• Investigators have developed and tested a targeted contrast agent that can detect blood clots in the hearts of patients with atrial fibrillation, or an irregular heartbeat.
  • The strategy could be used to find clots in other parts of the body as well, such as in vessels that, when blocked, can lead to stroke.

Atrial fibrillation—an irregular and often rapid heart rate—is a common condition that can cause clots to form in the heart that may then dislodge and flow to the brain, potentially leading to a stroke. The standard way to detect these clots requires patients to be sedated and to have a fairly large tube inserted down the throat and esophagus for a transesophageal ultrasound. Investigators at Massachusetts General Hospital (MGH) have now developed and tested a targeted contrast agent to detect and image these clots noninvasively. They verified the potential of this strategy in a study published in JACC: Cardiovascular Imaging.

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The agent has a strong affinity for fibrin, a component of blood clots, and is detected with a radioactive copper tag. "The idea behind the technology is that the agent will find and bind to blood clots anywhere in the body—not just in the heart—and make the clots detectable like a bright star in the night sky," says senior author David Sosnovik, MD, FACC, director of the Program in Cardiovascular Imaging within MGH's Martinos Center for Biomedical Imaging and an associate professor of Medicine at Harvard Medical School. "In some ways this is analogous to doing a smart search with a search engine such as Google, where the search terms one uses guide the search. We inject the agent into a small peripheral vein and it circulates throughout the human body on its search for clots." If it doesn't find any clots, then it's rapidly excreted from the body; however, if it finds a clot and binds to it, clinicians can detect it with an imaging technique known as positron emission tomography.

Sosnovik and his colleagues first examined how the agent reacts (specifically, its metabolism and pharmacokinetics) in eight healthy volunteers. After injection, the agent was initially stable within the body and then was cleared from tissues within several hours, suggesting that it was safe. Next, the team administered the agent to patients with atrial fibrillation, some with clots in the heart and some without. Imaging tests of the heart revealed bright signals within the clots that were not seen in patients without clots.