ARFI ultrasound for in vivo monitoring of soft-tissue bleeding and hemostasis in a dog model of hemophilia

Dogs with hemophilia A and hemophilia B recapitulate the severe bleeding phenotype that occurs in humans with these disorders. We have investigated the use of Acoustic Radiation Force Impulse (ARFI) imaging as a method for assessing hemostasis in vivo in dogs with hemophilia A. ARFI imaging was performed in 6 normal, 7 hemophilia A, and 4 hemophilic dogs expressing canine factor FVIIa following gene transfer. Bleeding was induced by needle puncture in muscle and a 1-2 mm vein, and subcutaneous bleeding was monitored with ARFI for 100 minutes. Results showed delayed time to hemostasis in the hemophilia A dogs, consistent with the bleeding phenotype, but lower times to hemostasis in the FVIIa expressing dogs. These data suggest that ARFI imaging could be a relevant new hemostatic challenge for characterizing hemophilic phenotype.