Fibrin-targeted MR contrast agent detects white cell coronary artery thrombi

CONTEXT: MR thrombus imaging has, until now, concentrated on the depiction of red blood cell thrombus composition. Another type of thrombus is involved, however. Fibrin-rich white cell thrombi are important during the early stages of acute coronary artery syndrome and in-stent restenosis. Dr. Rene Botnar and colleagues at Beth Israel Deaconess Medical Center in Boston tested the feasibility of imaging white thrombi in swine with EP-2104R, an investigational gadolinium-labeled fibrin-binding peptide.

RESULTS: Thrombi fabricated from human fibrogen, calcium, and blood were implanted in the right coronary, left anterior descending, and left circumflex arteries of three swine. All three thrombi in each animal were detected during free-breathing 3D balanced gradient-echo and navigator-gated T1-weighted inversion recovery MR imaging performed about two hours after contrast infusion. Botnar's findings were presented in February at the Society for Cardiovascular Magnetic Resonance meeting in Barcelona.

IMAGE: A fibrin-targeted contrast agent aids the delineation of an implanted thrombus (arrow) during T1-weighted imaging. Signal to noise in the thrombus rose about fivefold after contrast administration.

IMPLICATIONS: The feasibility of in vivo white thrombus imaging was confirmed. The fibrin-binding contrast medium EP-2104R, developed by Epix Medical in Cambridge, MA, may eventually find a place in the imaging of acute coronary syndrome, atrial fibrillation, and suspected pulmonary embolism, Botnar said.