in a device that performed well in both lab and animal models. The team has since launched a company to bring the technology to market.
Zhao’s team is also exploring other potential uses for the spinner’s suction-based mechanics, including removing kidney stone fragments and developing an untethered version that could swim through blood vessels to treat clots remotely.
“We’re exploring other biomedical applications for the milli-spinner design, and even possibilities beyond medicine,“ Zhao said. “There are some very exciting opportunities ahead.“
The device is not yet approved for use in humans, but the researchers say they are moving quickly toward trials.
“What makes this technology truly exciting is its unique mechanism to actively reshape and compact clots, rather than just extracting them,“ Zhao said. “We’re working to bring this into clinical settings, where it could significantly boost the success rate of thrombectomy procedures and save patients’ lives.“
