797-1 Differential Expression of Tissue Factor Protein in Directional Atherectomy Specimens from Patients with Stable and Unstable Coronary Syndromes

Tissue factor (TF) is a cell membrane-associated protein that catalyzes the rate-limiting step of the extrinsic coagulation pathway, which is the major source of thrombin production in-vivo. To examine the potential role that TF may play in the pathogenesis of different coronary syndromes, we studied directional coronary atherectomy specimens ftom 57 patients, using immunohistochemical techniques. Patients were classified according to their admission diagnosis as having either an unstable coronary syndrome, which required the presence of rest angina or post-infarction (<1 week) angina, or stable coronary syndromes which included stable, progressive and newonset angina without rest chest pain. Lesions were also classified as a denovo or a restenosis lesion. Frozen sections were examined for the presence of TF using a murine IgG monoclonal antibody against human tissue factor. Samples were read independently by two investigators without knowledge of the clinical information. The results were expressed dichotomously as positive or negative using human skin sections as a positive control and a nonsense murine monoclonal antibody as a negative control. Statistical analysis were performed using a Chi-Square or Fischer's Exact Test. For the entire study group, TF was detected in 15 (45%) of 33 patients with unstable coronary syndromes versus only 3 (13%) of 24 patients with stable coronary syndromes; p ≤ 0.02. Moreover, within the subgroup of patients with unstable coronary syndromes, TF protein was detected in 14 (61%) of 23 patients with de-novo lesions versus only 1 (10%) of 10 patients with rest angina from a restenosis lesion; p ≤ 0.01. An additional 7 patients with stable coronary syndromes due to a restenosis lesion were also all negative for TF, for an overall incidence of only 1 (6%) of 17 restenosis lesions. In conclusion, tissue factor is readily detected in atherectomy specimens from de-novo lesions in patients with unstable coronary syndromes, suggesting a role for this protein in the pathogenesis of this disease process. Conversely, tissue factor is rarely detected in patients with restenosis lesions even if the clinical presentation is an unstable coronary syndrome. These results may have implications in regard to the management of patients with unstable angina from de-novo lesions and all patients with recurrent symptoms from restenosis lesions