Pediatric Heart Transplantation Over 36 Years and Contemporary Volume-Outcome Analysis of UNOS

BACKGROUND

This study examines 36 years of national pediatric heart transplantation data to 1) identify trends in transplant volume, centers, and one-year graft survival, and 2) assess how center transplant volume impacts outcomes over a contemporary 11-year period.

METHODS

We performed a retrospective review of pediatric patients (<18 years) undergoing heart transplantation from 1/1/1987 to 12/31/2022 using the United Network for Organ Sharing Database. Trend analyses included the whole cohort, while volume-outcome analyses included a contemporary cohort to account for the temporal changes observed in transplant survival. Highest volume centers were defined by the number of heart transplants performed per center per year.

RESULTS

Over 36 years, 11,828 pediatric heart transplants were performed. Transplant volume steadily rose, the number of centers remained stable, and one-year graft survival has improved significantly. In the contemporary era (2012-2022), 89 centers conducted 4,959 pediatric heart transplants. The top 15% high-volume centers (13 centers) accounted for 48.3% (2,393) of transplants, with an average of 16.7±3.8 transplants per center annually, compared to 3.9±3.1 for lower volume centers. Despite transplanting higher risk patients, high-volume centers had similar postoperative outcomes and improved long-term survival.

CONCLUSIONS

While the number of US pediatric heart transplant centers has remained stable, pediatric heart transplant volume is steadily increasing, as is one-year graft survival. In a contemporary cohort, the top 15th percentile highest volume centers accounted for 48.3% of US pediatric heart transplants and transplanted higher risk patients with similar postoperative outcomes and improved longitudinal survival.

Socioeconomic disparities in procedural choice and outcomes after aortic valve replacement

Objective

To identify potential socioeconomic disparities in the procedural choice of patients undergoing surgical aortic valve replacement (SAVR) versus transcatheter aortic valve replacement (TAVR) and in readmission outcomes after SAVR or TAVR.

Methods

The Nationwide Readmissions Database was queried to identify a total of 243,691 patients who underwent isolated SAVR and TAVR between January 2016 and December 2018. Patients were stratified according to a tiered socioeconomic status (SES) metric comprising patient factors including education, literacy, housing, employment, insurance status, and neighborhood median income. Multivariable analyses were used to assess the effect of SES on procedural choice and risk-adjusted readmission outcomes.

Results

SAVR (41.4%; 100,833 of 243,619) was performed less frequently than TAVR (58.6%; 142,786 of 243,619). Lower SES was more frequent among patients undergoing SAVR (20.2% [20,379 of 100,833] vs 19.4% [27,791 of 142,786]; P < .001). Along with such variables as small hospital size, drug abuse, arrhythmia, and obesity, lower SES was independently associated with SAVR relative to TAVR (adjusted odds ratio [aOR], 1.17; 95% confidence interval [CI], 1.11 to 1.24). After SAVR, but not after TAVR, lower SES was independently associated with increased readmission at 30 days (aOR, 1.19; 95% CI, 1.07-1.32), 90 days (aOR, 1.27; 95% CI, 1.15-1.41), and 1 year (adjusted hazard ratio, 1.19; 95% CI, 1.11 to 1.28; P < .05 for all).

Conclusions

Our study findings indicate that socioeconomic disparities exist in the procedural choice for patients undergoing AVR. Patients with lower SES had increased odds of undergoing SAVR, as well as increased odds of readmission after SAVR, but not after TAVR, supporting that health inequities exist in the surgical care of socioeconomically disadvantaged patients.

Influence of concomitant ablation of nonparoxysmal atrial fibrillation during coronary artery bypass grafting on mortality and readmissions

Objective

We determined the utilization rate of surgical ablation (SA) during coronary artery bypass grafting (CABG) and compared outcomes between CABG with or without SA in a national cohort.

Methods

The January 2016 to December 2018 Nationwide Readmissions Database was searched for all patients undergoing isolated CABG with preoperative persistent or chronic atrial fibrillation by using the International Classification of Diseases, 10th Revision classification. Propensity score matching and multivariate logistic regressions were performed to compare outcomes, and Cox proportional hazards model was used to assess risk factors for 1-year readmission.

Results

Of 18,899 patients undergoing CABG with nonparoxysmal atrial fibrillation, 78% (n = 14,776) underwent CABG alone and 22% (n = 4123) underwent CABG with SA. In the propensity score-matched cohort (n = 8116), CABG with SA (n = 4054) (vs CABG alone [n = 4112]) was not associated with increased in-hospital mortality (3.4% [139 out of 4112] vs 3.9% [159 ut of 4054]; P = .4), index-hospitalization length of stay (10 days vs 10 days; P = .3), 30-day readmission (19.1% [693 out of 3362] vs 17.2% [609 out of 3537]; P = .2), or 90-day readmission (28.9% [840 out of 2911] vs 26.2% [752 out of 2875]; P = .1). Index hospitalization costs were significantly higher for those undergoing SA ($52,556 vs $47,433; P < .001). Rates of readmission at 300 days were similar between patients receiving SA (43.8%) and no SA (42.8%; log-rank P = .3). The 3 most common causes of readmission were not different between groups and included heart failure (24.3% [594 out of 2444]; P = .6), infection (16.8% [411 out of 2444]; P = .5), and arrhythmia (11.7% [286 out of 2444]; P = .2).

Conclusions

In patients with nonparoxysmal atrial fibrillation, utilization of SA during CABG remains low. SA during CABG did not adversely influence mortality or short-term readmissions. These findings support increased use of SA during CABG.

Two Decades of Declining Medicare Reimbursement in Cardiac Surgery

BACKGROUND

Given the uncertainty of US health care finances, an understanding of reimbursement trends has become increasingly important in the field of cardiac surgery. We aimed to assess Medicare reimbursement trends for common cardiac surgical procedures from 2000 to 2022.

METHODS

Reimbursement data were extracted from the Centers for Medicare and Medicaid Services Physician Fee Schedule Look-Up Tool during the study period for 6 common cardiac operations: aortic valve replacement, mitral valve repair and replacement, tricuspid valve replacement, Bentall procedure, and coronary artery bypass grafting. Reimbursement rates were adjusted for inflation to 2022 US dollars using the Consumer Price Index. Total percentage change and compound annual growth rate were calculated. A split-time analysis was performed to assess trends before and after 2015. Least squares and linear regressions were performed. The R2 value was calculated for each procedure, and slope was used to determine change in reimbursements over time.

RESULTS

Inflation-adjusted reimbursement decreased by 34.1% during the study period. The overall compound annual growth rate was -1.8%. Reimbursement trends differed by procedure (P < .001), with all reimbursements trending down (R2 > 0.62), except for mitral valve replacement (P = .21) and tricuspid valve replacement (P = .43). Coronary artery bypass grafting decreased the most (-44.4%), followed by aortic valve replacement (-40.1%), mitral valve repair (-38.5%), mitral valve replacement (-29.8%), Bentall procedure (-28.5%), and tricuspid valve replacement (-25.3%). In split-time analysis, reimbursement rates did not significantly change from 2000 to 2015 (P = .24) but decreased significantly from 2016 to 2022 (P = .001).

CONCLUSIONS

Medicare reimbursement significantly decreased for most cardiac surgical procedures. These trends justify further advocacy by The Society of Thoracic Surgeons to maintain access to quality cardiac surgical care.

A Standardized Approach to Orthotopic (Life-supporting) Porcine Cardiac Xenotransplantation in a Nonhuman Primate Model

Cardiac xenotransplantation from swine has been proposed to "bridge the gap" in supply for heart failure patients requiring transplantation. Recent preclinical success using genetically modified pig donors in baboon recipients has demonstrated survival greater than 6 mo, with a modern understanding of xenotransplantation immunobiology and continued experience with large animal models of cardiac xenotransplantation. As a direct result of this expertise, the Food and Drug Administration approved the first in-human transplantation of a genetically engineered cardiac xenograft through an expanded access application for a single patient. This clinical case demonstrated the feasibility of xenotransplantation. Although this human study demonstrated proof-of-principle application of cardiac xenotransplantation, further regulatory oversight by the Food and Drug Administration may be required with preclinical trials in large animal models of xenotransplantation with long-term survival before approval of a more formalized clinical trial. Here we detail our surgical approach to pig-to-primate large animal models of orthotopic cardiac xenotransplantation, and the postoperative care of the primate recipient, both in the immediate postoperative period and in the months thereafter. We also detail xenograft surveillance methods and common issues that arise in the postoperative period specific to this model and ways to overcome them. These studies require multidisciplinary teams and expertise in orthotopic transplantation (cardiac surgery, anesthesia, and cardiopulmonary bypass), immunology, genetic engineering, and experience in handling large animal donors and recipients, which are described here. This article serves to reduce the barriers to entry into a field with ever-growing enthusiasm, but demands expertise knowledge and experience to be successful.

Quality analysis of publicly available information about hypoplastic left heart syndrome

PURPOSE

Publicly available health information is increasingly important for patients and their families. While the average US citizen reads at an 8th-grade level, electronic educational materials for patients and families are often advanced. We assessed the quality and readability of publicly available resources regarding hypoplastic left heart syndrome (HLHS).

METHODS

We queried four search engines for "hypoplastic left heart syndrome", "HLHS", and "hypoplastic left ventricle". The top 30 websites from searches on Google, Yahoo!, Bing, and Dogpile were combined into a single list. Duplicates, commercial websites, physician-oriented resources, disability websites, and broken links were removed. Websites were graded for accountability, content, interactivity, and structure using a two-reviewer system. Nonparametric analysis of variance was performed.

RESULTS

Fifty-two websites were analysed. Inter-rater agreement was high (Kappa = 0.874). Website types included 35 hospital/healthcare organisation (67.3%), 12 open access (23.1%), 4 governmental agency (7.7%), and 1 professional medical society (1.9%). Median total score was 19 of 39 (interquartile range = 15.8-25.3): accountability 5.5 of 17 (interquartile range = 2.0-9.3), content 8 of 12 (interquartile range = 6.4-10.0), interactivity 2 of 6 (interquartile range = 2.0-3.0), and structure 3 of 4 (interquartile range = 2.8-4.0). Accountability was low with 32.7% (n = 17) of sites disclosing authorship and 26.9% (n = 14) citing sources. Forty-two percent (n = 22) of websites were available in Spanish. Total score varied by website type (p = 0.03), with open access sites scoring highest (median = 26.5; interquartile range = 20.5-28.6) and hospital/healthcare organisation websites scoring lowest (median = 17.5; interquartile range = 13.5-21.5). Score differences were driven by differences in accountability (p = 0.001) - content scores were similar between groups (p = 0.25). Overall readability was low, with median Flesch-Kincaid Grade Level of 11th grade (interquartile range = 10th-12th grade).

CONCLUSIONS

Our evaluation of popular websites about HLHS identifies multiple opportunities for improvement, including increasing accountability by disclosing authorship and citing sources, enhancing readability by providing material that is understandable to readers with the full spectrum of educational background, and providing information in languages besides English, all of which would enhance health equity.

An analysis of vascular surgery education publications reveals an educational shortage

BACKGROUND

As vascular surgery training continues to evolve with the growth of integrated vascular surgery residency (0+5) programs and the consolidation of fellowship programs, optimizing all aspects of the education for vascular surgery trainees, both fellows and 0+5 residents, has become increasingly important. In the present study, we aimed to determine the prevalence, quality, and content of vascular surgery education publications across journals.

METHODS

Journal websites (n = 26) and PubMed were queried to identify vascular surgery education publications from 2012 to 2021. The publications were organized into 11 content categories: (1) curriculum, (2) simulation, (3) trainee assessment, (4) program evaluation, (5) wellness/burnout, (6) diversity/inclusion, (7) mentorship/career, (8) case outcomes, (9) perceptions of training, (10) social media, and (11) other. Publication interactivity and quality were measured via PlumX data and Medical Education Research Study Quality Instrument scores. The data were analyzed via univariate analysis and linear regression.

RESULTS

A total of 115 vascular surgery education publications (0.2% [interquartile range (IQR), 0.04%-0.5%] of total publications) were identified from the selected journals. The Journal of Vascular Surgery had the highest proportion (0.8%) of vascular surgery education publications, followed by the Journal of Surgical Education (0.7%) and Annals of Vascular Surgery (0.6%). Vascular surgery journals constituted most (79%) of the publications. Of the authors, 15% (IQR, 0%-25%) had a master's or doctorate degree in education. Senior authors were more often identified as male gender (77%), and more first authors (41%) were identified as female gender. An interactivity analysis showed that there were 10.3 citations (IQR, 12), 33.1 captures (IQR, 34), and 8.4 social media interactions (IQR 14) per publication. The educational quality had a median Medical Education Research Study Quality Instrument score of 11 (IQR, 9-12.5), with 49% of publications having a score greater than the median. Publications on training (44% curriculum and 20% simulation) were significantly more frequent than other topics (P < .001), with no change in the publication content over 10 years (P = .29). The volume of vascular surgery education publications did not change during the study period (P = .13) despite the ongoing changes in the educational environment.

CONCLUSIONS

Despite the increasing importance placed on vascular surgery education by national vascular societies, publications on vascular surgery education have remained sparse among all journals. Also, the vascular surgery educational content has not changed during the past 10 years, with a primary focus on curriculum and simulation training. Further promotion of vascular surgery educational research is required to increase the quality, volume, and diversity of education publications.

Chronic kidney disease, risk of readmission, and progression to end-stage renal disease in 519,387 patients undergoing coronary artery bypass grafting

Objective

The association between chronic kidney disease and adverse outcomes after coronary artery bypass grafting is well established; in contrast, the association between chronic kidney disease and readmission has been less thoroughly investigated. We hypothesized that patients at higher chronic kidney disease stages have greater risk of readmission, poorer operative outcomes, and greater hospitalization cost.

Methods

Using the 2016-2018 Nationwide Readmissions Database, we identified 519,387 patients who underwent isolated coronary artery bypass grafting. Patients were stratified by chronic kidney disease stage based on International Classification of Diseases 10^th Revision classification. Multivariable logistic regression was used to assess risk factors for in-hospital mortality and 90-day readmission.

Results

Hospital readmission, in-hospital mortality, and cost progressively increased with worsening chronic kidney disease stage; patients with end-stage renal disease had the highest in-hospital mortality rate (7.2%), hospitalization costs ($59,616) (P < .001), and 90-day readmission rate (40%) (P < .001). Chronic kidney disease stage greater than 3 was associated with in-hospital mortality (odds ratio, 1.56, 95% confidence interval, 1.40-1.73; P < .001) and 90-day readmission (odds ratio, 1.66, 95% confidence interval, 1.56-1.76; P < .001). At 30 days after discharge, new-onset dialysis dependence was more frequent in patients readmitted with chronic kidney disease 4 to 5 (8.9%; n = 1495) than in patients with chronic kidney disease 1 to 3 (1.4%; n = 8623) and patients without chronic kidney disease (0.3%; n = 38,885). At 90 days after discharge, dialysis dependence increased to 11.1% (n = 1916) in readmitted patients with chronic kidney disease 4 to 5 but remained stable for patients with chronic kidney disease 1 to 3 (1.4%; n = 10,907) and patients without chronic kidney disease (0.3%; n = 50,200).

Conclusions

Chronic kidney disease stage is strongly associated with mortality, new-onset dialysis dependence, readmission, and higher cost after coronary artery bypass grafting. Patients with chronic kidney disease 4 and 5 and patients with end-stage renal disease are readmitted at the highest rates. Although further research is needed, a targeted approach may reduce costly readmissions and improve outcomes after coronary artery bypass grafting in patients with chronic kidney disease.

Nationwide database analysis of one-year readmission rates after open surgical or thoracic endovascular repair of Stanford Type B aortic dissection

OBJECTIVE

We examined readmissions and resource use during the first postoperative year in patients who underwent thoracic endovascular aortic repair or open surgical repair of Stanford type B aortic dissection.

METHODS

The Nationwide Readmissions Database (2016-2018) was queried for patients with type B aortic dissection who underwent thoracic endovascular aortic repair or open surgical repair. The primary outcome was readmission during the first postoperative year. Secondary outcomes included 30-day and 90-day readmission rates, in-hospital mortality, length of stay, and cost. A Cox proportional hazards model was used to determine risk factors for readmission.

RESULTS

During the study period, type B aortic dissection repair was performed in 6456 patients, of whom 3517 (54.5%) underwent thoracic endovascular aortic repair and 2939 (45.5%) underwent open surgical repair. Patients undergoing thoracic endovascular aortic repair were older (63 vs 59 years; P < .001) with fewer comorbidities (Elixhauser score of 11 vs 17; P < .001) than patients undergoing open surgical repair. Thoracic endovascular aortic repair was performed electively more often than open surgical repair (29% vs 20%; P < .001). In-hospital mortality was 9% overall and lower in the thoracic endovascular aortic repair cohort than in the open surgical repair cohort (5% vs 13%; P < .001). However, the 90-day readmission rate was comparable between the thoracic endovascular aortic repair and open surgical repair cohorts (28% vs 27%; P = .7). Freedom from readmission for up to 1 year was also similar between cohorts (P = .6). Independent predictors of 1-year readmission included length of stay more than 10 days (P = .005) and Elixhauser comorbidity risk index greater than 4 (P = .033).

CONCLUSIONS

Approximately one-third of all patients with type B aortic dissection were readmitted within 90 days after aortic intervention. Surprisingly, readmission during the first postoperative year was similar in the open surgical repair and thoracic endovascular aortic repair cohorts, despite marked differences in preoperative patient characteristics and interventions.

How Competitive are Integrated Vascular Surgery Residency Programs? A Ten-Year Comparison Using a Normalized Competitive Index

OBJECTIVE

Integrated vascular surgery residency (VS) programs have increased in popularity and offer an accelerated track compared to the traditional fellowship pathway. We sought to create a simple metric for medical students to better assess the competitiveness of VS training programs compared to general surgery (GS) programs.

METHODS

GS and VS programs were compared using National Resident Matching Program match data from 2012-2021. Applicant metrics (board scores, research output and experiences, work experiences, and volunteer experiences) from 2015-2019 were obtained using the Association of American Medical Colleges Report on Residents. A competitive index (CI) was created (number of programs ranked per applicant divided by match rate) for each specialty and normalized (NCI) to a value of 1 to improve longitudinal comparisons. NCI and number of programs ranked per applicant were plotted across time and a linear regression was performed to evaluate a ten-year trend.

RESULTS

The match rate of both specialties was 52% and was similar for GS and VS programs. CI was higher for VS compared to GS (18.4±3.0 vs 14.5±0.4; P<0.001). The number of programs ranked per applicant was higher in VS compared to GS (9.4 vs. 7.7, P<0.05). The linear regression revealed increasing NCI and number of programs ranked per applicant over time for VS programs compared to GS with all R²>0.61 (P<0.001).

CONCLUSIONS

Matching into a VS programs is becoming increasingly competitive. The average competitive index was approximately 27% higher for VS programs compared to GS programs despite similar match rates. As VS programs continue to evolve, NCI may be a more useful metric for applicants.

An intrinsic link to an extrinsic cause of cardiac xenograft growth after xenotransplantation: Commentary (in response to): Zaman, R. et al. Selective loss of resident macrophage-derived insulin-like growth factor-1 abolishes adaptive cardiac growth to stress. Immunity 54, 2057-2071.e6 (2021).: Commentary (in response to): Zaman, R. et al. Selective loss of resident macrophage-derived insulin-like growth factor-1 abolishes adaptive cardiac growth to stress. Immunity 54, 2057-2071.e6 (2021)

Post-transplantation cardiac xenograft growth in an orthotopic pig to baboon model is a life-limiting phenomenon that is poorly understood. Possible causes of growth include both intrinsic and extrinsic etiologies. Extrinsic causes are thought to be attributed to maladaptive hypertrophy as a result of increased mean arterial pressure experienced by the cardiac xenograft after transplantation. Intrinsic causes are thought to be a result of discordant growth between pig xenografts and recipients. This results in intrinsic xenograft growth that parallels the donor and continues in a recipient in which growth is relatively minimal, controlled in part by the growth hormone receptor, IGF-1 axis. Recently, Zaman, et al. published a study titled, "Selective loss of resident macrophage-derived insulin-like growth factor-1 abolishes adaptive cardiac growth to stress," in Immunity, Volume 54; Issue 9, pp. 2057-2071. They demonstrated that insulin growth factor-secreting resident macrophages that sense hypertensive stress are a mechanistic link to hypertension and maladaptive hypertrophy in the setting of hypertension. While notable in its own right, we comment on how this work may shed light on a new underlying mechanism for the use of growth hormone receptor knockout (GHRKO) pig donors and its role in addressing post-transplantation xenograft growth. We hypothesize that GHRKO pig donors contain syngeneic resident cardiac macrophages that abrogate IGF-1 mediated maladaptive hypertrophy from hypertension. Futures studies in post-transplantation cardiac xenotransplantation growth should examine this mechanism as a potential contributor.