Circulating cell-free DNA enables noninvasive diagnosis of heart transplant rejection

Monitoring allograft health is an important component of posttransplant therapy. Endomyocardial biopsy is the current gold standard for cardiac allograft monitoring but is an expensive and invasive procedure. Proof of principle of a universal, noninvasive diagnostic method based on high-throughput screening of circulating cell-free donor-derived DNA (cfdDNA) was recently demonstrated in a small retrospective cohort. We present the results of a prospective cohort study (65 patients, 565 samples) that tested the utility of cfdDNA in measuring acute rejection after heart transplantation. Circulating cell-free DNA was purified from plasma and sequenced (mean depth, 1.2 giga-base pairs) to quantify the fraction of cfdDNA. Through a comparison with endomyocardial biopsy results, we demonstrate that cfdDNA enables diagnosis of acute rejection after heart transplantation, with an area under the receiver operating characteristic curve of 0.83 and sensitivity and specificity that are comparable to the intrinsic performance of the biopsy itself. This noninvasive genome transplant dynamics approach is a powerful and informative method for routine monitoring of allograft health without incurring the risk, discomfort, and expense of an invasive biopsy.

Temporal response of the human virome to immunosuppression and antiviral therapy

There are few substantive methods to measure the health of the immune system, and the connection between immune strength and the viral component of the microbiome is poorly understood. Organ transplant recipients are treated with posttransplant therapies that combine immunosuppressive and antiviral drugs, offering a window into the effects of immune modulation on the virome. We used sequencing of cell-free DNA in plasma to investigate drug-virome interactions in a cohort of organ transplant recipients (656 samples, 96 patients) and find that antivirals and immunosuppressants strongly affect the structure of the virome in plasma. We observe marked virome compositional dynamics at the onset of the therapy and find that the total viral load increases with immunosuppression, whereas the bacterial component of the microbiome remains largely unaffected. The data provide insight into the relationship between the human virome, the state of the immune system, and the effects of pharmacological treatment and offer a potential application of the virome state to predict immunocompetence.

The International Thoracic Organ Transplant Registry of the International Society for Heart and Lung Transplantation: Thirty-eighth adult lung transplantation report - 2021; Focus on recipient characteristics

For over 30 years, the International Society for Heart and Lung Transplantation (ISHLT) International Thoracic Organ Transplant (TTX) Registry has gathered data regarding transplant procedures, donor and recipient characteristics, and outcomes from a global community of transplant centers. Almost 70,000 adult lung transplant procedures have been reported to the Registry since its inception, each one providing an opportunity for a recipient with end-stage lung disease to regain quality of life and longevity. With each year's report, we provide more detailed analyses on a particular focus theme important to recipient outcomes. Since 2013, these have been donor and recipient age; retransplantation; early graft failure; indication for transplant; allograft ischemic time; multiorgan transplantation; and donor and recipient size matching.^1-7 In response to a changing regulatory environment, the ISHLT TTX Registry is undergoing an update in data acquisition, and the patient cohort examined in this report is therefore derived from the same data source or datasets as that examined in the 2019 annual reports.^2,8-10 We refer the reader to the 2019 and prior reports for a detailed description of the baseline characteristics of the cohort, and additional core analyses not directly related to the focus explored in this year's report. To complement the 2020 report which focussed on donor characteristics, the goal of this year's report was to focus entirely on changes in recipient factors over the past 3 decades and to identify important recipient characteristics and transplant processes that may influence post-transplant outcomes. Due to small numbers, heart-lung transplant recipient characteristics and transplant outcomes have not been included. This 38th annual adult lung transplant report is hence based on data submitted to the ISHLT TTX Registry on 67,493 adult recipients of deceased recipient transplants between January 1, 1992 and June 30, 2018.

Noninvasive detection of graft injury after heart transplant using donor-derived cell-free DNA: A prospective multicenter study

Standardized donor-derived cell-free DNA (dd-cfDNA) testing has been introduced into clinical use to monitor kidney transplant recipients for rejection. This report describes the performance of this dd-cfDNA assay to detect allograft rejection in samples from heart transplant (HT) recipients undergoing surveillance monitoring across the United States. Venous blood was longitudinally sampled from 740 HT recipients from 26 centers and in a single-center cohort of 33 patients at high risk for antibody-mediated rejection (AMR). Plasma dd-cfDNA was quantified by using targeted amplification and sequencing of a single nucleotide polymorphism panel. The dd-cfDNA levels were correlated to paired events of biopsy-based diagnosis of rejection. The median dd-cfDNA was 0.07% in reference HT recipients (2164 samples) and 0.17% in samples classified as acute rejection (35 samples; P = .005). At a 0.2% threshold, dd-cfDNA had a 44% sensitivity to detect rejection and a 97% negative predictive value. In the cohort at risk for AMR (11 samples), dd-cfDNA levels were elevated 3-fold in AMR compared with patients without AMR (99 samples, P = .004). The standardized dd-cfDNA test identified acute rejection in samples from a broad population of HT recipients. The reported test performance characteristics will guide the next stage of clinical utility studies of the dd-cfDNA assay.

Single-stranded DNA library preparation uncovers the origin and diversity of ultrashort cell-free DNA in plasma

Circulating cell-free DNA (cfDNA) is emerging as a powerful monitoring tool in cancer, pregnancy and organ transplantation. Nucleosomal DNA, the predominant form of plasma cfDNA, can be adapted for sequencing via ligation of double-stranded DNA (dsDNA) adapters. dsDNA library preparations, however, are insensitive to ultrashort, degraded cfDNA. Drawing inspiration from advances in paleogenomics, we have applied a single-stranded DNA (ssDNA) library preparation method to sequencing of cfDNA in the plasma of lung transplant recipients (40 samples, six patients). We found that ssDNA library preparation yields a greater portion of sub-100 bp nuclear genomic cfDNA (p 10⁻⁵, Mann-Whitney U Test), and an increased relative abundance of mitochondrial (10.7x, p 10⁻⁵) and microbial cfDNA (71.3x, p10⁻⁵). The higher yield of microbial sequences from this method increases the sensitivity of cfDNA-based monitoring for infections following transplantation. We detail the fragmentation pattern of mitochondrial, nuclear genomic and microbial cfDNA over a broad fragment length range. We report the observation of donor-specific mitochondrial cfDNA in the circulation of lung transplant recipients. A ssDNA library preparation method provides a more informative window into understudied forms of cfDNA, including mitochondrial and microbial derived cfDNA and short nuclear genomic cfDNA, while retaining information provided by standard dsDNA library preparation methods.

Effect of High-Dose Atorvastatin on Hospitalizations for Heart Failure

Background— Statins reduce the rate of major cardiovascular events in high-risk patients, but their potential benefit as treatment for heart failure (HF) is less clear.

Methods and Results— Patients (n=10 001) with stable coronary disease were randomized to treatment with atorvastatin 80 or 10 mg/d and followed up for a median of 4.9 years. A history of HF was present in 7.8% of patients. A known ejection fraction <30% and advanced HF were exclusion criteria for the study. A predefined secondary end point of the study was hospitalization for HF. The incidence of hospitalization for HF was 2.4% in the 80-mg arm and 3.3% in the 10-mg arm (hazard ratio, 0.74; 95% confidence interval, 0.59 to 0.94; P =0.0116). The treatment effect of the higher dose was more marked in patients with a history of HF: 17.3% versus 10.6% in the 10- and 80-mg arms, respectively (hazard ratio, 0.59; 95% confidence interval, 0.4 to 0.88; P =0.009). Among patients without a history of HF, the rates of hospitalization for HF were much lower: 1.8% in the 80-mg group and 2.0% in the 10-mg group (hazard ratio, 0.87; 95% confidence interval, 0.64 to 1.16; P =0.34). Only one third of patients hospitalized for HF had evidence of preceding angina or myocardial infarction during the study period. Blood pressure was almost identical during follow-up in the treatment groups.

Conclusions— Compared with a lower dose, intensive treatment with atorvastatin in patients with stable coronary disease significantly reduces hospitalizations for HF. In a post hoc analysis, this benefit was observed only in patients with a history of HF. The mechanism accounting for this benefit is unlikely to be due primarily to a reduction in interim coronary events or differences in blood pressure.

Donor predictors of allograft use and recipient outcomes after heart transplantation

BACKGROUND

Despite a national organ-donor shortage and a growing population of patients with end-stage heart disease, the acceptance rate of donor hearts for transplantation is low. We sought to identify donor predictors of allograft nonuse, and to determine whether these predictors are in fact associated with adverse recipient post-transplant outcomes.

METHODS AND RESULTS

We studied a cohort of 1872 potential organ donors managed by the California Transplant Donor Network from 2001 to 2008. Forty-five percent of available allografts were accepted for heart transplantation. Donor predictors of allograft nonuse included age >50 years, female sex, death attributable to cerebrovascular accident, hypertension, diabetes mellitus, a positive troponin assay, left-ventricular dysfunction and regional wall motion abnormalities, and left-ventricular hypertrophy. For hearts that were transplanted, only donor cause of death was associated with prolonged recipient hospitalization post-transplant, and only donor diabetes mellitus was predictive of increased recipient mortality.

CONCLUSIONS

Whereas there are many donor predictors of allograft discard in the current era, these characteristics seem to have little effect on recipient outcomes when the hearts are transplanted. Our results suggest that more liberal use of cardiac allografts with relative contraindications may be warranted.

Cost-effectiveness of Dapagliflozin for Treatment of Patients With Heart Failure With Reduced Ejection Fraction

Importance

In the Dapagliflozin and Prevention of Adverse Outcomes in Heart Failure (DAPA-HF) trial, dapagliflozin was shown to reduce cardiovascular mortality and hospitalizations due to heart failure while improving patient-reported health status. However, the cost-effectiveness of adding dapagliflozin therapy to standard of care (SOC) is unknown.

Objective

To estimate the cost-effectiveness of dapagliflozin therapy among patients with chronic heart failure with reduced ejection fraction (HFrEF).

Design, Setting, and Participants

This Markov cohort cost-effectiveness model used estimates of therapy effectiveness, transition probabilities, and utilities from the DAPA-HF trial and other published literature. Costs were derived from published sources. Patients with HFrEF included subgroups based on diabetes status and health status impairment due to heart failure. We compiled parameters from the literature including DAPA-HF, on which our model is based, and many other sources from December 2019 to February 27, 2021. We performed our analysis in February 2021.

Exposures

Dapagliflozin or SOC.

Main Outcomes and Measures

Hospitalizations for heart failure, life-years, quality-adjusted life-years (QALYs), costs, and the cost per QALY gained (incremental cost-effectiveness ratio).

Results

In the model, dapagliflozin therapy yielded a mean of 0.78 additional life-years and 0.46 additional QALYs compared with SOC at an incremental cost of $38 212, resulting in a cost per QALY gained of $83 650. The cost per QALY was similar for patients with or without diabetes and for patients with mild or moderate impairment of health status due to heart failure. The cost-effectiveness was most sensitive to estimates of the effect on mortality and duration of therapy effectiveness. If the cost of dapagliflozin decreased from $474 to $270 (43% decline), the cost per QALY gained would drop below $50 000.

Conclusions and Relevance

These findings suggest that dapagliflozin provides intermediate value compared with SOC, based on American College of Cardiology/American Heart Association benchmarks. Additional data regarding the magnitude of mortality reduction would improve the precision of cost-effectiveness estimates.

Effect of pulmonary hypertension on clinical outcomes in advanced heart failure: analysis of the Evaluation Study of Congestive Heart Failure and Pulmonary Artery Catheterization Effectiveness (ESCAPE) database

BACKGROUND

Pulmonary hypertension has been shown to predict hospitalizations and mortality in patients with heart failure. We aimed to define the prevalence of mixed pulmonary hypertension (MPH; mean pulmonary artery pressure > or = 25 mm Hg, pulmonary capillary wedge pressure >15 mm Hg, and pulmonary vascular resistance > or = 3 Wood units), identify clinical predictors of MPH, and determine whether MPH predicts adverse outcomes in patients hospitalized with severe heart failure.

METHODS

This is a subgroup analysis of patients assigned to pulmonary artery catheter placement in the Evaluation Study of Congestive Heart Failure and Pulmonary Artery Catheterization Effectiveness (ESCAPE) trial. Patients with and without MPH were compared with respect to baseline characteristics and clinical outcomes, including NYHA class, 6-minute walk distance, quality of life, days hospitalized, and 6-month mortality.

RESULTS

Of the 171 patients studied, 80 (47%) had MPH. Older age was the only significant predictor of MPH. MPH patients had lower cardiac index (1.8 +/- 0.5 L/min vs 2.1 +/- 0.5 L/min, P = .001) and higher systemic vascular resistance index (3,179 +/- 1,454 vs 2,550 +/- 927 dynes x s/cm5 x m2, P < .001) compared to those without MPH. Importantly, right ventricular function was relatively preserved (median RVSWI 8.7 gm-m/m2/beat) in MPH patients. There were no significant differences in clinical outcomes between the two groups.

CONCLUSIONS

Mixed pulmonary hypertension is common in patients hospitalized with advanced heart failure and is not associated with adverse short-term clinical outcomes over and above the poor prognosis of ADHF patients without MPH.

Quantification of transplant-derived circulating cell-free DNA in absence of a donor genotype

Quantification of cell-free DNA (cfDNA) in circulating blood derived from a transplanted organ is a powerful approach to monitoring post-transplant injury. Genome transplant dynamics (GTD) quantifies donor-derived cfDNA (dd-cfDNA) by taking advantage of single-nucleotide polymorphisms (SNPs) distributed across the genome to discriminate donor and recipient DNA molecules. In its current implementation, GTD requires genotyping of both the transplant recipient and donor. However, in practice, donor genotype information is often unavailable. Here, we address this issue by developing an algorithm that estimates dd-cfDNA levels in the absence of a donor genotype. Our algorithm predicts heart and lung allograft rejection with an accuracy that is similar to conventional GTD. We furthermore refined the algorithm to handle closely related recipients and donors, a scenario that is common in bone marrow and kidney transplantation. We show that it is possible to estimate dd-cfDNA in bone marrow transplant patients that are unrelated or that are siblings of the donors, using a hidden Markov model (HMM) of identity-by-descent (IBD) states along the genome. Last, we demonstrate that comparing dd-cfDNA to the proportion of donor DNA in white blood cells can differentiate between relapse and the onset of graft-versus-host disease (GVHD). These methods alleviate some of the barriers to the implementation of GTD, which will further widen its clinical application.

More than 180,000 people live with organ transplants in the US. Monitoring the health of the allograft is a critically important component of post-transplant therapy. Recently, we have demonstrated that cell-free DNA (cfDNA) enables diagnosis of post-transplant rejection. In this approach, genotyping of the recipient and the donor together with shotgun sequencing of cfDNA are used to quantify the proportion of donor-derived cfDNA (dd-cfDNA). This approach offers key advantages over the current practice of organ biopsy, which is invasive, costly, and risky. However, the difficulty and cost of establishing a pure reference donor genotype is a major barrier to its widespread clinical implementation. Here, we developed a computational approach that enables an accurate estimation of dd-cfDNA levels without the need for a donor genotype. In addition, we provide a solution of closely related recipients and donors—a scenario which is common in bone marrow and kidney transplants—by accounting for the identity-by-descent between the recipient and the donor. Last, we demonstrate a new application of cfDNA in the noninvasive diagnosis of Graft Versus Host Disease, a serious and difficult-to-diagnose complication of allogeneic bone marrow and stem cell transplantation.

Survival Outcomes After Heart Transplantation: Does Recipient Sex Matter?

BACKGROUND

Currently, women represent <25% of heart transplant recipients. Reasons for this female underrepresentation have been attributed to selection and referral bias and potentially poorer outcomes in female recipients. The aim of this study was to compare long-term posttransplant survival between men and women, when matched for recipient and donor characteristics.

METHODS AND RESULTS

Using the International Society for Heart and Lung Transplantation Registry, we performed descriptive analyses and estimated overall freedom from posttransplant death stratified by sex using Kaplan-Meier survival methods. Male and female recipients were matched according to the Index for Mortality Prediction After Cardiac Transplantation and Donor Risk Index score using 1:1 propensity score matching. The study cohort comprised 34 198 heart transplant recipients (76.3% men, 23.7% women) between 2004 and 2014. Compared with men, women were more likely younger (51 [39-59] versus 55 [46-61] years; P<0.001) and had a different distribution of heart failure etiology (P<0.001). In general, the prevalence of comorbidities was lower in women than in men. Women were less likely to have diabetes mellitus (19.1% versus 26.2%; P<0.001), hypertension (40.7% versus 47.9%; P<0.001), peripheral vascular disease (2.4% versus 3.3%; P=0.002), tobacco use (36.5% versus 52.3%; P<0.001), and prior cardiovascular surgery (38.6% versus 50.7%; P<0.001). Women were more likely to have a history of malignancy (10.5% versus 5.3%; P<0.001), require intravenous inotropes (41.4% versus 37.2%; P<0.001), and were less likely supported by an intra-aortic balloon pump (3.3% versus 3.8%; P=0.03) or durable ventricular assist device (22% versus 31.5%; P<0.001). Transplanted male recipients had a higher Index for Mortality Prediction After Cardiac Transplantation score (5 [2-7] versus 4 [1-6]; P<0.001). When male and female heart transplant recipients were matched for recipient and donor characteristics, there was no significant survival difference (P=0.57).

CONCLUSIONS

Overall survival does not differ between men and women after cardiac transplantation. Women who survive to heart transplantation appear to have lower risk features than male recipients but receive hearts from higher risk donors.

Donor selection in the modern era

The growing disparity between the supply of donor hearts for transplantation and the demand for such organs has led to liberalization of the criteria for donor heart acceptance over the past few decades. The upper age limit and size restrictions for donor heart acceptance continue to be revised and hearts are being routinely used from donors with left ventricular dysfunction, left ventricular hypertrophy (LVH), cocaine use, multiple medical co-morbidities and after cardiopulmonary resuscitation. This article reviews recent data for use of such "expanded criteria" donor hearts and suggests ways to further increase the donor pool, including use of hearts from donors with hepatitis C and after circulatory determination of death. Donor biomarkers and risk scores may eventually aid in heart acceptance decisions, while ethical issues surrounding information sharing with transplant recipients remain a topic of great debate.

Incidence and impact of primary graft dysfunction in adult heart transplant recipients: A systematic review and meta-analysis

PURPOSE

Primary graft dysfunction (PGD) is a leading cause of early mortality after heart transplant (HTx). To identify PGD incidence and impact on mortality, and to elucidate risk factors for PGD, we systematically reviewed studies using the ISHLT 2014 Consensus Report definition and reporting the incidence of PGD in adult HTx recipients.

METHODS

We conducted a systematic search in January 2020 including studies reporting the incidence of PGD in adult HTx recipients. We used a random effects model to pool the incidence of PGD among HTx recipients and, for each PGD severity, the mortality rate among those who developed PGD. For prognostic factors evaluated in ≥2 studies, we used random effects meta-analyses to pool the adjusted odds ratios for development of PGD. The GRADE framework informed our certainty in the evidence.

RESULTS

Of 148 publications identified, 36 observational studies proved eligible. With moderate certainty, we observed pooled incidences of 3.5%, 6.6%, 7.7%, and 1.6% and 1-year mortality rates of 15%, 21%, 41%, and 35% for mild, moderate, severe and isolated right ventricular-PGD, respectively. Donor factors (female sex, and undersized), recipient factors (creatinine, and pre-HTx use of amiodarone, and temporary or durable mechanical support), and prolonged ischemic time proved associated with PGD post-HTx.

CONCLUSION

Our review suggests that the incidence of PGD may be low but its risk of mortality high, increasing with PGD severity. Prognostic factors, including undersized donor, recipient use of amiodarone pre-HTx and recipient creatinine may guide future studies in exploring donor and/or recipient selection and risk mitigation strategies.