Paroxysmal Nocturnal Hemoglobinuria (PNH) is a clonal disorder of the bone marrow resulting from an acquired mutation in the PIG-A gene. The mutation decreases production of the glycosylphosphatidylinositol membrane anchor for a variety of membrane proteins. Loss of cell membrane CD59 and CD55 results in enhanced complement-mediated cell membrane injury. PNH is associated with an increased risk of venous (VTE) and arterial thrombosis. Eculizumab, a monoclonal antibody to complement C5, has received FDA approval for the treatment of PNH. Recent published data demonstrates a 92% reduction in thrombotic events with the use of eculizumab. However, the mechanism for this reduction is unclear. We have enrolled eight PNH patients (pts) in an ongoing IRB-approved study on the effect of eculizumab treatment on markers of thrombin generation and inflammation. Patients were treated by the FDA-approved treatment protocol with blood samples obtained prior to treatment day 1 and prior to each dose on days 8, 15, 22, 29, 43 and 90. Patients receiving anticoagulants and corticosteroids were continued on their baseline medications. Plasma samples were assayed for D-dimers (D-D), thrombin-antithrombin complex (TAT), interleukin 6 (Il-6) by ELISA and tissue factor microparticles (TFMP) by impedance-based flow cytometry. Mean age of pts was 40.8 years (26–70); 6 male pts and 2 females. One patient had a prior history of VTE; 4 pts were receiving anticoagulants (1 full dose low molecular weight heparin (LMWH), 2 prophylactic LMWH, 1 warfarin) and 2 pts were receiving prednisone at the initiation of eculizumab. The effect of eculizumab on markers of hemostatic activation and inflammation was evaluated using Wilcoxon signed-rank test and multilevel models. Results: Pretreatment levels of D-D were significantly elevated in all but two of the patients who were receiving anticoagulants. Pretreatment Il-6 levels were significantly elevated in all but two patients taking prednisone. With eculizumab treatment, there was a statistically significant decrease in LDH (p=0.0001), D-D (p=0.0057), TAT (0.0138) and Il-6 (p=0.0362) during the 4 week induction phase of treatment (days 1–29). TAT levels significantly decreased by day 8 (p=0.008), with little subsequent change to day29 and day 90. All decreases in D-D, TAT, Il-6 and LDH were sustained in the maintenance phase of treatment (days29–90). Plasma TFMP were detectable and significantly increased in all patients prior to treatment. There was a statistically significant decrease in TFMP by day 8 (p=0.0234) and TFMP levels remained below pretreatment levels for the duration of the study (p=0.030). However, there were wide individual variations in TFMP levels over the course of treatment. There were significant Spearman correlations between changes in D-D and TAT (0.521; p<0.0001), in D-D and IL-6 (0.4400; p=0.0007). Changes in LDH did not correlate with changes in D-D, TAT, TFMP or Il-6. Changes in TFMP did not correlate with changes in markers of thrombin generation (TAT or D-D). Conclusion: Eculizumab treatment of patients with PNH results in a rapid decrease in plasma tissue factor microparticles, thrombin generation and inflammation. These changes appear to be independent of eculizumab suppression of RBC hemolysis as characterized by decreases in serum LDH. A direct relationship between plasma TFMP levels and thrombin generation in PNH patients could not be confirmed in this study. Taken together, these data indicate the broader impact of eculizumab treatment to suppress inflammation and prothrombotic activity in patients with PNH.

Background: Head-up tilt table testing (HUTT) is time-consuming and associated with increased patient morbidity. Hemodynamic changes that occur during the early phase of HUTT may be predictive of neurocardiogenic syncope. Methods: A retrospective chart review was performed in 119 consecutive African Americans ( 57 ± 19) who underwent HUTT for evaluation of syncope of unknown etiology. Positive responses were defined as the development of symptoms linked with a systolic blood pressure (BP) <90 mm Hg, heart rate <50 b.p.m. or sinus arrest >3 s. Hemodynamic variables during the passive phase of HUTT were analyzed and results were then classified as a function of various predictors. Results: Sixty-two subjects (52%) had positive HUTT, and 57 (48%) had negative HUTT. Early changes in BP variables from baseline significantly predicted HUTT responses (p < 0.05). There was also a significant interaction between age and BP. An algorithm based on age and BP was developed which had positive and negative predictive values of 67.7 and 93%, respectively, with an accuracy of 79.8%. Conclusion: A novel algorithm utilizing the patients' age and changes in both systolic and diastolic BP during the early phase of HUTT enables the prediction of HUTT results without the use of vasoactive stimulation, allowing for rapid diagnosis, decreased patient morbidity and reduction in costs.