Abstract
Background.
Understanding perioperative risks and long-term benefits of kidney transplantation is essential for patient counseling and optimization of posttransplant outcomes. Currently, there is a lack of generalizable data on cardiovascular complications of kidney transplantation.
Methods.
We performed a retrospective, cross-sectional analysis of adult kidney transplantation hospitalizations in the National Inpatient Sample from 2016 to 2022. Cardiac events were defined as cardiac arrest, cardiogenic shock, acute myocardial infarction, ventricular tachycardia, or a related cardiac intervention (cardiopulmonary resuscitation, extracorporeal membrane oxygenation, percutaneous coronary intervention, left or right heart catheterization, intra-aortic balloon pump). Outcomes included cardiac event incidence, mortality, length of stay (LOS), and cost.
Results.
Among 139 720 kidney transplantation hospitalizations, cardiac events occurred in 3165 (2.3%). Patients with cardiac events were older (59.2 versus 52.3 y; P < 0.001) and had higher comorbidity burden (Charlson Comorbidity Index 4.4 versus 3.2; P < 0.001). In-hospital mortality among those with cardiac events was 9.2%, compared with 0.4% among those without. Mean LOS (13.4 versus 5.7 d) and hospitalization cost ($108 876 versus $66 985) were increased in those with a cardiac event (P < 0.001 for both). Cardiac intervention was recorded in 0.8% of transplant recipients and was associated with a 16.6% mortality rate. Risk factors for cardiac events included older age, male sex, coronary artery disease, congestive heart failure, atrial fibrillation, cerebrovascular disease, diabetes, and Charlson Comorbidity Index > 4 (odds ratio, 4.95; 95% confidence interval, 4.21-5.82; P < 0.001).
Conclusions.
Cardiac events complicate approximately 2% of index kidney transplantation hospitalizations and are associated with markedly increased mortality, LOS, and cost.
INTRODUCTION
End-stage renal disease (ESRD) is a significant cause of global morbidity and mortality, with 1.2–1.5 million deaths attributed to chronic kidney disease in the world each year.1-5 In the United States alone, there are >500 000 patients currently being treated with dialysis.6,7 Unfortunately, the impact of ESRD is likely to grow because of an overall aging global population and increasing rates of diabetes.3,8
Kidney transplantation is associated with improved quality of life and long-term survival in patients with ESRD compared with dialysis.9-11 However, short-term risks of kidney transplantation do exist.12 Patients with ESRD often have a high burden of comorbid illness, particularly cardiovascular disease, and the risk of a cardiovascular complication related to major surgery warrants consideration when evaluating a patient for kidney transplantation.13,14 Additionally, donor organs are a limited resource with nearly 150 000 patients in the United States currently awaiting kidney transplantation, and a primary focus of transplant teams is to ensure that potential recipients have maximal chances of survival and that the grafts function well.15
Understanding the risks and benefits of kidney transplantation is critical to educating patients and maximizing posttransplant outcomes. Defining the incidence of cardiovascular complications after kidney transplantation and assessing patient risk factors for such complications is critical to this process. Although previous studies have assessed complications of kidney transplantation and patient risk factors, smaller sample sizes and single-center study designs have limited the generalizability of previous findings.16-18
To address this important clinical question, we performed a large-scale analysis of nearly 140 000 kidney transplantations within a generalizable, US nationwide database. We quantified the incidence of cardiovascular complications and interventions during the index hospitalization. In addition, we assessed patient factors associated with cardiovascular complications. Our findings provide up-to-date, generalizable information on complications of kidney transplantation, which have the potential to improve risk stratification and the appropriate selection of transplant candidates.
MATERIALS AND METHODS
Study Design and Database
This was a retrospective, cross-sectional analysis of hospitalizations with documented kidney transplantation in the National Inpatient Sample (NIS). The NIS is an all-payer United States inpatient database developed as part of the Healthcare Cost and Utilization Project. It contains approximately 7 million hospitalizations annually, selected via a stratified, systematic process. Healthcare Cost and Utilization Project provides standardized weighting procedures that, when applied to NIS data, generate estimates intended to represent the entire US inpatient population (≈35 million hospitalizations per year). All study results were weighted. The NIS is de-identified and publicly available; Institutional Review Board approval and patient consent were waived.
Study Sample and Variables
We assessed all adult hospitalizations in the NIS from 2016 to 2022 with a documented kidney transplantation. Kidney transplantation was defined using relevant procedure codes from the International Classification of Diseases (ICD), 10th Revision, Procedure Coding System (Table S1, SDC, https://links.lww.com/TXD/A875). We excluded hospitalizations with documentation of another solid organ transplant (liver, heart, pancreas) during the same admission.
For each included hospitalization, we evaluated the presence of a cardiac event, defined as a cardiac complication or cardiac intervention. Cardiac complication was defined by any of the following secondary diagnoses: cardiac arrest, cardiogenic shock, acute myocardial infarction, or ventricular tachycardia. In cases of acute myocardial infarction, separate analyses were also performed for cases of ST-elevation myocardial infarction and non-ST-elevation myocardial infarction. If acute myocardial infarction was documented without specification of ST-elevation versus non-ST-elevation, the hospitalization was included in the acute myocardial infarction group but not included in either of the subgroups. The NIS does not specify whether secondary diagnoses are chronic conditions, present on admission, or complications that occurred during the admission.19 To avoid misclassifying chronic disease as an acute complication of transplantation, diagnostic codes that suggested chronic conditions were excluded from the cardiac-complication definition.
Cardiac intervention was defined as any of the following documented on the day of transplantation or thereafter: cardiopulmonary resuscitation (CPR), extracorporeal membrane oxygenation (ECMO), percutaneous coronary intervention (PCI), left heart catheterization (LHC), right heart catheterization (RHC), and intra-aortic balloon pump (IABP). ICD, 10th Revision, Procedure Coding System codes identified the presence of cardiac interventions. In the NIS, a procedure day is provided for documented procedures; cardiac procedures recorded before the transplant day were excluded, as our objective was to assess complications related to the transplant.
Objectives
The primary objective was to provide generalizable estimates of the incidence of cardiac events during kidney transplantation index hospitalizations. We determined the incidence of each cardiac complication and intervention, as well as in-hospital mortality, mean length of stay (LOS), and mean hospitalization cost among kidney transplant recipients with relevant events. To provide context, we also estimated the incidence of each intervention among hospitalizations with the corresponding complication diagnosis (eg, the rate of CPR among those with acute myocardial infarction) and, conversely, the incidence of each complication among hospitalizations that underwent the corresponding intervention. To examine whether the timing of intervention was associated with outcomes, we compared mortality by timing (relative to the transplant day) for CPR, PCI, LHC, and RHC. ECMO and IABP were not included in timing analyses because of limited sample sizes.
The secondary objective was to assess transplant recipient factors associated with cardiac events. Candidate variables included age, sex, race, Charlson Comorbidity Index, diabetes, tobacco use, obesity, coronary artery disease, congestive heart failure, chronic atrial fibrillation, and history of cerebrovascular disease. The Charlson Comorbidity Index was calculated using secondary diagnostic ICD, 10th Revision codes within the NIS. To avoid classifying complications as baseline conditions, diagnostic codes indicating acute diagnoses were excluded from covariate definitions.
Statistical Analysis
Categorical variables in Table 1 were compared using the chi-square test. Outcome rates are presented as percentages or as events per 1000 hospitalizations. LOS and cost outcomes are presented as means. LOS assessments were restricted to patients who survived to discharge. For analyses of intervention timing and mortality, we used univariable logistic regression and report odds ratios (ORs) with 95% confidence intervals (CIs). Same-day intervention served as the reference group; interventions 1–2 d after transplantation and >2 d after transplantation were compared with the reference. Univariable logistic regression was also used to assess factors associated with cardiac events, with ORs and 95% CIs reported. A 2-sided P < 0.05 was considered statistically significant. All analyses were performed using Stata, Version 17.0.
TABLE 1.
Demographic and clinical information for kidney transplant recipients in the United States, 2016–2022, stratified by the presence of a postoperative cardiac event
| Variable | Cardiovascular complication or intervention (n = 3165) | No cardiovascular complication or intervention (n = 136 555) | P |
|---|---|---|---|
| Age, y, % | |||
| 18–45 (n = 42 035) | 11.2 | 30.5 | <0.001b |
| 46–64 (n = 67 330) | 53.1 | 48.1 | 0.013a |
| 65 + (n = 30 355) | 35.7 | 21.4 | <0.001b |
| Female, % (n = 139 720) | 30.7 | 40.2 | <0.001b |
| Race, % | |||
| White (n = 59 460) | 43.7 | 44.0 | 0.855 |
| Black (n = 36 975) | 30.8 | 27.3 | 0.055 |
| Hispanic (n = 23 805) | 14.5 | 17.7 | 0.052 |
| Asian or Pacific Islander (n = 9285) | 6.6 | 6.9 | 0.779 |
| Other (n = 5595) | 4.5 | 4.1 | 0.703 |
| Hospital region, % | |||
| Northeast (n = 26 430) | 24.0 | 18.8 | 0.002a |
| Midwest (n = 30 425) | 21.5 | 21.8 | 0.868 |
| South (n = 52 860) | 36.3 | 37.9 | 0.494 |
| West (n = 30 005) | 18.2 | 21.6 | 0.080 |
| Charlson Comorbidity Index, % | |||
| 0–2 (n = 57 570) | 11.7 | 41.9 | <0.001b |
| 3–4 (n = 58 790) | 39.8 | 42.1 | 0.262 |
| >4 (n = 23 360) | 48.5 | 16.0 | <0.001b |
| Diabetes, % (n = 139 720) | 58.5 | 39.6 | <0.001b |
| Hypertension, % (n = 139 720) | 96.4 | 95.3 | 0.220 |
| Tobacco use, % (n = 139 720) | 3.3 | 3.0 | 0.664 |
| Obesity, % (n = 139 720) | 22.9 | 21.5 | 0.393 |
| Coronary artery disease, % (n = 139 720) | 14.5 | 4.4 | <0.001b |
| Congestive heart failure, % (n = 139 720) | 26.4 | 8.6 | <0.001b |
| Chronic atrial fibrillation, % (n = 139 720) | 23.4 | 7.5 | <0.001b |
| History of cerebrovascular disease, % (n = 139 720) | 10.9 | 7.0 | <0.001b |
| Chronic obstructive pulmonary disease, % (n = 139 720) | 8.9 | 8.2 | 0.524 |
| Length of hospital say, calendar days, % | |||
| 0–5 (n = 91 490) | 24.2 | 66.4 | <0.001b |
| 6–10 (n = 37 640) | 39.7 | 26.7 | <0.001b |
| 11–20 (n = 2335) | 20.4 | 5.4 | <0.001b |
| >20 (n = 7990) | 14.8 | 1.3 | <0.001b |
| Cost of hospitalization, US dollars, % | |||
| 0–50 000 (n = 39 205) | 12.3 | 28.4 | <0.001b |
| 50 001–100 000 (n = 84 200) | 51.2 | 60.5 | <0.001b |
| 100 001–250 000 (n = 14 430) | 30.3 | 9.8 | <0.001b |
| >250 000 (n = 1985) | 6.2 | 1.3 | <0.001b |
Cardiac event defined as documentation of any of the following: cardiac arrest, cardiogenic shock, acute myocardial infarction, ventricular tachycardia, cardiopulmonary resuscitation, extracorporeal membrane oxygenation, percutaneous coronary intervention, left heart catheterization, right heart catheterization, or intra-aortic balloon pump.
aP < 0.05.
bP < 0.001.
RESULTS
Demographic and Clinical Characteristics
A total of 139 720 kidney transplantation recipients were included in the analysis. The mean age for all recipients was 52.4 y, and 21.7% of recipients were 65 y or older. The cohort was predominately male (60.1%) and White (44.0%). A cardiac event was recorded in 3165 hospitalizations (2.3%). Transplant recipients who experienced a cardiac event tended to be older (mean age 59.2 versus 52.3 y; P < 0.001) and were more likely to be male (69.4% versus 59.8%; P < 0.001; Table 1). There was a high burden of comorbid illness in the cohort, with the mean Charlson Comorbidity Index of all recipients being 3.3 and 16.7% of recipients having a Charlson Comorbidity Index >4. The burden of comorbid illness tended to be higher in transplant recipients who experienced a cardiac event (mean Charlson Comorbidity Index 4.4 versus 3.2; P < 0.001).
Cardiac Outcomes in Kidney Transplantation Hospitalizations
A cardiac complication diagnosis (cardiac arrest, cardiogenic shock, acute myocardial infarction, ventricular tachycardia) was present in 2845 hospitalizations (2.0%), with rates ranging from 0.2% for cardiogenic shock to 1.0% for acute myocardial infarction (Table 2). A cardiac intervention (CPR, ECMO, PCI, LHC, RHC, IABP) was documented in 735 transplant recipients who had a cardiac complication diagnosis (25.8%). There were 275 deaths recorded for transplant recipients who had a cardiac complication diagnosis, for an overall mortality of 9.7%, while individual mortality rates ranged from 6.1% in ventricular tachycardia to 30.6% in cases of cardiac arrest. The mean LOS for transplant recipients with a cardiac complication diagnosis was 13.4 d, which was significantly increased compared with those without a cardiac complication diagnosis (5.7 d; P < 0.001). Cost was also increased in transplant recipients with a cardiac complication diagnosis (mean $108 876 versus $66 985; P < 0.001).
TABLE 2.
Posttransplant complications, outcomes, and associated interventions during the index hospitalization for kidney transplantation in the United States, 2016–2022
| Diagnosis | Rate | Mortality | Mean LOSa (d) | Mean cost | CPR | ECMO | PCI | LHC | RHC | IABP |
|---|---|---|---|---|---|---|---|---|---|---|
| Cardiac arrest | 0.4% | 30.6% | 23.0 | $136 591 | 54.8% | 4.0% | 4.8% | 5.6% | 4.0% | 1.6% |
| Cardiogenic shock | 0.2% | 28.6% | 24.1 | $159 298 | 19.6% | 8.9% | 14.3% | 19.6% | 16.1% | 5.4% |
| Acute myocardial infarction | 1.0% | 7.8% | 12.9 | $108 563 | 6.7% | 0.4% | 15.3% | 19.4% | 5.6% | 1.5% |
| Acute ST-elevation myocardial infarction | 0.1% | 25.0% | 18.0 | $107 002 | 16.7% | 4.2% | 41.7% | 37.5% | 16.7% | 8.3% |
| Acute non-ST-elevation myocardial infarction | 0.4% | 5.0% | 13.4 | $107 767 | 5.9% | 0.0% | 5.0% | 11.9% | 4.0% | 1.0% |
| Ventricular tachycardia | 0.8% | 6.1% | 11.3 | $97 694 | 4.8% | 0.9% | 3.9% | 5.7% | 2.6% | 0.4% |
Procedures performed before kidney transplantation were excluded. The category “acute myocardial infarction” included cases of ST-elevation myocardial infarction, non-ST-elevation myocardial infarction, and cases where the specific type of myocardial infarction was not specified.
aAnalysis restricted to patients who survived to discharge.
CPR, cardiopulmonary resuscitation; ECMO, extracorporeal membrane oxygenation; IABP, intra-aortic balloon pump; LHC, left heart catheterization; LOS, length of stay; PCI, percutaneous coronary intervention; RHC, right heart catheterization.
A cardiac intervention was recorded in 1055 hospitalizations (0.8%). LHC was the most commonly recorded procedure, occurring in 0.3% of hospitalizations (Table 3). An evaluated cardiac complication diagnosis was present in 70.0% of hospitalizations with a documented cardiac intervention. A total of 175 deaths were recorded for transplant recipients who underwent a cardiac intervention, for a total mortality of 16.6%, and individual mortalities ranging from 6.1% for PCI to 87.5% for ECMO. Both mean LOS (17.0 versus 5.8 d; P < 0.001) and mean cost ($139 800 versus $67 292; P < 0.001) were significantly increased in transplant recipients who underwent a cardiac intervention compared with those who did not.
TABLE 3.
Posttransplant interventions and outcomes during the index hospitalization for kidney transplantation in the United States, 2016–2022
| Outcome | Rate per 1000 patients | Mortality | Same day as transplant | Mean LOSa (d) | Mean cost | Other intervention(s) | Cardiac arrest | Cardiogenic shock | Acute MI | V-tach |
|---|---|---|---|---|---|---|---|---|---|---|
| CPR | 2.8 | 33.3% | 34.6% | 20.1 | $140 610 | 9.0% | 87.2% | 14.1% | 23.1% | 14.1% |
| ECMO | 0.3 | 87.5% | 25.0% | 67.0 | $238 039 | 25.0% | 62.5% | 62.5% | 12.5% | 25.0% |
| PCI | 1.8 | 6.1% | 0.0% | 16.4 | $136 222 | 73.5% | 12.2% | 16.3% | 83.7% | 18.4% |
| LHC with PCI | 1.2 | 9.1% | 0.0% | 16.9 | $143 976 | 27.3% | 12.1% | 15.2% | 87.9% | 21.2% |
| LHC without PCI | 1.9 | 7.4% | 40.7% | 11.7 | $127 816 | 24.1% | 5.6% | 11.1% | 42.6% | 11.1% |
| RHC | 1.8 | 10.2% | 18.4% | 18.9 | $151 309 | 42.9% | 10.2% | 18.4% | 30.6% | 12.2% |
| IABP | 0.2 | 33.3% | 0.0% | 15.5 | $140 817 | 83.3% | 33.3% | 50.0% | 66.7% | 16.7% |
Procedures performed before kidney transplantation were excluded.
aAnalysis restricted to patients who survived to discharge.
CPR, cardiopulmonary resuscitation; ECMO, extracorporeal membrane oxygenation; IABP, intra-aortic balloon pump; LHC, left heart catheterization; LOS, length of stay; MI, myocardial infarction; PCI, percutaneous coronary intervention; RHC, right heart catheterization; V-tach, ventricular tachycardia.
The impact of the timing of cardiac interventions was also evaluated: transplant recipients who underwent CPR >2 d after kidney transplantation had increased mortality compared with those who underwent CPR on the same day as kidney transplantation (OR, 5.72; 95% CI, 1.55-21.11; P = 0.009). There were no transplant recipients who underwent PCI on the day of kidney transplantation, and mortality did not significantly differ between those who underwent PCI 1–2 d after transplantation and those who underwent PCI >2 d after transplantation (Table 4). Timing of intervention was not associated with changes in mortality for both LHC and RHC.
TABLE 4.
Posttransplant interventions and intervention outcomes during the index hospitalization for kidney transplantation in the United States, 2016–2022, stratified by timing of intervention compared with kidney transplantation
| Outcome | Proportion | Mortality | Odds ratio (95% CI) | P |
|---|---|---|---|---|
| CPR | ||||
| Same day | 34.6% | 18.5% | Reference | – |
| 1–2 d | 35.9% | 28.6% | 1.76 (0.51-6.08) | 0.371 |
| >2 d | 29.5% | 56.5% | 5.72 (1.55-21.11) | 0.009a |
| Percutaneous coronary intervention | ||||
| Same day | 0.0% | – | – | – |
| 1–2 d | 28.6% | 7.1% | Reference | – |
| >2 d | 71.4% | 5.7% | 0.79 (0.06-10.10) | 0.855 |
| Left heart catheterization | ||||
| Same day | 25.3% | 0.0% | – | – |
| 1–2 d | 19.5% | 11.8% | Reference | – |
| >2 d | 55.2% | 10.4% | 0.87 (0.15-5.12) | 0.880 |
| Right hearth catheterization | ||||
| Same day | 18.4% | 0.0% | – | – |
| 1–2 d | 20.4% | 30.0% | Reference | – |
| >2 d | 61.2% | 6.7% | 0.17 (0.02-1.20) | 0.075 |
indicates not applicable, because that category served as the reference group (eg, odds ratio for the reference category).
aP < 0.05.
CI, confidence interval; CPR, cardiopulmonary resuscitation.
Patient Factors Associated With Cardiac Events
Of the assessed variables, only race, tobacco use, and obesity did not have statistically significant associations with a cardiac event (Table 5). A Charlson Comorbidity Index >4 had the strongest association with a cardiac event of all evaluated factors (OR, 4.95; 95% CI, 4.21-5.82; P < 0.001). A cardiac event was recorded in 7.1% of transplant recipients with coronary artery disease, 6.7% of transplant recipients with congestive heart failure, and 6.8% of transplant recipients with atrial fibrillation, and each diagnosis had a statistically significant association with documentation of a cardiac event (P < 0.001).
TABLE 5.
Univariable logistic regression assessing for patient factors associated with cardiovascular events in the after kidney transplant setting
| Variable | Odds ratio (95% CI) | P |
|---|---|---|
| Age 65 y or older | 2.04 (1.74-2.39) | <0.001b |
| Female sex | 0.66 (0.55-0.78) | <0.001b |
| Race, % | ||
| White | Reference | – |
| Black | 1.14 (0.95-1.37) | 0.169 |
| Hispanic | 0.83 (0.64-1.06) | 0.132 |
| Asian or Pacific Islander | 0.97 (0.70-1.34) | 0.836 |
| Charlson Comorbidity Index >4 | 4.95 (4.21-5.82) | <0.001b |
| Age 65+ and Charlson Comorbidity Index >4 | 4.55 (3.74-5.55) | <0.001b |
| Diabetes | 2.33 (1.76-3.08) | <0.001b |
| Tobacco use | 1.10 (0.71-1.71) | 0.664 |
| Obesity | 1.09 (0.90-1.32) | 0.393 |
| Coronary artery disease | 3.73 (2.99-4.65) | <0.001b |
| Congestive heart failure | 3.83 (3.18-4.63) | <0.001b |
| Chronic atrial fibrillation | 3.78 (3.09-4.63) | <0.001b |
| History of cerebrovascular disease | 1.63 (1.27-2.09) | <0.001b |
Cardiovascular event defined as documentation of any of the following: cardiac arrest, cardiogenic shock, acute myocardial infarction, ventricular tachycardia, cardiopulmonary resuscitation, extracorporeal membrane oxygenation, percutaneous coronary intervention, left heart catheterization, right heart catheterization, or intra-aortic balloon pump.
indicates not applicable, because that category served as the reference group (eg, odds ratio for the reference category).
aP < 0.05.
bP < 0.001.
CI, confidence interval.
DISCUSSION
In this large, nationally representative study of nearly 140 000 hospitalizations, we found that cardiac events—defined as cardiac arrest, cardiogenic shock, acute myocardial infarction, ventricular tachycardia, or related cardiac interventions—occurred in 2.3% of kidney transplant recipients during the index transplantation hospitalization. Mortality was high (9.2%) among those with cardiac events, and both LOS and cost were substantially increased compared with hospitalizations without such events. Older age and pretransplant cardiac comorbidities were strongly associated with cardiac complications.
While there is a large body of literature evaluating long-term cardiovascular outcomes in kidney transplant recipients, acute cardiovascular complications of kidney transplantation have been less well studied.20-22 Large-scale registry data are available primarily only for acute myocardial infarction.23,24 Smaller-scale studies have assessed similar questions to ours, but retrospective, single-center design and longer follow-up windows in those studies make it difficult to isolate perioperative surgical risk.18,25,26 Most studies of acute kidney-transplant complications have instead focused on graft function, urologic events, and infection, with relatively little attention to cardiovascular outcomes.27-29
A previous study by Goyal et al,30 which also used the NIS, found that 6.5% of patients experienced a major cardiac event during the index transplantation hospitalization. However, that definition included ICD, 9th Revision codes for chronic heart failure without specification of acute exacerbation. Because secondary diagnoses in the NIS can represent either chronic conditions or acute complications, those results likely overestimated the rate of true postoperative cardiac events.19 This definitional difference likely explains why our estimate of 2.3%—based on restrictive criteria targeting acute presentations—was lower.
Our study adds a new level of detail by examining a broader spectrum of acute cardiac events—including arrhythmia, cardiogenic shock, and cardiac arrest—together with the corresponding interventions and their outcomes. This dual approach allowed us to capture the clinical trajectory of these events and quantify their impact on mortality, LOS, and cost. Tables 2 and 3 represent the first national-level assessment linking each cardiac complication to its associated procedural management and outcome. Additionally, our assessment of outcomes by timing of intervention provides further key insight into outcomes and could guide efforts to improve perioperative outcomes.
Cardiovascular events can occur in the postoperative period for multiple reasons. Inflammation, sympathetic-induced hemodynamic changes, procoagulant states, and hypoxia are among the potential triggers for postoperative cardiac events.31 Preexisting cardiovascular disease is an established risk factor for postoperative cardiac complications, and we observed strong correlations between several chronic cardiovascular conditions and cardiac events in our cohort.32,33 Age, male sex, and comorbidity burden (as measured by the Charlson Comorbidity Index) were also strongly associated with cardiovascular events. The Charlson Comorbidity Index was developed to classify mortality risk in longitudinal studies based on comorbid conditions and has since been shown to predict postoperative complications in a variety of surgical settings, including hip fracture repair and colorectal surgery.34-37 Our results suggest that the Charlson Comorbidity Index may also have value in risk stratifying kidney transplant candidates for postoperative cardiovascular complications.
Cardiac events in the post-kidney transplantation setting can be devastating. In our study, mortality among transplant recipients with a cardiac event approached 10%, and these events were associated with substantial increases in LOS and cost. Given this burden, a thorough pretransplant evaluation and individualized discussion of risk and benefit appear warranted to educate patients and maximize outcomes, particularly for patients with multiple comorbidities or established cardiovascular disease. Integration of structured perioperative cardiac risk assessment and monitoring protocols may help improve outcomes in this high-risk population.
Strengths of this study include the large, nationally representative population and the combined use of secondary diagnoses and procedural data to comprehensively evaluate post-kidney transplantation complications. While cardiovascular complications of kidney transplantation have been studied, the novelty in our study lies in the variety of complications we assessed, the evaluation of invasive procedures associated with each complication, and the assessment of outcomes for each individual complication and procedure. This level of data on a large, national scale provides a unique view on cardiovascular complications of kidney transplantation. Limitations include the absence of postdischarge follow-up and the administrative nature of the NIS. The NIS only encompasses a discrete hospitalization for a given patient. Without postdischarge follow-up data, we are unable to comment on long-term mortality or long-term graft outcomes, which are certainly outcomes of key importance in this population. The lack of granular clinical and narrative detail within the database limits our ability to identify specific intraoperative or perioperative factors contributing to cardiac events. Accordingly, associations between patient characteristics and complications should be interpreted as correlations rather than evidence of causation.
We found acute cardiac events during index kidney transplantation hospitalizations to be relatively uncommon but clinically significant, contributing to increased mortality, longer hospitalizations, and higher costs. Older age, preexisting cardiovascular disease, and greater comorbidity burden were the strongest predictors of these complications. These findings highlight the importance of pretransplant cardiovascular risk stratification, individualized risk counseling, and vigilant perioperative monitoring.
Supplementary Material
Footnotes
The authors declare no funding or conflicts of interest.
S.R.G. participated in conceptualization, methodology, formal analysis, data curation, writing—original draft, and writing—review and editing. T.M.L. and J.R.P. participated in conceptualization, methodology, and writing—review and editing.
Supplemental digital content (SDC) is available for this article. Direct URL citations appear in the printed text, and links to the digital files are provided in the HTML text of this article on the journal’s Web site (www.transplantationdirect.com).
Contributor Information
Spencer R. Goble, Email: goble012@umn.edu.
Thomas M. Leventhal, Email: leven049@umn.edu.
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