Polymorphisms of protein tyrosine phosphatase CD148 influence FcγRIIA-dependent platelet activation and the risk of heparin-induced thrombocytopenia.

Heparin-induced thrombocytopenia (HIT) is due primarily to IgG antibodies specific to platelet factor 4/heparin complexes (PF4/Hs) that activate platelets via FcγRIIA. CD148 is a protein tyrosine phosphatase that regulates Src kinases and collagen-induced platelet activation. Three polymorphisms affecting CD148 (Q276P, R326Q, and D872E) were studied in HIT patients and 2 control groups, with or without antibodies to PF4/Hs. Heterozygote status for CD148 276P or 326Q alleles was less frequent in HIT patients, suggesting a protective effect of these polymorphisms. Aggregation tests performed with collagen, HIT plasma, and monoclonal antibodies cross-linking FcγRIIA showed consistent hyporesponsiveness of platelets expressing the 276P/326Q alleles. In addition, platelets expressing the 276P/326Q alleles exhibited a greater sensitivity to the Src family kinases inhibitor dasatinib in response to collagen or ALB6 cross-linking FcγRIIA receptors. Moreover, the activatory phosphorylation of Src family kinases was considerably delayed as well as the phosphorylation of Linker for activation of T cells and phospholipase Cγ2, 2 major signaling proteins downstream from FcγRIIA. In conclusion, this study shows that CD148 polymorphisms affect platelet activation and probably exert a protective effect on the risk of HIT in patients with antibodies to PF4/Hs.

Carotid artery stenting using a transapical approach for the treatment of radiation-induced carotid stenosis.

Radiation-induced stenosis of the carotid artery is considered a challenging entity for direct revascularization. We performed a carotid artery stenting for a radiation-induced stenosis using a transapical approach on an asymptomatic 63-year-old male patient. Transapical approach, which is often used for cardiac surgery, was not yet described for the endovascular treatment of carotid stenosis. The transapical approach could be an attractive alternative path for patients presenting significant supra-aortic trunks lesions and unfit for direct approach or peripheral access. This case reports the feasibility and the safety of carotid artery stenting using the transapical approach in well-trained teams.

Variable serotonin release assay pattern and specificity of PF4-specific antibodies in HIT, and clinical relevance.

BACKGROUND: The diagnosis of heparin-induced thrombocytopenia (HIT) requires functional assays to demonstrate that platelet factor 4 (PF4)-specific antibodies activate platelets, typically when therapeutic heparin (H) concentrations are tested ("classical" pattern). Some HIT samples also activate platelets without heparin ("atypical" pattern), but with unclear clinical significance. OBJECTIVES: We aimed to assess whether platelet activation pattern and some characteristics of PF4-specific antibodies were associated with the severity of HIT. PATIENTS/METHODS: Serotonin release assay (SRA) pattern of 81 HIT patients were analyzed and compared with their clinical and biological data, including levels of anti-PF4/H immunoglobulin G (IgG) and anti-PF4 IgG in 47 of them. RESULTS: Higher anti-PF4/H IgG titers were measured in patients with an "atypical" SRA (optical density 2.52 vs. 1.94 in those with a "classical" pattern, p < .001). Patients of both groups had similar platelet count (PC) nadir and time to recovery, but those with an "atypical" SRA more frequently developed thrombotic events (69% vs. 34%, p = .037). Significant levels of anti-PF4 IgG were detected in both groups (38% and 61%, respectively). Whatever the SRA pattern, a lower PC nadir (35 vs. 53 G/L, p = .006) and a longer PC recovery time (6 vs. 3 days, p = .015) were evidenced in patients with anti-PF4 antibodies, compared with those with anti-PF4/H IgG only. CONCLUSIONS: An atypical SRA pattern with elevated anti-PF4/H IgG titers seems associated with an increased risk of thrombosis in HIT. IgG antibodies to native PF4 may contribute to more severe and persistent thrombocytopenia, and their detection could be useful in clinical practice.

Frequency and Clinical Impact of Platelet Factor 4-Specific Antibodies in Patients Undergoing Extracorporeal Membrane Oxygenation.

INTRODUCTION/OBJECTIVES: Extracorporeal membrane oxygenation (ECMO) provides circulatory support in patients with severe heart failure, but the frequent use of unfractionated heparin exposes patients to high risk of heparin-induced thrombocytopenia (HIT). We prospectively evaluated the development and clinical impact of platelet factor 4 (PF4)-specific antibodies (Abs) during ECMO and whether specific biological characteristics could predict HIT. MATERIALS AND METHODS: From 2014 to 2018, we studied 57 adults who underwent an ECMO for at least 5 days. The plasma samples collected daily were tested for PF4-specific Abs using immunoassays to detect immunoglobulin (Ig) G, A, and M isotypes or only IgG. Serotonin release assay was performed without and with PF4 to detect pathogenic Abs. RESULTS: Twenty-nine patients (50%) were positive for PF4-specific Abs (IgG, A, M), with IgG in 17/57 (30%) and 16 of them (94%) were immunized within 10 days. PF4-specific IgG Abs did not affect the clinical or biological course of most patients. HIT was suspected in only two patients with ECMO circuit dysfunction and unexpected platelet count decrease after day 5. High levels of PF4-specific IgG were detected in both patients, and HIT was confirmed by a serotonin release assay, which was also more sensitive when exogenous PF4 was present. CONCLUSION: PF4-specific Abs are common during ECMO but are mostly non-pathogenic and not associated with a less favorable prognosis. However, an abnormal platelet count evolution, in particular if associated with ECMO circuit dysfunction, should prompt the search for pathogenic PF4-specific IgG.

Very long-term outcomes of the Carpentier-Edwards Perimount valve in aortic position.

BACKGROUND: The Carpentier-Edwards Perimount pericardial bioprosthesis (Edwards Lifesciences, Irvine, CA) has demonstrated good long-term outcomes, but its durability remains unclear depending on age at implantation. We report our 20-year experience with the Perimount valve implanted in the aortic position, with particular attention to the probability and time to reoperation required due to bioprosthesis deterioration. METHODS: From 1984 to 2008 at our center, 2,659 patients (mean age, 70.7 ± 10.4 years) underwent aortic valve replacement using the Perimount pericardial bioprostheses. Patients were prospectively followed on an annual basis (mean 6.7 ± 4.8 years, range 0 to 24.6 years) with an echocardiogram at the time of follow-up. Cumulative follow-up was 18,404 valve-years. Bioprosthesis structural valve deterioration was determined by strict echocardiographic assessment. RESULTS: Overall operative mortality was 2.8%. Actuarial survival rates including early deaths averaged 52.4% ± 1.2%, 31.1% ± 1.4%, and 14.4% ± 1.7% after 10, 15, and 20 years of follow-up, respectively. Age-stratified freedom from reoperation due to structural valve deterioration at 15 and 20 years was 70.8% ± 4.1% and 38.1% ± 5.6%, respectively, for the group aged 60 years or less, 82.7% ± 2.9% and 59.6% ± 7.6% for those 60 to 70 years, and 98.1% ± 0.8% at 15 years and above for the oldest group. Expected valve durability is 19.7 years for the entire cohort. CONCLUSIONS: With a low rate of valve-related events at 20 years, and particularly a low rate of structural valve deterioration, the Carpentier-Edwards Perimount pericardial bioprosthesis remains a reliable choice for a tissue valve in the aortic position, especially in patients over 60 years of age.

Incidence of antibodies to protamine sulfate/heparin complexes incardiac surgery patients and impact on platelet activation and clinical outcome.

A new ELISA (Zymutest HIA®), based on incubation of diluted plasma with protamine/heparin (PRT/H) complexes without and with platelet factor 4 (PF4) provided by a platelet lysate, was used to detect heparin-dependent antibodies in a cohort of 232 cardiac surgery (CS) patients and in 47 patients with heparin-induced thrombocytopenia (HIT). Significant binding of IgG/A/M to PRT/H complexes was demonstrated in 59 CS patients (25.4%), with similar absorbances whether platelet lysate was added to the plasma or not, and significant reactivity to PF4/H in 29 of them. Antibodies to PRT or heparin alone were present in 15 and two of these patients, respectively. Importantly, antibodies to PRT/H were detected in only three of the 47 HIT patients, who had also undergone recent CS. The Zymutest HIA® was positive in another 41 CS patients (17%), but only or mainly when their plasma was tested with platelet lysate, with significant levels of antibodies to PF4/H in 40 of them without detectable reactivity to PRT or heparin alone. Slight antibody binding to PRT/H complexes was also measured in six of these 41 patients. Therefore, a total of 35 CS patients exhibited dual antibody reactivity towards PRT/H and PF4/H complexes. Serotonin release assay performed with PRT alone was positive in 17 CS patients with antibodies to PRT/H, but all had normal platelet count evolution without thrombosis postoperatively. In conclusion, antibodies to PRT/H are frequently present in CS patients postoperatively (25.4%), and can activate platelets in vitro, but their clinical impact remains questionable.

A 25-year experience with Carpentier-Edwards Perimount in the mitral position.

Data of 401 patients who underwent mitral valve replacement with the Carpentier-Edwards Perimount bioprosthesis between 1984 and 2009 were evaluated. Their mean age was 68.1 ± 10.4 years (range, 22-90 years) and 54.9% were female. The most common etiology was degenerative disease (33.2%) and 62.1% of patients had mitral insufficiency. Follow-up was 3,178 patient-years, and 96.8% complete; the mean follow-up was 8.9 ± 3.1 years. Overall survival at 25 years was 10.2% ± 3%. Late mortality was 2.48% per patient-year, and valve-related deaths occurred at 1.62% per patient-year. The actuarial freedom from reoperation due to structural valve deterioration at 20 years was 24.3% ± 2% for degenerative disease and 15% ± 1.4% for non-degenerative disease. For degenerative valve disease, the freedom from structural valve deterioration at 18-years was 39% ± 1% for recipients <60-years old and 66% ± 2% for those ≥60-years old. Our data confirm the excellent durability and low mortality associated with the Carpentier-Edwards Perimount for mitral valve replacement. The rate of calcification of the valve was unrelated to degenerative valve disease, but our findings suggest that this prosthesis gives better results in recipients ≥60-years old than in younger patients.

Changes in platelet count after cardiac surgery can effectively predict the development of pathogenic heparin-dependent antibodies.

Cardiopulmonary bypass (CPB) induces the release of platelet factor 4 (PF4) and patients are at risk of heparin-induced thrombocytopenia (HIT). This study was aimed to determine whether an abnormal evolution in platelet count (PC) after CPB is predictive of the development of HIT antibodies. Two abnormal PC patterns were defined: pattern P1, characterized by a decrease in PC following previous correction of thrombocytopenia occurring during CPB, and pattern P2, defined as a persistent low PC in the days following CPB. PC was evaluated for 10 d in 305 consecutive patients before and after CPB. Serotonin release assay (SRA) was carried out between days 8 and 10 to detect pathogenic heparin-dependent antibodies. Moreover, antibodies to heparin-PF4 (H-PF4) complexes were assayed by enzyme-linked immunosorbent assay. PC evolution after CPB was normal in 300 patients although antibodies to H-PF4 were frequently present (53.4%). Changes in PC were abnormal in five patients with pattern P1 (n = 4) or P2 (n = 1). As SRA was positive in four of the five cases, the positive predictive value of abnormal PC pattern for pathogenic HIT antibodies was 80%. Careful follow-up of PC after CPB makes it possible to predict with high specificity (99%) for those patients who develop pathogenic HIT antibodies.