Hypothermic Circulatory Arrest in Cardiac Transplantation.

PURPOSE: Infrequently, hypothermic circulatory arrest (HCA) must be used during cardiac transplantation. Such cases may include concomitant aortic arch surgery, explantation of ventricular assist devices with outflow grafts or pseudoaneurysms closely abutting the sternum, and other scenarios for which dense mediastinal adhesions preclude exposure and anatomic dissection by conventional methods of adhesiolysis. Outcomes of heart transplantations performed with HCA have not been previously catalogued in the literature and are presented in the current case series. METHODS: Between November 2012 and December 2014, 193 patients underwent heart transplantation at a single institution. Of these, 7 cases (3.6%) required implementation of HCA. Postoperative outcomes in these patients were analyzed using a prospectively maintained clinical database. RESULTS: The HCA patients included 28% females, with mean age of 46 years, and 71% had nonischemic cardiomyopathies. The majority (N = 5, 71%) had prior ventricular assist device implantation, including 1 patient with a paracorporeal biventricular assist device. One of the remaining 2 patients had three previous surgeries for repair of tetralogy of Fallot, with a completely calcified right ventricular outflow tract and pulmonary arterial system. Mean HCA and cold ischemic times were 25 minutes (range, 9-34 minutes) and 285 minutes (range, 181-425 minutes), respectively. Mean postoperative length of stay was 31 days, and six of seven patients (86%) survived to hospital discharge. One patient expired as an outpatient 2 months following transplant. Rates of postoperative renal failure, respiratory failure, and stroke were 43%, 43%, and 29%, respectively. CONCLUSION: On rare occasions, HCA must be instituted to safely conduct a complex heart transplantation procedure. Based on this small case series, these patients can be salvaged and discharged from the hospital, but may experience prolonged lengths of stay with moderate rates of other end-organ complications.

Have changes in ECMO technology impacted outcomes in adult patients developing postcardiotomy cardiogenic shock?

Extracorporeal membrane oxygenation (ECMO) technology has undergone several advancements over the last decade. We sought to compare current ECMO technology to older ones to determine how these technological improvements have impacted outcomes in patients suffering from postcardiotomy cardiogenic shock (PCS). Between 2005 and 2010, 49 patients received ECMO as support for PCS following elective cardiac surgery. Patients were divided into three groups. Group 1 (Gp 1, n = 11) patients received a Biomedicus pump with an Affinity oxygenator, Group 2 (Gp 2, n = 11) patients received a Biomedicus pump with a Quadrox D oxygenator, and Group 3 (Gp 3, n = 27) patients received a Rotaflow pump with a Quadrox D oxygenator. Groups were compared with regards to adverse events and ability to wean. Adverse event analysis showed no statistically significant difference between groups in incidence of stroke (p = 0.08), renal failure (p = 0.88), or bleeding requiring reexploration (p = 0.10). Changes in technology did little to improve weaning rates from ECMO (Gp 1 = 63.6%, Gp 2 = 45.5%, and Gp 3 = 55.6%). Similar trends were detected in hospital survival (Gp 1 = 27.3%, Gp 2 = 27.3%, and Gp 3 = 33.3%). Technology did impact oxygenator durability with Gp 1 requiring seven (63.6%) oxygenator exchanges compared to zero (0.0%) in Gp 2 and two (7.4%) in Gp 1. While advancements in ECMO technology have resulted in improved oxygenator durability, outcomes in patients requiring such support for PCS continue to be poor.

Correlation of donor-specific antibodies, complement and its regulators with graft dysfunction in cardiac antibody-mediated rejection.

Antibody-mediated rejection (AMR) is an immunopathologic process in which activation of complement often results in allograft injury. This study correlates C4d and C3d with HLA serology and graft function as diagnostic criteria for AMR. Immunofluorescence staining for C4d and C3d was performed on 1511 biopsies from 330 patients as part of routine diagnostic work-up of rejection. Donor-specific antibodies were detected in 95% of those with C4d+C3d+ biopsies versus 35% in the C4d+C3d- group (p = 0.002). Allograft dysfunction was present in 84% in the C4d+ C3d+ group versus 5% in the C4d+C3d- group (p < 0.0001). Combined C4d and C3d positivity had a sensitivity of 100% and specificity of 99% for the pathologic diagnosis of AMR and a mortality of 37%. Since activation of complement does not always result in allograft dysfunction, we correlated the expression pattern of the complement regulators CD55 and CD59 in patients with and without complement deposition. The proportion of patients with CD55 and/or CD59 staining was highest in C4d+C3d- patients without allograft dysfunction (p = 0.03). We conclude that a panel of C4d and C3d is diagnostically more useful than C4d alone in the evaluation of AMR. CD55 and CD59 may play a protective role in patients with evidence of complement activation.

Palliation of malignant aerodigestive fistulae with self-expanding metallic stents.

Malignant aerodigestive fistulae are rare but devastating sequelae of thoracic cancers, most commonly associated with esophageal cancer. Survival following development of a malignant aerodigestive fistula is measured in weeks. Palliation is the primary goal of therapy and to this end, we report the use of self-expanding metallic stents (SEMS) as treatment. Between May 1999 and January 2004, 12 patients were treated for malignant aerodigestive fistulae. The underlying diagnosis was esophageal cancer for 10 patients, and non-small cell lung cancer for two others. All patients were symptomatic and fistulae were diagnosed by esophagoscopy in seven, bronchoscopy in two, and esophagram in three. Seven covered Wallstents (seven esophageal) and eight covered Ultraflex (five tracheal and three esophageal) were used. A single stent was placed in eight patients (seven esophageal and one tracheal). Three patients required esophageal and tracheal stents and one patient needed two tracheal stents. General anesthesia was required in 50% of the patients. There were no procedure-related complications. Symptoms were palliated in 100% of patients and oral intake was reinstituted in 42% (5/12). All the patients were discharged from hospital after SEMS placement and one patient returned for an uneventful tracheal stent replacement secondary to mucus impaction 2 months later. SEMS placement is an effective strategy to palliate malignant aerodigestive fistulae. Complications are rare and symptoms are alleviated in most patients.

Attrition from heart transplant waiting list for patients on ventricular assist devices is not affected by desensitization strategies.

BACKGROUND: Ventricular assist device (VAD) patients, who are commonly sensitized, can be successfully transplanted using strategies aimed at diminishing antibody burden. However, the impact of these therapies on outcomes for VAD patients on the waiting list is ill-defined. The following study was conducted to ascertain the relationship between desensitization therapies and attrition rate from the waiting list for VAD patients. METHODS: The VAD patients listed between July 1996 and June 2002 were used for this report. Transplant and inpatient pharmacy databases were queried for demographics, date of transplantation, degree of allosensitization, use of desensitization therapy, immunosuppressive strategies, and specific causes of death. RESULTS: Among 232 patients listed for heart transplantation who required bridging to transplantation with a VAD, 79 (34%) died while on the waiting list. Common causes of death included multisystem organ failure in 32 (40.5%), sepsis in 19 (24.0%), and stroke in 10 (12.6%) patients. While nearly 50% of these patients were sensitized at listing, only 5 (6.3%) patients received desensitization therapy following VAD implantation. Therapies included mycophenolate mofetil in 3 (3.7%) and IVIG in 2 (2.5%) patients. Not a single patient underwent plasmapheresis or OKT3 therapy. CONCLUSION: For patients bridged to heart transplantation with a VAD, attrition from the waiting list was associated with factors other than desensitization or induction regimens.

Prolonged function of macrophage, von Willebrand factor-deficient porcine pulmonary xenografts.

Porcine von Willebrand factor (vWF) activates human and primate platelets. Having determined the importance of pulmonary intravascular macrophages (PIMs) in pulmonary xenotransplantation, we evaluated whether, in the absence of PIMs, vWF might play a role in pulmonary xenograft dysfunction. Utilizing a left single-lung transplant model, baboons depleted of anti-alphaGal antibodies received lungs from either vWF-deficient (n = 2); MCP-expressing (n = 5); MCP PIM-depleted (n = 5); or vWF-deficient PIM-depleted swine (n = 3). Two out of three of the PIM-depleted, pvWF deficient grafts survived longer than any previously reported pulmonary xenografts, including PIM-depleted xenografts expressing human complement regulatory proteins. Depletion of PIM's from vWF-deficient lungs, like depletion of PIM's from hMCP lungs, resulted in abrogation of the coagulopathy associated with pulmonary xenotransplantation. Thus, in terms of pulmonary graft survival, control of adverse reactions involving pvWF appears to be equally or even more important than is complement regulation using hMCP expression. However, based on the rapid failure of PIM-sufficient, pvWF-deficient pulmonary xenografts, pVWF-deficient pulmonary xenografts appear to be particularly sensitive to macrophage-mediated damage. These data provide initial evidence that vWF plays a role in the 'delayed' (24 h) dysfunction observed in pulmonary xenotransplantation using PIM depleted hMCP organs.

Early and late rejection and HLA sensitization at the time of heart transplantation in patients bridged with left ventricular assist devices.

Over the years, the frequency of heart transplant candidates with HLA sensitization has increased as a result of the number of patients bridged to transplant using left ventricular assist devices (LVAD). Here we have examined 119 patients who were bridged to transplant with LVAD for a relationship between HLA antibodies and early (30 days) and late (2 years or more) rejection, as evidenced by endomyocardial biopsies. Both cytotoxic panel-reactive antibody reactions against a panel of T lymphocytes (T-PRA) and the percentage of transplants that occurred across a positive class I flow cross-match were examined. Biopsies were scored using ISHLT criteria. At 30 days, patients who had a biopsy grade of 0 had a mean T-PRA at transplant of 2.2%, while the mean PRAs of the other biopsy grades were significantly higher (P < .001). A similar pattern was seen with the highest biopsy results at 2 years or later (P < .001). None of the patients who had a grade 0 biopsy at 30 days posttransplant had a positive flow cytometry class I cross-match (P = .02), although the same pattern did not occur later due to a small number of patients (n = 3) who had negative biopsies. Thus, when biopsy results were examined early or late posttransplant, patients with negative biopsy results tended to have less HLA sensitization. While the methods of HLA sensitization involve humoral responses, more aggressive immunosuppression might be warranted to attempt to reduce cellular rejection posttransplant if HLA class I antibodies are present at the time of transplant.

Cardiac transplantation at the Cleveland Clinic.

The cardiac transplant program at the Cleveland Clinic began in 1984 and has performed nearly 1,100 heart transplants. One-year actual graft and patient survival was 88% among 185 adult recipients transplanted between 1997-1999. In the past 20 years, we have seen a significant evolution of recipient selection criteria, donor suitability, immunosuppressive therapies, and posttransplant patient surveillance. Many of the changes in our program are a result of the bleak forecast, that even in a utopian situation, there would be an inadequate supply of donors. Since the potential growth in transplantable organs appears to be finite, every mechanism possible should be utilized to decrease the demand for this scarce resource. It is of utmost importance that all medical and surgical options have been exhausted prior to listing a patient for transplantation. More than 90% of our transplants are performed in patients who are UNOS Status 1A or 1B. Every patient on the waiting list must be reviewed periodically, to ensure that transplantation is still the most viable option. Finally, to reduce the risk of rejection and preserve graft survival, we must continue the search for novel immunosuppressants.

Evidence for polyreactive xenoreactive antibodies in the repertoire of human anti-swine antibodies: the 'next' humoral barrier to xenotransplantation?

The xenoreactive nature of anti-Galalpha1-3Gal antibodies, and to a lesser extent, polyreactive antibodies, has been characterized by a number of investigators. With the advent of therapies that avoid hyperacute xenograft rejection due to anti-Galalpha1-3Gal antibodies coupled with the possible development of Galalpha1-3Gal deficient swine, the Galalpha1-3Gal antigen may soon cease to be a barrier to xenotransplantation. With this in mind, the potential xenoreactive nature of polyreactive antibodies was investigated using several approaches. The levels of polyreactive antibodies from the serum of newborn (n = 2) and adult (n = 4) baboons undergoing pulmonary xenotransplantation were evaluated. Depletion of 95% and 94% of total serum IgM, without any decrease in albumin levels, was observed in the newborn baboons. This finding indicates that the IgM present at birth and germ line polyreactive IgM was adsorbed by the xenografts. The depletion of polyreactive antibodies (43-83% reduction of anti-DNP IgM) from adult baboons was also observed following pulmonary xenotransplantation or immunoadsorption therapy plus pulmonary xenotransplantation. Additional experiments using human cord serum indicated that most human polyreactive IgM were adsorbed by pig lung homogenate and that the human polyreactive IgM bound approximately two-fold more to immobilized pig lung antigens than to immobilized human lung antigens. These findings indicate that germline polyreactive antibodies are, for the most part, xenoreactive. These data suggest that polyreactive antibodies, although autoreactive, may be more xenoreactive than autoreactive.

Hapten-induced primary and memory humoral responses are inhibited by the infusion of anti-CD20 monoclonal antibody (IDEC-C2B8, Rituximab).

Blocking the elicited humoral immune response has proven useful in treating individuals with autoimmune disorders or those who are at risk of developing antibodies which might be pathologic, e.g., transplant patients. Unfortunately, humoral immunity has evaded efforts at ablation and those therapies aimed at ameliorating it have resulted in only partial success. In addition, some of the current anti-humoral therapies not only target B-cells but also cross-react with other elements of immune response, making these therapies nonspecific. Thus there is a need in the clinical arena for specific anti-humoral therapies. Here we report the impact of infusion of a chimeric monoclonal, an anti-CD20 IgG, on the primary humoral and memory response against a simple hapten (DNP) in a nonhuman primate model. Anti-CD20 IgG interfered with the elicited humoral response and with the memory response when administered prior to antigen exposure. Furthermore, we provide evidence that anti-CD20 blocks the humoral response by eliminating those B-cells capable of responding to the hapten.

The role of anti-Galalpha1-3Gal antibodies in acute vascular rejection and accommodation of xenografts.

BACKGROUND: A major impediment to the transplanting of porcine organs into humans is the susceptibility of porcine organs to acute vascular rejection, which can destroy a vascularized xenograft over a period of hours to days. Acute vascular rejection of porcine-to-primate xenografts is thought to be triggered by binding of xenoreactive antibodies to the graft. We tested whether antibodies, binding to Galalpha1-3Gal epitopes in porcine tissue, initiate this phenomenon. METHODS AND RESULTS: Specific depletion of anti-Galalpha1-3Gal antibodies from the blood of baboons, using extracorporeal perfusion of separated plasma through columns of Sepharose beads covalently linked to the antigenic trisaccharide, Galalpha1-3Galbeta1-4GlcAc, averted the development of acute vascular rejection in porcine organs transgenic for human decay-accelerating factor and CD59. More importantly, after immunodepletion was stopped and Gala1-3Gal antibodies were allowed to return, these same organs continued to function and remained pathologically normal and thus seemed to achieve a state of accommodation. CONCLUSION: These results demonstrate that anti-Galalpha1-3Gal antibodies cause acute vascular rejection and suggest that depletion of these antibodies leads to accommodation of the donor cardiac xenograft and could supply an important model for additional study.

Partial sequence of human platelet heparitinase and evidence of its ability to polymerize.

Heparitinase cleaves heparan sulfate, a glycosaminoglycan associated with all nucleated mammalian cells and extracellular matrices. Despite the important physiologic role heparitinase is postulated to play in such processes as tumor metastasis and inflammation, the identity of the enzyme remains a matter of controversy and there is a question of whether heparitinase is CTAP III. We report a 900,000-fold purification of heparitinase from human platelets. A multi-step procedure utilizing chromatography on heparin, DEAE, hydroxyapatite and size exclusion matrices was employed and yielded a single protein as judged by Coomassie staining of protein separated by SDS-PAGE. The purified protein had an apparent molecular mass of 35 kDa by size exclusion chromatography and 55 kDa by SDS-PAGE. During purification, heparitinase activity co-eluted from the hydroxyapatite and size exclusion columns with the 35-55 kDa protein, confirming that the purified protein was indeed heparitinase. The 35-55 kDa protein reacted strongly with concanavalin A, a lectin known to bind to heparitinase, further confirming that the protein was heparitinase. Platelet heparitinase formed dimers and tetramers upon storage in a purified form, possibly accounting for the various molecular weights previously reported for the enzyme. A partial amino acid sequence of the protein revealed that heparitinase has not been previously sequenced.