Photo series of unblocking a mock blood vessel
What's the study: For a faster, safer way to treat pulmonary embolism—potentially deadly blood clots stuck in the lungs—engineers and vascular surgeons are joining forces to develop a minimally invasive "vortex ultrasound" device.
The tiny ultrasound source will be mounted on the end of a catheter, to be delivered to the clot through blood vessels. Once there, it will send out twisting sound waves to break up the clot without damaging the blood vessel walls. The team believes that the swirling waves break up the clot's internal structure more quickly by creating bubbles within it.
Why it matters: Pulmonary embolism is the third most common cardiovascular killer in the United States after heart attack and stroke. When large blood clots break loose from the legs and travel to the lungs, they block oxygen exchange and put sudden, deadly strain on the heart.
Current emergency options present tough trade-offs: clot-busting drugs can take up to 24 hours to work, fail about a third of the time and carry a serious risk of internal bleeding, while mechanically removing the clot with a catheter device risks tearing fragile blood vessel walls. The most severe clots must be removed through open-chest surgery.
External ultrasound approaches may sound safer for blood vessel walls than catheter removal or surgery, but they often fail to accurately target the clot and hardly work in the lung because its internal structures interfere with ultrasound waves. However, by changing the kind of ultrasound used and administering it inside the blood vessel, the team believes they can achieve fast treatment while reducing the risk of internal bleeding. Preliminary tests suggest that their twisted ultrasound waves could break up clots in as little as 30 minutes.
How much and for how long: A $3.74 million grant from the National Institutes of Health will fund the five-year project.
The current project builds on early proof-of-concept testing in which the research team demonstrated that vortex ultrasound could restore blood flow through a three-inch-long blood clot in just eight minutes, using blood from cows. Over the next five years, the team will refine the catheter design, optimize the shape and frequency of the ultrasound waves, and evaluate short- and long-term safety in pigs to prepare the technology for human clinical use.
Who's involved: Principal investigator Chengzhi Shi is an associate professor of mechanical engineering whose research focuses on physical acoustics, metamaterials and ultrasound technologies for medical treatments.
"With this approach, we hope to treat clots in the lungs more quickly and safely while potentially providing an alternative to open-chest surgery for severe pulmonary embolism," Shi said.
Key collaborators on the grant include Daniel Myers , the Conrad and Caroline Jobst Research Professor of Vascular Surgery, and Andrea Obi , the Wakefield Family Research Professor, both from the U-M Medical School; Zhen Xu , the Li Ka Shing Endowed Professor of Biomedical Engineering at U-M; and Xiaoning Jiang , professor of mechanical and aerospace engineering at North Carolina State University.