Abstract 19348: The Impact of Hypothyroidism on Platelet-Fibrin Clot Characteristics in Patients Undergoing Cardiac Catheterization

Hypothyroidism and accompanying hypercholesterolemia are associated with accelerated atherosclerosis. Hypothyroidism has been associated with inflammation, endothelial dysfunction, and platelet function abnormalities. However, impact of hypothyroidism on the physical characteristics of the platelet-fibrin clot is unknown. We sought to determine the impact of hypothyroidism on platelet-fibrin clot characteristics in patients undergoing cardiac catheterization. Methods: Patients on 325 mg daily aspirin with (n=41) and without (n=286) a history of hypothyroidism undergoing cardiac catheterization were studied. Hypothyroidism was defined as treatment with thyroid hormone replacement. Blood samples were collected immediately prior to coronary angiography to determine clotting characteristics by thrombelastography (TEG). Urinary 11-dehydrothromboxane B 2 was performed by immunoassay method. Results: Baseline demographics and cardiac risk factors were similar between groups. Thyroid stimulating hormone levels were within the normal range with no significant difference between groups. Patients with a history of hypothyroidism had significantly higher thrombin-induced platelet fibrin clot strength(67.9±5.3 mm vs.66.1±5.8 mm, p=0.04) , faster time to initial thrombin formation (6.9±1.9 vs. 7.8±2.1, p=0.02) , and higher clotting index(0.7±2.4 vs. -0.4±2.0, p=0.005). There were no differences in urinary 11-dehydrothromboxane B 2 between groups. Conclusion: This is the first report that a history of hypothyroidism is associated with altered physical characteristics of the platelet-fibrin clot; an increase in the tensile strength of the clot. Further studies are needed to confirm this association and its relation to ischemic outcomes.