Safety and effectiveness of oral anticoagulants in patients with atrial fibrillation and stage 4 chronic kidney disease: a real-world experience.

It is still uncertain whether direct oral anticoagulants (DOACs) perform better than vitamin K antagonists (VKAs) in subjects with non-valvular atrial fibrillation (NVAF) and advanced chronic kidney disease (CKD). The aim of the study was to compare safety and effectiveness of DOACs and VKAs in patients with NVAF and stage 4 CKD (creatinine clearance 15-29 mL/min). We searched the hospital databases of two academic centers to retrospectively identify patients with stage 4 CKD who were on treatment with DOACs or VKAs for NVAF. Safety was the primary outcome of the study and was assessed in terms of incidence of major bleeding (MB). Secondary outcomes were clinically relevant non-major bleeding (CRNMB) and death for any cause. A total of 176 patients (102 on DOACs and 74 on VKAs) were found and included in the analysis. The incidence rate of MB was not statistically different between groups (8.6 per 100 patients-year in the DOAC group and 5.6 per 100 patients-year in the VKA group). Rates of IS/SSE and CRNMB were statistically similar in the two treatment groups, as well. There were less deaths for any cause in the DOAC group than in the VKA group (8.6 and 15.8 per 100 patients-year, respectively), but the difference was not statistically significant. This study found no difference in terms of safety and effectiveness between patients with NVAF and stage 4 CKD treated with DOACs and VKAs. Larger prospective or randomized studies are needed to confirm these findings.

Cell Surface Platelet Tissue Factor Expression: Regulation by P2Y12 and Link to Residual Platelet Reactivity.

BACKGROUND: ADP-induced platelet activation leads to cell surface expression of several proteins, including TF (tissue factor). The role of ADP receptors in platelet TF modulation is still unknown. We aimed to assess the (1) involvement of P2Y1 and P2Y12 receptors in ADP-induced TF exposure; (2) modulation of TFpos-platelets in anti-P2Y12-treated patients with coronary artery disease. Based on the obtained results, we revisited the intracellular localization of TF in platelets. METHODS: The effects of P2Y1 or P2Y12 antagonists on ADP-induced TF expression and activity were analyzed in vitro by flow cytometry and thrombin generation assay in blood from healthy subjects, P2Y12-/-, and patients with gray platelet syndrome. Ex vivo, P2Y12 inhibition of TF expression by clopidogrel/prasugrel/ticagrelor, assessed by VASP (vasodilator-stimulated phosphoprotein) platelet reactivity index, was investigated in coronary artery disease (n=238). Inhibition of open canalicular system externalization and electron microscopy (TEM) were used for TF localization. RESULTS: In blood from healthy subjects, stimulated in vitro by ADP, the percentage of TFpos-platelets (17.3±5.5%) was significantly reduced in a concentration-dependent manner by P2Y12 inhibition only (-81.7±9.5% with 100 nM AR-C69931MX). In coronary artery disease, inhibition of P2Y12 is paralleled by reduction of ADP-induced platelet TF expression (VASP platelet reactivity index: 17.9±11%, 20.9±11.3%, 40.3±13%; TFpos-platelets: 10.5±4.8%, 9.8±5.9%, 13.6±6.3%, in prasugrel/ticagrelor/clopidogrel-treated patients, respectively). Despite this, 15% of clopidogrel good responders had a level of TFpos-platelets similar to the poor-responder group. Indeed, a stronger P2Y12 inhibition (130-fold) is required to inhibit TF than VASP. Thus, a VASP platelet reactivity index <20% (as in prasugrel/ticagrelor-treated patients) identifies patients with TFpos-platelets <20% (92% sensitivity). Finally, colchicine impaired in vitro ADP-induced TF expression but not α-granule release, suggesting that TF is open canalicular system stored as confirmed by TEM and platelet analysis of patients with gray platelet syndrome. CONCLUSIONS: Data show that TF expression is regulated by P2Y12 and not P2Y1; P2Y12 antagonists downregulate the percentage of TFpos-platelets. In clopidogrel good-responder patients, assessment of TFpos-platelets highlights those with residual platelet reactivity. TF is stored in open canalicular system, and its membrane exposure upon activation is prevented by colchicine.

Detection of Platelet-Activating Antibodies Associated with Vaccine-Induced Thrombotic Thrombocytopenia by Flow Cytometry: An Italian Experience.

Rare cases of thrombocytopenia and thrombosis after anti-COVID-19 adenovirus-associated mRNA vaccines (VITT) due to platelet-activating anti-platelet-factor 4 (PF4)/polyanion antibodies have been reported. VITT laboratory diagnosis, similarly to heparin-induced thrombocytopenia (HIT) diagnosis, requires immunoassays for anti-PF4/polyanion antibodies identification, such as ELISA assays and platelet-activating functional tests, such as heparin-induced platelet activation test (HIPA), to confirm their pathogenicity. We compared the flow cytometry (FC) measurement of platelet p-selectin exposure to the gold standard functional test HIPA for diagnosis confirmation in 13 patients with a clinical VITT syndrome (6M/7F; median age 56 (33-78)) who resulted positive to anti-PF4/polyanion antibodies ELISA assays (12/13). FC and HIPA similarly identified three different patterns: (1) a typical non-heparin-dependent VITT pattern (seven and six patients by FC and HIPA, respectively); (2) low/no platelet activation in patients under IvIg therapy (five out of five and two out of four patients by FC and HIPA, respectively); (3) a HIT pattern. Antibodies investigated by FC became negative after 7, 17, and 24 days of therapy in three patients. FC measurement of P-selectin exposure was as sensitive as HIPA but simpler to detect anti-PF4/polyanion antibodies in VITT patients. FC could reliably discriminate VITT from HIT, thus helping for the choice of the anticoagulant.

Direct oral anticoagulants and therapeutic adherence: do not let your guard down.

BACKGROUND: Direct oral anticoagulants (DOAC) and vitamin K antagonist drugs (VKA) are recommended for stroke prevention in atrial fibrillation and for treatment of venous thromboembolism. Undoubtedly, DOAC have contributed to improve quality of life of these patients, but unfortunately, available 'real world' data show a very high variable compliance to DOAC. AIMS AND OBJECTIVES: to evaluate predictors that adversely affect therapeutic adherence in patients naive naïve  to DOAC. METHODS AND POPULATION: this study was conducted on an outpatient population in oral anticoagulant therapy in a period between January 2019 and February 2020. Patients naiveto DOAC and treated for at least 6 months were enrolled. Non-Italian-speaking patients, cognitive or psychiatric disorders, refusal to participate or non-consent to the interview were exclusion criteria. A socio-demographic scale and the 8-item Morisky scale (MMAS-8) questionnaire assessed therapeutic adherence. RESULTS: One hundred two DOAC-naïve patients were selected from a population of 407 patients on the first visit at our centre. The population was homogeneously represented for gender (males 48%). The mean age was 79.5 years. Atrial fibrillation (65.7%) resulted the main reason for DOAC prescription and a polypharmacy was detected in 47.1% of the patients. Moreover, an optimal adherence to DOAC therapy was assessed in less than 30% of patients. CONCLUSIONS: Polypharmacy, patient's isolation, such as a low education level were statistically associated with a low therapeutic adherence. Therapeutic adherence remains an unsolved problem for anticoagulated patient. To identify patients at higher risk of poor compliance and therapeutic failure and establish targeted care pathways is a priority.

Autoimmune disorders of platelet function: systematic review of cases of acquired Glanzmann thrombasthenia and acquired delta storage pool disease.

Acquired platelet function disorders (PFD) are rare bleeding diseases that should be suspected in all patients with unexplained mucocutaneous bleedings of recent onset, with no previous history of haemorrhages, and with normal coagulation test and platelet count. Drug-induced platelet function bleeding disorders are the most frequent PFDs and can easily be identified on the basis of recent administration of platelet-inhibiting drugs. Apart from these, the most challenging acquired PFDs are those caused by autoimmune mechanisms. In fact, demonstration of autoantibodies inhibiting platelet function may be difficult in most non-specialised centres. Among autoimmune PFDs (aPFDs), acquired Glanzmann thrombasthenia (aGT), which is caused by autoantibodies that bind to platelet αIIbß3 integrin, inhibiting its function, is the most frequent. aGT can be associated with underlying haematological malignancies or autoimmune diseases but can also be idiopathic. More rarely, other immune-mediated PFDs can occur, such as acquired delta storage pool disease (aδSPD). Treatment of aPFDs must rely on the control of acute and chronic bleedings, treatment of the underlying disease in secondary forms, and immunosuppressive treatment for autoantibody reduction or eradication. aPFDs may completely resolve upon treatment of any underlying disease that may be present. In primary aPFDs, and in the majority of secondary forms, treatment relies on immunosuppressive therapies.Here we present a systematic review of previously described immune-mediated aGT and aδSPD cases. Clinical and laboratory characteristics, treatments for the control of bleedings and for the eradication of autoantibodies, and responses to treatments are also discussed. Although no guidelines are available for the management of these very rare conditions, presentation of all cases reported so far can help clinicians in the diagnosis and treatment of these life-threatening diseases.

Nonalcoholic fatty liver disease (NAFLD) severity is associated to a nonhemostatic contribution and proinflammatory phenotype of platelets.

Nonalcoholic fatty liver disease (NAFLD) is the main cause of chronic liver disease and ranges from simple steatosis to nonalcoholic steatohepatitis. Recently, a platelet role in NAFLD pathogenesis and progression has been reported in mouse models and in patients. We investigated whether platelets are involved in liver and systemic inflammation processes in NAFLD. In this exploratory study we recruited 24 consecutive patients with biopsy-proven diagnosis of NAFLD and 17 healthy volunteers. We measured plasma levels of inflammatory markers by ELISA. We investigated hemostatic and inflammatory transcripts in circulating platelets and leukocytes from NAFLD patients. We analyzed platelet and neutrophil extracellular traps (NET) accumulations in liver sinusoids using CD42 and H3 citrullinated histones immunohistochemical staining on liver biopsies. NAFLD patients had increased inflammation markers and lipolysaccharides plasma levels. We found significant increase of inflammatory transcripts in circulating platelets and not in leukocytes of NAFLD subjects compared with healthy controls. We demonstrated increased intrahepatic platelet accumulation that correlated with NAFLD activity score (NAS) score and intrahepatic neutrophil extracellular traps (NET) formation in liver biopsies of NAFLD patients. NET formation was higher in livers with higher NAS and inflammation scores. The presence of low-grade systemic inflammation and proinflammatory changes of circulating platelets indicate that platelets participate on systemic inflammatory changes associated with NAFLD. Liver platelet accumulation and liver NET formation, together with low-grade endotoxemia, suggest that platelets may act to protect the liver from invading microorganisms by favoring local NET formation.

Novel manifestations of immune dysregulation and granule defects in gray platelet syndrome.

Gray platelet syndrome (GPS) is a rare recessive disorder caused by biallelic variants in NBEAL2 and characterized by bleeding symptoms, the absence of platelet α-granules, splenomegaly, and bone marrow (BM) fibrosis. Due to the rarity of GPS, it has been difficult to fully understand the pathogenic processes that lead to these clinical sequelae. To discern the spectrum of pathologic features, we performed a detailed clinical genotypic and phenotypic study of 47 patients with GPS and identified 32 new etiologic variants in NBEAL2. The GPS patient cohort exhibited known phenotypes, including macrothrombocytopenia, BM fibrosis, megakaryocyte emperipolesis of neutrophils, splenomegaly, and elevated serum vitamin B12 levels. Novel clinical phenotypes were also observed, including reduced leukocyte counts and increased presence of autoimmune disease and positive autoantibodies. There were widespread differences in the transcriptome and proteome of GPS platelets, neutrophils, monocytes, and CD4 lymphocytes. Proteins less abundant in these cells were enriched for constituents of granules, supporting a role for Nbeal2 in the function of these organelles across a wide range of blood cells. Proteomic analysis of GPS plasma showed increased levels of proteins associated with inflammation and immune response. One-quarter of plasma proteins increased in GPS are known to be synthesized outside of hematopoietic cells, predominantly in the liver. In summary, our data show that, in addition to the well-described platelet defects in GPS, there are immune defects. The abnormal immune cells may be the drivers of systemic abnormalities such as autoimmune disease.

Antithrombotic prophylaxis for surgery-associated venous thromboembolism risk in patients with inherited platelet disorders. The SPATA-DVT Study.

Major surgery is associated with an increased risk of venous thromboembolism (VTE), thus the application of mechanical or pharmacologic prophylaxis is recommended. The incidence of VTE in patients with inherited platelet disorders (IPD) undergoing surgical procedures is unknown and no information on the current use and safety of thromboprophylaxis, particularly of low-molecular-weight-heparin in these patients is available. Here we explored the approach to thromboprophylaxis and thrombotic outcomes in IPD patients undergoing surgery at VTE-risk participating in the multicenter SPATA study. We evaluated 210 surgical procedures carried out in 155 patients with well-defined forms of IPD (VTE-risk: 31% high, 28.6% intermediate, 25.2% low, 15.2% very low). The use of thromboprophylaxis was low (23.3% of procedures), with higher prevalence in orthopedic and gynecological surgeries, and was related to VTE-risk. The most frequently employed thromboprophylaxis was mechanical and appeared to be effective, as no patients developed thrombosis, including patients belonging to the highest VTE-risk classes. Low-molecular-weight-heparin use was low (10.5%) and it did not influence the incidence of post-surgical bleeding or of antihemorrhagic prohemostatic interventions use. Two thromboembolic events were registered, both occurring after high VTE-risk procedures in patients who did not receive thromboprophylaxis (4.7%). Our findings suggest that VTE incidence is low in patients with IPD undergoing surgery at VTE-risk and that it is predicted by the Caprini score. Mechanical thromboprophylaxis may be of benefit in patients with IPD undergoing invasive procedures at VTE-risk and low-molecular-weight-heparin should be considered for major surgery.

Eltrombopag for the treatment of inherited thrombocytopenias: a phase II clinical trial.

Patients with inherited thrombocytopenias often require platelet transfusions to raise their platelet count before surgery or other invasive procedures; moreover, subjects with clinically significant spontaneous bleeding may benefit from an enduring improvement of thrombocytopenia. The hypothesis that thrombopoietin-mimetics can increase platelet count in inherited thrombocytopenias is appealing, but evidence is scarce. We conducted a prospective, phase II clinical trial to investigate the efficacy of the oral thrombopoietin-mimetic eltrombopag in different forms of inherited thrombocytopenia. We enrolled 24 patients affected by MYH9-related disease, ANKRD26-related thrombocytopenia, X-linked thrombocytopenia/ Wiskott-Aldrich syndrome, monoallelic Bernard-Soulier syndrome, or ITGB3-related thrombocytopenia. The average pre-treatment platelet count was 40.4 ×109/L. Patients received a 3- to 6-week course of eltrombopag in a dose-escalated manner. Of 23 patients evaluable for response, 11 (47.8%) achieved a major response (platelet count >100 ×109/L), ten (43.5%) had a minor response (platelet count at least twice the baseline value), and two patients (8.7%) did not respond. The average increase of platelet count compared to baseline was 64.5 ×109/L (P<0.001). Four patients with clinically significant spontaneous bleeding entered a program of long-term eltrombopag administration (16 additional weeks): all of them obtained remission of mucosal hemorrhages, with the remission persisting throughout the treatment period. Treatment was globally well tolerated: five patients reported mild adverse events and one patient a moderate adverse event. In conclusion, eltrombopag was safe and effective in increasing platelet count and reducing bleeding symptoms in different forms of inherited thrombocytopenia. Despite these encouraging results, caution is recommended when using thrombopoietinmimetics in inherited thrombocytopenias predisposing to leukemia. ClinicalTrials.gov identifier: NCT02422394.

Murine platelet production is suppressed by S1P release in the hematopoietic niche, not facilitated by blood S1P sensing.

The bioactive lipid mediator sphingosine 1-phosphate (S1P) was recently assigned critical roles in platelet biology: whereas S1P1 receptor-mediated S1P gradient sensing was reported to be essential for directing proplatelet extensions from megakaryocytes (MKs) toward bone marrow sinusoids, MK sphingosine kinase 2 (Sphk2)-derived S1P was reported to further promote platelet shedding through receptor-independent intracellular actions, and platelet aggregation through S1P1 Yet clinical use of S1P pathway modulators including fingolimod has not been associated with risk of bleeding or thrombosis. We therefore revisited the role of S1P in platelet biology in mice. Surprisingly, no reduction in platelet counts was observed when the vascular S1P gradient was ablated by impairing S1P provision to plasma or S1P degradation in interstitial fluids, nor when gradient sensing was impaired by S1pr1 deletion selectively in MKs. Moreover, S1P1 expression and signaling were both undetectable in mature MKs in situ, and MK S1pr1 deletion did not affect platelet aggregation or spreading. When S1pr1 deletion was induced in hematopoietic progenitor cells, platelet counts were instead significantly elevated. Isolated global Sphk2 deficiency was associated with thrombocytopenia, but this was not replicated by MK-restricted Sphk2 deletion and was reversed by compound deletion of either Sphk1 or S1pr2, suggesting that this phenotype arises from increased S1P export and S1P2 activation secondary to redistribution of sphingosine to Sphk1. Consistent with clinical observations, we thus observe no essential role for S1P1 in facilitating platelet production or activation. Instead, S1P restricts megakaryopoiesis through S1P1, and can further suppress thrombopoiesis through S1P2 when aberrantly secreted in the hematopoietic niche.

Bleeding risk of surgery and its prevention in patients with inherited platelet disorders.

Excessive bleeding at surgery is a feared complication in patients with inherited platelet disorders. However, very few studies have evaluated the frequency of surgical bleeding in these hemorrhagic disorders. We performed a worldwide, multicentric, retrospective study to assess the bleeding complications of surgery, the preventive and therapeutic approaches adopted, and their efficacy in patients with inherited platelet disorders: the Surgery in Platelet disorders And Therapeutic Approach (SPATA) study. We rated the outcome of 829 surgical procedures carried out in 423 patients with well-defined forms of inherited platelet disorders: 238 inherited platelet function disorders and 185 inherited platelet number disorders. Frequency of surgical bleeding was high in patients with inherited platelet disorders (19.7%), with a significantly higher bleeding incidence in inherited platelet function disorders (24.8%) than in inherited platelet number disorders (13.4%). The frequency of bleeding varied according to the type of inherited platelet disorder, with biallelic Bernard Soulier syndrome having the highest occurrence (44.4%). Frequency of bleeding was predicted by a pre-operative World Health Organization bleeding score of 2 or higher. Some types of surgery were associated with a higher bleeding incidence, like cardiovascular and urological surgery. The use of pre-operative pro-hemostatic treatments was associated with a lower bleeding frequency in patients with inherited platelet function disorders but not in inherited platelet number disorders. Desmopressin, alone or with antifibrinolytic agents, was the preventive treatment associated with the lowest bleedings. Platelet transfusions were used more frequently in patients at higher bleeding risk. Surgical bleeding risk in inherited platelet disorders is substantial, especially in inherited platelet function disorders, and bleeding history, type of disorder, type of surgery and female sex are associated with higher bleeding frequency. Prophylactic pre-operative pro-hemostatic treatments appear to be required and are associated with a lower bleeding incidence.

Abnormal proplatelet formation and emperipolesis in cultured human megakaryocytes from gray platelet syndrome patients.

The Gray Platelet Syndrome (GPS) is a rare inherited bleeding disorder characterized by deficiency of platelet α-granules, macrothrombocytopenia and marrow fibrosis. The autosomal recessive form of GPS is linked to loss of function mutations in NBEAL2, which is predicted to regulate granule trafficking in megakaryocytes, the platelet progenitors. We report the first analysis of cultured megakaryocytes from GPS patients with NBEAL2 mutations. Megakaryocytes cultured from peripheral blood or bone marrow hematopoietic progenitor cells from four patients were used to investigate megakaryopoiesis, megakaryocyte morphology and platelet formation. In vitro differentiation of megakaryocytes was normal, whereas we observed deficiency of megakaryocyte α-granule proteins and emperipolesis. Importantly, we first demonstrated that platelet formation by GPS megakaryocytes was severely affected, a defect which might be the major cause of thrombocytopenia in patients. These results demonstrate that cultured megakaryocytes from GPS patients provide a valuable model to understand the pathogenesis of GPS in humans.

Megakaryocytic emperipolesis and platelet function abnormalities in five patients with gray platelet syndrome.

The gray platelet syndrome (GPS) is a rare congenital platelet disorder characterized by mild to moderate bleeding diathesis, macrothrombocytopenia and lack of azurophilic α-granules in platelets. Some platelet and megakaryocyte (MK) abnormalities have been described, but confirmative studies of the defects in larger patient cohorts have not been undertaken. We studied platelet function and bone marrow (BM) features in five GPS patients with NBEAL2 autosomal recessive mutations from four unrelated families. In 3/3 patients, we observed a defect in platelet responses to protease-activated receptor (PAR)1-activating peptide as the most consistent finding, either isolated or combined to defective responses to other agonists. A reduction of PAR1 receptors with normal expression of major glycoproteins on the platelet surface was also found. Thrombin-induced fibrinogen binding to platelets was severely impaired in 2/2 patients. In 4/4 patients, the BM biopsy showed fibrosis (grade 2-3) and extensive emperipolesis, with many (36-65%) MKs containing 2-4 leukocytes engulfed within the cytoplasm. Reduced immunolabeling for platelet factor 4 together with normal immunolabeling for CD63 in MKs of two patients demonstrated that GPS MKs display an alpha granule-specific defect. Increased immunolabeling for P-selectin and decreased immunolabeling for PAR1, PAR4 and c-MPL were also observed in MKs of two patients. Marked emperipolesis, specific defect of MK alpha-granule content and defect of PAR1-mediated platelet responses are present in all GPS patients that we could study in detail. These results help to further characterize the disease.

Surgical bleeding after pre-operative unfractionated heparin and low molecular weight heparin for coronary bypass surgery.

BACKGROUND AND OBJECTIVES: Since the impairment of platelet function may cause excess peri-operative bleeding, pre-operative discontinuation of aspirin and heparin bridging are common for cardiac surgery. We evaluated the impact of pre-operative administration of enoxaparin and unfractionated heparin (UFH) on coagulation parameters and peri-operative bleeding in patients undergoing elective coronary artery bypass grafting (CABG) surgery after discontinuation of aspirin. DESIGN AND METHODS: Forty-three patients with three-vessel coronary artery disease undergoing elective CABG surgery discontinued aspirin and were randomized to receive either UFH 180 UI/Kg x 2/day s.c. or enoxaparin 100 UI/Kg x 2/day s.c. until 12 h before surgery (median pre-operative treatment 8 days, range 6-12 days). Surgery was performed as usual with UFH. Neither UFH nor any low molecular weight heparin was given in the immediate post-operative period. The effects of UFH and enoxaparin were monitored by the activated partial thromboplastin time (aPTT) and the Enox-test (sensitive to factor Xa inhibition) using a Rapidpoint Coagulation Analyzer. aPTT and factor Xa activity were also measured by standard methods. Peri-operative bleeding and the nadirs of hemoglobin concentration, hematocrit and platelet count were monitored post-operatively. RESULTS: Patients in the two groups were similar for number of bypasses, on-pump time, total surgery time, and time from the last heparin administration. Coagulation parameters increased significantly and similarly at 30 min and 6 h with both treatments, but returned within the normal range at 12 h. Hemoglobin, hematocrit and platelet counts significantly decreased to the same extent after CABG and re-normalized at the same time. Transfusional requirements of blood and plasma units were similar in the two groups. INTERPRETATION AND CONCLUSIONS: From the kinetics of coagulation parameters and the evaluation of bleeding, enoxaparin is a safe alternative to UFH as a bridging therapy to CABG after discontinuation of aspirin.

Lipophilicity-related inhibition of blood platelet aggregation by nipecotic acid anilides.

Using N-[4-(hexyloxy)phenyl]piperidine-3-carboxamide (17c) as a structural lead, a number of isomers, derivatives, and ring-opened analogs were synthesized and tested for their ability to block the in vitro aggregation of human platelets induced by adenosine 5'-diphosphate (ADP). For the most active compounds, inhibition of the platelet aggregation triggered by arachidonic acid (AA) and ADP-induced intraplatelet calcium mobilization was also demonstrated. Based on quantitative structure-activity relationships (QSARs), we proved the impact of hydrophobicity on antiplatelet activity by a nonlinear (parabolic or bilinear) relationship between pIC(50) and lipophilicity, as assessed by RP-HPLC capacity factors and ClogP (i.e. calculated 1-octanol-water partition coefficients). This study highlighted the following additional SARs: quasi-isolipophilic isomers of 17c (isonipecotanilides and pipecolinanilides) and ring-opened analogs (e.g. anilide of beta-alanine) exhibited lower antiplatelet activity; methylation of the piperidine nitrogen of 17c has no effect, whereas alkylation with an n-propyl group decreases the activity by a factor of approximately 2, most likely due to a conformation-dependent decrease in lipophilicity.

Combined role of the Lewis antigenic system, Chlamydia pneumoniae, and C-reactive protein in unstable angina.

OBJECTIVES: The goal of this study was to assess the prognostic role of the Lewis antigenic system, Chlamydia pneumoniae (CP) seropositivity (CP+), and C-reactive protein (CRP) levels in unstable angina (UA). BACKGROUND: The role of CP infection in acute coronary syndromes is contradictory. The Lewis antigenic system, a genetically determined blood group system associated with infections and several disorders, including ischemic heart disease, might influence the susceptibility to CP infection, inflammatory response, and risk of cardiac ischemic events. METHODS: The CRP levels, Lewis antigens, and CP+ were measured in 54 patients with Braunwald's class IIIB UA. All patients were followed up for one year, and the occurrence of new coronary events (coronary death, myocardial infarction, and recurrence of instability) were recorded. RESULTS: Twenty-five coronary events occurred during follow-up. At univariate analysis CRP >3 mg/l (CRP+) (p = 0.0056), Lewis antigen b (Leb+) (p = 0.028), and the combination of Leb+ and CP+ (p = 0.006) and of CRP+ and Leb+ (p = 0.003) were associated with new coronary events, while CP+ alone was not. At multivariate analysis, CRP+ (p = 0.008) and combined Leb+CP+ (p = 0.03) were independent predictors of worse outcome. The event rate was 64% in CRP+ patients, 67% in Leb+CP+ patients, and 86% in CRP+Leb+CP+ patients. Combined Leb+CP+, but not Leb+ and CP+ alone, was related to CRP levels (p = 0.03). Among CP+ patients, CRP levels were higher in Leb+ than Leb- (p = 0.028). CONCLUSIONS: Our data demonstrate that in UA the Lewis antigenic system plays an important role, probably determining individual susceptibility to the detrimental effects of CP infection and by determining an enhanced inflammatory response.