Abstract 531: In Patients with Uncontrolled Arterial Hypertension Platelets and Coagulation Factor XI are Responsible of Modifications of Thrombin Generation

Abstract

Background: Hypertensive crisis is an extreme phenotype of increased blood pressure that can lead to organ failure and thrombotic complications. We recently found in experimental hypertension an angiotensin II driven factor XI (FXI)-thrombin amplification loop leading to vascular injury. Objective: We wanted to evaluate, in patients with uncontrolled hypertension (HT), the role of platelet and factor XI in thrombin generation (TG). Patients and methods: Prospectively, 52 patients with uncontrolled HT (16 grade I and 36 grade II/III) were examined at the outpatient clinic and emergency room of the University Medical Center Mainz, and 16 controls. Calibrated automated thrombography (CAT) was used to measure TG in platelet rich plasma (PRP, adjusted to 150.109/L of platelets), platelet free plasma (PFP), with platelets from controls and uncontrolled HT patients resupsended in a pool of healthy controls and in the presence or absence of an antibody blocking FXI activation pathway. Results: We found an increased systolic blood pressure in HT patients, compared to control patients (179±1.9 mmHg for grade II/III patients, 139±1.2 mmHg for grade I patients and 123±2.5 mmHg for controls); age, BMI as well as weight were not different. TG in PRP showed a positive and significant correlation between blood pressure and the other TG parameters as Endogenous thrombin potential (ETP), peak TG and velocity of TG. ETP was significantly increased in grade II/III patients compared to the control group. TG parameters in HT patients and controls were completely blunted by the inhibition of FXI pathway by blocking its apple 3 domain. This result indicates an involvement of the FXI thrombin loop in thrombin generation in PRP of uncontrolled HT patients. Without platelets TG showed no difference between HT patients and controls. Platelets resuspended from HT or controls restored the differences in ETP, peak and velocity between the 2 groups indicating that increased TG in HT patient mostly depends on platelet overreactivity. Conclusion: These results point out the important role of platelet overreactivity as well as FXI-dependent thrombin activation pathway in hypertension. Monitoring the prothrombotic state of platelets might add to risk stratification of patients with HT.