Indium-III is 2.8 day half-life gamma emitting radionuclide which is suitable for scintigraphic study and has been used to label platelets without causing significant attenuation of function. The purpose of this study was to utilize this technique for localization of left ventricular mural thrombi in patients with regional LV dysfunction. The patient population consisted of 55 patients between the ages of 24 and 77 (53.4 ± 11.3, mean ± 1SD). Twenty-four required coronary artery bypass surgery with aneurysmectomy for intractable angina and/or heart failure. This provided an opportunity to validate the preoperative findings at surgery. Platelets were separated from 43 ml blood in ACD solution by centrifugation and were labelled in ACD:saline (1:7) solution at a pH of 6.5-7.0. A total of 3.8 ± 2.9 × 109 (mean ± 1SD) platelets labelled with 451.9 ± 111.6 μCi with a final labelling efficiency of 72.1±14.1% were injected IV. Platelet recovery at 15 minutes was 51.1 ± 17.7% (mean ± 1SD). EM studies before and after labelling showed no morphological change due to the labelling procedure. Aggregation of platelets in response to ADP and collagen was not altered significantly during the labelling process. Patients on aspirin showed the expected inhibitory effect of aspirin on collagen and ADP induced aggregation. Patients were imaged in multiple views on at least alternate days for a maximum of 8 days. Seventeen had positive studies. In those patients in which surgical confirmation of the scintigraphic studies was possible, a sensitivity of 72% and specificity of 100% was found. We conclude that: 1) Indium-111 platelet scintigraphy promises to be a reliable method of identifying intracardiac thrombi. 2) It may also be useful in monitoring thrombus activity in vivo. 3) Patients on aspirin incorporated platelets onto the thrombus surface in spite of showing the expected inhibitory response to ADP and collagen induced aggregation in vitro.
Identification of intracardiac thrombi in stroke patients with indium-111 platelet scintigraphy.