111In platelet deposition following peripheral arterial thrombolysis

Streptokinase (Sk) and recombinant tissue plasminogen activator (rt-PA) have widely different effects on platelet aggregation. We have therefore undertaken a prospective evaluation of the deposition of indium-111 platelets following peripheral arterial thrombolysis. Seventeen patients were studied using autologous indium-111 labelled platelets. Patients were randomly allocated to receive 0.5 mg h-1 intra-arterial rt-PA (ten patients), or 5000 units h-1 Sk and 250 units h-1 heparin intra-arterially (seven patients). Initial uptake ratios (comparing affected limb to contra-lateral limb) at 24 h were usually low for both agents (medians: Sk 1.17; rt-PA 1.20) despite previous angioplasty or extensive thrombosis. There were minimally higher uptake ratios at 48 h and 72 h following Sk (1.64-1.45), than with intra-arterial rt-PA (0.93-1.43). Overall, two patients (one from each group) failed to achieve complete lysis or incurred early rethrombosis. Both were associated with a progressive increase in uptake ratio which was not present in those patients with successful initial lysis and continued patency at 30 days (1.18-0.94-1.19). We have been unable to demonstrate any significant difference in post-lysis platelet deposition between intra-arterial streptokinase and recombinant tissue plasminogen activator in this preliminary study. However, higher platelet deposition was associated with failure to achieve complete lysis and early rethrombosis. Concurrent therapy with antiplatelet agents may therefore be indicated in these patients.