Improvement In Cardiac Surgery Program Research Articles

Completeness of coronary revascularization and survival: Impact of age and off-pump surgery

We conducted a multicenter observational cohort study of the effect of completeness of revascularization on long-term survival after coronary artery bypass grafting. We also investigated the impact of age and off-pump surgery. The Veterans Affairs Continuous Improvement in Cardiac Surgery Program was used to identify all patients (N=41,139) with left main and 3-vessel coronary artery disease who underwent nonemergency coronary artery bypass grafting from October 1997 to April 2011. The primary outcome measure, all-cause mortality, was compared between patients with complete revascularization and patients with incomplete revascularization. Survival functions were estimated with the Kaplan-Meier method and compared by using the log-rank test. Propensity scores calculated for each patient were used to match 5509 patients undergoing complete revascularization to 5509 patients undergoing incomplete revascularization. A subgroup analysis was performed in patients aged at least 70 years and patients who underwent off-pump coronary artery bypass grafting. In the unmatched groups, several risk factors were more common in the incomplete revascularization group, as was off-pump coronary artery bypass grafting. In the matched groups, risk-adjusted mortality was higher in the incomplete revascularization group than in the complete revascularization group at 1 year (6.96% vs 5.97%; risk ratio [RR], 1.17; 95% confidence interval [CI], 1.01-1.34), 5 years (18.50% vs 15.96%; RR, 1.16; 95% CI, 1.07-1.26), and 10 years (32.12% vs 27.40%; RR, 1.17; 95% CI, 1.11-1.24), with an overall hazard ratio of 1.18 (95% CI, 1.09-1.28; P<.0001). The hazard ratio for patients aged 70 years or more was 1.125 (95% CI, 1.001-1.263; P=.048). The hazard ratio was 1.47 (95% CI, 1.303-1.655) for the unmatched off-pump coronary artery bypass grafting group and 1.156 (95% CI, 1.000-1.335) for the matched off-pump coronary artery bypass grafting group. Incomplete revascularization is associated with decreased long-term survival, even in elderly patients. Surgeons should consider these findings when choosing a revascularization strategy, particularly if off-pump coronary artery bypass grafting is contemplated.

The Eyeball Test

As physicians, we strive to provide the most appropriate care for our patients and to provide them with accurate assessments of both the risks and benefits they can expect to realize. Unfortunately, as humans, we are notoriously bad at estimating risk.1,2 However, as the choices of treatments for cardiac disease expand, accurate assessment of risk becomes increasingly important. A patient with coronary artery disease may have the option of medical therapy, coronary artery bypass grafting, or percutaneous intervention. Transcatheter aortic valve replacement may soon be a viable alternative to surgical aortic valve replacement for patients with aortic valve disease. For patients to be able to make the choice that best suits their goals, they must have accurate information regarding risks and benefits. Article see p 151 In the current article, Jain et al3 compared cardiac surgeons’ assessments of mortality after coronary artery bypass grafting and valve surgery and that calculated from the Veterans Affairs Continuous Improvement in Cardiac Surgery Program (VA CICSP) risk model with actual mortality rates. The focus of the study was perioperative mortality; however, 1- and 5-year mortality rates were also considered. Although neither the statistical risk model nor surgeon estimates were perfect, the risk models performed somewhat better at all time points. Both the risk models and the surgeons’ estimates were better at estimating perioperative mortality than they were at estimating late mortality. These findings are informative and may help us to improve our estimates of procedural risk. When examining the predictive validity of a risk model (or surgeons’ estimates), 2 factors are regularly used: calibration and discrimination. Calibration measures to what degree the model assigns risk to the population, or in a population of 100 patients with an estimated mortality risk of 3%, were there 3 observed deaths? The current article …

Performing Coronary Artery Bypass Grafting Off-Pump May Compromise Long-Term Survival in a Veteran Population

There are ample data regarding the short-term outcomes of on-pump and off-pump coronary artery bypass grafting (CABG), but little is known about the long-term survival associated with these approaches. Using the Veterans Affairs (VA) Continuous Improvement in Cardiac Surgery Program, we identified all VA patients (n = 65,097) who underwent primary isolated CABG from October 1997 to April 2011. The primary outcome measure was all-cause mortality. Age, 17 preoperative risk factors, and year of operation were used to calculate propensity scores for each patient. A greedy-match algorithm using the propensity scores matched 8,911 off-pump with 26,733 on-pump patients. Survival functions were estimated by the Kaplan-Meier method and compared by using the log-rank test. In the complete cohort, off-pump was used in 11,629 of 65,097 (17.9%) operations. For the matched cohort, the median follow-up was 6.7 years (interquartile range, 3.72 to 9.35 years). Risk-adjusted mortality did not differ significantly between the off-pump and on-pump groups at 1 year (4.67% vs 4.78%; risk ratio [RR], 0.98; 95% confidence interval [CI], 0.88 to 1.09) or 3 years (9.21% vs 8.89%; RR, 1.04; 95% CI, 0.96 to 1.12). However, risk-adjusted mortality was higher in the off-pump group at 5 years (14.47% vs 13.45%; RR, 1.08; 95% CI 1.02 to 1.15) and 10 years (25.18% vs 23.57%; RR, 1.07; 95% CI, 1.03 to 1.12). Overall, the hazard ratio for off-pump vs on-pump was 1.06 (95% CI, 1.00 to 1.13; p = 0.04). Off-pump CABG may be associated with decreased long-term survival. Further studies are needed to identify the reasons behind this finding.

Invited Commentary

This study by Okada and colleagues [1Okada K. Omura A. Kano H. et al.Short and midterm outcomes of elective total aortic arch replacement combined with coronary artery bypass grafting.Ann Thorac Surg. 2012; 94: 530-536Abstract Full Text Full Text PDF PubMed Scopus (11) Google Scholar] presents a large (n = 200) institutional experience with total aortic arch replacement (TAR) performed to treat nondissecting aneurysm. The 30-day mortality for the entire cohort was remarkably low at 0.5%, and hospital mortality was 3.5%. The authors examined the surgical outcomes of TAR with and without coronary artery bypass grafting (CABG). Unadjusted outcomes for the patients who underwent both TAR and CABG included higher operative mortality, lower survival, and a higher incidence of major cardiac and cerebrovascular events. Although CABG was associated with prolonged operative times—reflecting the greater complexity of a combined procedure—only operative time emerged as an important independent predictor of both perioperative and mid-term mortality. In established cardiac risk models, including the STS model and the Veterans Affairs Continuous Improvement in Cardiac Surgery Program, the addition of CABG to valve procedures increases risk independently of other patient-related comorbidities. In fact, in the Japanese thoracic aortic surgery model (cited by the authors as reference 9), the addition of unexpected CABG to a thoracic aortic procedure was independently associated with increased 30-day mortality, and the addition of any CABG was associated with an increased rate of the composite outcome of major morbidity and mortality. Beyond the immediate perioperative risk posed by CABG, coronary artery disease is a clearly an additional life-limiting disease that is palliated by CABG but perhaps not cured. Therefore, one would expect the TAR-plus-CABG cohort to have worse long-term survival than the TAR-only cohort. Although this study had an impressive sample size for a single-center TAR series, the number of patients and events is small; therefore, the study might not have had enough power to detect any increase in risk caused by the addition of CABG to TAR. The confidence intervals in some instances are wide and in others approach or encompass 1.0. Regardless of how concomitant CABG might affect TAR outcomes, this study serves as a good example of the excellent short- and mid-term outcomes achieved in modern-day TAR performed at an experienced center. These results set the bar high for emerging endovascular and hybrid approaches to treating aortic arch aneurysms. Short and Midterm Outcomes of Elective Total Aortic Arch Replacement Combined With Coronary Artery Bypass GraftingThe Annals of Thoracic SurgeryVol. 94Issue 2PreviewThis study was performed to investigate the early and late outcomes of total aortic arch replacement (TAR) with or without coronary artery bypass grafting (CABG). Full-Text PDF

Predicting Mortality in High-Risk Coronary Artery Bypass: Surgeon Versus Risk Model

Risk models are useful in evaluating and comparing surgical outcomes, but surgeons may not always agree with the risk estimates derived from these models, particularly in high-risk cases. We examined the concordance between surgeons' and a risk model's predictions of operative mortality in high-risk coronary artery bypass grafting (CABG) patients, and we attempted to identify the reasons for any discrepancies. From the Veterans Affairs Continuous Improvement in Cardiac Surgery Program (CICSP), a prospective database and cardiac surgery risk model, we obtained data regarding 181 high-risk, isolated CABG cases performed at a single institution between April 1998 and April 2008. Cases were considered high risk if the surgeon estimated the patient's operative mortality risk to be ≥ 10%. We compared the mortality predictions made by surgeons and the risk model by using the signed-rank test and investigated cases in which there was a significant discrepancy (at least 2-fold) between the two predictions. The observed 30-d/in-hospital and 180-d mortality rates were 6.1% (11/181) and 11.0% (20/181), respectively. The mean operative mortality prediction made by surgeons (12.0% ± 5.3%) was higher than that made by the risk model (7.5% ± 8.5%) (P < 0.001). There was significant discrepancy between the surgeon and risk model estimates in 62% (113/181) of cases. In 53% (60/113) of these cases, the surgeon reported having considered risk factors not included in the CICSP model, including (most commonly) possible need for an additional procedure (n = 15), compromised mobility (n = 11), liver disease (n = 9), hematologic or immunologic disease (n = 6), and quality of targets (n = 5). In high-risk CABG cases, surgeon and CICSP risk estimates often disagreed markedly, partly because some disease entities of concern to surgeons are not included in the risk model. The higher mortality risk estimated by the surgeons is a better reflection of the considerable mortality risk that extends up to 180 days after surgery.

Outcomes of circulatory arrest procedures for the treatment of thoracic aortic disease at a veterans facility

BackgroundThe outcomes of thoracic aortic surgery involving hypothermic circulatory arrest at a US Department of Veterans Affairs medical center were evaluated. MethodsUsing the Veterans Affairs Continuous Improvement in Cardiac Surgery Program, all thoracic aortic operations performed with hypothermic circulatory arrest between December 1999 and December 2009 were identified (n = 24). Operative mortality and morbidity were evaluated, and survival was assessed by using the Kaplan-Meier method. ResultsAortic dissection was the underlying disease in 10 patients (42%). Full or hemiarch aortic repair was performed in 16 patients (67%); of these operations, 3 (13%) involved elephant trunk repair. There was 1 operative death (4%). Four patients (17%) had strokes (all but 1 fully recovered), and 1 (4%) had renal failure. The survival rate was 90% at 1 year and 67% at 3 years. ConclusionsDespite the magnitude and risk of thoracic aortic surgery involving hypothermic circulatory arrest, good outcomes can be achieved when such surgery is performed at an experienced Veterans Affairs center.

Is an Age of 80 Years or Greater an Important Predictor of Short-Term Outcomes of Isolated Aortic Valve Replacement in Veterans?

There is a popular perception that aortic valve replacement (AVR) in octogenarians carries a high risk related primarily to advanced age. Using the Department of Veterans Affairs Continuous Improvement in Cardiac Surgery Program, we identified patients who underwent AVR between 1991 and 2007. A prediction model was constructed using stepwise logistic regression methodology for outcome comparisons. Compared with younger patients (age < 80 years; n = 6,638), older patients (age > or = 80; n = 504) had a higher prevalence of baseline comorbidities. In a comparison of patients propensity-matched by risk profile (459 from each group), the older group had a higher morbidity rate (21.1% vs 15.5%; p < 0.03) but a similar mortality rate (5.2% vs 3.3%; p = 0.19) compared with the younger group. After risk adjustment, age of 80 years or greater was independently associated with higher AVR-related morbidity but not mortality. Further work is needed to identify ways to reduce operative morbidity in the extremely elderly.

Aortic Valve Replacement: Mortality Predictions of Surgeons Versus Risk Model

We compared the abilities of surgeons and of an established risk model to predict operative mortality after aortic valve replacement (AVR), and we investigated scenarios that give rise to discrepancies between these predictions. We reviewed all AVR procedures performed at a Veterans Affairs institution between 1993 and 2008 (n = 317). The abilities of the Continuous Improvement in Cardiac Surgery Program (CICSP) risk model and of the surgeons to predict operative mortality were assessed by computing the area under the receiver operating characteristic curve (AUC). We investigated cases in which there was a significant discrepancy (2-fold or greater) between the surgeons' and the CICSP model's predictions. The predictive abilities of both the surgeons and the CICSP risk model were good-AUC values were 0.73 and 0.75, respectively (P = 0.84)-but the surgeons' mean estimate of mortality risk (8.3% +/- 8.3%) exceeded both the CICSP model's estimate (6.6% +/- 8.3%) (P < 0.0001) and the actual mortality rate (5.4%). There was significant discrepancy between the two sources of prediction in 38% (122/317) of cases. In this subset of cases, the CICSP did not adjust for factors that influenced risk stratification by the surgeon in 33% (40/122) of cases; the most common of these factors were anticipation of a more extensive procedure, severe pulmonary disease other than chronic obstructive pulmonary disease, hepatic disease, and pulmonary hypertension. Both surgeons and the CICSP model performed well in risk-stratifying AVR patients, but the surgeons tended to overestimate the risk. The CICSP model did not capture some disease entities considered relevant in estimating mortality by surgeons.

Operative Mortality after Aortic Valve Replacement: Predictions Made by Surgeons versus Risk Model

Background: Risk models are useful tools for computing risk-adjusted outcomes. However, the models are only as good as the data on which they are based and therefore have limitations. Our aim was to compare the abilities of surgeons and an established risk model to predict operative mortality after aortic valve replacement (AVR). We also investigated scenarios that give rise to discrepancies between surgeons' and the risk model's predictions. Methods: The Veterans Affairs Continuous Improvement in Cardiac Surgery Program (CICSP) is a prospective database and a well-validated cardiac surgery risk model.

Contemporary outcomes of open thoracic aortic surgery in a veteran population: do risk models exaggerate mortality?

Background We evaluated contemporary outcomes of open thoracic aortic surgery at a Veterans Affairs (VA) medical center affiliated with a major academic aortic program and examined the predictive value of 2 established cardiac risk models. Methods We retrospectively reviewed all open thoracic aortic operations performed between April 1998 and April 2008 (n = 100). Both the EuroSCORE and the VA Continuous Improvement in Cardiac Surgery Program (CICSP) scores were evaluated. Results Procedures included ascending aortic repair (n = 74, 15 with arch repair), descending thoracic repair (n = 11, 1 with arch repair), and thoracoabdominal aortic repair (n = 15). Emergency surgery was necessary in 15 cases, and 19 procedures were reoperations. The patients' logistic EuroSCORE and the CICSP scores were similar (18.7% and 18.2%, respectively), but both scores significantly exceeded the observed operative mortality rate (8.0%, P = .008). Conclusions Good outcomes can be achieved when thoracic aortic surgery is performed at an experienced VA center. The cardiac risk models we examined overpredicted operative mortality.

The July Effect: Impact of the Beginning of the Academic Cycle on Cardiac Surgical Outcomes in a Cohort of 70,616 Patients

Because surgical residents' level of experience may be at its nadir early in the academic year, academic seasonality-or the "July effect"-could affect cardiac surgical outcomes. Prospectively collected data from the Department of Veterans Affairs Continuous Improvement in Cardiac Surgery Program were used to identify 70,616 consecutive cardiac surgical procedures performed between October 1997 and October 2007. Morbidity and mortality rates were compared between early (July 1 to August 31, n = 11,975) and late (September 1 to June 30, n = 58,641) periods in the academic year. A prediction model was constructed by using stepwise logistic regression modeling. The two patient groups had similar demographic and risk variables. Isolated coronary artery bypass grafting accounted for 76.7% of early-period procedures and 75.8% of later-period procedures (p = 0.03). Morbidity rates did not differ significantly between the early (14.0%) and later periods (14.2%; odds ratio [OR], 1.01; 95% confidence interval [CI], 0.96 to 1.07; p = 0.67) and operative mortality was similar, 3.7% vs 3.9% (OR, 0.99; 95% CI, 0.89 to 1.11; p = 0.90). The early portion of the year was associated with longer cardiac ischemia times (84 +/- 40 vs 83 +/- 42 minutes), cardiopulmonary bypass times (126 +/-52 vs 124 +/-56 minutes), and total surgical times (295 +/- 90 vs 288 +/- 90 minutes; p < 0.05 for all). The early part of the academic year was associated with slightly longer operative times; however, risk-adjusted outcomes were similar in both periods. This finding should lessen concerns about the quality of cardiac surgical care at the beginning of the academic year.

Improving Quality of Care in Cardiac Surgery: Evaluating Risk Factors, Processes of Care, Structures of Care, and Outcomes

The 1985 release of hospital report cards by the Health Care Financing Administration awakened the public's awareness of variations in outcomes following patient treatment. In 1972, the Department of Veterans Affairs initiated an oversight process for all VA-based cardiac surgery programs. In response to Public Law 99-166, the Continuous Improvement in Cardiac Surgery Program (CICSP) national database was developed in 1987. This CICSP effort reported variations in outcomes across VA cardiac programs. In 1997, the CICSP expanded (CICSP-X) to identify the interrelationships of risk factors with processes and structures of care, as well as clinical outcomes. Based on VA findings to date, these quality improvement endeavors appear to have positively affected short-term and longer-term cardiac surgical outcomes. To advance a new patient-focused paradigm for continuous improvement in cardiac surgical care quality for all US citizens, an integrated data-driven reporting approach with broad-based participation should be implemented to optimally improve patient care.

Invited commentary

Invited commentary

Cardiovascular medication use after coronary bypass surgery in patients with renal dysfunction: A National Veterans Administration study

Cardiovascular medication use after coronary bypass surgery in patients with renal dysfunction: A national Veterans Administration study. Background Chronic kidney disease is now recognized as an independent risk factor for cardiovascular events. We sought to determine if cardiovascular medications were utilized less in patients with renal dysfunction following coronary artery bypass grafting (CABG) and if the association of decreased medication use was independent of comorbid conditions. We also examined associations between cardiovascular medication use and mortality at 6 months. Methods Data from the National Veterans Adminstration (VA) Continuous Improvement in Cardiac Surgery Program were merged with the national VA pharmacy database. Prescription rates within 6 months of discharge for CABG were obtained for four classes of medicines: beta blockers, lipid-lowering agents, antiplatelet agents, and angiotensin antagonists. Utilization of medications in patients with estimated glomerular filtration rate (GFR) 60 to 90, 30 to 60, and 90. Results In a retrospective analysis of 19,411 patients, the frequency of nonprescription increased with declining GFR. Decreased utilization for patients with GFR 30 to 60 and Conclusion In a large VA population undergoing CABG, renal disease is associated with highly significant decreases in utilization of cardiovascular medications. Nonprescription of medications was associated with adverse outcomes in those with renal dysfunction.

Long-Term Results of Coronary Artery Bypass Grafting in Patients With Ischemic Cardiomyopathy: The Impact of Renal Insufficiency and Noncardiac Vascular Disease

Background We examined outcomes of patients with ischemic cardiomyopathy (ICMP), defined by left ventricular ejection fraction (LVEF) <35%, compared with patients with better-preserved LVEF, undergoing coronary bypass graft surgery (CABG). In addition, we examined the relative impact of a reduced LVEF in comparison with other comorbidities on long-term mortality in these patients. Methods and Results We evaluated 1381 patients (114 with ICMP, 1267 with better-preserved LVEF) who underwent isolated CABG at a tertiary Veterans Administration (VA) hospital between 1990 and 2000 using data from the VA Continuous Improvement in Cardiac Surgery Program and other VA databases. The 5-year survival was 74.0% in patients with ICMP and 84.4% in the group with better-preserved LVEF ( p = .005). LVEF <35% remained a significant predictor of long-term mortality in multivariable models (hazard ratio [HR] 1.55, 95% confidence interval [CI] 1.02–2.35). However, the presence of comorbidities, especially renal insufficiency, peripheral vascular disease, and cerebrovascular disease, had a similar or greater impact on long-term mortality. Renal insufficiency (serum creatinine >1.5 mg/dL) was associated with the highest risk of long-term mortality (HR 2.02, 95% CI 1.46–2.80). The use of a left internal thoracic artery graft reduced the risk of long-term mortality (HR 0.72, 95% CI 0.54–0.98). Conclusion Even though severely depressed LVEF is associated with an increased risk of long-term mortality, the presence of comorbid factors, especially renal dysfunction and noncardiac vascular disease, increase the risk of long-term mortality by a similar or even larger magnitude. These comorbid factors should be given important consideration when evaluating the risks and benefits of CABG.

Mortality After Cardiac Bypass Surgery

Risk-adjusted outcome rates frequently are used to make inferences about hospital quality of care. We calculated risk-adjusted mortality rates in veterans undergoing isolated coronary artery bypass surgery (CABS) from administrative data and from chart-based clinical data and compared the assessment of hospital high and low outlier status for mortality that results from these 2 data sources. We studied veterans who underwent CABS in 43 VA hospitals between October 1, 1993, and March 30, 1996 (n=15,288). To evaluate administrative data, we entered 6 groups of International Classification of Diseases (ICD)-9-CM codes for comorbid diagnoses from the VA Patient Treatment File (PTF) into a logistic regression model predicting postoperative mortality. We also evaluated counts of comorbid ICD-9-CM codes within each group, along with 3 common principal diagnoses, weekend admission or surgery, major procedures associated with CABS, and demographic variables. Data from the VA Continuous Improvement in Cardiac Surgery Program (CICSP) were used to create a separate clinical model predicting postoperative mortality. For each hospital, an observed-to-expected (O/E) ratio of mortality was calculated from (1) the PTF model and (2) the CICSP model. We defined outlier status as an O/E ratio outside of 1.0 (based on the hospital's 90% confidence interval). To improve the statistical and predictive power of the PTF model, selected clinical variables from CICSP were added to it and outlier status reassessed. Significant predictors of postoperative mortality in the PTF model included 1 group of comorbid ICD-9-CM codes, intraortic balloon pump insertion before CABS, angioplasty on the day of or before CABS, weekend surgery, and a principal diagnosis of other forms of ischemic heart disease. The model's c-index was 0.698. As expected, the CICSP model's predictive power was significantly greater than that of the administrative model (c=0.761). The addition of just 2 CICSP variables to the PTF model improved its predictive power (c=0.741). This model identified 5 of 6 high mortality outliers identified by the CICSP model. Additional CICSP variables were statistically significant predictors but did not improve the assessment of high outlier status. Models using administrative data to predict postoperative mortality can be improved with the addition of a very small number of clinical variables. Limited clinical improvements of administrative data may make it suitable for use in quality improvement efforts.

Factors influencing risk-adjusted patient satisfaction after coronary artery bypass grafting

Factors influencing risk-adjusted patient satisfaction after coronary artery bypass grafting

The comparative assessment and improvement of quality of surgical care in the Department of Veterans Affairs.

Prompted by the need to assess comparatively the quality of surgical care in 133 Veterans Affairs (VA) hospitals, the Department of Veterans Affairs conducted the National VA Surgical Risk Study between October 1, 1991, and December 31, 1993, in 44 VA medical centers. The study developed and validated models for risk adjustment of 30-day morbidity and 30-day mortality after major surgery in 8 noncardiac surgical specialties. Similar models were developed for cardiac surgery by the VA's Continuous Improvement in Cardiac Surgery Program. Based on the results of the National VA Surgical Risk Study and the Continuous Improvement in Cardiac Surgery Program, the VA established in 1994 a VA National Surgical Quality Improvement Program (NSQIP), in which all the medical centers performing major surgery participated. An NSQIP nurse at each center oversees the prospective collection of data and their electronic transmission for analysis at 1 of 2 data coordinating centers. Feedback to the providers and managers is aimed at achieving continuous quality improvement. It consists of (1) comparative, site-specific, and outcome-based annual reports; (2) periodic assessment of performance; (3) self-assessment tools; (4) structured site visits; and (5) dissemination of best practices. The NSQIP also provides an infrastructure to enable the VA investigators to query the database and produce scientific presentations and publications. Since the inception of the NSQIP data collection process, the 30-day postoperative mortality after major surgery in the VA has decreased by 27%, and the 30-day morbidity by 45%. The future of the NSQIP lies in expanding it to the private sector and in enhancing its capabilities by incorporating additional measures of outcome, structure, process, and cost.

Off-pump coronary artery bypass is associated with improved risk-adjusted outcomes

Background. The impact of off-pump median sternotomy coronary artery bypass grafting procedures on risk-adjusted mortality and morbidity was evaluated versus on-pump procedures. Methods. Using the Department of Veterans Affairs Continuous Improvement in Cardiac Surgery Program records from October 1997 through March 1999, nine centers were designated as having experience (with at least 8% coronary artery bypass grafting procedures performed off-pump). Using all other 34 Veterans Affairs cardiac surgery programs, baseline logistic regression models were built to predict risk of 30-day operative mortality and morbidity. These models were then used to predict outcomes for patients at the nine study centers. A final model evaluated the impact of the off-pump approach within these nine centers adjusting for preoperative risk. Results. Patients treated off-pump (n = 680) versus on-pump (n = 1,733) had lower complication rates (8.8% versus 14.0%) and lower mortality (2.7% versus 4.0%). Risk-adjusted morbidity and mortality were also improved for these patients (0.52 and 0.56 multivariable odds ratios for off-pump versus on-pump, respectively, p < 0.05). Conclusions. An off-pump approach for coronary artery bypass grafting procedures is associated with lower risk-adjusted morbidity and mortality.

Predicting acute renal failure after coronary bypass surgery: Cross-validation of two risk-stratification algorithms

Acute renal failure (ARF) requiring dialysis after coronary artery bypass grafting (CABG) occurs in 1 to 5% of patients and is independently associated with postoperative mortality, even after case-mix adjustment. A risk-stratification algorithm that could reliably identify patients at increased risk of ARF could help improve outcomes. To assess the validity and generalizability of a previously published preoperative renal risk-stratification algorithm, we analyzed data from the Quality Measurement and Management Initiative (QMMI)1 patient cohort. The QMMI includes all adult patients (N = 9498) who underwent CABG at 1 of 12 academic tertiary care hospitals from August 1993 to October 1995. ARF requiring dialysis was the outcome of interest. Cross-validation of a recursive partitioning algorithm developed from the VA Continuous Improvement in Cardiac Surgery Program (CICSP) was performed on the QMMI. An additive severity score derived from logistic regression was also cross-validated on the QMMI. The CICSP recursive partitioning algorithm discriminated well (ARF vs. no ARF) in QMMI patients, even though the QMMI cohort was more diverse. Rates of ARF were similar among risk subgroups in the CICSP tree, as was the overall ranking of subgroups by risk. Using logistic regression, independent predictors of ARF in the QMMI cohort were similar to those found in the CICSP. The CICSP additive severity score performed well in the QMMI cohort, successfully stratifying patients into low-, medium-, high-, and very high-risk groups. The CICSP preoperative renal-risk algorithms are valid and generalizable across diverse populations.