Noninvasive radioisotopic technique for detection of platelet deposition on bovine pericardial mitral-valve prosthesis and in vitro quantification of visceral microembolism in dogs

Platelet deposition on bovine pericardial-tissue mitral-valve prostheses in dogs was observed noninvasively by use of 111In-labeled platelets and quantified after sacrifice at one, 14 and 30 days postimplantation (300-400 microCi of labeled platelets having been injected 24 hrs previously). Thrombosis on the sewing ring and pericardial leaflets at one and 14 days and on the leaflets at 30 days was delineated in scintiphotos. In vitro quantification (% injected dose) indicated that the sewing ring and perivalvular tissue retained 0.75% of labeled platelets at one day postimplantation, 0.084% at 14 days, and 0.0042% at 30 days. Platelet survival was reduced to 38 hrs at 21 days postimplantation but returned toward the normal (50 hrs) with endothelial covering of the sewing ring. Microemboli in lung and kidney, as measured by tissue/blood radioactivity ratio, decreased significantly at 30 days. 111In-labeled platelets thus provide a sensitive marker for noninvasive imaging and in vitro quantification of platelet deposition on valvular prostheses and microemboli trapped in viscera