Can a coated Dacron vascular graft maintain a heparin-induced thrombocytopenia type II?

In the course of reconstruction of peripheral arterial occlusion processes, two gelatin-coated Dacron grafts and one collagen-coated Dacron patch were implanted in a 52-year-old male patient. Eight days following low-dose heparinization (5 days prior to surgery, 3 days postoperatively) with unfractionated heparin, with no clinical symptoms present, a dramatic isolated thrombocyte depression occurred, from 212 Gpt/l prior to surgery to 14 Gpt/l on postoperative day 3. Laboratory tests verified an HIT type II [heparin-induced platelet aggregation assay (HIPAA) and ELISA]. Despite immediate discontinuation of heparin and commencement of an anticoagulant therapy with Revasc and Refludan, an 8-week thrombocyte depression occurred which was eliminated only temporarily by administration of gammaglobulin. The specific antibody tests turned out positive for more than 5 months. Having ruled out other causes of thrombocytopenia, we assume that the case presented was either due to an interaction not elucidated to date or triggered by the grafts (gelatin/collagen/Dacron). The manufacturers of the grafts have disputed a heparinoid action.