Letter to the Editor: Thrombocytopenia After Sutureless Aortic Valve Implantation: Does It Really Matter?

Despite the limited clinical relevance of thrombocytopenia after bioprosthetic aortic valve replacement (AVR), the postoperative depletion of platelet count continues to attract the attention of many authors. The development of thrombocytopenia has been evaluated either in patients receiving a sutureless bioprosthesis (1,2) or in those undergoing transcatheter aortic valve implantation, where cardiopulmonary bypass bears little or no relation to this phenomenon (3). Recently, Sánchez et al. (1) have published their findings on this topic, but their limited experience with the devices used makes their study of doubtful interest. Over three years, 27 patients were implanted with a sutureless bioprosthetic valve and were compared with 50 patients receiving a stented aortic valve. No risk factors that may have predisposed to platelet dysfunction were described in either group.Mortality and number of units of transfused red blood cells also seems to be extremely high for a patient population undergoing elective isolated AVR: it is not clear whether bleeding complications occurred in any patients and re-thoracotomy could not be performed, or whether more liberal transfusion protocols were used. In addition, platelet transfusions in patients from the sutureless group could represent a bias that renders the comparison of postoperative mean platelet volume and platelet distribution width between groups unreliable. It would have been more appropriate to consider postoperative echocardiographic findings because, in case of suboptimal placement of the prosthesis, paravalvular leakage may cause severe hemolysis and thrombocytopenia. At present, clinical data can be derived from other case series (4). At our Center, over a six-year period, AVR was performed using a sutureless, stentless, or stented bioprosthesis in 432, 193, and 180 patients, respectively, with all devices being supplied by the same manufacturer. Perioperative trends in platelet count after sutureless AVR did not show progression towards thrombocytopenia as occurs after stentless AVR (5), but compared favourably with conventional stented AVR (Fig. 1), where platelet depletion has no clinical relevance. Figure 1: Perioperative trends in platelet count after aorticvalve replacement with the sutureless Perceval, stentlessSolo, and stented Crown bioprosthetic valves.References1. Sánchez E, Corrales JA, Fantidis P, Tarhini IS, Khan I, Pineda T, González JR. Thrombocytopenia after aortic valve replacement with Perceval S sutureless bioprosthesis. J Heart Valve Dis 2016;25:75-812. Jiritano F, Cristodoro L, Malta E, Mastroroberto P. Thrombocytopenia after sutureless aortic valve implantation: Comparison between Intuity and Perceval bioprostheses. J Thorac Cardiovasc Surg 2016;152:1631-16333. McCabe JM, Huang PH, Riedl LA, et al. Incidence and implications of idiopathic thrombocytopenia following transcatheter aortic valve replacement with the Edwards Sapien® valves: A single center experience. Catheter Cardiovasc Interv 2014;83:633-6414. Santarpino G, Fischlein T, Pfeiffer S. A word of caution is needed before uttering a word of caution: Thrombocytopenia and sutureless valves. Heart Surg Forum 2016;19:E1695. Pozzoli A, De Maat GE, Hillege HL, Boogaard JJ, Natour E, Mariani MA. Severe thrombocytopenia and its clinical impact after implant of the stentless Freedom Solo bioprosthesis. Ann Thorac Surg 2013;96:1581-1586.

First experience with the new Sorin Crown PRT bioprosthetic aortic valve: early postoperative outcome and hemodynamic performance in 90 patients

AIM

The Crown PRT (The Phospholipid Reduction Treatment) is a new stent bovine bioprosthesis for aortic valve replacement (AVR). Aim of this paper is to report the postoperative clinical and hemodynamic results after ninety consecutive implants.

METHODS

After receiving CE mark in July 2014, two European university centers implanted the new Crown PRT (Sorin Group, Burnaby, Canada) for the first time. Up to now, ninety patients underwent aortic valve replacement, in isolated or combined procedures, for aortic stenosis or insufficiency. Intraoperative transesophageal echocardiogram was used to assess the prosthesis's function. In hospital outcomes and echocardiographic parameters were recorded.

RESULTS

Age and Log Euroscore were 71.8±7.9 years and 10.2%±4.5 respectively. In-hospital mortality for isolated AVR was 0%; one patient died after a multiple procedure (overall 30-days mortality 1.1%). No adverse device effects were recorded. Intensive Care Unit stay was 2±5.8 days. At discharge, echocardiogram showed no paravalvular leaks and normal postoperative gradients.

CONCLUSION

Our starting results showed that the Crown PRT is safe and reliable, with excellent hemodynamic performance. Further clinical results with a larger population and long term follow-up are needed to assess the versatility and the durability of this new device.

Characterization of a bispecific FLT3 X CD3 antibody in an improved, recombinant format for the treatment of leukemia

FLT3 is a receptor-tyrosine-kinase that is expressed on leukemic cells of the myeloid and lymphoid lineage rather specifically. We here report on the construction and selection of bispecific FLT3 X CD3 antibodies in a new recombinant format, termed Fabsc, that resembles the normal antibody structure more closely than the well-established bispecific single chain (bssc)-format. Our preferred antibody, which emerged from an initial selection procedure utilizing different FLT3- and CD3-antibodies, contains the FLT3-antibody 4G8 and the CD3-antibody UCHT1. The 4G8 X UCHT1 Fabsc-antibody was found to be superior to a bssc-antibody with identical specificities with respect to (i) affinity to the target antigen FLT3, (ii) production yield by transfected cells, and (iii) the diminished formation of aggregates. T-cell activation in the presence and absence of cultured leukemic cells and killing of these cells was comparable for both molecules. In addition, the 4G8 X UCHT1 Fabsc-antibody was found to induce T-cell activation and efficient killing of leukemic blasts in primary peripheral blood mononuclear cell (PBMC) cultures of acute myeloid leukemia (AML) patients. In these experiments, the bispecific molecule was clearly superior to an Fc-optimized monospecific FLT3-antibody described previously, indicating that within PBMC of AML patients the recruitment of T cells is more effective than that of natural killer cells.

γδ T Cell-Mediated Antibody-Dependent Cellular Cytotoxicity with CD19 Antibodies Assessed by an Impedance-Based Label-Free Real-Time Cytotoxicity Assay

γδ T cells are not MHC restricted, elicit cytotoxicity against various malignancies, are present in early post-transplant phases in novel stem cell transplantation strategies and have been shown to mediate antibody-dependent cellular cytotoxicity (ADCC) with monoclonal antibodies (mAbs). These features make γδ T cells promising effector cells for antibody-based immunotherapy in pediatric patients with B-lineage acute lymphoblastic leukemia (ALL). To evaluate combination of human γδ T cells with CD19 antibodies for immunotherapy of B-lineage ALL, γδ T cells were expanded after a GMP-compliant protocol and ADCC of both primary and expanded γδ T cells with an Fc-optimized CD19 antibody (4G7SDIE) and a bi-specific antibody with the specificities CD19 and CD16 (N19-C16) was evaluated in CD107a-degranulation assays and intracellular cytokine staining. CD107a, TNFα, and IFNγ expression of primary γδ T cells were significantly increased and correlated with CD16-expression of γδ T cells. γδ T cells highly expressed CD107a after expansion and no further increased expression by 4G7SDIE and N19-C16 was measured. Cytotoxicity of purified expanded γδ T cells targeting CD19-expressing cells was assessed in both europium-TDA release and in an impedance-based label-free method (using the xCELLigence system) measuring γδ T cell lysis in real-time. Albeit in the 2 h end-point europium-TDA release assay no increased lysis was observed, in real-time xCELLigence assays both significant antibody-independent cytotoxicity and ADCC of γδ T cells were observed. The xCELLigence system outperformed the end-point europium-TDA release assay in sensitivity and allows drawing of conclusions to lysis kinetics of γδ T cells over prolonged periods of time periods. Combination of CD19 antibodies with primary as well as expanded γδ T cells exhibits a promising approach, which may enhance clinical outcome of patients with pediatric B-lineage ALL and requires clinical evaluation.

Describing readmissions to an Ebola case management centre (CMC), Sierra Leone, 2014

Case management centres (CMCs) are part of the outbreak control plan for Ebola virus disease (EVD). A CMC in Sierra Leone had 33% (138/419) of primary admissions discharged as EVD negative (not a case). Fifteen of these were readmitted within 21 days, nine of which were EVD positive. All readmissions had contact with an Ebola case in the community in the previous 21 days indicating that the infection was likely acquired outside the CMC.

Describing readmissions to an Ebola case management centre (CMC), Sierra Leone, 2014

Case management centres (CMCs) are part of the outbreak control plan for Ebola virus disease (EVD). A CMC in Sierra Leone had 33% (138/419) of primary admissions discharged as EVD negative (not a case). Fifteen of these were readmitted within 21 days, nine of which were EVD positive. All readmissions had contact with an Ebola case in the community in the previous 21 days indicating that the infection was likely acquired outside the CMC.