Enhancing the Prediction of Cardiac Allograft Vasculopathy Using Intravascular Ultrasound and Machine Learning: A Proof of Concept.

BACKGROUND: Cardiac allograft vasculopathy (CAV) is the leading cause of late graft dysfunction in heart transplantation. Building on previous unsupervised learning models, we sought to identify CAV clusters using serial maximal intimal thickness and baseline clinical risk factors to predict the development of early CAV. METHODS: This is a single-center retrospective study including adult heart transplantation recipients. A latent class mixed-effects model was used to identify patient clusters with similar trajectories of maximal intimal thickness posttransplant and pretransplant covariates associated with each cluster. RESULTS: Among 186 heart transplantation recipients, we identified 4 patient phenotypes: very low, low, moderate, and high risk. The 5-year risk (95% CI) of the International Society for Heart and Lung Transplantation-defined CAV in the high, moderate, low, and very low risk groups was 49.1% (35.2%-68.5%), 23.4% (13.3%-41.2%), 5.0% (1.3%-19.6%), and 0%, respectively. Only patients in the moderate to high risk cluster developed the International Society for Heart and Lung Transplantation CAV 2-3 at 5 years (P=0.02). Of the 4 groups, the low risk group had significantly younger female recipients, shorter ischemic time, and younger female donors compared with the high risk group. CONCLUSIONS: We identified 4 clusters characterized by distinct maximal intimal thickness trajectories. These clusters were shown to discriminate against the development of angiographic CAV. This approach allows for the personalization of surveillance and CAV-directed treatment before the development of angiographically apparent disease.

Reintervention Before Bidirectional Cavopulmonary Shunt and Intermediate Outcomes in Children with Single Ventricle Who Underwent Main Pulmonary Artery Banding.

Unplanned reinterventions following pulmonary artery banding (PAB) in single ventricle patients are common before stage 2 palliation (S2P) but associated risk factors are unknown. We hypothesized that reintervention is more common when PAB is placed at younger age and with a looser band, reflected by lower PAB pressure gradient. Retrospective single center study of single ventricle patients undergoing PAB between Jan 2000 and Dec 2020. The association with reintervention and successful S2P was modeled using exploratory cause-specific hazard regression. A multivariable model was developed adjusting for clinical and statistically relevant predictors. The cumulative proportion of patients undergoing reintervention were summarized using a competing risk model. 77 patients underwent PAB at median (IQR) 47 (24-66) days and 3.73 (3.2-4.5) kg. Within18 months of PAB, 60 (78%) reached S2P, 9 (12%) died, 1 (1%) transplanted and 7 (9%) were alive without S2P. Within 18 months of PAB 10 (13%) patients underwent reintervention related to pulmonary blood flow modification: PAB adjustment (n = 6) and conversion to Damus-Kaye-Stansel/Blalock-Taussig-Thomas shunt (n = 4). 6/10 (60%) reached S2P following reintervention. A trend toward higher intervention in patients with a genetic syndrome (p-0.06) and weight < 3 kg (p-0.057) at time of PAB was noted. Only genetic syndrome was a risk factor associated with poor outcome (p-0.025). PAB has a reasonable outcome in SV patients with unobstructed systemic and pulmonary blood flow, but with a high reintervention rate. Only a quarter of patients with genetic syndromes reach S2P and further study is required to explore the benefits from an alternative palliative strategy.

Rethinking Donor and Recipient Risk Matching in Europe and North America: Using Heart Transplant Predictors of Donor and Recipient Risk.

BACKGROUND: In Europe, there is greater acceptance of hearts from higher-risk donors for transplantation, whereas in North America, the donor heart discard rate is significantly higher. A Donor Utilization Score (DUS) was used to compare European and North American donor characteristics for recipients included in the International Society for Heart and Lung Transplantation registry from 2000 to 2018. DUS was further evaluated as an independent predictor for 1-year freedom from graft failure, after adjusting for recipient risk. Lastly, we assessed donor-recipient risk matching with the outcome of 1-year graft failure. METHODS: DUS was applied to the International Society for Heart and Lung Transplantation cohort using meta-modeling. Posttransplant freedom from graft failure was summarized by Kaplan-Meier survival. Multivariable Cox proportional hazard regression was applied to quantify the effects of DUS and Index for Mortality Prediction After Cardiac Transplantation score on the 1-year risk of graft failure. We present 4 donor/recipient risk groups using the Kaplan-Meier method. RESULTS: European centers accept significantly higher-risk donor hearts compared to North America. DUS 0.45 versus 0.54, P<0.005). DUS was an independent predictor for graft failure with an inverse linear relationship when adjusted for covariates (P<0.001). The Index for Mortality Prediction After Cardiac Transplantation score, a validated tool to assess recipient risk, was also independently associated with 1-year graft failure (P<0.001). In North America, 1-year graft failure was significantly associated with donor-recipient risk matching (log-rank P<0.001). One-year graft failure was highest with pairing of high-risk recipients and donors (13.1% [95% CI, 10.7%-13.9%]) and lowest among low-risk recipients and donors (7.4% [95% CI, 6.8%-8.0%]). Matching of low-risk recipients with high-risk donors was associated with significantly less graft failure (9.0% [95% CI, 8.3%-9.7%]) than high-risk recipients with low-risk donors (11.4% [95% CI, 10.7%-12.2%]) Conclusions: European heart transplantation centers are more likely to accept higher-risk donor hearts than North American centers. Acceptance of borderline-quality donor hearts for lower-risk recipients could improve donor heart utilization without compromising recipient survival.

Melody Mitral Valve Is a Promising Alternative to Mechanical Valve Replacement for Young Children.

PURPOSE: The purpose of this study was to compare outcomes of Melody mitral valve to mechanical mitral valve replacement (MVR) for young children. DESCRIPTION: Children who underwent Melody MVR from 2014 to 2020 were case-matched to mechanical MVR patients. Transplant-free survival and cumulative incidence of reintervention were compared. A subanalysis was performed for infants aged < 1 year (9 Melody MVRs and their matches). EVALUATION: Twelve children underwent Melody MVR. Two children (17%) salvaged from mechanical support died. Five of 10 survivors (50%) had subsequent MVR. At 1 and 3 years, transplant-free survival (Melody: 83%, 83%; mechanical: 83%, 67%; P = .180) and reintervention (Melody: 9%, 39%; mechanical: 0%, 18%; P = .18) were equivalent between groups. For children < 1 year of age, Melody MVR had a modest survival benefit (Melody: 89%, 89%; mechanical: 80%, 60%; P = .046), while rate of reintervention remained equivalent (Melody: 13%, 32%; mechanical: 0%, 22%; P = .32). CONCLUSIONS: For patients < 1 year old, Melody MVR offers a promising alternative and is a reasonable bridge to mechanical MVR, which can be performed safely at an older age. Further studies are necessary to corroborate these findings.

Comparison between Del Nido and conventional blood cardioplegia in pediatric open-heart surgery.

BACKGROUND: Del Nido cardioplegia (DNc) was designed for superior myocardial protection during cardiopulmonary bypass (CPB). We conducted a retrospective review to explore if DNc was associated with increase in systemic ventricle dysfunction (sVD) following pediatric CPB. METHODS AND RESULTS: This single-center, retrospective study included 1534 patients undergoing CPB between 2013 and 2016, 997 prior to center-wide conversion to DNc and 537 following. The primary outcome was new postoperative ≥moderate sVD by echocardiogram. Secondary outcomes included sVD of any severity and right ventricular dysfunction. Data was evaluated by interrupted time-series analysis. Groups had similar cardiac diagnoses and surgical complexity. Del Nido cardioplegia was associated with longer median (IQR) CPB [117 (84-158) vs 108 (81-154), p = 0.04], and aortic cross-clamp [83 (55-119) vs 76 (53-106), p = 0.03], and fewer cardioplegia doses [2 (1-2) vs 3 (2-4), p < 0.0001]. Mortality was similar in both groups. Frequency of sVD was unchanged following DNc, including predetermine subgroups (neonates, infants, and prolonged cross-clamp). Logistic regression showed a significant rise in right ventricular dysfunction (OR 5.886 [95% CI: 0.588, 11.185], p = 0.03) but similar slope. CONCLUSIONS: Use of DNc was not associated with increased in reported sVD, and provided similar myocardical protection to the systemic ventricle compared to conventional cardioplegia but may possibly impact right ventricular function. Studies evaluating quantitative systolic and diastolic function are needed.

Clonal haematopoiesis is associated with higher mortality in patients with cardiogenic shock.

AIMS: Cardiogenic shock (CS) with variable systemic inflammation may be responsible for patient heterogeneity and the exceedingly high mortality rate. Cardiovascular events have been associated with clonal haematopoiesis (CH) where specific gene mutations in haematopoietic stem cells lead to clonal expansion and the development of inflammation. This study aims to assess the prevalence of CH and its association with survival in a population of CS patients in a quaternary centre. METHODS AND RESULTS: We compared the frequency of CH mutations among 341 CS patients and 345 ambulatory heart failure (HF) patients matched for age, sex, ejection fraction, and HF aetiology. The association of CH with survival and levels of circulating inflammatory cytokines was analysed. We detected 266 CH mutations in 149 of 686 (22%) patients. CS patients had a higher prevalence of CH-related mutations than HF patients (odds ratio 1.5; 95% confidence interval [CI] 1.0-2.1, p = 0.02) and was associated with decreased survival (30 days: hazard ratio [HR] 2.7; 95% CI 1.3-5.7, p = 0.006; 90 days: HR 2.2; 95% CI 1.3-3.9, p = 0.003; and 3 years: HR 1.7; 95% CI 1.1-2.8, p = 0.01). TET2 or ASXL1 mutations were associated with lower survival in CS patients at all time-points (p ≤ 0.03). CS patients with TET2 mutations had higher circulating levels of SCD40L, interferon-γ, interleukin-4, and tumour necrosis factor-α (p ≤ 0.04), while those with ASXL1 mutations had decreased levels of CCL7 (p = 0.03). CONCLUSIONS: Cardiogenic shock patients have high frequency of CH, notably mutations in TET2 and ASXL1. This was associated with reduced survival and dysregulation of circulating inflammatory cytokines in those CS patients with CH.

Machine learning approaches to the human metabolome in sepsis identify metabolic links with survival.

BACKGROUND: Metabolic predictors and potential mediators of survival in sepsis have been incompletely characterized. We examined whether machine learning (ML) tools applied to the human plasma metabolome could consistently identify and prioritize metabolites implicated in sepsis survivorship, and whether these methods improved upon conventional statistical approaches. METHODS: Plasma gas chromatography-liquid chromatography mass spectrometry quantified 411 metabolites measured ≤ 72 h of ICU admission in 60 patients with sepsis at a single center (Brigham and Women's Hospital, Boston, USA). Seven ML approaches were trained to differentiate survivors from non-survivors. Model performance predicting 28 day mortality was assessed through internal cross-validation, and innate top-feature (metabolite) selection and rankings were compared across the 7 ML approaches and with conventional statistical methods (logistic regression). Metabolites were consensus ranked by a summary, ensemble ML ranking procedure weighing their contribution to mortality risk prediction across multiple ML models. RESULTS: Median (IQR) patient age was 58 (47, 62) years, 45% were women, and median (IQR) SOFA score was 9 (6, 12). Mortality at 28 days was 42%. The models' specificity ranged from 0.619 to 0.821. Partial least squares regression-discriminant analysis and nearest shrunken centroids prioritized the greatest number of metabolites identified by at least one other method. Penalized logistic regression demonstrated top-feature results that were consistent with many ML methods. Across the plasma metabolome, the 13 metabolites with the strongest linkage to mortality defined through an ensemble ML importance score included lactate, bilirubin, kynurenine, glycochenodeoxycholate, phenylalanine, and others. Four of these top 13 metabolites (3-hydroxyisobutyrate, indoleacetate, fucose, and glycolithocholate sulfate) have not been previously associated with sepsis survival. Many of the prioritized metabolites are constituents of the tryptophan, pyruvate, phenylalanine, pentose phosphate, and bile acid pathways. CONCLUSIONS: We identified metabolites linked with sepsis survival, some confirming prior observations, and others representing new associations. The application of ensemble ML feature-ranking tools to metabolomic data may represent a promising statistical platform to support biologic target discovery.

Predicted heart mass for size matching in obese heart transplant donors and recipients.

INTRODUCTION: Predicted heart mass (PHM) was neither derived nor evaluated in an obese population. Our objective was to evaluate size mismatch using actual body weight or ideal body weight (IBW)-adjusted PHM on mortality and risk assessment. METHODS: We conducted a retrospective cohort study of adult recipients with BMI ≥30 kg/m2 or recipients of donors with BMI≥30 kg/m2 from the ISHLT registry. We used multivariable Cox proportional hazard models to evaluate 30-day and 1-year mortality. The two models were compared using net reclassification index. RESULTS: 10,817 HT recipients, age 55 (IQR 46-62) years, 23% female, BMI 31 kg/m2 (IQR 28-33) were included. Donors were age 34 (IQR 24-44) years, 31% female, and BMI 31 kg/m2 (IQR 26-34). There was a significant nonlinear association between mortality and actual PHM but not IBW-adjusted PHM. Undersizing using actual PHM was associated with higher 30-day and 1-year mortality (p < .01), not seen with IBW-adjusted PHM. Actual PHM better risk classified .6% (95% CI .3-.8) patients compared to IBW-adjusted PHM. CONCLUSION: Actual PHM can be used for size matching when assessing mortality risk in obese recipients or recipients of obese donors. There is no advantage to re-calculating PHM using IBW to define candidate risk at the time of organ allocation.

Cardiovascular signatures of COVID-19 predict mortality and identify barrier stabilizing therapies.

BACKGROUND: Endothelial cell (EC) activation, endotheliitis, vascular permeability, and thrombosis have been observed in patients with severe coronavirus disease 2019 (COVID-19), indicating that the vasculature is affected during the acute stages of SARS-CoV-2 infection. It remains unknown whether circulating vascular markers are sufficient to predict clinical outcomes, are unique to COVID-19, and if vascular permeability can be therapeutically targeted. METHODS: Prospectively evaluating the prevalence of circulating inflammatory, cardiac, and EC activation markers as well as developing a microRNA atlas in 241 unvaccinated patients with suspected SARS-CoV-2 infection allowed for prognostic value assessment using a Random Forest model machine learning approach. Subsequent ex vivo experiments assessed EC permeability responses to patient plasma and were used to uncover modulated gene regulatory networks from which rational therapeutic design was inferred. FINDINGS: Multiple inflammatory and EC activation biomarkers were associated with mortality in COVID-19 patients and in severity-matched SARS-CoV-2-negative patients, while dysregulation of specific microRNAs at presentation was specific for poor COVID-19-related outcomes and revealed disease-relevant pathways. Integrating the datasets using a machine learning approach further enhanced clinical risk prediction for in-hospital mortality. Exposure of ECs to COVID-19 patient plasma resulted in severity-specific gene expression responses and EC barrier dysfunction, which was ameliorated using angiopoietin-1 mimetic or recombinant Slit2-N. INTERPRETATION: Integration of multi-omics data identified microRNA and vascular biomarkers prognostic of in-hospital mortality in COVID-19 patients and revealed that vascular stabilizing therapies should be explored as a treatment for endothelial dysfunction in COVID-19, and other severe diseases where endothelial dysfunction has a central role in pathogenesis. FUNDING: This work was directly supported by grant funding from the Ted Rogers Center for Heart Research, Toronto, Ontario, Canada and the Peter Munk Cardiac Center, Toronto, Ontario, Canada.

Understanding Complex Interactions in Pediatric Diastolic Function Assessment.

BACKGROUND: Diagnosing left ventricular diastolic dysfunction (DD) noninvasively in children is difficult as no validated pediatric diagnostic algorithm is available. The aim of this study is to explore the use of machine learning to develop a model that uses echocardiographic measurements to explain patterns in invasively measured markers of DD in children. METHODS: Children at risk for developing DD were enrolled, including patients with Kawasaki disease, heart transplantation, aortic stenosis, and coarctation of the aorta when undergoing clinical left heart catheterization. Simultaneous invasive pressure measurements were made using a high-fidelity catheter (time constant of isovolumic relaxation [Tau, τ], left ventricular end-diastolic pressure, and maximum negative rate of pressure change) and echocardiographic DD measurements. Spearman correlations were performed for each echocardiographic feature with invasive markers to understand pairwise relationships. Separate random forest (RF) models were implemented to assess all echocardiographic features, key demographic data, and clinical diagnosis in predicting invasive markers. A backward stepwise regression model was simultaneously implemented as a comparative conventional reference model. The relative importance of all parameters was ranked in terms of accuracy reduction. Model approximation was then performed using a regression tree with the top-ranked features of each RF model to improve model interpretability. Regression coefficients of the linear models were presented. RESULTS: Fifty-nine children were included. Spearman correlations were generally low. The RF models' performance measures were noninferior to those of the linear model. However, the linear model's regression coefficients were unintuitive. The highest ranked important features for the RF models were propagation velocity for Tau, E/propagation velocity ratio for left ventricular end-diastolic pressure, and systolic global longitudinal strain rate for maximum negative rate of pressure change. CONCLUSIONS: Estimating individual components of DD can potentially improve the noninvasive assessment of pediatric DD. Although pairwise correlations measured were weak and linear regression coefficients unintuitive, approximated machine learning models aided in understanding how echocardiographic and invasive parameters of DD are related. This machine learning approach could help in further development of pediatric-specific diagnostic algorithms.

Associations between the spatiotemporal distribution of Kawasaki disease and environmental factors: evidence supporting a multifactorial etiologic model.

The etiology of Kawasaki Disease (KD), the most common cause of acquired heart disease in children in developed countries, remains elusive, but could be multifactorial in nature as suggested by the numerous environmental and infectious exposures that have previously been linked to its epidemiology. There is still a lack of a comprehensive model describing these complex associations. We present a Bayesian disease model that provides insight in the spatiotemporal distribution of KD in Canada from 2004 to 2017. The disease model including environmental factors had improved Watanabe-Akaike information criterion (WAIC) compared to the base model which included only spatiotemporal and demographic effects and had excellent performance in recapitulating the spatiotemporal distribution of KD in Canada (98% and 86% spatial and temporal correlations, respectively). The model suggests an association between the distribution of KD and population composition, weather-related factors, aeroallergen exposure, pollution, atmospheric concentration of spores and algae, and the incidence of healthcare encounters for bacterial pneumonia or viral intestinal infections. This model could be the basis of a hypothetical data-driven framework for the spatiotemporal distribution of KD. It also generates novel hypotheses about the etiology of KD, and provides a basis for the future development of a predictive and surveillance model.

The Effect of Age on Outcomes After Destination-Therapy Left Ventricular Assist Device Implantation: An Analysis of the IMACS Registry.

BACKGROUND: As patients with advanced heart failure are living longer, defining the impact of left ventricular assist devices (LVADs) on outcomes in an aging population is of great importance. We describe overall survival, rates of adverse events (AEs), and post-AE survival in patients age ≥ 70 years vs age 50-69 years after destination-therapy (DT) LVAD implantation. METHODS: A retrospective analysis was conducted with the use of the International Society for Heart and Lung Transplantation Mechanically Assisted Circulatory Support (IMACS) registry. All adults age ≥ 50 years with a continuous-flow DT LVAD from 2013 to 2017 were included. The primary outcome was all-cause mortality. The secondary outcomes were the incidence of and survival after gastrointestinal (GI) bleeding, infection, stroke, pump thrombosis, pump exchange, and right-side heart failure. Mortality and AEs were assessed with the use of competing risk models. RESULTS: At total of 5,572 patients were included: 3,700 aged 50-69 and 1,872 aged ≥ 70. All-cause mortality by 42 months was 55.8% in patients aged ≥ 70 and 44.8% in patients aged 50-69 (P = 0.001). Patients aged ≥ 70 had a 37.8% higher risk of death after DT LVAD implantation (hazard ratio 1.378, 95% CI 1.251-1.517). Patients aged ≥ 70 had higher risk of GI bleeding but lower risk of right-side heart failure. There was no difference between age groups for risk of infection or stroke. Experiencing any AE was associated with an increased risk of death that did not vary with age. CONCLUSIONS: Patients aged ≥ 70 years have reduced survival after DT LVAD, in part because of increased GI bleeding, while the incidence of other AEs is similar to that of patients aged 50-69 years. Careful patient selection beyond age alone may allow for optimal outcomes after DT LVAD implantation.

Risk factors for early development of cardiac allograft vasculopathy by intravascular ultrasound.

BACKGROUND: Cardiac allograft vasculopathy (CAV) is the leading cause of late graft loss. While there are numerous post-transplant factors which may increase the risk of the development of CAV, there is a paucity of data on the impact of donor-derived atherosclerosis (DA), early discontinuation of prednisone, and early initiation of proliferation signal inhibitors (PSI) as assessed by intravascular ultrasound (IVUS). METHODS: Retrospective single-center study of all adult transplant patients (2008-2017) with serial IVUS at baseline and annually for 5 years. DA was defined as a baseline maximal intimal thickness (MIT) ≥0.5 mm, and CAV development was defined as MIT ≥1 mm or an increase in MIT ≥0.5 mm at year 1 compared with baseline or an increase in 0.3 mm annually thereafter. Clinical risk factors for CAV were identified using multivariable hazard regression. Separate multistate models were applied to assess the association of prednisone discontinuation and PSI initiation and CAV. RESULTS: Of 282 patients screened, 186 patients had a 1-year angiogram. The mean age of those included in the cohort was 51 ± 11 years, 70% were male, 58% were Caucasian, and 27% were supported by a left ventricular assist device. Donor atherosclerosis was present in 40%. The cumulative incidence of CAV at 5 years is 41% in DA- vs. 59% in DA + (p = .012). Donor age was a strong predictor of DA (p = .016). Significant risk factors for CAV included male sex (HR = 4.141, p = .001), non-Caucasian race (HR = 1.98, p = .011), BMI < 18 kg/m2 (HR = 4.596, p = .042), longer ischemic time (HR = 1.374, p = .028), older donor age (HR = 1.158, p = .009), and rejection with hemodynamic compromise within the first year (HR = 2.858, p = .043). Prednisone discontinuation within 1 year was associated with a lower risk of CAV (HR 0.58 p = .047). Initiation of proliferation signal inhibitors (PSI) within 2 years resulted in fewer cases of CAV (HR 0.397 p < .001). CONCLUSION: In patients with an angiogram at 1 year, those with DA were significantly more likely to develop CAV. Lower incidence of CAV by IVUS was seen in patients who discontinued prednisone in the first year or had initiation of a PSI within two years of transplantation. Knowledge of early IVUS may allow a more tailored approach to patient management.

Rapid Advancement in Enteral Nutrition Does Not Affect Systemic Inflammation and Insulin Homeostasis Following Pediatric Cardiopulmonary Bypass Surgery.

OBJECTIVES: To determine impact of enteral nutrition delivery on the relationship among inflammation, insulin resistance, and outcomes following pediatric cardiopulmonary bypass surgery. DESIGN: Pilot, randomized study analyzed according to intention-to-treat analysis. SETTING: Pediatric cardiac ICU. PATIENTS: Infants (≤ 6 mo) undergoing cardiopulmonary bypass. INTERVENTIONS: Patients randomly assigned to receive rapid escalation to enteral nutrition reaching goal feeds by 27 hours or standard feeding practice reaching goal feeds by 63 hours. Feeds were initiated on the first postoperative day. MEASUREMENTS AND MAIN RESULTS: Fifty patients were randomized equally to study arms. Patients were a median (interquartile range) of 16 days old (7-110 d old), undergoing biventricular surgery (88%) with a median cardiopulmonary bypass time of 125 minutes (105-159 min). Serial blood samples were drawn before and after cardiopulmonary bypass, cardiac ICU admission, and every 12 hours (up to 96 hr) for glucose, insulin, and cytokines (interleukin-1α, interleukin-6, interleukin-8, interleukin-10, and tumor necrosis factor-α) levels. Glucose-insulin ratio was calculated to quantify insulin resistance. Patient characteristics, time to enteral nutrition initiation, enteral nutrition interruptions, and insulin administration were similar across intervention arms. FF reached goal feeds at similar intervals as standard feeding (39 hr [30-60 hr] vs 60 hr [21-78 hr]; p = 0.75). No difference in cytokine, insulin, or glucose-insulin ratio was noted between groups. Higher inflammation was associated with increased glucose-insulin ratio and higher risk of adverse events. In multivariable models of interleukin-8, FF was associated with increased glucose-insulin ratio (estimate of effect [95% CI], 0.152 [0.033-0.272]; p = 0.013). Although higher interleukin-8 was associated with an elevated risk of adverse event, this relationship was possibly mitigated by FF (odds ratio [95% CI], 0.086 [0.002-1.638]; p = 0.13). CONCLUSIONS: A FF strategy was not associated with changes to early enteral nutrition delivery. Inflammation, insulin resistance, and morbidity were similar, but FF may modify the relationship between inflammation and adverse event. Multicenter nutrition studies are possible and necessary in this vulnerable population.

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.

Gene expression profiling and racial disparities in outcomes after heart transplantation.

BACKGROUND: African Americans (AAs) have lower survival rates after heart transplantation (HTx) than Caucasians. The aim of this analysis was to evaluate racial differences in gene expression and their associations with survival and the composite outcome of death, retransplant, rejection with hemodynamic compromise, and graft dysfunction in the Outcomes AlloMap Registry. METHODS: Registry participants included low-risk Caucasian and AA heart transplant recipients with a baseline and at least 1 follow-up gene expression test (AlloMap(C)) within the first year after HTx. The Kaplan-Meier method with delayed entry was used to describe differences in outcomes. Multivariable Cox hazard regression was used to evaluate the associations of overall gene expression profiling score, MARCH8 and FLT3 expression, and tacrolimus levels with each outcome, and stratified Cox models were developed to quantify race-specific associations. RESULTS: Among 933 eligible recipients, 737 (79%) were Caucasian and 196 (21%) were AA. Compared with Caucasians, AAs were significantly younger (55 vs 59 years, p < 0.001), with higher rates of non-ischemic cardiomyopathy (68% vs 50%, p < 0.001), sensitization (>10% panel reactive antibody, 16% vs 9.1%, p = 0.009), and human leukocyte antigen mismatches (7 vs 7, p = 0.01), but less frequent primary cytomegalovirus serostatus mismatch (14.31% vs 27.3%, p < 0.001). Overall, AAs had an increased adjusted mortality risk (hazard ratio [HR] 4.13, p = 0.007). Higher tacrolimus levels were associated with decreased mortality in AAs (HR 0.62, p = 0.009). Overall gene expression profiling score was associated with increased mortality among Caucasians (HR 1.21, p = 0.048). In Caucasians, but not AAs, overexpression of MARCH8 was associated with increased mortality (HR 2.90, p = 0.001). FLT3 upregulation was associated with increased mortality (HR 2.42, p = 0.033) in AAs. There was an inverse relationship between FLT3 expression and tacrolimus levels (-0.029 and -0.176, respectively) in Caucasians and AAs. CONCLUSIONS: AAs have a significantly higher mortality risk after HTx than Caucasians, even in the low-risk Outcomes AlloMap Registry population. AAs and Caucasians had differential outcomes based upon the varying expression of MARCH8 and FLT3 genes following HTx.

The effect of pre-heart transplant body mass index on posttransplant outcomes: An analysis of the ISHLT Registry Data.

We evaluated the effect of pre-heart transplant body mass index (BMI) on posttransplant outcomes using the International Society for Heart and Lung Transplantation Registry. Kaplan-Meier analysis and a multivariable Cox proportional hazard regression model were used for all-cause mortality, and cause-specific hazard regression for cause-specific mortality and morbidity. We assessed 38 498 recipients from 2000 to 2014 stratified by pretransplant BMI. Ten-year survival was 56% in underweight, 59% in normal weight, 57% in overweight, 52% in obese class I, 54% in class II, and 47% in class III patients (P < 0.001). Mortality was increased in underweight (HR 1.29, 95% CI 1.24-1.35), obese class I (HR 1.19, 95% CI 1.13-1.26), class II (HR 1.20, 95% CI 1.08-1.32), and class III patients (HR 1.45, 95% CI 1.15-1.83). Obesity was independently associated with increased death from myocardial infarction, chronic rejection, infection, and renal dysfunction. An underweight BMI lead to increased death from infection, acute and chronic rejection, malignancy, and bleeding. Obese patients had a higher incidence of renal dysfunction, diabetes, stroke, acute rejection, cardiac allograft vasculopathy, and malignancy, and underweight recipients had increased acute rejection. We have shown that pretransplant obese and underweight patients have increased post-heart transplant mortality and morbidity. This has implications for candidate selection and posttransplant management.

Infectious complications after heart transplantation in patients screened with gene expression profiling.

BACKGROUND: The risk of infection after heart transplantation is highest within the first year and represents the leading cause of early mortality. In this cohort of patients enrolled in the Outcomes AlloMap Registry (OAR), we sought to describe infection episodes (IEp) resulting in hospitalization, in the early (<1 year) and late (≥1 year) post-transplant period and determine the impact of immunosuppression on incidence of infection. METHODS: The primary aim was to assess the incidence and nature of IEp. The secondary aim was to evaluate the effect of potential risk factors, such as recipient age; sex; body mass index; panel-reactive antibodies; cytomegalovirus (CMV) primary mismatch; prednisone, tacrolimus, and sirolimus levels; and gene expression profile (GEP) score, in the development of IEp. RESULTS: The OAR comprises 1,504 patients, of whom 220 patients (14.6%) had an IEp during a median follow-up period of 382 days (interquartile range [IQR] 230 to 579 days). The cause-specific 5-year hazard ratio for any infection was 2.029 (p = 0.12). The pattern of early infection was consistent with nosocomial and opportunistic causes, whereas later infection was consistent with late-onset opportunistic and community-acquired etiologies. Sixty-two percent of the infections occurred early. In the time-dependent analysis, higher prednisone dose (log prednisone, hazard ratio [HR] 1.30, p = 0.022) was the most significant risk factor for all IEp. CONCLUSIONS: In the OAR cohort, the majority of infections occurred within 1 year after transplantation. Clinicians may consider more aggressive prednisone withdrawal in low-risk patients to reduce IEp.

The evolving risk of sudden cardiac death after heart transplant. An analysis of the ISHLT Thoracic Transplant Registry.

Sudden cardiac death (SCD) is responsible for ~10% of post-heart transplant deaths. We conducted a retrospective analysis of the ISHLT registry evaluating the risk of post-transplant SCD. Adult heart transplant recipients (2004-2014) surviving the first year were included. We used multivariable multistate competing risk survival analysis to evaluate the impact of history of treated rejection and cardiac allograft vasculopathy (CAV) on SCD risk. We used a probabilistic analytical model and Monte Carlo simulation to estimate the impact of CAV severity and graft dysfunction on SCD. We included 25 242 recipients. During a median follow-up of 4.7 (2.3-7.0) years, 582 patients died suddenly. Treated rejection (HR 1.76, 95% CI 1.36-2.31) and CAV (HR 3.32, 95% CI 2.73-4.03) were important risk factors for SCD. The estimated SCD risk in patients with severe CAV without and with graft dysfunction was 3.2% (95% CI 2.0-4.6) and 5.4% (95% CI 3.8-7.0), respectively, at 2 years from the CAV diagnosis, and 4.9% (95% CI 3.4-6.5) and 8.0% (95% CI 6.1-10.0), respectively, in those who also had treated rejection. These results provide evidence that recipients with severe CAV and graft dysfunction or treated rejection are at clinically significant increased SCD risk. The benefit of ICD post-transplant remains uncertain.

Impact of organ prioritization for immunologic sensitization and waiting times for heart transplantation.

BACKGROUND: The Canadian status 4S category prioritizes highly sensitized patients with a calculated panel reactive antibody (CPRA) > 80% awaiting heart transplantation. We examined the effect of sensitization and status 4S and developed a predictive model to estimate waiting time in Canada. METHODS: A retrospective review was performed of patients listed for heart transplant at the Ottawa Heart Institute and Toronto General Hospital (Ontario, Canada). We evaluated the association of CPRA and priority listing status on waiting time and post-transplant outcomes. Waiting time risk factor analysis was performed using a multivariable parametric accelerated failure time model with a Weibull distribution. RESULTS: Of 394 patients listed (75% male, 51 ± 12 years), 291 (74%) received a transplant and 33 (8%) died waiting. The cumulative incidence of transplant decreased across higher CPRA groups but was similar for moderately and highly sensitized groups: 67%, 70%, 50%, and 40% at 12 months for CPRA 0%, 1% to 50%, 51% to 80%, and > 80%, respectively (p = 0.020). Status 4S patients experienced longer waiting times compared with other high priority status 3.5 and 4 and had increased risk of death on the waiting list (p = 0.014). Over a median follow-up of 2.4 years (interquartile range, 1.2-4.1), rejection occurred in 64 sensitized patients (24%) compared with 24 non-sensitized patients (9%; p = 0.019), but there was no difference in survival, allograft dysfunction, or cardiac allograft vasculopathy. A model predicting transplant waiting time, including CPRA, blood group, priority listing status, age, and weight, was developed and showed adequate discrimination and calibration. CONCLUSIONS: Waiting time to heart transplant is increased for highly and moderately sensitized patients, suggesting the need to reevaluate the CPRA > 80% threshold for status 4S prioritization in Canada. Extended waiting times, despite 4S prioritization, supports consideration of additional factors to CPRA in ensuring equitable organ access for sensitized patients.