Ann Thorac Surg 2005;80:948-949
© 2005 The Society of Thoracic Surgeons
Original article: Cardiovascular
Invited commentary
William L. Holman, MD
Department of Surgery, University of Alabama at Birmingham, 1530 3rd Ave S, ZRB 719, Birmingham, AL 35294-0007
(Email: wholman{at}its.uab.edu).
This study [1] is a nicely performed, non-randomized prospective analysis of anti-leukocyte antigen (HLA) antibodies measured in patients receiving DeBakey/MicroMed left ventricular assist devices (VADs) (MicroMed Technology, Inc, Houston, TX) as a bridge to heart transplantation. No patients had IgG antibodies develop to class I or II antigens. Retrospective cross matches were negative and the prevalence of acute rejection was 6% in the first 6 months and 4.3% in the second 6 months after transplantation.
This article addresses an important problem in patients who receive mechanical assist devices as a bridge to cardiac transplantation. However, these are preliminary results that may not stand the test of time.
Anti-HLA antigens are formed in reaction to a number of stimuli. One of these is the presence of a circulatory assist device. However, allogeneic blood (ie, especially components that contain leukocytes) is a major source of antigen stimulation in VAD patients. The investigators were careful to use leuko-reduced blood components. This by itself may have contributed to the low prevalence of anti-HLA antibody formation. Moreover, the patients were all male. Women who are often exposed to fetal HLA stimulation during pregnancy may not have such favorable results.
The duration of VAD support was relatively short at a mean of 87 days with a range of 31 to 224 days. Longer durations of exposure to the DeBakey/MicroMed pump may uncover a higher prevalence of antibody development during the pre-transplantation period.
What characteristics of the DeBakey/MicroMed pump might account for a lower prevalence of antibody development? First, this pump has a smaller blood contacting surface area than the pulsatile pumps that are typically associated with antibody formation. These larger pumps have components made from polyurethane and other materials, and these materials may be responsible for immunologic stimulation. The DeBakey/MicroMed pump only presents polished titanium to the blood. Furthermore, the contact time of the DeBakey/MicroMed pump surface with the patient’s blood is relatively short compared with the larger pulsatile pumps, and the rough surface of some pulsatile pumps may harbor cells that influence anti-HLA antibody development.
I truly hope that the authors are correct in their assessment of the DeBakey/MicroMed left VAD. However, I will remain somewhat skeptical until their results are reproduced in women and in a larger number of patients with longer durations of support.
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References
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- Grinda J-M, Bricourt M-O, Amrein C, et al. Human leukocyte antigen sensitization in ventricular assist device recipientsa lesser risk with the DeBakey axial pump. Ann Thorac Surg 2005;80:945-949.[Abstract/Free Full Text]
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