Every minute counts during an ischemic stroke, a devastating event caused by a blood clot blocking vital oxygen flow to the brain. The faster doctors can remove the blockage and restore blood flow, the greater the chance of preserving brain cells and improving patient recovery. Tragically, data highlights the urgency: for every minute during a stroke, an estimated 1.9 million neurons and 14 billion synapses are destroyed.
Current methods for removing these dangerous clots, known as thrombectomy procedures, are only successful on the first attempt about half the time and fail entirely in roughly 15% of cases. A major challenge is that existing tools often rely on deforming or rupturing the clot to extract it. This can inadvertently break the tough, thread-like fibrin proteins that bind the clot, causing fragments to break off and lodge elsewhere in the circulatory system, making treatment even more difficult.
However, groundbreaking research from Stanford University is set to change this. Scientists at Stanford Engineering have developed a novel device called the milli-spinner thrombectomy, a potential game-changer for treating blood clots in conditions like stroke, heart attacks, and pulmonary embolisms.
Published in the journal Nature, the research demonstrates through advanced flow models and animal studies that the milli-spinner offers a significantly faster, simpler, and more complete way to tackle clots compared to existing technologies.
A Novel Approach to Clot Removal
Unlike conventional tools that pull or fragment clots, the milli-spinner utilizes a unique mechanical action to safely shrink and remove them. Delivered via a catheter inserted into the artery, the device is a long, hollow tube designed to rotate rapidly near the clot. It features specialized fins and slits that create localized suction.
This innovative design applies two primary forces – compression and shear – directly to the blood clot. Think of how you might compact a loose ball of tangled thread or hair: pressing it between your palms (compression) while moving your hands in a circular motion (shear) rolls the fibers into a smaller, denser ball without breaking the individual threads.
The milli-spinner works similarly on the fibrin network within a blood clot. The suction pulls the clot against the end of the tube, while the rapid spinning generates the shear force. This action effectively rolls and compacts the fibrin tangles into a significantly smaller, dense ball.
“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,” explains Renee Zhao, a Stanford assistant professor of mechanical engineering and senior author on the paper.
This process is incredibly effective, capable of shrinking a clot to just 5% of its original volume. A critical benefit is that it shakes free the trapped red blood cells, allowing them to flow freely, while the compacted fibrin ball is safely drawn into the milli-spinner’s hollow tube and removed from the body. Because the fibrin network remains largely intact, the risk of dangerous fragmentation is dramatically reduced.
Remarkable Improvements in Efficacy
The impact of this new technique on treatment success rates is profound.
“For most cases, we’re more than doubling the efficacy of current technology,” says Jeremy Heit, chief of Neuroimaging and Neurointervention at Stanford and an associate professor of radiology, who co-authored the study. “And for the toughest clots – which we’re only removing about 11% of the time with current devices – we’re getting the artery open on the first try 90% of the time.”
This nearly tenfold increase in first-attempt success for difficult-to-treat clots represents a major step forward. “It’s unbelievable. This is a sea-change technology that will drastically improve our ability to help people,” Heit adds.
The milli-spinner’s ability to treat a wide range of clot compositions and sizes, including those tough, fibrin-rich clots previously considered nearly impossible to remove, highlights its versatility and power.
Unexpected Origins and Future Potential
Interestingly, the milli-spinner’s design evolved from Zhao’s earlier work on tiny, origami-based millirobots intended for tasks like drug delivery. The spinning structure with fins and slits was initially conceived as a propulsion system. When researchers noticed it also generated localized suction, they explored its potential for blood clot removal. Early tests produced a “striking clot color change… along with a dramatic reduction in volume,” which Zhao described as feeling “like magic.” This unexpected observation spurred extensive research and design optimization.
While the initial focus is on stroke and other blood clot-related diseases like heart attacks and pulmonary embolisms, the milli-spinner’s unique mechanism has broader potential. Researchers are already exploring using its localized suction capability to capture and remove kidney stone fragments and investigating other biomedical and even non-medical applications. The team is also developing an untethered version that could potentially navigate blood vessels autonomously.
Driven by the potential to save lives and improve outcomes for patients, Zhao, Heit, and their colleagues are working rapidly to bring the milli-spinner thrombectomy to clinical use. A new company has been formed to license the technology from Stanford and accelerate its development, with clinical trials planned for the near future.
As Zhao emphasizes, “What makes this technology truly exciting is its unique mechanism to actively reshape and compact clots, rather than just extracting them. We’re working to bring this into clinical settings, where it could significantly boost the success rate of thrombectomy procedures and save patients’ lives.” This innovative approach represents a significant leap forward in the fight against devastating clot-related conditions.
