Predicting outcomes in cardiac surgery: risk stratification matters?

Gait speed assessment as a prognostic tool for morbidity and mortality in vulnerable older adult patients following vascular surgery

INTRODUCTION

Predicting the risk associated with vascular surgery in older adult patients has become increasingly challenging, primarily due to limitations in existing risk assessment tools. This study aimed to evaluate the utility of gait speed, a clinical indicator of frailty, in enhancing the prediction of mortality and morbidity in older adult patients undergoing vascular surgery.

METHODS

A single-center prospective cohort study was conducted, involving older adult patients undergoing vascular surgery at four tertiary care hospitals between 2021 and 2022. Eligible patients were aged 80 years or older and scheduled for surgical treatment of peripheral arterial disease of the lower limbs (IIb Leriche-Le Fontaine). The primary factor of interest was gait speed, defined as taking more than 6 s to walk 5 meters. The primary outcomes were in-hospital postoperative mortality and major morbidity.

RESULTS

The cohort comprised 131 patients with a mean age of 82.8 ± 1.4 years, with 34 % being female. Before vascular surgery, 60 patients (46 %) were categorized as slow walkers. Slow walkers were more likely to be female (43 % vs. 25 %, p < 0.03) and diabetic (50 % vs. 28 %, p < 0.01). Among the patients, 30 (23 %) experienced the primary composite outcome of mortality or major morbidity following vascular surgery. After adjusting for the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP®) Surgical Risk Calculator, slow gait speed independently predicted the composite outcome (odds ratio: 3.05; 95 % confidence interval: 1.23 to 7.54).

CONCLUSIONS

Gait speed is a straightforward and effective test that can help identify a subgroup of frail older adult patients at an elevated and incremental risk of mortality and major morbidity after vascular surgery. While gait speed remains a valuable clinical indicator of frailty, it is important to recognize that the broader context of mobility plays a pivotal role in postoperative outcomes.

Prognostic implications of Global Leadership Initiative on Malnutrition-defined malnutrition in older patients who underwent cardiac surgery in China

BACKGROUND

The proportion of older patients who are candidates for cardiac surgery is increasing. Growing evidence has shown that malnutrition is associated with a poor prognosis after cardiac surgery. The present study aimed to investigate the prognostic implications of malnutrition defined by the Global Leadership Initiative on Malnutrition in older patients who underwent cardiac surgery.

METHODS

From November 2015 to January 2021, 401 older patients who underwent cardiac surgery were retrospectively enrolled and evaluated using the Global Leadership Initiative on Malnutrition criteria. The perioperative characteristics and clinical outcomes were collected. The independent risk factors for postoperative complications and overall survival were analyzed.

RESULTS

The prevalence of Global Leadership Initiative on Malnutrition-defined malnutrition was 22.7% in this study. Patients with Global Leadership Initiative on Malnutrition-defined malnutrition had higher risks of postoperative complications (65.9% vs 49.7%, P = .006) and poor overall survival (68.1% vs 83.9%, P = .0019). Global Leadership Initiative on Malnutrition-defined malnutrition was also related to a longer postoperative hospital stay and prolonged intensive care stay. Five factors were identified as independent risk factors for overall survival: Global Leadership Initiative on Malnutrition-defined malnutrition (P = .009), chronic heart failure (P = .007), atrial fibrillation (P = .029), operative time (P < .001) and hemoglobin (P = .044).

CONCLUSION

We demonstrated the prognostic implications of Global Leadership Initiative on Malnutrition-defined malnutrition in older patients who underwent cardiac surgery for the first time. This study highlights the necessity of using the Global Leadership Initiative on Malnutrition assessment in the comprehensive preoperative risk assessment of cardiac surgery.

Pre-operative kidney biomarkers and risks for death, cardiovascular and chronic kidney disease events after cardiac surgery: the TRIBE-AKI study

BACKGROUND

Soluble tumor necrosis factor receptor (sTNFR)1, sTNFR2, and plasma kidney injury molecule-1 (KIM-1) are associated with kidney events in patients with and without diabetes. However, their associations with clinical outcomes when obtained pre-operatively have not been explored.

METHODS

The TRIBE-AKI cohort study is a prospective, multicenter, cohort study of high-risk adults undergoing cardiac surgery. We assessed the associations between pre-operative concentrations of plasma sTNFR1, sTNFR2, and KIM-1 and post-operative long-term outcomes including mortality, cardiovascular events, and chronic kidney disease (CKD) incidence or progression after discharge.

RESULTS

Among 1378 participants included in the analysis with a median follow-up period of 6.7 (IQR 4.0-7.9) years, 434 (31%) patients died, 256 (19%) experienced cardiovascular events and out of 837 with available long-term kidney function data, 30% developed CKD. After adjustment for clinical covariates, each log increase in biomarker concentration was independently associated with mortality with 95% CI adjusted hazard ratios (aHRs) of 3.0 (2.3-4.0), 2.3 (1.8-2.9), and 2.0 (1.6-2.4) for sTNFR1, sTNFR2, and KIM-1, respectively. For cardiovascular events, the 95% CI aHRs were 2.1 (1.5-3.1), 1.9 (1.4-2.6) and 1.6 (1.2-2.1) for sTNFR1, sTNFR2 and KIM-1, respectively. For CKD events, the aHRs were 2.2 (1.5-3.1) for sTNFR1, 1.9 (1.3-2.7) for sTNFR2, and 1.7 (1.3-2.3) for KIM-1. Despite the associations, each of the biomarkers alone or in combination failed to result in robust discrimination on an absolute basis or compared to a clinical model.

CONCLUSION

sTNFR1, sTNFR2, and KIM-1 were independently associated with longitudinal outcomes after discharge from a cardiac surgery hospitalization including death, cardiovascular, and CKD events when obtained pre-operatively in high-risk individuals. Pre-operative plasma biomarkers could serve to assist during the evaluation of patients in whom cardiac surgery is planned.

Machine Learning in Cardiac Surgery: Predicting Mortality and Readmission

Predicting outcomes in open-heart surgery can be challenging. Unexpected readmissions, long hospital stays, and mortality have economic implications. In this study, we investigated machine learning (ML) performance in data visualization and predicting patient outcomes associated with open-heart surgery. We evaluated 8,947 patients who underwent cardiac surgery from April 2006 to January 2018. Data visualization and classification were performed at cohort-level and patient-level using clustering, correlation matrix, and seven different predictive models for predicting three outcomes ("Discharged," "Died," and "Readmitted") at binary level. Cross-validation was used to train and test each dataset with the application of hyperparameter optimization and data imputation techniques. Machine learning showed promising performance for predicting mortality (AUC 0.83 ± 0.03) and readmission (AUC 0.75 ± 0.035). The cohort-level analysis revealed that ML performance is comparable to the Society of Thoracic Surgeons (STS) risk model even with limited number of samples ( e.g. , less than 3,000 samples for ML versus more than 100,000 samples for the STS risk models). With all cases (8,947 samples, referred as patient-level analysis), ML showed comparable performance to what has been reported for the STS models. However, we acknowledge that it remains unknown at this stage as to how the model might perform outside the institution and does not in any way constitute a comparison of the performance of the internal model with the STS model. Our study demonstrates a systematic application of ML in analyzing and predicting outcomes after open-heart surgery. The predictive utility of ML in cardiac surgery and clinical implications of the results are highlighted.

Pre-operative physical performance as a predictor of in-hospital outcomes in older patients undergoing elective cardiac surgery

OBJECTIVE

Risk stratification of cardiac surgery patients is usually based on the Society of Thoracic Surgeons (STS) score, that has limited predictive value in older persons. We aimed assessing whether the Short Physical Performance Battery (SPPB) improves, beyond the STS score, assessment of hospital prognosis in older patients undergoing elective cardiac surgery.

METHODS

All patients aged 75+ years referred for elective cardiac surgery to Careggi University Hospital (Florence, Italy) from April 2013 to March 2017 were evaluated pre-operatively. Participants were classified according to the STS-Predicted Risk Of Mortality (STS-PROM): low (<4%), intermediate (4 to 8%), and high risk (>8%). Primary study outcomes were hospital mortality and STS-defined major morbidity. Length of hospital stay was an additional outcome.

RESULTS

Out of 235 participants (females: 46.5%; mean age: 79.6 years), 144 (61.3%) were at low, 67 (28.5%) at intermediate and 24 (10.2%) at high risk, based on the STS-PROM. SPPB (mean±SEM) was 8.8 ± 0.2, 7.0 ± 0.5, and 6.0 ± 0.8 in participants at low, intermediate, and high risk, respectively (p<0.001). The primary outcome occurred in 62 participants (26.4%). In low-risk participants, the SPPB score predicted the primary endpoint (adjusted OR 0.77, 95% CI 0.66-0.89 per each point increase; p<0.001) controlling for STS-Major Morbidity or Operative Mortality (STS-MM) score. This result was not observed in the intermediate-high risk group.

CONCLUSIONS

SPPB predicts mortality and major morbidity in older patients undergoing elective cardiac surgery, classified as low risk with the STS risk score. The SPPB, applied preoperatively, might improve risk stratification in older patients undergoing elective cardiac surgery.

Role of Frailty on Risk Stratification in Cardiac Surgery and Procedures

The number of older people candidates for interventional cardiology, such as PCI but especially for transcatheter aortic valve implantation (TAVI) , would increase in the future. Generically, the surgical risk, the amount of complications in the perioperative period, mortality and severe disability remain significantly higher in the elderly than in younger. For this reason it's important to determine the indication for surgical intervention, using tools able to predict not only the classics outcome (length of stay, mortality), but also those more specifically geriatrics, correlate to frailty: delirium, cognitive deterioration, risk of institutionalization and decline in functional status. The majority of the most used surgical risks scores are often specialist-oriented and many variables are not considered. The need of a multidimensional diagnostic process, focused on detect frailty, in order to program a coordinated and integrated plan for treatment and long term follow up, led to the development of a specific geriatric tool: the Comprehensive Geriatric Assessment (CGA). The CGA has the aim to improve the prognostic ability of the current risk scores to capture short long term mortality and disability, and helping to resolve a crucial issue providing solid clinical indications to help physician in the definition of on interventional approach as futile. This tool will likely optimize the selection of TAVI older candidates could have the maximal benefit from the procedure.

Risk Stratification for Transcatheter Aortic Valve Replacement

Risk assessment models developed from administrative and clinical databases are used for clinical decision making. Since these models are derived from a database, they have an inherent limitation of being as good as the data they are derived from. Many of these models under or overestimate certain clinical outcomes particularly mortality in certain group of patients. Undeniably, there is significant variability in all these models on account of patient population studied, the statistical analysis used to develop the model and the period during which these models were developed. This review aims to shed light on development and application of risk assessment models for cardiac surgery with special emphasis on risk stratification in severe aortic stenosis to select patients for transcatheter aortic valve replacement.

Predicting operative mortality in octogenarians for isolated coronary artery bypass grafting surgery: a retrospective study

Background

Available cardiac surgery risk scores have not been validated in octogenarians. Our objective was to compare the predictive ability of the Society of Thoracic Surgeons (STS) score, EuroSCORE I, and EuroSCORE II in elderly patients undergoing isolated coronary artery bypass grafting surgery (CABG).

Methods

All patients who underwent isolated CABG (2002 – 2008) were identified from the Alberta Provincial Project for Outcomes Assessment in Coronary Heart Disease (APPROACH) registry. All patients aged 80 and older (n = 304) were then matched 1:2 with a randomly selected control group of patients under age 80 (n = 608 of 4732). Risk scores were calculated. Discriminatory accuracy of the risk models was assessed by plotting the areas under the receiver operator characteristic (AUC) and comparing the observed to predicted operative mortality.

Results

Octogenarians had a significantly higher predicted mortality by STS Score (3 ± 2% vs. 1 ± 1%; p < 0.001), additive EuroSCORE (8 ± 3% vs. 4 ± 3%; p < 0.001), logistic EuroSCORE (15 ± 14% vs. 5 ± 6%; p < 0.001), and EuroSCORE II (4 ± 3% vs. 2 ± 2%; p < 0.001) compared to patients under age 80 years. Observed mortality was 2% and 1% for patients age 80 and older and under age 80, respectively (p = 0.323). AUC revealed areas for STS, additive and logistic EuroSCORE I and EuroSCORE II, respectively, for patients age 80 and older (0.671, 0.709, 0.694, 0.794) and under age 80 (0.829, 0.750, 0.785, 0.845).

Conclusion

All risk prediction models assessed overestimated surgical risk, particularly in octogenarians. EuroSCORE II demonstrated better discriminatory accuracy in this population. Inclusion of new variables into these risk models, such as frailty, may allow for more accurate prediction of true operative risk.

Emergent aortic surgery in octogenarians: is the advanced age a contraindication?

Surgery of both the ascending and descending aortic segments in the context of an acute aortic syndrome is one of the greatest challenges for the cardiac surgeon. In the case of surgery of the descending aorta, surgical risk increases due to the technical complexity, the required aggressive approach and because surgical indication is usually established as a result of complications and therefore involves, almost always, critically ill patients. The aging of the population is causing such surgery to be considered in an increasing number of octogenarians. The present review analyzes the available scientific evidence on the surgical indications and outcomes of these complex procedures in this population, particularly in the emergent scenario. Ascending and descending thoracic aortic diseases are reviewed separately, and the role of both the current risk scores and frailty assessments are comprehensively discussed.

Derivation and Validation of Prognosis-Based Age Cutoffs to Define Elderly in Cardiac Surgery

Background—

The age cutoff to define elderly is controversial in cardiac surgery, empirically ranging from ≥65 to ≥80 years. Beyond semantics, this has important implications as a starting point for clinical care pathways and inclusion in trials. We sought to characterize the relationship between age and adverse outcomes in patients undergoing cardiac surgery and to derive and validate prognosis-based age cutoffs.

Methods and Results—

Six thousand five hundred seventy one consecutive adult patients undergoing cardiac surgery at 3 hospitals in the United States and Canada were included in the cohort. Logistic regression models and generalized additive models with thin-plate splines were fit to the data. The age distribution was 50 to 59 years in 1244 (18.9%), 60 to 69 years in 2144 (32.6%), 70 to 79 years in 2000 (30.4%), ≥80 years in 1183 (18.0%) patients. After controlling for sex and type of operation, the relationship between age and 30-day operative mortality was found to be nonlinear. Receiver operating characteristic analysis showed that the optimal cutoffs to identify older patients at higher risk of operative mortality were greater than 74, 78, and 75 years for isolated coronary bypass, isolated valve surgery, and coronary bypass plus valve surgery, respectively. These age cutoffs were validated in an independent cohort.

Conclusions—

The relationship between age and operative mortality is not linear, manifesting a steeper rise after age 75 for coronary bypass and approaching octogenarian age for isolated valve surgery. Rather than using arbitrary age cutoffs to define elderly, the outcomes-based cutoff of ≥75 years should be used to identify the population of older adults that has higher risk and may benefit from preoperative geriatric evaluation and optimization.

Risk Prediction in Aortic Valve Replacement: Incremental Value of the Preoperative Echocardiogram

Background

Risk prediction is a critical step in patient selection for aortic valve replacement (AVR), yet existing risk scores incorporate very few echocardiographic parameters. We sought to evaluate the incremental predictive value of a complete echocardiogram to identify high‐risk surgical candidates before AVR.

Methods and Results

A cohort of patients with severe aortic stenosis undergoing surgical AVR with or without coronary bypass was assembled at 2 tertiary centers. Preoperative echocardiograms were reviewed by independent observers to quantify chamber size/function and valve function. Patient databases were queried to extract clinical data. The cohort consisted of 432 patients with a mean age of 73.5 years and 38.7% females. Multivariable logistic regression revealed 3 echocardiographic predictors of in‐hospital mortality or major morbidity: E/e’ ratio reflective of elevated left ventricular (LV) filling pressure; myocardial performance index reflective of right ventricular (RV) dysfunction; and small LV end‐diastolic cavity size. Addition of these echocardiographic parameters to the STS risk score led to an integrated discrimination improvement of 4.1% (P<0.0001). After a median follow‐up of 2 years, Cox regression revealed 5 echocardiographic predictors of all‐cause mortality: small LV end‐diastolic cavity size; LV mass index; mitral regurgitation grade; right atrial area index; and mean aortic gradient <40 mm Hg.

Conclusions

Echocardiographic measures of LV diastolic dysfunction and RV performance add incremental value to the STS risk score and should be integrated in prediction when evaluating the risk of AVR. In addition, findings of small hypertrophied LV cavities and/or low mean aortic gradients confer a higher risk of 2‐year mortality.

Caregiver status: a simple marker to identify cardiac surgery patients at risk for longer postoperative length of stay, rehospitalization, or death

BACKGROUND

Patients who have undergone cardiac surgery, especially those with greater comorbidities, may be cared for by family members or paid aides.

OBJECTIVE

The purpose of this study was to evaluate the association between having a caregiver among patients who underwent cardiac surgery and clinical outcomes at 1 year. We hypothesized that patients with a caregiver would have longer lengths of stay and higher rehospitalization or death rates 1 year after surgery.

METHODS

We studied 665 patients consecutively admitted for cardiac surgery as part of the Family Cardiac Caregiver Investigation To Evaluate Outcomes sponsored by the National Heart, Lung, and Blood Institute. The participants (mean age, 65 years; women, 35%; racial/ethnic minorities, 21%) completed an interviewer-assisted questionnaire to determine caregiver status. Outcomes were documented by a hospital-based information system; demographics/comorbidities, by electronic records. Associations between having a caregiver and outcomes were evaluated by logistic regression, adjusted for demographic and comorbid conditions.

RESULTS

At baseline, 28% of the patients (n = 183) had a caregiver (8%, paid; 20%, informal only). Having a caregiver was associated with longer (>7 days) postoperative length of stay in univariate analysis among the patients with paid (odds ratio [OR], 3.00; 95% confidence interval [CI], 1.57-5.74) or informal (OR, 1.55; 95% CI, 1.04-2.31) caregivers versus none; the association remained significant for the patients with paid (OR, 2.13; 95% CI, 1.00-4.55) but not with informal (OR, 1.12; 95% CI, 0.70-1.80) caregivers after adjustment. Having a paid caregiver was significantly associated with rehospitalization/death at 1 year in univariate analysis (OR, 2.09; 95% CI, 1.18-3.69); having an informal caregiver was not (OR, 1.39; 95% CI, 0.94-2.06). Increased odds of rehospitalization/death associated with having a paid caregiver attenuated after adjustment (OR, 1.39; 95% CI, 0.74-2.62).

CONCLUSIONS

The patients who underwent cardiac surgery who had a paid caregiver had a significantly longer length of stay independent of comorbidity. The increased risk of rehospitalization/death associated with having a paid caregiver was explained by demographics and comorbidity. These data suggest that caregiver status assessment may be a simple method to identify cardiac surgery patients at increased risk for adverse clinical outcomes.

Incremental value of the preoperative echocardiogram to predict mortality and major morbidity in coronary artery bypass surgery

BACKGROUND

Although echocardiography is commonly performed before coronary artery bypass surgery, there has yet to be a study examining the incremental prognostic value of a complete echocardiogram.

METHODS AND RESULTS

Patients undergoing isolated coronary artery bypass surgery at 2 hospitals were divided into derivation and validation cohorts. A panel of quantitative echocardiographic parameters was measured. Clinical variables were extracted from the Society of Thoracic Surgeons database. The primary outcome was in-hospital mortality or major morbidity, and the secondary outcome was long-term all-cause mortality. The derivation cohort consisted of 667 patients with a mean age of 67.2±11.1 years and 22.8% females. The following echocardiographic parameters were found to be optimal predictors of mortality or major morbidity: severe diastolic dysfunction, as evidenced by restrictive filling (odds ratio, 2.96; 95% confidence interval, 1.59-5.49), right ventricular dysfunction, as evidenced by fractional area change <35% (odds ratio, 3.03; 95% confidence interval, 1.28-7.20), or myocardial performance index >0.40 (odds ratio, 1.89; 95% confidence interval, 1.13-3.15). These results were confirmed in the validation cohort of 187 patients. When added to the Society of Thoracic Surgeons risk score, the echocardiographic parameters resulted in a net improvement in model discrimination and reclassification with a change in c-statistic from 0.68 to 0.73 and an integrated discrimination improvement of 5.9% (95% confidence interval, 2.8%-8.9%). In the Cox proportional hazards model, right ventricular dysfunction and pulmonary hypertension were independently predictive of mortality over 3.2 years of follow-up.

CONCLUSIONS

Preoperative echocardiography, in particular right ventricular dysfunction and restrictive left ventricular filling, provides incremental prognostic value in identifying patients at higher risk of mortality or major morbidity after coronary artery bypass surgery.

Frailty in Patients with Cardiovascular Disease: Why, When, and How to Measure

Frailty is a geriatric syndrome of impaired resistance to stressors due to a decline in physiologic reserve. Frailty and cardiovascular disease (CVD) share a common biological pathway, and CVD may accelerate the development of frailty. Frailty is identified in 25% to 50% of patients with CVD, depending on the frailty scale used and the population studied. Frail patients with CVD, especially those undergoing invasive procedures or suffering from coronary artery disease and heart failure, are more likely to suffer adverse outcomes as compared to their non-frail counterparts. Five-meter gait speed is a simple and effective way of objectively measuring frailty in patients with CVD and should be incorporated in risk assessment.

Poor performances of EuroSCORE and CARE score for prediction of perioperative mortality in octogenarians undergoing aortic valve replacement for aortic stenosis

BACKGROUND AND OBJECTIVE

Although results of cardiac surgery are improving, octogenarians have a higher procedure-related mortality and more complications with increased length of stay in ICU. Consequently, careful evaluation of perioperative risk seems necessary. The aims of our study were to assess and compare the performances of EuroSCORE and CARE score in the prediction of perioperative mortality among octogenarians undergoing aortic valve replacement for aortic stenosis and to compare these predictive performances with those obtained in younger patients.

METHODS

This retrospective study included all consecutive patients undergoing cardiac surgery in our institution between November 2005 and December 2007. For each patient, risk assessment for mortality was performed using logistic EuroSCORE, additive EuroSCORE and CARE score. The main outcome measure was early postoperative mortality. Predictive performances of these scores were assessed by calibration and discrimination using goodness-of-fit test and area under the receiver operating characteristic curve, respectively.

RESULTS

During this 2-year period, we studied 2117 patients, among whom 134/211 octogenarians and 335/1906 nonoctogenarians underwent an aortic valve replacement for aortic stenosis. When considering patients with aortic stenosis, discrimination was poor in octogenarians and the difference from nonoctogenarians was significant for each score (0.58, 0.59 and 0.56 vs. 0.82, 0.81 and 0.77 for additive EuroSCORE, logistic EuroSCORE and CARE score in octogenarians and nonoctogenarians, respectively, P < 0.05). Moreover, in the whole cohort, logistic EuroSCORE significantly overestimated mortality among octogenarians.

CONCLUSION

Predictive performances of these scores are poor in octogenarians undergoing cardiac surgery, especially aortic valve replacement. Risk assessment and therapeutic decisions in octogenarians should not be made with these scoring systems alone.

Gait speed as an incremental predictor of mortality and major morbidity in elderly patients undergoing cardiac surgery

OBJECTIVES

The purpose of this study was to test the value of gait speed, a clinical marker for frailty, to improve the prediction of mortality and major morbidity in elderly patients undergoing cardiac surgery.

BACKGROUND

It is increasingly difficult to predict the elderly patient's risk posed by cardiac surgery because existing risk assessment tools are incomplete.

METHODS

A multicenter prospective cohort of elderly patients undergoing cardiac surgery was assembled at 4 tertiary care hospitals between 2008 and 2009. Patients were eligible if they were 70 years of age or older and were scheduled for coronary artery bypass and/or valve replacement or repair. The primary predictor was slow gait speed, defined as a time taken to walk 5 m of ≥ 6 s. The primary end point was a composite of in-hospital post-operative mortality or major morbidity.

RESULTS

The cohort consisted of 131 patients with a mean age of 75.8 ± 4.4 years; 34% were female patients. Sixty patients (46%) were classified as slow walkers before cardiac surgery. Slow walkers were more likely to be female (43% vs. 25%, p = 0.03) and diabetic (50% vs. 28%, p = 0.01). Thirty patients (23%) experienced the primary composite end point of mortality or major morbidity after cardiac surgery. Slow gait speed was an independent predictor of the composite end point after adjusting for the Society of Thoracic Surgeons risk score (odds ratio: 3.05; 95% confidence interval: 1.23 to 7.54).

CONCLUSIONS

Gait speed is a simple and effective test that may identify a subset of vulnerable elderly patients at incrementally higher risk of mortality and major morbidity after cardiac surgery.

Validation of clinical scores predicting severe acute kidney injury after cardiac surgery

BACKGROUND

Acute kidney injury (AKI) requiring renal replacement therapy (RRT) in patients undergoing cardiac surgery is associated strongly with adverse patient outcomes. Recently, 3 predictive risk models for RRT have been developed. The aims of our study are to validate the predictive scoring models for patients requiring postoperative RRT and test applicability to the broader spectrum of patients with postoperative severe AKI.

STUDY DESIGN

Diagnostic test study.

SETTING & PARTICIPANTS

12,096 patients undergoing cardiac surgery with cardiopulmonary bypass at Mayo Clinic, Rochester, MN, from 2000 through 2007.

INDEX TEST

Cleveland Clinic score, Mehta score, and Simplified Renal Index (SRI) score.

REFERENCE TEST OR OUTCOME

Incidence of postoperative RRT or composite outcome of severe AKI, defined as serum creatinine level >2.0 mg/dL, and a 2-fold increase compared with the preoperative baseline creatinine level or RRT.

RESULTS

RRT was used in 254 (2.1%) patients, whereas severe AKI was present in 467 (3.9%). Discrimination for the prediction of RRT and severe AKI was good for all scoring models measured using areas under the receiver operating characteristic curve (AUROCs): 0.86 (95% CI, 0.84-0.88) for RRT and 0.81 (95% CI, 0.79-0.83) for severe AKI using the Cleveland score, 0.81 (95% CI, 0.78-0.86) and 0.76 (95% CI, 0.73-0.80) using the Mehta score, and 0.79 (95% CI, 0.77-0.82) and 0.75 (95% CI, 0.72-0.77) using the SRI score. The Cleveland score and Mehta score consistently showed significantly better discrimination compared with the SRI score (P < 0.001). Despite lower AUROCs for the prediction of severe AKI, the Cleveland score AUROC was still >0.80. The Mehta score is applicable in only a subgroup of patients.

LIMITATIONS

Single-center retrospective cohort study.

CONCLUSIONS

The Cleveland scoring system offers the best discriminative value to predict postoperative RRT and covers most patients undergoing cardiac surgery. It also can be used for prediction of the composite end point of severe AKI, which enables broader application to patients at risk of postoperative kidney dysfunction.