Evaluating threshold for donor fraction cell-free DNA using clinically available assay for rejection in pediatric and adult heart transplantation.

BACKGROUND: The aims of the study were to assess the performance of a clinically available cell-free DNA (cfDNA) assay in a large cohort of pediatric and adult heart transplant recipients and to evaluate performance at specific cut points in detection of rejection. METHODS: Observational, non-interventional, prospective study enrolled pediatric and adult heart transplant recipients from seven centers. Biopsy-associated plasma samples were used for cfDNA measurements. Pre-determined cut points were tested for analytic performance. RESULTS: A total of 487 samples from 160 subjects were used for the analysis. There were significant differences for df-cfDNA values between rejection [0.21% (IQR 0.12-0.69)] and healthy samples [0.05% (IQR 0.01-0.14), p < .0001]. The pediatric rejection group had a median df-cfDNA value of 0.93% (IQR 0.28-2.84) compared to 0.09% (IQR 0.04-0.23) for healthy samples, p = .005. Overall negative predictive value was 0.94 while it was 0.99 for pediatric patients. Cut points of 0.13% and 0.15% were tested for various types of rejection profiles and were appropriate to rule out rejection. CONCLUSION: The study suggests that pediatric patients with rejection show higher levels of circulating df-cfDNA compared to adults and supports the specific cut points for clinical use in pediatric and adult patients with overall acceptable performance.

Validation of donor fraction cell-free DNA with biopsy-proven cardiac allograft rejection in children and adults.

OBJECTIVES: Donor-specific cell-free DNA shows promise as a noninvasive marker for allograft rejection, but as yet has not been validated in both adult and pediatric recipients. The study objective was to validate donor fraction cell-free DNA as a noninvasive test to assess for risk of acute cellular rejection and antibody-mediated rejection after heart transplantation in pediatric and adult recipients. METHODS: Pediatric and adult heart transplant recipients were enrolled from 7 participating sites and followed for 12 months or more with plasma samples collected immediately before all endomyocardial biopsies. Donor fraction cell-free DNA was extracted, and quantitative genotyping was performed. Blinded donor fraction cell-free DNA and clinical data were analyzed and compared with a previously determined threshold of 0.14%. Sensitivity, specificity, negative predictive value, positive predictive value, and receiver operating characteristic curves were calculated. RESULTS: A total of 987 samples from 144 subjects were collected. After applying predefined clinical and technical exclusions, 745 samples from 130 subjects produced 54 rejection samples associated with the composite outcome of acute cellular rejection grade 2R or greater and pathologic antibody-mediated rejection 2 or greater and 323 healthy samples. For all participants, donor fraction cell-free DNA at a threshold of 0.14% had a sensitivity of 67%, a specificity of 79%, a positive predictive value of 34%, and a negative predictive value of 94% with an area under the curve of 0.78 for detecting rejection. When analyzed independently, these results held true for both pediatric and adult cohorts at the same threshold of 0.14% (negative predictive value 92% and 95%, respectively). CONCLUSIONS: Donor fraction cell-free DNA at a threshold of 0.14% can be used to assess for risk of rejection after heart transplantation in both pediatric and adult patients with excellent negative predictive value.

Relationship between donor fraction cell-free DNA and clinical rejection in heart transplantation.

BACKGROUND: Clinical rejection (CR) defined as decision to treat clinically suspected rejection with change in immunotherapy based on clinical presentation with or without diagnostic biopsy findings is an important part of care in heart transplantation. We sought to assess the utility of donor fraction cell-free DNA (DF cfDNA) in CR and the utility of serial DF cfDNA in CR patients in predicting outcomes of clinical interest. METHODS: Patients with heart transplantation were enrolled in two sequential, multi-center, prospective observational studies. Blood samples were collected for surveillance or clinical events. Clinicians were blinded to the results of DF cfDNA. RESULTS: A total of 835 samples from 269 subjects (57% pediatric) were included for this analysis, including 28 samples associated with CR were analyzed. Median DF cfDNA was 0.43 (IQR 0.15, 1.36)% for CR and 0.10 (IQR 0.07, 0.16)% for healthy controls (p < .0001). At cutoff value of 0.13%, the area under curve (AUC) was 0.82, sensitivity of 0.86, specificity of 0.67, and negative predictive value of 0.99. There was serial decline in DF cfDNA post-therapy, however, those with cardiovascular events (cardiac arrest, need for mechanical support or death) showed significantly higher levels of DF cfDNA on Day 0 (2.11 vs 0.31%) and Day 14 (0.51 vs 0.22%) compared to those who did not have such an event (p < .0001). CONCLUSION: DF cfDNA has excellent agreement with clinical rejection and, importantly, serial measurement of DF cfDNA predict clinically significant outcomes post treatment for rejection in these patients.

Increase in nuclear cell-free DNA is associated with major adverse events in adult and pediatric heart transplant recipients.

BACKGROUND: Cell-free DNA is an emerging biomarker. While donor fraction may detect graft events in heart transplant recipients, the prognostic value of total nuclear cell-free DNA (ncfDNA) itself is largely unexplored. OBJECTIVE: Explore the relationship between ncfDNA and clinical events in heart transplant recipients. METHODS: We conducted a multi-center prospective study to investigate the value of cell-free DNA in non-invasive monitoring following heart transplantation. Over 4000 blood samples were collected from 388 heart transplant patients. Total ncfDNA and donor fraction were quantified. Generalized linear models with maximum likelihood estimation for repeated measures with subjects as clusters were used to explore the relationship of ncfDNA and major adverse events. Receiver operating characteristic curves were used to help choose cutpoints. RESULTS: A ncfDNA threshold (50 ng/ml) was identified that was associated with increased risk of major adverse events. NcfDNA was elevated in patients who suffered cardiac arrest, required mechanical circulatory support or died post heart transplantation as well as in patients undergoing treatment for infection. CONCLUSIONS: Elevated ncfDNA correlates with risk for major adverse events in adult and pediatric heart transplant recipients and may indicate a need for enhanced surveillance after transplant.

Impact of increased donor distances following adult heart allocation system changes: A single center review of 1-year outcomes.

BACKGROUND: On October 18, 2018, several changes to the donor heart allocation system were enacted. We hypothesize that patients undergoing orthotopic heart transplantation (OHT) under the new allocation system will see an increase in ischemic times, rates of primary graft dysfunction, and 1-year mortality due to these changes. METHODS: In this single-center retrospective study, we reviewed the charts of all OHT patients from October 2017 through October 2019. Pre- and postallocation recipient demographics were compared. Survival analysis was performed using the Kaplan-Meier method. RESULTS: A total of 184 patients underwent OHT. Recipient demographics were similar between cohorts. The average distance from donor increased by more than 150 km (p = .006). Patients in the postallocation change cohort demonstrated a significant increase in the rate of severe left ventricle primary graft dysfunction from 5.4% to 18.7% (p = .005). There were no statistically significant differences in 30-day mortality or 1-year survival. Time on the waitlist was reduced from 203.8 to 103.7 days (p = .006). CONCLUSIONS: Changes in heart allocation resulted in shorter waitlist times at the expense of longer donor distances and ischemic times, with an associated negative impact on early post-transplantation outcomes. No significant differences in 30-day or 1-year mortality were observed.

Donor fraction cell-free DNA and rejection in adult and pediatric heart transplantation.

BACKGROUND: Endomyocardial biopsy (EMB) is the current standard for rejection surveillance in heart transplant recipients. The quantification of donor-specific cell-free DNA (cfDNA) may be an appropriate biomarker for non-invasive rejection surveillance. A multicenter prospective blinded study (DNA-Based Transplant Rejection Test, DTRT) investigated the value of donor fraction (DF), defined as the ratio of cfDNA specific to the transplanted organ to the total amount of cfDNA present in a blood sample. METHODS: A total of 241 heart transplant patients were recruited from 7 centers. Age at transplant ranged from 8 days to 73 years, with 146 subjects <18 years and 95 ≥18 years. All the patients were followed for at least 1 year, with blood samples drawn at routine and for-cause biopsies. A total of 624 biopsy-paired samples were included for analysis through a commercially available cfDNA assay (myTAIHEART, TAI Diagnostics Inc.). A blinded analysis of repeated measures compared the outcomes using receiver operating characteristic (ROC) curves. All primary clinical end-points were monitored at 100%. All analysis and conclusions were reviewed by both an independent external oversight committee and the National Institutes of Health-mandated DTRT steering committee. RESULTS: DF in acute cellular rejection (ACR) 1R/2R (n = 15) was higher than ACR 0R (n = 42) (p = 0.02); DF in antibody-mediated rejection pAMR1 (n = 8) and pAMR2 (n = 12) (p = 0.05) were higher than pAMR0 (n = 466) (p = 0.04 and p = 0.05 respectively). An optimal DF threshold was determined by the use of an ROC analysis, which ruled out the presence of either ACR or antibody-mediated rejection. CONCLUSIONS: The cell-free DNA DF holds promise as a non-invasive diagnostic test to rule out acute rejection in both adult and pediatric heart transplant populations.

Marginal Donor Use in Patients Undergoing Heart Transplantation With Left Ventricular Assist Device Explantation.

BACKGROUND: The use of continuous flow (CF) left ventricular assist devices (LVAD) as a bridge to orthotopic heart transplantation (OHT) has increased. This study examined survival outcomes after CF-LVAD explantation and OHT using marginal donors. METHODS: Adults undergoing OHT with or without LVAD explant using marginal donors between 2007 and 2014 were identified in the Scientific Registry for Transplant Recipients database. A previously validated donor risk score was used to define marginal donors. Patients were stratified into four groups based on utilization of a marginal donor with or without LVAD explantation at OHT. Graft survival was analyzed at 1 and 5 years. RESULTS: Overall, 7,798 patients with OHT were analyzed. Whereas 1,862 patients (24%) underwent direct OHT utilizing marginal donors, only 626 patients (30% [group A]) underwent OHT with LVAD explant (HeartMate II [Thoratec, Pleasanton, CA], n =581, 93%; HVAD [HeartWare, Framingham, MA], n = 45, 7%) and 1,236 (70%) underwent direct OHT (group B). Standard donors were utilized for 2,334 patients with CF-LVAD explant (group C), and 3,602 patients underwent direct OHT (group D). Utilization of marginal donors in patients undergoing LVAD explantation was associated with decreased posttransplant graft survival (p < 0.001). After adjusting for recipient age, sex, listing status at OHT, body mass index, creatinine, and duration of LVAD support, Cox regression analysis found that patients bridged with LVADs, recipients receiving transplants from marginal donors, recipients with highest age and body mass index, and highest creatinine were at increased risk of graft failure (all p < 0.01). CONCLUSIONS: Utilization of marginal donors in patients undergoing CF-LVAD explantation and OHT is associated with reduced early and late graft survival. These findings support cautionary use of marginal donors in patients bridged with CF-LVAD.

Perioperative blood product use: a comparison between HeartWare and HeartMate II devices.

BACKGROUND: The HeartWare (HW) (Framingham, MA) and the HeartMate II (HM II) (Thoratec Inc, Pleasanton, CA) continuous-flow left ventricular assist devices (CF-LVADs) are commonly used to bridge patients to transplantation. We hypothesized that there are differences in perioperative blood product (BP) use and chest tube (CT) output between CF-LVAD types. METHODS: We retrospectively evaluated BP use in 71 patients who were implanted with a CF-LVAD (HM II = 38; HW = 33) by median sternotomy for bridge to transplantation (BTT) indications from 2009 to 2013. Detailed BP use data were collected during the intraoperative and postoperative periods and included packed red blood cells, platelets, fresh frozen plasma, and cryoprecipitate. RESULTS: Preoperative characteristics (age, left ventricular ejection fraction, previous sternotomy, ischemic cause), and risk stratification scores (Interagency Registry for Mechanically Assisted Circulatory Support [INTERMACS]) profile, Leitz-Miller score, Kormos score) were comparable between groups (all p > 0.05). Total average intraoperative and postoperative BP use was different between device types: HW = 8.3 ± 13 versus HM II = 12.6 ± 14.0 units (p = 0.002) and HW = 6.1 ± 12.0 units compared with HM II = 13.5 ± 24.1 units (p = 0.022), respectively. Average postoperative CT output for HW (3,231 ± 3,648 mL) and HM II (3,463 ± 3,050) (p < 0.008) were different between device types. Multivariate analysis revealed that a higher preoperative Leitz-Miller score, implantation of an HM II CF-LVAD, previous sternotomy, and a longer duration of cardiopulmonary bypass (CPB) time were independently associated with increased need for BP use, whereas only use of the HM II device and a longer bypass time predicted a greater CT output. CONCLUSIONS: Compared with HM II, implantation of the HW CF-LVAD was associated with reduced intraoperative and postoperative BP use and decreased CT output. Increased awareness of device-related differences in bleeding and BP use may improve CF-LVAD patient outcomes.

Does renal dysfunction and method of bridging support influence heart transplant graft survival?

BACKGROUND: Renal insufficiency is common in status 1B patients supported with inotropes or a continuous flow left ventricular device (CF-LVAD) as a bridge to heart transplantation. We evaluated the association of renal function and inotrope versus CF-LVAD support on posttransplant graft survival in status 1B patients. METHODS: The Scientific Registry for Transplant Recipients database was analyzed for posttransplant survival in status 1B patients bridged with inotropes or CF-LVAD who underwent transplantation between 2003 and 2012. Pretransplant renal function was measured by estimating glomerular filtration rate (GFR) and was stratified as less than 45 mL · min(-1) · 1.73 m(-2), 45 to 59, and 60 or greater. Univariate Kaplan-Meier and multivariate Cox regression models were used to evaluate the main effects of GFR strata and inotropes versus CF-LVAD, and the interaction effect of GFR strata by CF-LVAD, on graft survival. RESULTS: This study included 4,158 status 1B patients (74% male, aged 53 ± 12 years). Of those, 659 patients had a CF-LVAD (HeartMate-II [Thoratec, Pleasanton, CA], n = 638; HVAD [HeartWare, Framingham, MA], n = 21), and 3,530 were receiving inotropes (31 CF-LVAD patients were also receiving inotropes). Kaplan-Meier analyses demonstrated reduced graft survival (p = 0.022) in patients with pretransplant GFR less than 45 versus GFR 45 to 59 (p = 0.062) and versus GFR 60 or greater (p = 0.007), and no effect of inotrope versus CF-LVAD support on graft survival (p = 0.402). Multivariate analysis demonstrated that, after adjusting for the main effects of GFR stratum, CF-LVAD, and inotropes, status 1B patients bridged with a CF-LVAD and GFR in the lowest stratum had reduced graft survival (interaction effect p = 0.040). CONCLUSIONS: Pretransplant renal insufficiency was associated with reduced posttransplant graft survival in status 1B patients. This risk is increased for patients bridged with a CF-LVAD (versus inotropes) who have GFR in the lowest stratum.

Institutional volume of heart transplantation with left ventricular assist device explantation influences graft survival.

BACKGROUND: There are increasing numbers of patients undergoing orthotopic heart transplantation (OHT) with left ventricular assist device (LVAD) explantation (LVAD explant-OHT). We hypothesized that LVAD explant-OHT is a more challenging surgical procedure compared to OHT without LVAD explantation and that institutional LVAD explant-OHT procedural volume would be associated with post-transplant graft survival. We sought to assess the impact of institutional volume of LVAD explant-OHT on post-transplant graft survival. METHODS: This is a retrospective analysis of the Scientific Registry of Transplant Recipients for adult OHTs with long-term LVAD explantation. LVAD explant-OHT volume was characterized on the basis of the center's year-specific total OHT volume (OHTvol) and year-specific LVAD explant-OHT volume quartile (LVADvolQ). The effect of LVADvolQ on graft survival (death or re-transplantation) was analyzed. RESULTS: From 2004 to 2011, 2,681 patients underwent OHT with LVAD explantation (740 with HeartMate XVE, 1,877 with HeartMate II and 64 with HeartWare devices). LVAD explant-OHT at centers falling in the lowest LVADvolQ was associated with reduced post-transplant graft survival (p = 0.022). After adjusting for annualized OHTvol (HR = 0.998, 95% CI 0.993 to 1.003, p = 0.515 and pulsatile XVE (HR = 0.842, 95% CI 0.688 to 1.032, p = 0.098), multivariate analysis confirmed a significantly (approximately 37%) increased risk of post-transplant graft failure among explant-OHT procedures occurring at centers in the lowest volume quartile (HR = 1.371, 95% CI 1.030 to 1.825, p = 0.030). CONCLUSION: Graft survival is decreased when performed at centers falling in the lowest quartile of LVAD explant-OHT for a given year. This volume-survival relationship should be considered in the context of limited donor organ availability and the rapidly growing number of LVAD centers.

Are peripherally inserted central catheters associated with increased risk of adverse events in status 1B patients awaiting transplantation on continuous intravenous milrinone?

BACKGROUND: Peripherally inserted central catheters (PICCs) are used to deliver continuous intravenous (IV) milrinone in stage D heart failure (HF) patients awaiting heart transplantation (HT). METHODS: We retrospectively analyzed PICC adverse events (AEs) and associated cost in 129 status 1B patients from 2005 to 2012. End points were HT, left ventricular assist device (LVAD), and death. Regression analysis was used to identify AE risk factors. RESULTS: Fifty-three PICC AEs occurred in 35 patients (27%), consisting of 48 infections, 4 thromboses, and 1 bleeding event. Median duration of PICC support was 63 (interquartile range [IQR] 34-131) days, and median time to first PICC infection was 44 (IQR 14-76) days. Among PICC infections, 9% required defibrillator removal and 30% were inactivated on the HT list for a mean of 23 ± 17 days. Rate of HT, LVAD, or death was similar between groups (P > .05). Regression analysis found that a double lumen PICC was associated with a shorter time to first PICC infection (hazard ratio 7.59, 95% CI 1.97-29.23; P = .003). Median cost per PICC infection was $10,704 (IQR $7,401-$26,083). CONCLUSIONS: PICC infections were the most frequent AEs. PICCs with >1 lumen were associated with increased risk of infection. PICC AEs accounted for increased intensive care unit admissions, HT list inactivations, and overall cost.

Mechanical circulatory support and heart transplantation: donor and recipient factors influencing graft survival.

BACKGROUND: Mechanical circulatory support is an accepted strategy to bridge patients to heart transplantation (HTx). Among mechanical circulatory support patients who go on to HTx, factors associated with improved graft survival have not been fully elucidated. METHODS: Using the Scientific Registry for Transplant Recipients, we identified adults who were treated with a left ventricular assist device (LVAD) or total artificial heart (TAH) before HTx. Kaplan-Meier and multivariate Cox regression models were used to identify patient, donor, and device characteristics associated with graft survival. RESULTS: Between January 1997 and February 2012, 2,785 adults underwent HTx. Before HTx, 2,674 patients were treated with a LVAD (HeartMate XVE, 724; HeartMate II, 1,882; HeartWare, 68), and 111 were treated with a TAH. Follow-up averaged 25 ± 24 months. Gender mismatch occurred in 23%. Graft survival did not differ between LVAD groups (all p > 0.168), but TAH was associated with reduced graft survival compared with LVADs (p < 0.001). After controlling for device type (LVAD vs TAH), lower recipient pulmonary vascular resistance, shorter ischemic time, younger donor age, donor-to-recipient gender match, and higher donor-to-recipient body mass index ratio were independent predictors of longer graft survival (all p < 0.05). CONCLUSIONS: TAH was associated with reduced graft survival after transplant, and survival did not differ between the LVAD device groups. Additional variables that were independently associated with graft survival were donor age, recipient peripheral vascular resistance, ischemic time, gender match, and donor-to-recipient body mass index ratio. Recognition of these factors may inform decisions regarding device support and donor suitability.

Benefits of ambulatory axillary intra-aortic balloon pump for circulatory support as bridge to heart transplant.

OBJECTIVE: Axillary intra-aortic balloon pump therapy has been described as a bridge to transplant. Advantages over femoral intra-aortic balloon pump therapy include reduced incidence of infection and enhanced patient mobility. We identified the patients who would benefit most from this therapy while awaiting heart transplantation. METHODS: We conducted a single-center, retrospective observational study to evaluate outcomes from axillary intra-aortic balloon pump therapy. These included hemodynamic parameters, duration of support, and success in bridging to transplant. We selected patients on the basis of history of sternotomy, elevated panel-reactive antibody, and small body habitus. Patients were made to ambulate aggressively beginning on postoperative day 1. RESULTS: Between September 2007 and September 2010, 18 patients underwent axillary intra-aortic balloon pump therapy. All patients had the devices placed through the left axillary artery with a Hemashield side graft (Boston Scientific, Natick, Mass). Before axillary placement, patients underwent femoral placement to demonstrate hemodynamic benefit. Duration of support ranged from 5 to 63 days (median = 19 days). There was marked improvement in ambulatory potential and hemodynamic parameters, with minimal blood transfusion requirements. There were no device-related infections. Some 72% of the patients (13/18) were successfully bridged to transplantation. CONCLUSIONS: Axillary intra-aortic balloon pump therapy provides excellent support for selected patients as a bridge to transplant. The majority of the patients were successfully bridged to transplant and discharged. Although this therapy has been described in previous studies, this is the largest series to incorporate a regimen of aggressive ambulation with daily measurements of distances walked.