Acute Kidney Injury in Patients Undergoing Cardiac Transplantation: A Meta-Analysis

A contemporary simple risk score for prediction of severe acute kidney injury after heart transplantation

BACKGROUND

The aim of this study was to develop a simple risk score to estimate severe acute kidney injury (AKI) risk based on a large contemporary heart transplantation (HT) cohort.

METHODS

From 1 January 2015 to 31 December 2021, all consecutive HT recipients in our institute were included and analysed for the occurrence of AKI within the first seven postoperative days. Patients transplanted between 2015 and 2019 comprised the derivation cohort, and those transplanted between 2020 and 2021 formed the validation cohort. The primary endpoint was severe AKI (AKI stages 2-3). The impact of severe AKI on 90 day mortality was also evaluated.

RESULTS

Overall, 430 HT patients were included in the derivation cohort, and 108 were included in the validation cohort. Postoperative AKI occurred in 388 (72%) patients, including 162 (30%) severe AKI. The risk of 90 day mortality significantly increased in patients with severe-AKI. Seven independent predictors of severe AKI were found in the derivation cohort, including recipients' body mass index, history of diabetes, anaemia, preoperative inotropes, estimated glomerular filtration rate, cardiopulmonary bypass duration and intraoperative red blood cell transfusion. The occurrence of severe AKI increased gradually from the lowest to the highest of the four risk score groups in the derivation and validation cohort. The scoring prediction model showed a highly acceptable discriminating power for severe-AKI [C statistic: 0.76, 95% confidence interval (CI): 0.71-0.80 for derivation cohort; C statistic: 0.79, 95% CI: 0.71-0.89 for validation cohort].

CONCLUSIONS

A contemporary simple risk score based on available variables from patients undergoing HT can accurately discriminate the risk of severe AKI.

Occurrence rate and risk factors for acute kidney injury after lung transplantation: a systematic review and meta-analysis

Background

Compared with other solid organ transplantation, the morbidity rate of acute kidney injury is higher in lung transplantation. Our research was designed to examine the occurrence rate and risk factors for acute kidney injury after lung transplantation through a systematic review and meta-analysis.

Methodology

We conducted a database search for case-control studies and cohort studies on the occurrence rate and risk factors for acute kidney injury after lung transplantation up to August 19, 2023. Stata 15.0 was used for data analysis.

Results

Nineteen case-control or cohort studies were included, involving 1,755 cases of acute kidney injury after lung transplantation and 1,404 cases of non-acute kidney injury after lung transplantation. Based on the meta-analysis, the risk factors for acute kidney injury after lung transplantation included pulmonary fibrosis (OR, 1.34; CI [1.09-1.65]), hypertension (OR, 1.30; CI [1.07-1.58]), pre-op mechanical ventilation (OR, 3.30; CI [1.84-5.90]), pre-op extracorporeal membrane oxygenation (OR, 3.70; CI [2.51-5.45]), double lung transplantation (OR, 1.91; CI [1.45-2.53]), cardiopulmonary bypass support (OR, 1.82; CI [1.38-2.40]), cardiovascular events (OR, 1.50; CI [1.15-1.96]), intra-op hypotension (OR, 2.70; CI [1.42-5.14]), post-op extracorporeal membrane oxygenation (OR, 1.90; CI [1.20-3.01]), sepsis (OR, 3.20; CI [2.16-4.73]), dialysis (OR, 12.79; CI [6.11-26.8]).

Conclusions

Based on the existing evidence, clinical professionals can implement early detection, diagnosis and treatment of patients with acute kidney injury after lung transplantation, to improve the quality of life of these patients.

Early Pacemaker Dependency After Heart Transplantation Is Associated with Permanent Pacemaker Implantation, Graft Failure and Mortality

AIMS

Patients after heart transplantation (HTX) often experience post-transplant bradycardia, but little is known about the outcomes of early pacemaker dependency after HTX. We compared post-transplant mortality, graft failure, and the requirement for the permanent pacemaker implantation of patients with and without early pacemaker dependency after HTX.

METHODS

We screened all adult patients for early pacemaker dependency after HTX (defined as immediately after surgery) who underwent HTX at Heidelberg Heart Center between 1989 and 2022. Patients were stratified by diagnosis and type of early pacemaker dependency after HTX (sinoatrial or atrioventricular conduction disturbance).

RESULTS

A total of 127 of 699 HTX recipients (18.2%) had early pacemaker dependency after HTX, including 52 patients with sinoatrial conduction disturbances (40.9%) and 75 patients with atrioventricular conduction disturbances (59.1%). Patients with early pacemaker dependency after HTX showed both increased 1-year overall mortality after HTX (55.9% vs. 15.2%, p < 0.001) and higher mortality due to graft failure (25.2% vs. 4.2%, p < 0.001). Multivariate analysis revealed early pacemaker dependency after HTX (HR: 5.226, 95% CI: 3.738-7.304, p < 0.001) as an independent risk factor for 1-year mortality after HTX. Patients with early pacemaker dependency after HTX had a higher rate of 30-day (7.1% vs. 0.4%, p < 0.001) and 1-year (11.8% vs. 0.5%, p < 0.001) permanent pacemaker implantation after HTX compared to patients without early pacemaker dependency after HTX.

CONCLUSIONS

Patients with early pacemaker dependency after HTX had a significantly higher rate of post-transplant mortality, graft failure, and the requirement for permanent pacemaker implantation.

Assessing Pharmacokinetics and Safety of Therapeutic Alpha-1-Microglobulin in First-in-Human Kidney Transplantation: A Noncomparative Open-Label Multiple-Dose Phase 1b Study

Background

RMC-035 is a modified version of alpha-1-microglobulin, an endogenous protein developed as a renoprotective agent. Its intended use is to reduce the risk of irreversible loss of kidney function in cardiac surgery patients and to reduce delayed graft function in kidney transplant recipients. This first-in-human study aimed to evaluate the pharmacokinetics and safety of RMC-035 in kidney transplant recipients.

Methods

Eight living-donor kidney transplant recipients were included in 2 dose cohorts. The study drug RMC-035 was administered starting with the first dose during transplantation. Four additional doses were administered once daily following transplantation. In the first cohort, all 5 doses of RMC-035 were equal, whereas in the second cohort, the last 3 doses were doubled. Safety monitoring, laboratory tests, and pharmacokinetic measurements were performed according to protocol for 4 d post-transplantation and during the 90-d follow-up period.

Results

All 5 administrations of the study drug were completed in 5 out of 8 treated participants. Pharmacokinetic concentrations were approximately dose proportional, and AUC0-24h decreased between the first and fifth doses, reflecting improved kidney function and RMC-035 renal clearance over time. No accumulation was observed between the administrations. No clinically significant changes were observed in the hematological or biochemical laboratory parameters, electrocardiogram findings, or vital signs. A total of 22 treatment-emergent adverse events (AEs) were reported in 6 subjects. Mild and transient AEs suggestive of infusion-related reactions, such as chills, were reported in 5 patients. There was a clinically significant reduction in serum creatinine levels, reflecting post-transplant improvement in kidney function.

Conclusions

Based on the safety data obtained from 8 subjects in the 2 dose cohorts treated with RMC-035, the drug was considered safe. Safety and AE profiles were in line with expectations of the target population, and infusion-related reactions were short-lived and manageable. Dose-limiting toxicity signals were not observed.

Early Renal Outcomes Following Heart Transplantation Using Organs Procured After Circulatory Death

BACKGROUND

Transplantation using hearts obtained through donation after circulatory death (DCD) is increasing, but data on recipient renal outcomes are limited.

METHODS AND RESULTS

Patients at a single institution who underwent heart transplantation using organs procured through DCD or donation after brain death (DBD) from April 2016 to August 2022 were included in this retrospective cohort study. Hemodynamic measures were collected via right heart catheterization performed 1 week after transplantation. Posttransplantation renal outcomes included estimated glomerular filtration rate at 1 week, 4 weeks, and 16 weeks, and the incidence of acute kidney injury (AKI) and renal replacement therapy within 1 week. The analysis included 225 patients (55 recipients of DCD). Baseline characteristics were comparable between recipients of DCD and DBD. Renal outcomes within 1 week posttransplantation in recipients of DCD were similar to recipients of DBD, including percent change in estimated glomerular filtration rate (-37.9% [-58.6 to -6.2] versus -31.9% [-52.4 to -9.9]; P=0.91), incidence of AKI (47.3% versus 46.5%; P>0.99) and incidence of renal replacement therapy (3.6% versus 4.7%; P>0.99). Recipients of DCD with AKI within 1 week ("early AKI") did not recover to baseline estimated glomerular filtration rate (75.8 [60.2-91.3] mL/min per 1.73 m2) by week 16 (59.3 [46.9-73.6] mL/min per 1.73 m2; P=0.002), whereas recipients without early AKI exhibited comparable estimated glomerular filtration rate to baseline by week 4 (84.5 [70.8-98.5] mL/min per 1.73 m2; P=0.084). Similar trends were observed in recipients of DBD.

CONCLUSIONS

Recipients of DCD demonstrated similar renal outcomes compared with recipients of DBD, supporting the ongoing use of DCD transplantation. Early AKI was associated with persistent renal dysfunction for recipients of both DCD and DBD.

Impact of Age of Heart Transplant Program on Patient Survival and Post-Transplant Outcomes

BACKGROUND

The relationship between age of a heart transplant (HT) program and outcomes has not been explored.

METHODS

We performed a retrospective cohort analysis of the United Network for Organ Sharing database of all adult HTs between 2009 and 2019. For each patient, we created a variable that corresponded to program age: new (<5), developing (≥5 but <10) and established (≥10) years.

RESULTS

Of 20 997 HTs, 822 were at new, 908 at developing, and 19 267 at established programs. Patients at new programs were significantly more likely to have history of cigarette smoking, ischemic cardiomyopathy, and prior sternotomy. These programs were less likely to accept organs from older donors and those with a history of hypertension or cigarette use. As compared to patients at new programs, transplant patients at established programs had less frequent rates of treated rejection during the index hospitalization (HR 0.43 [95% CI, 0.36-0.53] p < 0.001) and at 1 year (HR 0.58 [95% CI, 0.49-0.70], p < 0.001), less frequently required pacemaker implantations (HR 0.50 [95% CI, 0.36-0.69], p < 0.001), and less frequently required dialysis (HR 0.66 [95% CI, 0.53-0.82], p < 0.001). However, there were no significant differences in short- or long-term survival between the groups (log-rank p = 0.24).

CONCLUSION

Patient and donor selection differed between new, developing, and established HT programs but had equivalent survival. New programs had increased likelihood of treated rejection, pacemaker implantation, and need for dialysis. Standardized post-transplant practices may help to minimize this variation and ensure optimal outcomes for all patients.

Acute Kidney Injury After Heart Transplantation: Risk Factors and Clinical Outcomes

OBJECTIVE

Acute kidney injury (AKI) requiring renal-replacement therapy (RRT) after heart transplantation (OHT) is common and impairs outcomes. This study aimed to identify independent donor and recipient risk factors associated with RRT after OHT.

DESIGN

A retrospective data analysis.

SETTING

Data were collected from clinical routines in a maximum-care university hospital.

PARTICIPANTS

Patients who underwent OHT.

INTERVENTIONS

The authors retrospectively analyzed data from 264 patients who underwent OHT between 2012 and 2021; 189 patients were eligible and included in the final analysis.

MEASUREMENTS AND MAIN RESULTS

The mean age was 48.0 ± 12.3 years, and 71.4% of patients were male. Ninety (47.6%) patients were on long-term mechanical circulatory support (lt-MCS). Posttransplant AKI with RRT occurred in 123 (65.1%) patients. In a multivariate analysis, preoperative body mass index >25 kg/m² (odds ratio [OR] 4.74, p < 0.001), elevated preoperative creatinine levels (OR for each mg/dL increase 3.44, p = 0.004), administration of red blood cell units during transplantation procedure (OR 2.31, p = 0.041) and ischemia time (OR for each hour increase 1.77, p = 0.004) were associated with a higher incidence of RRT. The use of renin-angiotensin-aldosterone system blockers before transplantation was associated with a reduced risk of RRT (OR 0.36, p = 0.013). The risk of mortality was 6.9-fold higher in patients who required RRT (hazard ratio 6.9, 95% CI: 2.1-22.6 p = 0.001). Previous lt-MCS, as well as donor parameters, were not associated with RRT after OHT.

CONCLUSIONS

The implementation of guideline-directed medical therapy, weight reduction, minimizing ischemia time (ie, organ perfusion systems, workflow optimization), and comprehensive patient blood management potentially influences renal function and outcomes after OHT.

Severe Acute Kidney Injury Postheart Transplantation: Analysis of Risk Factors

Background

Acute kidney injury (AKI) is a common complication postheart transplantation and is associated with significant morbidity and increased mortality.

Methods

We conducted a single-center, retrospective, observational cohort study of 109 consecutive patients undergoing heart transplantation between September 2019 and September 2021 to determine major risk factors for, and the incidence of, severe postoperative AKI as defined by Kidney Disease Improving Global Outcomes criteria in the first 48-h posttransplantation and the impact that this has on mortality and dialysis dependence.

Results

One hundred nine patients were included in our study, 83 of 109 (78%) patients developed AKI, 42 (39%) developed severe AKI, and 37 (35%) required renal replacement therapy in the first-week posttransplantation. We found preoperative estimated glomerular filtration rate (eGFR), postoperative noradrenaline dose, and the need for postoperative mechanical circulatory support to be independent risk factors for the development of severe AKI. Patients who developed severe AKI had a 19% 12-mo mortality compared with 1% for those without. Of those who survived to hospital discharge, 20% of patients in the severe AKI group required dialysis at time of hospital discharge compared with 3% in those without severe AKI.

Conclusion

Severe AKI is common after heart transplantation. Preoperative kidney function, postoperative vasoplegia with high requirements for vasoactive drugs, and graft dysfunction with the need for mechanical circulatory supports were independently associated with the development of severe AKI in the first-week following heart transplantation. Severe AKI is associated with a significantly increased mortality and dialysis dependence at time of hospital discharge.

Long-term post-transplantation outcomes in patients with hypertrophic cardiomyopathy: Single-center 35-year experience

BACKGROUND

Heart transplantation (HT) is the only option for most patients with end-stage heart failure and hypertrophic cardiomyopathy (HCM) who fail medical therapy. Data on the long-term outcomes post-transplant in HCM individuals remain scarce.

METHODS

We analyzed data of 319 adult patients who underwent HT between 1984 and 2019. Patients were followed for cardiac allograft rejection, cardiac allograft vasculopathy (CAV), death, or re-transplantation.

RESULTS

Outcomes of 24 patients with HCM, 160 with ischemic, and 135 with dilated cardiomyopathy were compared. During a mean follow-up of 11.6 ± 7.2 (max 27.8), 16.7 ± 8.2 (max 32.7), and 16.1 ± 9.7 (max 34.6) years after HT in hypertrophic, ischemic, and dilated cardiomyopathy groups, respectively: 10-year survival rate was 67%, 62%, 69%, respectively (p = .04). Post-transplantation, HCM individuals more often than the other two studied groups required prolonged inotropic support (37%, 12%, 17%, respectively, p = .02), temporary mechanical circulatory support (45%, 13%, 14%, respectively, p < .01), and renal replacement therapy immediately post-HT (55%, 19%, 24%, respectively, p < .01). No significant inter-group differences were noted in the 10-year freedom from acute allograft rejection (38%, 46%, 43%, respectively, p = .38) or 10-year freedom from CAV (88%, 78%, 81%, respectively, p = .57).

CONCLUSIONS

The long-term post-transplant prognosis of adult patients with hypertrophic cardiomyopathy is favorable despite more challenging immediate post-HT course.

Perioperative Management of Heart Transplantation: A Clinical Review

In this clinical review, the authors summarize the perioperative management of heart transplant patients with a focus on hemodynamics, immunosuppressive strategies, hemostasis and hemorrage, and the prevention and treatment of infectious complications.

Acute Kidney Injury Management Strategies Peri-Cardiovascular Interventions

In many countries, the aging population and the higher incidence of comorbid conditions have resulted in an ever-growing need for cardiac interventions. Acute kidney injury (AKI) is a common complication of these interventions, associated with higher mortalities, chronic or end-stage kidney disease, readmission rates, and hospital and post-discharge costs. The AKI pathophysiology includes contrast-associated AKI, hemodynamic changes, cardiorenal syndrome, and atheroembolism. Preventive measures include limiting contrast media dose, optimizing hemodynamic conditions, and limiting exposure to other nephrotoxins. This review article outlines the current state-of-art knowledge regarding AKI pathophysiology, risk factors, preventive measures, and management strategies in the peri-interventional period.

Ethical Implications of Chatbot Utilization in Nephrology

This comprehensive critical review critically examines the ethical implications associated with integrating chatbots into nephrology, aiming to identify concerns, propose policies, and offer potential solutions. Acknowledging the transformative potential of chatbots in healthcare, responsible implementation guided by ethical considerations is of the utmost importance. The review underscores the significance of establishing robust guidelines for data collection, storage, and sharing to safeguard privacy and ensure data security. Future research should prioritize defining appropriate levels of data access, exploring anonymization techniques, and implementing encryption methods. Transparent data usage practices and obtaining informed consent are fundamental ethical considerations. Effective security measures, including encryption technologies and secure data transmission protocols, are indispensable for maintaining the confidentiality and integrity of patient data. To address potential biases and discrimination, the review suggests regular algorithm reviews, diversity strategies, and ongoing monitoring. Enhancing the clarity of chatbot capabilities, developing user-friendly interfaces, and establishing explicit consent procedures are essential for informed consent. Striking a balance between automation and human intervention is vital to preserve the doctor-patient relationship. Cultural sensitivity and multilingual support should be considered through chatbot training. To ensure ethical chatbot utilization in nephrology, it is imperative to prioritize the development of comprehensive ethical frameworks encompassing data handling, security, bias mitigation, informed consent, and collaboration. Continuous research and innovation in this field are crucial for maximizing the potential of chatbot technology and ultimately improving patient outcomes.

A novel acute kidney injury scoring system for renal and clinical outcomes in pediatric heart transplant patients

BACKGROUND

The development of acute kidney injury (AKI) has been associated with worse outcomes in children after heart transplantation. Our study compares the application of a cumulative six-point Kidney Diseases Improving Global Outcomes (KDIGO) AKI scoring system, utilizing both creatinine and urine output criteria that we term as the AKI-6 criteria, to traditional AKI staging as a predictor for clinical and renal outcomes in the pediatric heart transplant recipients.

METHODS

We conducted a retrospective single-center chart review on 155 pediatric patients who underwent heart transplantation from May 2014 to December 2021. The primary independent variable was the presence of severe AKI. Severe AKI by KDIGO was defined as Stage ≥2, whereas severe AKI by AKI-6 was defined as cumulative scores ≥4 or Stage 3 AKI based on either KDIGO criterion alone. Primary outcomes included actuarial survival and renal dysfunction by 1-year post-transplant, defined as an estimated glomerular filtration rate <60 mL/min/1.73 m2 .

RESULTS

In total, 140 (90%) patients developed AKI; 98 (63%) patients developed severe AKI by KDIGO, and 60 (39%) by AKI-6. Severe AKI by AKI-6 was associated with worse actuarial survival following heart transplantation compared with KDIGO (p = 0.01). Of the 143 patients with 1-year creatinine data, 6 (11%) patients out of 54 with severe AKI by AKI-6 had evidence of renal dysfunction (p = 0.01), compared with 6 (7%) patients out of 88 by KDIGO (p = 0.3).

CONCLUSIONS

AKI-6 scoring provides greater prognostic utility for actuarial survival and renal dysfunction by 1-year post-heart transplantation in pediatric patients than traditional KDIGO staging.

Dual-Organ Transplantation: Indications, Evaluation, and Outcomes for Heart-Kidney and Heart-Liver Transplantation: A Scientific Statement From the American Heart Association

Although heart transplantation is the preferred therapy for appropriate patients with advanced heart failure, the presence of concomitant renal or hepatic dysfunction can pose a barrier to isolated heart transplantation. Because donor organ supply limits the availability of organ transplantation, appropriate allocation of this scarce resource is essential; thus, clear guidance for simultaneous heart-kidney transplantation and simultaneous heart-liver transplantation is urgently required. The purposes of this scientific statement are (1) to describe the impact of pretransplantation renal and hepatic dysfunction on posttransplantation outcomes; (2) to discuss the assessment of pretransplantation renal and hepatic dysfunction; (3) to provide an approach to patient selection for simultaneous heart-kidney transplantation and simultaneous heart-liver transplantation and posttransplantation management; and (4) to explore the ethics of multiorgan transplantation.

Pacemaker Implantation following Heart Transplantation: Analysis of a Nation-Wide Database

BACKGROUND

The 2018 United-Network-for-Organ-Sharing (UNOS) allocation-system changes resulted in greater recognition of mechanical circulatory support (MCS), leading to more heart transplantations (HTx) in patients with MCS. We aimed to investigate the effect of the new UNOS allocation system on the need for a permanent pacemaker and associated complications following HTx.

METHODS

The UNOS Registry was questioned, to identify patients that received HTx in the US between 2000 and 2021. The primary objectives were to identify risk factors for the need for a pacemaker implantation following HTx.

RESULTS

49,529 HTx patients were identified, 1421 (2.9%) requiring a pacemaker post-HTx. Patients who required a pacemaker were older (53.9 ± 11.5 vs. 52.6 ± 12.8 years, p < 0.001), more frequently white (73% vs. 67%; p < 0.001) and less frequently black (18% vs. 20%; p < 0.001). In the pacemaker group, UNOS status 1A (46% vs. 41%; p < 0.001) and 1B (31% vs. 27%; p < 0.001) were more prevalent, and donor age was higher (34.4 ± 12.4 vs. 31.8 ± 11.5 years; p < 0.001). One-year survival was no different between the groups (HR: 1.08; 95% CI: 0.85, 1.37; p = 0.515). An era effect was observed (per year: OR: 0.97; 95% CI: 0.96, 0.98; p = 0.003), while ECMO pre-transplant was associated with lower risk of a pacemaker (OR: 0.41; 95% CI: 0.19, 0.86; p < 0.001).

CONCLUSIONS

While associated with various patient and transplant characteristics, pacemaker implantation does not seem to impact one-year survival after HTx. The need for pacemaker implantation was lower in the more recent era and in patients who required ECMO pre-transplant, a finding explained by recent advances in perioperative care.

Higher Rates of Dialysis and Subsequent Mortality in the New Allocation Era for Heart Transplants

BACKGROUND

In 2018, a United Network for Organ Sharing (UNOS) policy change increased prioritization of patients bridged with temporary mechanical circulatory support devices, such as venoarterial ECMO, for cardiac transplantation. Considering increased waitlist acuity, we sought to characterize whether this was associated with an increased risk for development of postoperative acute renal failure requiring dialysis (AKI-D) and risk of death after transplantation.

METHODS

Dialysis-naive adults receiving single-organ heart transplant between November 2009 and February 2020 were stratified by receipt of AKI-D. Era 1 and era 2 were defined by the periods of UNOS allocation before and after policy change, respectively. Multivariable logistic regression was performed to determine risk factors for AKI-D. Rates of AKI-D were compared by propensity score-matched cohorts. Survival was compared by Kaplan-Meier analysis.

RESULTS

A total of 20 698 patients were included. Venoarterial ECMO use significantly increased in era 2 (5.6% vs 0.58%; P < .01). Overall prevalence of AKI-D was greater in era 2 (13.5% vs 10.2%; P < .01). Use of preoperative ECMO, intra-aortic balloon pump, and ventilators and longer ischemia times were identified as independent risk factors for development of AKI-D. Five- and 10-year survival rates were significantly decreased for patients with AKI-D. There was no short-term survival difference of patients with AKI-D between era 2 and the more contemporary era 1.

CONCLUSIONS

Patients in whom AKI-D develops after transplantation have significantly worse short- and long-term outcomes. Preoperative use of ECMO, preoperative ventilator support, and longer ischemia times are risk factors for development of AKI-D, and their prevalence has increased since the allocation policy change.

Managing Heart Failure in Patients on Dialysis: State-of-the-Art Review

Heart failure (HF) and end-stage kidney disease (ESKD) frequently coexist; 1 comorbidity worsens the prognosis of the other. HF is responsible for almost half the deaths of patients on dialysis. Despite patients' with ESKD composing an extremely high-risk population, they have been largely excluded from landmark clinical trials of HF, and there is, thus, a paucity of data regarding the management of HF in patients on dialysis, and most of the available evidence is observational. Likewise, in clinical practice, guideline-directed medical therapy for HF is often down-titrated or discontinued in patients with ESKD who are undergoing dialysis; this is due to concerns about safety and tolerability. In this state-of-the-art review, we discuss the available evidence for each of the foundational HF therapies in ESKD, review current challenges and barriers to managing patients with HF on dialysis, and outline future directions to optimize the management of HF in these high-risk patients.

Urinary Cell-Cycle Arrest Biomarkers as Early Predictors of Acute Kidney Injury After Ventricular Assist Device Implantation or Cardiac Transplantation

OBJECTIVES

Acute kidney injury (AKI) remains a leading source of morbidity and mortality after cardiothoracic surgery. Insulin-like growth factor-binding protein 7 (IGFBP7), and tissue inhibitor of metalloproteinases-2 (TIMP-2), are novel early-phase renal biomarkers that have been validated as sensitive predictors of AKI. Here the authors studied the efficacy of these biomarkers for predicting AKI after left ventricular assist device (LVAD) implantation and cardiac transplantation.

DESIGN/SETTING/PARTICIPANTS/INTERVENTIONS

This was a prospective study of 73 patients undergoing LVAD implantation (n = 37) or heart transplant (n = 36) from 2016 to 2017 at the authors' center. TIMP-2 and IGFBP7 were measured with the NephroCheck Test on urine samples before surgery and one-to-six hours after surgery. NephroCheck scores were assessed as predictors of moderate/severe AKI (Kidney Disease International Global Outcomes 2/3 creatinine criteria) within 48 hours of surgery, and the association with survival to one year was investigated.

MEASUREMENTS AND MAIN RESULTS

The LVAD and transplant cohorts overall were similar in demographics and baseline creatinine (p > 0.05), with the exception of having more African-American patients in the LVAD arm (p = 0.003). Eleven (30%) LVAD and 16 (44%) transplant patients developed moderate/severe AKI. Overall, AKI was associated with postsurgery NephroCheck (odds ratio [95% confidence interval] for 0.1 mg/dL increase: 1.36 [1.04-1.79]; p = 0.03), but not with baseline NephroCheck (p = 0.92). When analyzed by cohort, this effect remained for LVAD (1.68 [1.05-2.71]; p = 0.03) but not for transplant (p = 0.15). Receiver operating characteristic analysis showed postoperative NephroCheck to be superior to baseline creatinine in LVAD (p = 0.046). Furthermore, an increase of 0.1 mg/dL in postoperative NephroCheck was associated with a 10% increase in the risk of mortality (adjusted hazard ratio: 1.11 [1.01-1.21]; p = 0.04) independent of age and body mass index.

CONCLUSION

Assessment of TIMP-2 and IGFBP7 within six hours after surgery appeared effective at predicting AKI in patients with LVADs. Larger studies are warranted to validate these findings.

Machine learning to predict post-operative acute kidney injury stage 3 after heart transplantation

BACKGROUND

Acute kidney injury (AKI) stage 3, one of the most severe complications in patients with heart transplantation (HT), is associated with substantial morbidity and mortality. We aimed to develop a machine learning (ML) model to predict post-transplant AKI stage 3 based on preoperative and perioperative features.

METHODS

Data from 107 consecutive HT recipients in the provincial center between 2018 and 2020 were included for analysis. Logistic regression with L2 regularization was used for the ML model building. The predictive performance of the ML model was assessed using the area under the curve (AUC) in tenfold stratified cross-validation and was compared with that of the Cleveland-clinical model.

RESULTS

Post-transplant AKI occurred in 76 (71.0%) patients including 15 (14.0%) stage 1, 18 (16.8%) stage 2, and 43 (40.2%) stage 3 cases. The top six features selected for the ML model to predicate AKI stage 3 were serum cystatin C, estimated glomerular filtration rate (eGFR), right atrial long-axis dimension, left atrial anteroposterior dimension, serum creatinine (SCr) and FVII. The predictive performance of the ML model (AUC: 0.821; 95% confidence interval [CI]: 0.740-0.901) was significantly higher compared with that of the Cleveland-clinical model (AUC: 0.654; 95% [CI]: 0.545-0.763, p < 0.05).

CONCLUSIONS

The ML model, which achieved an effective predictive performance for post-transplant AKI stage 3, may be helpful for timely intervention to improve the patient's prognosis.

Risk factors of renal replacement therapy after heart transplantation: a retrospective single-center study

BACKGROUND

Acute kidney injury (AKI) and renal replacement therapy (RRT) are common after heart transplantation (HT). The need for RRT has been reported to be one of the most important predictors of a poor prognosis after HT. Therefore, it is important to early identify risk factors of RRT after HT. However, in the heart transplantation setting, the risk factors are less well studied, and some of the conclusions are controversial. This study aimed to identify the clinical predictors of RRT after HT.

METHODS

This single-center, retrospective study from January 2010 to June 2021 analyzed risk factors (pre-, intra-, and postoperative characteristics) of 163 patients who underwent HT. The endpoint of the study was RRT within 7 days of HT. Risk factors were analyzed by multivariable logistic regression models.

RESULTS

Fifty-five (33.74%) recipients required RRT within 7 days of HT. Factors independently associated with RRT after HT were as follows: a baseline estimated glomerular filtration rate (eGFR) <60 mL/min per 1.73 m² [odds ratio (OR) =3.123; 95% confidence interval (CI): 1.183-8.244; P=0.022], a dose of intraoperative methylprednisolone >10 mg/kg (OR =3.197; 95% CI: 1.290-7.923; P=0.012), the use of mechanical circulatory support (MCS) during surgery (OR =4.903; 95% CI: 1.628-14.766; P=0.005), a cardiopulmonary bypass (CPB) time ≥5 hours (OR =3.929; 95% CI: 1.222-12.634; P=0.022), and postoperative serum total bilirubin (TBIL) ≥60 umol/L (OR =5.105; 95% CI: 1.868-13.952; P=0.001). Protective factors were higher postoperative serum albumin (OR =0.907; 95% CI: 0.837-0.983; P=0.017) and higher postoperative left ventricular ejection fraction (LVEF) (OR =0.908; 95% CI: 0.838-0.985; P=0.020).

CONCLUSIONS

A low preoperative eGFR, a high intraoperative dose of methylprednisolone, a long CPB time, the use of mechanical circulatory support, and a high postoperative TBIL were risk factors for RRT after HT. While a high postoperative serum albumin level and a high left ventricular ejection fraction were protective factors. Understanding these risk factors may help us identify high-risk patients and intervene early.

Incidence and long-term outcome of heart transplantation patients who develop postoperative renal failure requiring dialysis

BACKGROUND

Acute renal failure requiring dialysis after heart transplantation remains a significant clinical issue because of its increasing incidence. We aimed to investigate its time trends, clinical predictors, and long-term outcomes.

METHODS

Adult heart transplantation recipients registered in the United Network for Organ Sharing registry between 2009 and 2020 were identified. The patients were grouped according to the requirement for dialysis in the postoperative heart transplantation period. The independent risk predictors were identified, and the association between post-heart transplantation renal failure requiring dialysis and long-term mortality accounting for re-transplantation was investigated.

RESULTS

A total of 28,170 patients were included in the study, of which 3,371 (12%) required dialysis immediately post-heart transplantation. The incidence increased from 7.9% to 13.9% during the study period. Longer ischemic time, serum creatinine at transplantation >1.2 mg/dL, prior cardiac surgery, higher recipient body mass index, support of mechanical ventilation or extracorporeal membrane oxygenation, and history of congenital heart disease or restrictive/hypertrophic cardiomyopathy were its predictors (all p < 0.05). Patients on posttransplant dialysis had a higher risk of all-cause mortality (adjusted hazard ratio [aHR]: 5.2, 95% CI: 4.7-5.7, p < 0.001), 30 day mortality (aHR: 7.7, 95% CI: 6.3-9.6, p < 0.001) and 1 year mortality (aHR: 7.5, 95% CI: 6.6-8.6, p < 0.001). Post-transplant dialysis was associated with a risk of treated rejection at 1 year.

CONCLUSION

Acute renal failure requiring dialysis after heart transplantation is associated with significantly worse 30 day and long-term mortalities, and thus, early identification of high-risk patients is crucial to prevent severe renal complications.

Risk Factors for Acute Kidney Injury Requiring Renal Replacement Therapy after Orthotopic Heart Transplantation in Patients with Preserved Renal Function

Acute kidney injury (AKI), requiring renal replacement therapy (RRT). is a serious complication after orthotopic heart transplantation (HTX). In patients with preexisting impaired renal function, postoperative AKI is unsurprising. However, even in patients with preserved renal function, AKI requiring RRT is frequent. Therefore, this study aimed to identify risk factors associated with postoperative AKI requiring RRT after HTX in this sub-cohort. This retrospective cohort study included patients ≥ 18 years of age with preserved renal function (defined as preoperative glomerular filtration rate ≥ 60 mL/min) who underwent HTX between 2010 and 2021. In total, 107 patients were included in the analysis (mean age 52 ± 12 years, 78.5% male, 45.8% AKI requiring RRT). Based on univariate logistic regression, use of extracorporeal membrane oxygenation, postoperative infection, levosimendan therapy, duration of norepinephrine (NE) therapy and maximum daily increase in tacrolimus plasma levels were chosen to be included into multivariate analysis. Duration of NE therapy and maximum daily increase in tacrolimus plasma levels remained as independent significant risk factors (NE: OR 1.01, 95%CI: 1.00–1.02, p = 0.005; increase in tacrolimus plasma level: OR 1.18, 95%CI: 1.01–1.37, p = 0.036). In conclusion, this study identified long NE therapy and maximum daily increase in tacrolimus plasma levels as risk factors for AKI requiring RRT in HTX patients with preserved renal function.

Early post-operative acute kidney injury after cardiac transplantation: Incidence and predictive factors

BACKGROUND

Heart transplantation, as a therapeutic option for patients with advanced heart failure, possesses a high rate of morbidity and mortality. One of the complications associated with this procedure is the development of postoperative acute kidney injury (AKI) MATERIAL AND METHODS: We aimed to evaluate the incidence of early postoperative AKI and the need for continuous renal replacement therapy (RRT) after heart transplantation. Data of 126 patients who underwent heart transplantation from January 2015 to November 2019 were collected. Statistical analysis was performed to identify the predictors of postoperative AKI.

RESULTS

Out of 126 patients, 74 (58.7 %) developed AKI and 13 (10%) required RRT after transplant. Independent predictors of AKI are shown to be factors associated with surgical procedures such as graft ischemic time as were previous cardiac operation, administered Voluven (starch) dose > 400 ml and transfusion of more than four blood units.

CONCLUSION

Our findings suggest that modifiable factors exist that can affect the risk of developing AKI following heart transplantation. This article is protected by copyright. All rights reserved.

Need for improvements in simultaneous heart-kidney allocation: The limitation of pretransplant glomerular filtration rate

The incidence of simultaneous heart-kidney transplant (SHK) has increased markedly in the last 15 years. There are no universally agreed upon indications for SHK vs. heart alone (HA) transplant, and center evaluation processes vary widely. We utilized Scientific Registry of Transplant Recipients data from 2003 to 2017 to quantify changes in the practice of SHK, examine the survival of SHK vs. HA, and identify patients with marginal benefit from SHK. We used Kaplan-Meier curves and Cox proportional hazards to assess differences in survival. The incidence of SHK increased more than fourfold between 2003 and 2017 from 1.6% to 6.6% of total hearts transplanted, while the proportion of dialysis-dependent patients undergoing SHK has remained constant. SHK was associated with increased survival in dialysis-dependent patients (Median Survival SHK: 12.6 vs. HA: 7.1 years p < .0001) but not with nondialysis-dependent patients (Median Survival SHK: 12.5 vs. HA 12.3, p = .24). The marginal effect of SHK in decreasing the hazard of death diminished with increasing eGFR. Delayed graft function occurred in 26% of SHK recipients. Posttransplant chronic dialysis was similar for both operations (6.4% of HA and 6.0% of SHK). Further study is needed to define patients who benefit from SHK.

Cardiac Surgery-Related Acute Kidney Injury _ Risk Factors, Clinical Course, Management Suggestions

OBJECTIVE

Acute kidney injury (AKI) is a common complication after cardiac surgery (CS). Because a therapeutic regimen remains scarce, the early implementation of preventive strategies is crucial. The authors investigated risk factors and the typical clinical course of CS-associated AKI (CS-AKI) to derive strategies for perioperative clinical routines.

DESIGN

Retrospective data analysis.

SETTING

The data were collected from clinical routines in a maximum care university hospital.

PARTICIPANTS

Patients.

INTERVENTIONS

The authors retrospectively analyzed data from 538 patients who underwent CS.

MEASUREMENTS AND MAIN RESULTS

The median age of the 466 patients included was 66.6 years; 65.7% were men. AKI occurred in 131 (28.1%) patients, mainly (89.0%) starting postoperatively within 72 hours p. Thirty-one (6.7%) patients showed Kidney Disease Improving Global Outcome AKI stage 3. AKI was significantly more frequent in patients with chronic kidney disease (p < 0.001), emergency admission (p < 0.001), heart failure (p < 0.001), and postoperative complications (p < 0.001). In a multivariate analysis, postoperative CS-AKI risk significantly decreased with each 1 or 10 mL/min preoperative glomerular filtration rate (GFR) (odds ratio, 0.962 and 0.677; 95% confidence interval, 0.947-0.977 and 0.577-0.793; p < 0.001 and p < 0.0001). Only in patients who developed Kidney Disease Improving Global Outcome AKI stage 3, an early postoperative trend to decreased GFR and increased creatinine levels was observed.

CONCLUSIONS

Especially in patients with preexisting CKD and signs of CS-AKI occurring on the day of surgery, close monitoring of renal function should be performed for at least 72 hours after CS to detect an onset of AKI early and initiate renal protective strategies. Optimal preoperative fluid management might prevent postoperative AKI.

Acute kidney injury among salicylate intoxication hospitalisations in the United States

BACKGROUND

This study aimed to evaluate the risk factors and the association of acute kidney injury (AKI) with outcomes, and resource utilisation in patients hospitalised because of salicylate intoxication in the United States.

METHODS

Hospitalised patients with a primary diagnosis of salicylate intoxication from 2003 to 2014 were identified in the National Inpatient Sample (NIS) database. End-stage kidney disease patients were excluded. The occurrence of AKI was identified using hospital diagnosis code. Clinical characteristics, in-hospital treatment, outcomes and resource utilisation were compared between patients with and without AKI.

RESULTS

A total of 13 787 eligible hospital admissions were included in the analysis. AKI occurred in 1279 (9.3%) admissions. Older age, male sex, more recent year of hospitalisation, anaemia, hypertension, congestive heart failure, chronic kidney disease, volume depletion, sepsis and ventricular arrhythmia/cardiac arrest were significantly associated with increased risk of AKI, whereas Hispanic race was associated with decreased risk. AKI was significantly associated with increased risk of organ failure, and in-hospital mortality. In addition, the need for ventilation support, blood component transfusion, renal replacement therapy, length of hospital stay and hospitalisation cost were higher in AKI patients.

CONCLUSION

Approximately one tenth of salicylate intoxication patients developed AKI during hospitalisation. AKI was associated with higher morbidity, mortality and resource utilisations.

Acute Kidney Injury After Heart Transplant: The Importance of Pulmonary Hypertension

OBJECTIVE

To determine whether relative pulmonary hypertension (PH), defined as the ratio of mean arterial pressure to mean pulmonary artery pressure, is associated with severe acute kidney injury (AKI) after heart transplant (HT).

DESIGN

An institutional review board-approved retrospective observational study.

SETTING

Tertiary care university hospital.

PARTICIPANTS

A total of 184 consecutive adult patients who underwent HT between January 2009 and December 2017 were included, and were followed up through December 2019. Using the Kidney Disease: Improving Global Outcomes classification, recipients were categorized into two groups: patients who developed stage 3 AKI (severe AKI) and those with minor or without AKI (nonsevere AKI) within seven days after transplant.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Of the included patients, 83.2% developed AKI, in whom 40.8%, 19.6%, and 22.8% were stage 1, 2, and 3, respectively. With use of the multivariate logistic regression analysis, independent risk factors for stage 3 AKI post-HT included preoperative relative PH (odds ratio [OR]: 1.62, 95% confidence interval [95% CI]: 1.05-2.49, p = 0.028), central venous-to-pulmonary capillary wedge pressure ratio ≥0.86 (OR: 3.59, 95% CI: 1.13-11.43, p = 0.030), and postoperative right ventricular dysfunction (OR: 3.63, 95% CI: 1.50-8.75, p = 0.004). Conversely, preoperative estimated glomerular filtration rate (OR: 0.99, 95% CI: 0.97-1.00, p = 0.143) was not related to the development of stage 3 AKI post-HT.

CONCLUSIONS

Preoperative relative PH, central venous-to-pulmonary capillary wedge pressure ratio, and postoperative right ventricular failure by echocardiographic assessment were associated with severe AKI post-HT.

Induction Immunosuppression and Renal Outcomes in Adult Heart Transplantation

BACKGROUND

This study explores the use of induction therapy in orthotopic heart transplantation as it relates to preoperative renal function and evaluates the impact of its utilization on post-transplant outcomes.

METHODS

We conducted a retrospective analysis using the United Network for Organ Sharing database from 2000 to 2018 evaluating the initiation of de novo dialysis after transplantation. We examined the relationship between induction immunosuppression and pre-transplant estimated glomerular filtration rate with post-transplant outcomes, accounting for inter-center variability through a mixed-effects logistic regression model.

RESULTS

In total, 16,201 patients were included with a median age of 57 y (interquartile range 47, 63); 26% were women (n = 4222) and 28% (n = 4552) had a history of diabetes mellitus. The median estimated glomerular filtration rate (eGFR) was 67.5 mL/min (interquartile range 53.1, 86.7); 51.2% (n = 3068) of the recipients with eGFR < 60 received induction therapy compared to 42.5% (n = 4336) within the eGFR ≥ 60 group (P < 0.001). Adjusted multivariable analysis found that induction therapy was associated with de novo dialysis (odds ratio 1.25, 95% confidence interval 1.10-1.43, P < 0.001), with the most significant effect on patients with eGFR ≥ 60. Although significant, there was a weak correlation between center-level induction utilization and mean eGFR (r = -0.2, P < 0.001).

CONCLUSION

In this analysis, the use of induction immunosuppression in orthotopic heart transplantation varied widely between centers and did not correlate strongly with pre-transplant eGFR. In addition, its utilization did not mitigate the risk of renal replacement therapy after transplantation and in fact was associated with increased risk even after adjusting for confounders most notably in patients with eGFR ≥ 60.

Role of Renal Replacement Therapy During the Peri-Transplant Period of Heart Transplantation

Background

Heart transplantation (HT) is the most useful treatment modality for heart failure. Although several studies have reported the impact of acute kidney injury (AKI) on clinical outcomes after transplantation, little is known about the impact of peri-transplant renal replacement therapy (RRT) on clinical outcomes. We compared the clinical outcomes according to RRT use status among patients with AKI during the peri-transplant period.

Material/Methods

The medical records of 21 patients who underwent HT from January 2006 to May 2019 were reviewed. We assessed the heart failure cause, comorbidities, immunosuppressant type, requirement for extracorporeal membrane oxygenation, AKI incidence, and cardiac and renal functions over time. The patients were divided into 3 groups: those without AKI (non-AKI group, n=6), those who underwent perioperative RRT (RRT group, n=10), and those who did not undergo RRT (non-RRT group, n=5).

Results

The most common cause of HT was dilated cardiomyopathy (52.4%). Fifteen patients (71.4%) experienced AKI during the peri-transplant period. Among them, 9 (90%) in the RRT group underwent continuous RRT and only 1 (10%) underwent intermittent hemodialysis. Until 6 months after HT, the renal function of the RRT group was worse than that of the non-RRT group (estimated glomerular filtration rate 44.2 vs. 69.2 mL/min/1.73 m², P=0.015), but the differences dissipated by 9 months. Finally, all patients, even in the RRT group, withdrew from dialysis.

Conclusions

RRT during the peri-transplant period in HT may be a good bridge therapy for renal function recovery in patients with cardiorenal AKI.

Incidence, risk factors and clinical outcomes of acute kidney injury after heart transplantation: a retrospective single center study

Objectives

This study aimed to identify the incidence rate of Acute kidney injury (AKI) in our center and predict in-hospital mortality and long-term survival after heart transplantation (HTx).

Methods

This single-center, retrospective study from October 2009 and March 2020 analyzed the pre-, intra-, and postoperative characteristics of 95 patients who underwent HTx. AKI was defined according to the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. Risk factors were analyzed by multivariable logistic regression models. The log-rank test was used to compare long-term survival.

Results

Thirty-three (34.7%) patients developed AKI. The mortality in hospital in HTx patients with and without AKI were 21.21 and 6.45%, respectively (P < 0.05). Recipients in AKI who required renal replacement therapy (RRT) had a hospital mortality rate of 43.75% compared to 6.45% in those without AKI or RRT (P < 0.0001). A long cardiopulmonary bypass (CPB) time (OR:11.393, 95% CI: 2.183 to 59.465, P = 0.0039) was positively related to the occurrence of AKI. A high intraoperative urine volume (OR: 0.031, 95% CI: 0.005 to 0.212, P = 0.0004) was negatively correlated with AKI. AKI requiring RRT (OR, 11.348; 95% CI, 2.418–53.267, P = 0.002) was a risk factor for mortality in hospital. Overall survival in patients without AKI at 1 and 3 years was not different from that in patients with AKI (P = 0.096).

Conclusions

AKI is common after HTx. AKI requiring RRT could contribute powerful prognostic information to predict mortality in hospital. A long CPB time and low intraoperative urine volume are associated with the occurrence of AKI.

A meta-analysis of the incidence rate of postoperative acute kidney injury in patients with congenital heart disease

Background

Acute kidney injury (AKI) is a common complication of cardiac surgery. However, the incidence rate of AKI in patients with congenital heart disease (CHD) greatly varies between reports owing to the different definitions used for AKI. Therefore, this study was designed as a meta-analysis aimed at summarizing the incidence rate of AKI in patients with congenital heart disease (CHD) on the basis of different AKI criteria.

Methods

Studies published till April 24, 2020, on the incidence rate of AKI in patients with CHD, were retrieved from electronic databases and printed literature. To pool data from the included studies, the effect size, a combined statistics, was chosen and presented with the incidence rate and 95% confidence interval (CI). Heterogeneity was evaluated using I² statistics and Cochran Q test. The incidence rates obtained from the subgroup analysis according to study location, type of surgery, type of cohort, age, and AKI criteria) were also evaluated to determine the correlation of AKI with these factors. Publication bias was estimated using the Egger test.

Results

Thirty studies, comprising 9925 patients with AKI who had CHD, were included. Overall, the pooled incidence rate of AKI in the patients with CHD was 38.4% (95% CI, 32.0–44.7%). However, the incidence rate was not significantly affected by gender, study location, type of surgery, type of cohort, and AKI criteria. Moreover, age was significantly associated with the incidence of AKI, and the incidence rate was higher in the patients aged < 1 month than in those aged 1 month to 18 years, < 18 years, and ≥ 18 years (P < 0.05).

Conclusions

In this study, the estimated incidence rate of AKI in patients with CHD was 38.4% and may be influenced by age. These findings highlight the importance of further investigation of the specific causes of and effective preventive measures for AKI.

Predicting Acute Kidney Injury after Cardiac Surgery by Machine Learning Approaches

Cardiac surgery-associated AKI (CSA-AKI) is common after cardiac surgery and has an adverse impact on short- and long-term mortality. Early identification of patients at high risk of CSA-AKI by applying risk prediction models allows clinicians to closely monitor these patients and initiate effective preventive and therapeutic approaches to lessen the incidence of AKI. Several risk prediction models and risk assessment scores have been developed for CSA-AKI. However, the definition of AKI and the variables utilized in these risk scores differ, making general utility complex. Recently, the utility of artificial intelligence coupled with machine learning, has generated much interest and many studies in clinical medicine, including CSA-AKI. In this article, we discussed the evolution of models established by machine learning approaches to predict CSA-AKI.

Diagnostics, Risk Factors, Treatment and Outcomes of Acute Kidney Injury in a New Paradigm

Acute kidney injury (AKI) is a common clinical condition among patients admitted in the hospitals. The condition is associated with both increased short-term and long-term mortality. With the development of a standardized definition for AKI and the acknowledgment of the impact of AKI on patient outcomes, there has been increased recognition of AKI. Two advances from past decades, the usage of computer decision support and the discovery of AKI biomarkers, have the ability to advance the diagnostic method to and further management of AKI. The increasingly widespread use of electronic health records across hospitals has substantially increased the amount of data available to investigators and has shown promise in advancing AKI research. In addition, progress in the finding and validation of different forms of biomarkers of AKI within diversified clinical environments and has provided information and insight on testing, etiology and further prognosis of AKI, leading to future of precision and personalized approach to AKI management. In this this article, we discussed the changing paradigms in AKI: from mechanisms to diagnostics, risk factors, and management of AKI.