Risk stratification for adverse economic outcomes in cardiac surgery

Validation of SinoSCORE for isolated CABG operation in East China

From January 2010 to December 2016, 1616 consecutive patients who underwent isolated coronary artery bypass grafting (CABG) were evaluated for their predicted mortality according to the online Sino System for Coronary Operative Risk Evaluation (SinoSCORE), European System for Cardiac Operative Risk Evaluation II (EuroSCORE II) and Society of Thoracic Surgeons (STS) risk evaluation system. The calibration and discrimination in the total and in the subsets were assessed by the Hosmer-Lemeshow (H-L) statistics and by the C statistics respectively, to evaluate the efficiency of the three risk evaluation systems. The realized mortality was 1.92% (31/1616). The predictive mortality of SinoSCORE, EuroSCORE II and STS risk evaluation system were 1.35%, 1.74% and 1.05%, respectively. SinoSCORE achieved best discrimination. When grouping by risk, SinoSCORE also achieved the best discrimination in high-risk group, followed by STS risk evaluation system and EuroSCORE II while SinoSCORE and EuroSCORE II had excellent performance in low-risk group. In terms of calibration, SinoSCORE, EuroSCORE II and STS risk evaluation system all achieved positive calibrations (H-L: P > 0.05) in the overall population and grouped subsets. SinoSCORE achieved good predictive efficiency in East China patients undergoing isolated CABG and showed no compromise when compared with EuroSCORE II and STS risk evaluation system.

The Economics of Cardiac Surgery

Health care practitioners are under increasing pressure to identify and reduce the costs of their interventions. Cardiac surgical procedures have been studied extensively to determine which factors increase costs so the costs of future interventions can be reliably predicted. Knowing the cost components of surgical interventions identifies opportunities for increased efficiency and cost reduction. New technologic advances may initially defy cost reduction efforts until randomized controlled trials and cost analyses can be performed.

Assessment of the EuroSCORE risk scoring system for patients undergoing coronary artery bypass graft surgery in a group of Iranian patients

Background and Aims:

Previous studies around the world indicated validity and accuracy of European System for Cardiac Operative Risk Evaluation (EuroSCORE) risk scoring system we evaluated the EuroSCORE risk scoring system for patients undergoing coronary artery bypass graft (CABG) surgery in a group of Iranian patients.

Materials and Methods:

In this cohort 2220 patients more than 18 years, who were performed CABG surgery in Massih Daneshvari Hospital, from January 2004 to March 2010 were recruited. Predicted mortality risk scores were calculated using logistic EuroSCORE and Acute Physiology and Chronic Health Evaluation II (APACHE II) and compared with observed mortality. Calibration was measured by the Hosmer–Lemeshow (HL) test and discrimination by using the receiver operating characteristic (ROC) curve area.

Results:

Of the 2220 patients, in hospital deaths occurred in 270 patients (mortality rate of 12.2%). The accuracy of mortality prediction in the logistic EuroSCORE and APACHE II model was 89.1%; in the local EuroSCORE (logistic) was 91.89%; and in the local EuroSCORE support vector machines (SVM) was 98.6%. The area under curve for ROC curve, was 0.724 (95% confidence interval [CI]: 0.57–0.88) for logistic EuroSCORE; 0.836 (95% CI: 0.731–0.942) for local EuroSCORE (logistic); 0.978 (95% CI: 0.937–1) for Local EuroSCORE (SVM); and 0.832 (95% CI: 0.723–0.941) for APACHE II model. The HL test showed good calibration for the local EuroSCORE (SVM), APACHE II model and local EuroSCORE (logistic) (P = 0.823, P = 0.748 and P = 0.06 respectively); but there was a significant difference between expected and observed mortality according to EuroSCORE model (P = 0.033).

Conclusion:

We detected logistic EuroSCORE risk model is not applicable on Iranian patients undergoing CABG surgery.

Pexelizumab reduces death and myocardial infarction in higher risk cardiac surgical patients

BACKGROUND

Morbidity and mortality after coronary artery bypass graft surgery are directly related to specific preoperative risk factors. We assessed the influence of preoperative risk factors on the effect of pexelizumab, a C5 complement inhibitor, to reduce postoperative morbidity and mortality in this post hoc analysis of the Pexelizumab for Reduction in Myocardial Infarction and MOrtality in Coronary Artery Bypass Graft surgery (PRIMO-CABG) trial, a phase III double-blind, placebo-controlled study of 3,099 patients undergoing coronary artery bypass graft surgery with cardiopulmonary bypass.

METHODS

The composite endpoint of death or myocardial infarction or both through postoperative day 30 was examined in subpopulations of patients with pre-specified risk factors, which included diabetes mellitus, prior coronary artery bypass graft, urgent intervention, female sex, history of neurologic event, history of congestive heart failure, and two or more previous myocardial infarctions or a recent myocardial infarction. Stratified post hoc analyses were also performed on patients presenting with two or more and three or more of those risk factors.

RESULTS

Pexelizumab significantly reduced the incidence of the composite endpoint of death or myocardial infarction through postoperative day 30 by 28% in patients with two or more risk factors (p = 0.004) and 44% in patients with three or more risk factors (p < 0.001).

CONCLUSIONS

The C5 complement inhibitor, pexelizumab, reduced morbidity and mortality among high-risk patients undergoing coronary artery bypass grafting with cardiopulmonary bypass.

Surgeons' economic profiles: can we get the "right" answers?

Hospitals and payers use economic profiling to evaluate physician and surgeon performance. However, there is significant variation in the data sources and analytic methods that are used. We used information from a hospital's cardiac surgery and cost accounting information systems to create surgeon economic profiles. Three scenarios were examined: (1) surgeon modeled as fixed effect with no patient-mix adjustment; (2) surgeon modeled as fixed effect with patient-mix adjustment; (3) and surgeon modeled as random effect with patient-mix adjustment. We included 574 patients undergoing coronary artery bypass surgery at Baptist Medical Center, Oklahoma City, OK between July 1, 1995 and April 30, 1996. We found that profiles reporting unadjusted average surgeon costs may incorrectly identify high- and low-cost outliers. Adjusting for patient-mix differences and treating surgeons as random effects was the preferred approach. These results demonstrate the need for hospitals to reexamine their economic profiling methods.

Renal function after cardiac surgery: adverse effect of furosemide

Renal failure is a frequent event after cardiopulmonary by-pass. Hemodynamic alterations that occur during surgery, as well as factors depending on the host, are the main risk factors for renal dysfunction. To evaluate the frequency and risk factors for renal dysfunction in this setting, a cohort of fifty patients with preoperative serum creatinine under 1.5 mg/dL, submitted to cardiac surgery with cardiopulmonary by-pass was analyzed. Variables related to preoperative patient condition, intraoperative and postoperative periods were recorded. Renal function was assessed by clearances of creatinine, urea and free water, also by fractional excretion of sodium (FENa), at baseline, at anesthetic induction and during postoperative period. Patients were arbitrarily divided in two groups, according to the serum creatinine (S(Cr)) value at the end of the postoperative period: Group 1: S(Cr) < 2 mg/dL (n = 44 patients (88.5%)) and Group II: S(Cr) > 2 mg/dL (n = 6 patients (11.5%)). A decrease of renal function was observed in all patients: creatinemia raised from 1.04 +/- 0.2 to 1.55 +/- 0.4 mg/dL (33%), associated with a rise in FENa. Differences between group I and group II using univariate analysis were: baseline serum creatinine (1.01 +/- 0.23 mg/dL vs. 1.26 +/- 0.19 mg/dL, p = 0.03), FENa (0.99 +/- 0.8 vs. 2.2 +/- 2.1, p = 0.04), furosemide dose during surgery normalized to body surface area (93.2 +/- 23 mg/1.73 m2 BSA vs. 135 +/- 38 mg/1.73 m2 BSA, p < 0.001), and hemodilution index (17.3 +/- 4.3% vs. 22.8 +/- 3.2%, p < 0.01). In the multiple regression model, baseline creatinemia and furosemide dose were associated to renal dysfunction.

Validation of four different risk stratification systems in patients undergoing off-pump coronary artery bypass surgery: a UK multicentre analysis of 2223 patients

BACKGROUND

Various risk stratification systems have been developed in coronary artery bypass graft surgery (CABG), based mainly on patients undergoing procedures with cardiopulmonary bypass.

OBJECTIVE

To assess the validity and applicability of the Parsonnet score, the EuroSCORE, the American College of Cardiology/American Heart Association (ACC/AHA) system, and the UK CABG Bayes model in patients undergoing off-pump coronary artery bypass surgery (OPCAB) in the UK.

METHODS

Data on 2223 patients who underwent OPCAB in eight cardiac surgical centres were collected. Predicted mortality risk scores were calculated using the four systems and compared with observed mortality. Calibration was assessed by the Hosmer-Lemeshow (HL) test. Discrimination was assessed using the receiver operating characteristic (ROC) curve area.

RESULTS

30 of 2223 patients (1.3%) died in hospital. For the Parsonnet score the HL test was significant (p < 0.001) and the receiver operating characteristic curve (ROC) area was 0.74. For the EuroSCORE the HL test was also significant (p = 0.008) and the ROC area was 0.75. For the ACC/AHA system the HL test was non-significant (p = 0.7) and the ROC area was 0.75. For the UK CABG Bayes model the HL test was also non-significant (p = 0.3) and the ROC area was 0.81.

CONCLUSIONS

The UK CABG Bayes model is reasonably well calibrated and provides good discrimination when applied to OPCAB patients in the UK. Among the other three systems, the ACC/AHA system is well calibrated but its discrimination power was less than for the UK CABG Bayes model. These data suggest that the UK CABG Bayes model could be an appropriate risk stratification system to use for patients undergoing OPCAB in the UK.

Hospital variability in length of stay after coronary artery bypass surgery: results from the Society of Thoracic Surgeon's National Cardiac Database

BACKGROUND

There is growing interest in comparing resource, as well as patient outcome metrics among coronary artery bypass graft surgery (CABG) providers, yet few tools exist for adjusting these provider comparisons for patient case-mix. In this study, we aimed to define the magnitude of hospital variability in postoperative length of stay (PLOS) in contemporary practice and to determine the degree to which this variability was accounted for by differences in patient case-mix. We also sought to determine the relationship between hospitals' risk-adjusted PLOS and mortality outcomes.

METHODS

We analyzed 496,797 isolated CABG procedures performed between January 1997 to January 2001 at 587 US hospitals participating in the Society of Thoracic Surgeon's National Cardiac Database. Logistic and linear regression were used to identify independent preoperative factors affecting a patient's likelihood for early discharge (PLOS < or = 5 day), prolonged stay (> 14 days), and overall PLOS. Hierarchical models were used to determine the degree to which hospital factors influenced PLOS beyond patient factors.

RESULTS

Overall, 53% of CABG patients were discharged within 5 days of CABG, whereas 5% required prolonged (> 14 days) stays. More than 25 preoperative patient factors were independently associated with a patients' likelihood for early discharge and prolonged stay (model C index 0.70 and 0.75, respectively). After adjusting for patient factors, however, there remained wide unexplained variability among hospitals in PLOS and limited correlation between these PLOS metrics and hospitals' risk-adjusted mortality results (Spearman correlation coefficient -0.15 and 0.35).

CONCLUSIONS

Our study provides a method for institutions to receive meaningful risk-adjusted bypass PLOS information. Given the marked variability among hospitals in CABG PLOS, institutions should consider benchmarking metrics of efficiency, as well as patient outcomes.

Inaccuracy of four coronary surgery risk-adjusted models to predict mortality in individual patients

OBJECTIVES

This study was undertaken to evaluate the accuracy of four different risk-adjusted models in predicting mortality in individual patients who are undergoing coronary artery by-pass graft surgery. In the last decade several models to stratify patients before open heart surgery, according to factors affecting mortality, were developed with the aim of retrospectively comparing outcomes of open heart surgery, based on reliable stratification of case-mix, and of prospectively identifying high risk patients as a basis for a meaningful informed consent for patients counseling.

METHODS

The pre-operative risk of death was calculated with four different models in 418 consecutive patients who underwent coronary artery by-pass surgery and then compared with the actual outcome. To discriminate patients with favorable and unfavorable outcome, the logistic regression analysis and the areas under the receiver-operating-characteristic curves were applied. The accuracy score was used to evaluate the reliability of each score to predict the individual outcome.

RESULTS

Seven deaths (1.7%) were observed within 30 days from the operation, and the overall incidence was similar to that predicted by all models. Only the NBI score was not able to discriminate survivors from patients who will die, and the areas under the curves were 0.596 for the Parsonnet score, 0.861 for the Cleveland Clinic Foundation score, 0.823 for the French score, and 0.806 for the EuroSCORE. The four models were highly accurate (between 0.97 and 0.98) to predict the overall mortality. In seven patients who died the mean predictive scores were very low and ranged between 2.1 and 4.6, but were significantly higher than those of patients who survived (between 1.1 and 2.2).

CONCLUSIONS

The four pre-surgical predictive models were similarly able to discriminate favorable vs. unfavorable outcomes and highly accurate to predict overall mortality, but very inaccurate to predict mortality in individual patients.

Variability in cost of coronary bypass surgery in New York State: potential for cost savings

OBJECTIVE

Previous analyses of variability in bypass resource use have not focused on hospital-level variation or adequately explored the influence of patient risk. We combined a clinical database with claims data to fully characterize patient level and hospital level variability in bypass surgery cost and length of stay in New York State and explored the extent to which lower cost is associated with worse quality of care.

METHODS

By use of 1992 clinical and claims data, we identified by multivariable regression which patient characteristics influence bypass cost and length of stay. Hospital was then incorporated as a random variable in mixed linear models to determine its impact on resource use. The relationship between risk-adjusted in-hospital mortality and cost was then explored.

RESULTS

In the 21 hospitals for which cost data were available, mean leveled cost (exclusive of professional fees and noncomparable costs) was $15,713, with a mean length of stay of 14 days (n = 12,087). One fifth of the variation in resource use was explained by baseline patient risk. After adjustment for patient risk, hospital explained an additional 42% of variation in cost and an additional 8% of variation in length of stay. Among hospitals, risk-adjusted cost varied almost 3-fold and risk-adjusted length of stay varied 50%. There was no association between cost and in-hospital mortality.

CONCLUSIONS

As of 1992, there was considerable interhospital variability in bypass surgery cost after patient baseline risk was accounted for. This suggests that reductions in bypass cost could be achieved by normalizing clinical practice.

Preoperative correlates of the cost of coronary artery bypass graft surgery: comparison of results from three hospitals

This article furthers our understanding of the cost of coronary artery bypass graft (CABG) surgery by analyzing the extent to which preoperative correlates of cost differ among hospitals. A total of 2828 patient who underwent bypass surgery at 3 hospitals (2 teaching and 1 nonteaching) were analyzed. The preoperative correlates of direct variable cost (marginal cost) were determined by ordinary least squares regression. Age, urgent/emergent surgical priority, previous CABG, and chronic obstructive pulmonary disease (COPD) were significant contributors (P < .05) to cost in all hospitals, but overall, there were many differences. The major contributor to cost was non-white race (31.3%) at teaching hospital A, previous CABG (30.5%) at teaching hospital B, and preop insertion of intra-aortic balloon pump (IABP) (35.9%) at the nonteaching hospital. The number of significant risk factors also differed. Preoperative characteristics that contribute to cost can be quite different among hospitals and therefore results from one hospital cannot be broadly generalized to others.

Early discharge after coronary artery bypass graft surgery: are patients really going home earlier?

OBJECTIVE

This study was undertaken to determine whether early discharge after coronary artery bypass grafting allows patients to return home earlier or merely increases the use of outpatient nursing and inpatient rehabilitation services.

METHODS

Patterns of discharge were analyzed in 407 patients undergoing bypass grafting in 1990, when there were no early extubations or fast track protocols, and compared with 379 patients in 1998, when these protocols were used.

RESULTS

Patients in 1998 had a higher prevalence of class IV angina (35.3% vs 22.8%; P =.006), urgent/emergency surgery (58.3% vs 44.9%; P =.015), and lower ejection fractions (48.9% +/- 16.4% vs 52.9% +/- 13.5%; P =.0002). Despite these increased risk factors, 1998 patients spent less time receiving ventilatory support (10.2 +/- 9.2 vs 26.7 +/- 15.7 hours; P <.001) and had a shorter length of stay (5.4 +/- 2.5 vs 9.2 +/- 4.3 days; P <.001). However, fewer 1998 patients were discharged home (56.7% vs 97.0%; P <.0001). A higher percentage of 1998 patients (43.3% vs 2.9%; P <.00001) were discharged to extended care facilities where their average length of stay was 10.6 +/- 15.1 days. Readmission to the Boston Medical Center was also more common in 1998 patients (5.3% vs 0.5%; P <.0001).

CONCLUSIONS

Early extubation and fast track protocols have resulted in earlier discharge from acute care facilities. However, the anticipated earlier return to home has been offset by the increased use of outpatient nursing services, discharges to extended care facilities, and hospital readmissions.

Perioperative predictors of ICU and hospital costs in coronary artery bypass graft surgery

STUDY OBJECTIVE

Economic forces have precipitated intense interest in cost-saving practices for patients undergoing coronary artery bypass grafting (CABG). While several preoperative variables have been implicated in higher costs, few studies have included perioperative factors. This study evaluated the predictive power of a preoperative mortality risk measurement (Parsonnet score) and of early extubation (< or = 6 h from ICU admission) in determining ICU and hospital costs.

DESIGN

Multivariate correlational design.

SETTING

University hospital in a large metropolitan area.

PATIENTS

All patients (n = 116) undergoing isolated CABG during a 6-month period were studied after the introduction of a clinical pathway.

MEASUREMENTS AND RESULTS

Clinical data were collected. Costs data were obtained retrospectively from the institutional data system and were derived from individual patient charges by application of department-specific cost-to-charge ratios. In multivariate logistic regression, Parsonnet score (per point odds ratio [OR], 1.09; confidence interval [CI], 1.03 to 1.17), in-hospital coronary angiography (OR, 3.51; CI, 1.23 to 10.01), delayed extubation (OR, 4.59; CI, 1.29 to 16.29), and presence of arrhythmia (OR, 3.50; CI, 1.15 to 10.64) were independent predictors of ICU costs. Only Parsonnet score (OR, 1.09; CI, 1.03 to 1.15) and cardiopulmonary bypass time (OR, 1.01; CI, 1.00 to 1.02) were independent predictors of hospital costs.

CONCLUSIONS

The Parsonnet score is a useful indicator of both ICU and hospital costs. Early extubation is associated with decreased ICU costs, but is not independently predictive of hospital costs.

Economic outcome of off-pump coronary artery bypass surgery: a prospective randomized study

BACKGROUND

Emphasis on cost containment in coronary artery bypass surgery is becoming increasingly important in modern hospital management. The revival of interest in off-pump (beating heart) coronary artery bypass surgery may influence the economic outcome. This study examines these effects.

METHODS

Two hundred patients undergoing first-time coronary artery bypass surgery were prospectively randomized to either conventional cardiopulmonary bypass and cardioplegic arrest or off-pump surgery. Variable and fixed direct costs were obtained for each group during operative and postoperative care. The data were analyzed using parametric methods.

RESULTS

There was no difference between the groups with respect to pre- and intraoperative patient variables. Off-pump surgery was significantly less costly than conventional on-pump surgery with respect to operating materials, bed occupancy, and transfusion requirements (total mean cost per patient: on pump, $3,731.6+/-1,169.7 vs off-pump, $2,615.13+/-953.6; p < 0.001). Morbidity was significantly higher in the on-pump group, which was reflected in an increased cost.

CONCLUSIONS

Off-pump revascularization offers a safe, cost-effective alternative to conventional coronary revascularization with cardiopulmonary bypass and cardioplegic arrest.