Abstract 14121: Molecular Imaging Using Bubble Immune-Liposomes and Echocardiography to Detect Thrombus in Left Atrial Appendage in Canine Hearts

Abstract

Background: Although the presence of thrombus in left atrial appendage was widely known to increase the risk of cerebral infarction in patients with atrial fibrillation, but its morphology was amorphous and has been difficult for the detection and histological evaluation using the conventional echocardiography in the clinical settings. Liposomes are nanoparticles that can deliver various agents to target tissues such as bubble and could be coated with antibody or peptide binding to the target molecule. We investigated whether immune-bubble liposomes could detect the thrombus in left atrial appendage in dogs.

Methods and Results:Bubble liposomes coated with RGD peptide (Arg-Gly-Asp) were prepared by reverse-phase evaporation lipid vesices (REV) and sonication methods. RGD peptide has an affinity to integrin (α_vβ₃)which was abundant in the thrombus. We ligated the left atrial appendage of anesthetic dogs for 120 minutes (n=4). After the identification of thrombus evaluated by echocardiography, firstly we intravenously administed saline under the observation of echocardiography as control study (Figure A). Ten minutes after the infusion of saline, we intravenously administered immune-bubble liposomes. Thrombus in left auricular appendage was clearly identified using echocardiography as indicated the white arrow (Figure B). The histological analysis of the amorphous material at left atrial appendage sampled at the end of the experimental protocol showed the presence of thrombus (Figure C).

Conclusion:By adding immune-bubble liposomes, thrombus in left atrial appendage can be clearly recognized. Echocardiography using immune-bubble liposomes provide the diagnostic information of the thrombus in left auricular appendage in dogs. Bubble liposomes targeting to the molecule could be a novel echocardiographic modality.