Elevated prothrombin and activated protein C resistance in patients with thoracic aortic atheroma.

Patients with protruding aortic atheroma containing mobile emboli are at risk for peripheral emboli and stroke. This risk may possibly be reduced by anticoagulation, but whether or not such patients have an increased prevalence of thrombotic risk factors has not been previously determined. Twenty-two patients were studied (11 with protruding thoracic aortic atheromas and superimposed mobile thrombi on transesophageal echocardiography were compared to 11 age-matched controls). The authors evaluated activated protein C resistance (APC-R) by measuring the prolongation of the partial thromboplastin time (PTT) in response to activated protein C (APC). Concentrations of fibrinogen, antithrombin III (AT III), factor II, factor V, and D-dimer were also determined in all patients. There was significant resistance to APC (a smaller prolongation in PTT) in patients with atheromas and thrombi. They also had significantly higher concentrations of factor II. Factor V and fibrinogen were higher, and AT III lower, in patients than in controls; however, these latter differences did not reach statistical significance. Patients with aortic atheroma and mobile thrombi may have an increased prevalence of thrombotic risk factors. There is significantly increased resistance to activated protein C in patients with protruding atheroma and mobile thrombi in their thoracic aorta. There was also a trend toward elevated fibrinogen, homocysteine, and apo (a) concentrations as well as lower antithrombin III concentrations in these patients.