The dynamics of platelet thrombus formation rate, thrombus retention time, and rate of embolization on a control and heparin bonded polyurethane angio-catheter. The dynamics of platelet deposition and embolization from control and heparin bonded polyurethane catheters (CPC and HBPC) was evaluated with In-111 labeled autologous platelets (IN-PLT) and a computerized gamma camera (CGC). Ten non-heparinized dogs (18-25 kg) were catheterized in both femoral arteries with 10 cm of CPC and HBPC (5 Fr., Cordis) 24 hr after injection of 300-420 microCi of In-PLT, and imaged for 3 hr with the computerized gamma camera. The regional platelet deposition curves (RPDC) indicated multiple peaks and valleys; the curves were analyzed for early rate of thrombus formation (upswing), thrombus retention time (full width at half maxima of the RPDC-peak), and rate of embolization (downswing) on both catheters. The four parameters (mean +/- SD) of thrombosis on catheters and integral of the radioactivity time curve for the 3 hr duration of imaging were calculated from normalized counts/sec. The rate of thrombus formation and rate of embolization are higher for the control than HBPC, suggesting that heparin-bonding decreases the early rate of thrombosis and embolization. The thrombus adhesivity and retention time appear shorter for the control catheter, indicating that the control thrombogenic catheter forms multiple thrombi and emboli than HBPC. The integral appears larger for the control catheter than HBPC. In vivo (dynamic) studies, in vitro studies, and critical analyses of the radioactivity time curve were essential for complete evaluation of thrombogenicity of catheters and other cardiovascular prostheses. 