Karl F. Welke

An empirically based tool for analyzing mortality associated with congenital heart surgery

OBJECTIVE Analysis of congenital heart surgery results requires a reliable method of estimating the risk of adverse outcomes. Two major systems in current use are based on projections of risk or complexity that were predominantly subjectively derived. Our goal was to create an objective, empirically based index that can be used to identify the statistically estimated risk of in-hospital mortality by procedure and to group procedures into risk categories. METHODS Mortality risk was estimated for 148 types of operative procedures using data from 77,294 operations entered into the European Association for Cardiothoracic Surgery (EACTS) Congenital Heart Surgery Database (33,360 operations) and the Society of Thoracic Surgeons (STS) Congenital Heart Surgery Database (43,934 patients) between 2002 and 2007. Procedure-specific mortality rate estimates were calculated using a Bayesian model that adjusted for small denominators. Each procedure was assigned a numeric score (the STS-EACTS Congenital Heart Surgery Mortality Score [2009]) ranging from 0.1 to 5.0 based on the estimated mortality rate. Procedures were also sorted by increasing risk and grouped into 5 categories (the STS-EACTS Congenital Heart Surgery Mortality Categories [2009]) that were chosen to be optimal with respect to minimizing within-category variation and maximizing between-category variation. Model performance was subsequently assessed in an independent validation sample (n = 27,700) and compared with 2 existing methods: Risk Adjustment for Congenital Heart Surgery (RACHS-1) categories and Aristotle Basis Complexity scores. RESULTS Estimated mortality rates ranged across procedure types from 0.3% (atrial septal defect repair with patch) to 29.8% (truncus plus interrupted aortic arch repair). The proposed STS-EACTS score and STS-EACTS categories demonstrated good discrimination for predicting mortality in the validation sample (C-index = 0.784 and 0.773, respectively). For procedures with more than 40 occurrences, the Pearson correlation coefficient between a procedures STS-EACTS score and its actual mortality rate in the validation sample was 0.80. In the subset of procedures for which RACHS-1 and Aristotle Basic Complexity scores are defined, discrimination was highest for the STS-EACTS score (C-index = 0.787), followed by STS-EACTS categories (C-index = 0.778), RACHS-1 categories (C-index = 0.745), and Aristotle Basic Complexity scores (C-index = 0.687). When patient covariates were added to each model, the C-index improved: STS-EACTS score (C-index = 0.816), STS-EACTS categories (C-index = 0.812), RACHS-1 categories (C-index = 0.802), and Aristotle Basic Complexity scores (C-index = 0.795). CONCLUSION The proposed risk scores and categories have a high degree of discrimination for predicting mortality and represent an improvement over existing consensus-based methods. Risk models incorporating these measures may be used to compare mortality outcomes across institutions with differing case mixes.

Cardiac surgery in infants with low birth weight is associated with increased mortality: Analysis of the Society of Thoracic Surgeons Congenital Heart Database

OBJECTIVE The evaluation of operative mortality risk for cardiac surgery in infants with low weight is limited. To determine whether low weight is a risk factor for increased mortality, we reviewed the experience within the Society of Thoracic Surgeons Congenital Heart Surgery Database of infants who have undergone surgical correction or palliation for congenital heart disease. METHODS We analyzed mortality in 3022 infants ages 0 to 90 days weighing 1 to 2.5 kg (n = 517) and greater than 2.5 to 4 kg (n = 2505) who underwent cardiac surgery from 2002 through 2004 at 32 participating centers. Patients were grouped according to the primary procedure performed and analyzed according to their weight at the time of surgical intervention. Patients were also analyzed according to Risk Adjustment for Congenital Heart Surgery-1 and Aristotle Basic Complexity scores. RESULTS Compared with infants weighing 2.5 to 4 kg, infants weighing less than 2.5 kg had a significantly higher mortality for the following operations: repair of coarctation of the aorta, total anomalous pulmonary venous connection repair, arterial switch procedure, systemic to pulmonary artery shunt, and the Norwood procedure. Lower infant weight remained strongly associated with mortality risk after stratifying the population by Risk Adjustment for Congenital Heart Surgery-1 levels 2 through 6 and Aristotle Basic Complexity levels 2 through 4. CONCLUSIONS Low weight at the time of surgical intervention is associated with increased mortality in patients undergoing several types of cardiovascular procedures. These data do not allow assessment of specific risks or benefits of any particular treatment strategy. However, they do support the need for prospective analysis of specific treatment strategies for these high-risk patients.

Atrial Fibrillation Correction Surgery: Lessons From The Society of Thoracic Surgeons National Cardiac Database

BACKGROUND We used The Society of Thoracic Surgeons National Cardiac Database to document the utilization of surgical atrial fibrillation (AF) correction procedures in North America. We also examined the subset of patients having mitral valve surgery to determine whether concurrent surgical AF correction procedures were associated with an increased risk of morbidity or mortality. METHODS Retrospective review of outcomes for 67,389 patients with AF having cardiac surgery between January 2004 and December 2006 was conducted. Multivariable logistic regression was performed to assess whether concomitant AF correction procedures increased risk in the mitral valve surgery cohort. RESULTS Overall, 38% (25,718 of 67,389) of patients with AF undergoing cardiac surgery had an AF correction procedure, increasing from 28.1% in 2004 to 40.2% in 2006. Surgical AF correction was performed in 52% (6,415 of 12,235) of mitral valve surgery patients, 28% (2,965 of 10,590) of those having aortic valve surgery, and 24% (5,438 of 22,388) of those having isolated coronary artery bypass grafting. After adjusting for differences in preoperative characteristics, mitral valve surgery patients with a surgical AF correction procedure did not have a significantly higher risk of mortality (adjusted odds ratio, 1.00; 95% confidence interval, 0.83 to 1.20) or major morbidity. The risk for new permanent pacemaker implantation was higher (adjusted odds ratio, 1.26; 95% confidence interval, 1.07 to 1.49) in the AF correction with mitral valve surgery group. CONCLUSIONS Although a growing number of patients with AF are treated with concurrent AF correction procedures during cardiac surgery, nearly 60% of patients are left untreated. Among patients with AF and mitral valve disease, the addition of an AF correction procedure does not increase perioperative morbidity or mortality.

The complex relationship between pediatric cardiac surgical case volumes and mortality rates in a national clinical database

OBJECTIVE We sought to determine the association between pediatric cardiac surgical volume and mortality using sophisticated case-mix adjustment and a national clinical database. METHODS Patients 18 years of age or less who had a cardiac operation between 2002 and 2006 were identified in the Society of Thoracic Surgeons Congenital Heart Surgery Database (32,413 patients from 48 programs). Programs were grouped by yearly pediatric cardiac surgical volume (small, <150; medium, 150-249; large, 250-349; and very large, >or=350 cases per year). Logistic regression was used to adjust mortality rates for volume, surgical case mix (Aristotle Basic Complexity and Risk Adjustment for Congenital Heart Surgery, Version 1 categories), patient risk factors, and year of operation. RESULTS With adjustment for patient-level risk factors and surgical case mix, there was an inverse relationship between overall surgical volume as a continuous variable and mortality (P = .002). When the data were displayed graphically, there appeared to be an inflection point between 200 and 300 cases per year. When volume was analyzed as a categorical variable, the relationship was most apparent for difficult operations (Aristotle technical difficulty component score, >3.0), for which mortality decreased from 14.8% (60/406) at small programs to 8.4% (157/1858) at very large programs (P = .02). The same was true for the subgroup of patients who underwent Norwood procedures (36.5% [23/63] vs 16.9% [81/479], P < .0001). After risk adjustment, all groups performed similarly for low-difficulty operations. Conversely, for difficult procedures, small programs performed significantly worse. For Norwood procedures, very large programs outperformed all other groups. CONCLUSION There was an inverse association between pediatric cardiac surgical volume and mortality that became increasingly important as case complexity increased. Although volume was not associated with mortality for low-complexity cases, lower-volume programs underperformed larger programs as case complexity increased.

National Practice Patterns for Management of Adult Congenital Heart Disease Operation By Pediatric Heart Surgeons Decreases In-Hospital Death

Background— Surgery for grown-up (age ≥18 years) patients with congenital heart disease (GUCH) is frequently performed by surgeons without specialization in pediatric heart surgery. We sought to define national practice patterns and to determine whether outcomes for GUCH patients are improved if they are treated by specialized pediatric heart surgeons (PHSs) compared with non-PHSs. Methods and Results— We identified index cardiac procedures in patients with 12 congenital heart disease diagnostic groups using the Nationwide Inpatient Sample 1988 to 2003. PHSs were defined as surgeons whose annual practice volumes were made of >75% annual pediatric heart cases. GUCH operations were defined as operations within these 12 diagnoses occurring in patients ≥18 years of age. We identified 30 250 operations, yielding a national estimate of 152 277±7875 operations. Of these, 111 816±7456 (73%) were pediatric operations, and 40 461±1365 (27%) were GUCH operations. PHSs performed 68% of pediatric operations in all diagnostic groups, whereas non-PHSs performed 95% of GUCH operations within the same diagnostic groups (P<0.0001). In-hospital death rates for GUCH patients operated on by PHSs were lower than death rates for GUCH patients operated on by non-PHSs (1.87% [95% CI, 0.62 to 3.13] versus 4.84% [95% CI, 4.30 to 5.38%]; P<0.0001). Survival advantage increased with increasing surgeon annual pediatric volume (P=0.0031). Conclusions— Pediatric patients within specific diagnostic groups are more likely to undergo operation by PHSs, whereas GUCH patients within the same diagnostic groups are more likely to undergo operation by non-PHSs. In-hospital death rates are lower for GUCH patients operated on by PHSs. GUCH patients should be encouraged to obtain surgical operation by PHS.

Variation in Outcomes for Benchmark Operations: An Analysis of The Society of Thoracic Surgeons Congenital Heart Surgery Database

BACKGROUND We evaluated outcomes for common operations in The Society of Thoracic Surgeons Congenital Heart Surgery Database (STS-CHSDB) to provide contemporary benchmarks and examine variation between centers. METHODS Patients undergoing surgery from 2005 to 2009 were included. Centers with greater than 10% missing data were excluded. Discharge mortality and postoperative length of stay (PLOS) among patients discharged alive were calculated for 8 benchmark operations of varying complexity. Power for analyzing between-center variation in outcome was determined for each operation. Variation was evaluated using funnel plots and Bayesian hierarchical modeling. RESULTS Eighteen thousand three hundred seventy-five index operations at 74 centers were included in the analysis of 8 benchmark operations. Overall discharge mortality was: ventricular septal defect (VSD) repair = 0.6% (range, 0% to 5.1%), tetralogy of Fallot (TOF) repair = 1.1% (range, 0% to 16.7%), complete atrioventricular canal repair (AVC) = 2.2% (range, 0% to 20%), arterial switch operation (ASO) = 2.9% (range, 0% to 50%), ASO + VSD = 7.0% (range, 0% to 100%), Fontan operation = 1.3% (range, 0% to 9.1%), truncus arteriosus repair = 10.9% (0% to 100%), and Norwood procedure = 19.3% (range, 0% to 100%). Funnel plots revealed that the number of centers characterized as outliers were VSD = 0, TOF = 0, AVC = 1, ASO = 3, ASO + VSD = 1, Fontan operation = 0, truncus arteriosus repair = 4, and Norwood procedure = 11. Power calculations showed that statistically meaningful comparisons of mortality rates between centers could be made only for the Norwood procedure, for which the Bayesian-estimated range (95% probability interval) after risk-adjustment was 7.0% (3.7% to 10.3%) to 41.6% (30.6% to 57.2%). Between-center variation in PLOS was analyzed for all operations and was larger for more complex operations. CONCLUSIONS This analysis documents contemporary benchmarks for common pediatric cardiac surgical operations and the range of outcomes among centers. Variation was most prominent for the more complex operations. These data may aid in quality assessment and quality improvement initiatives.

An empirically based tool for analyzing morbidity associated with operations for congenital heart disease

OBJECTIVE Congenital heart surgery outcomes analysis requires reliable methods of estimating the risk of adverse outcomes. Contemporary methods focus primarily on mortality or rely on expert opinion to estimate morbidity associated with different procedures. We created an objective, empirically based index that reflects statistically estimated risk of morbidity by procedure. METHODS Morbidity risk was estimated using data from 62,851 operations in the Society of Thoracic Surgeons Congenital Heart Surgery Database (2002-2008). Model-based estimates with 95% Bayesian credible intervals were calculated for each procedures average risk of major complications and average postoperative length of stay. These 2 measures were combined into a composite morbidity score. A total of 140 procedures were assigned scores ranging from 0.1 to 5.0 and sorted into 5 relatively homogeneous categories. RESULTS Model-estimated risk of major complications ranged from 1.0% for simple procedures to 38.2% for truncus arteriosus with interrupted aortic arch repair. Procedure-specific estimates of average postoperative length of stay ranged from 2.9 days for simple procedures to 42.6 days for a combined atrial switch and Rastelli operation. Spearman rank correlation between raw rates of major complication and average postoperative length of stay was 0.82 in procedures with n greater than 200. Rate of major complications ranged from 3.2% in category 1 to 30.0% in category 5. Aggregate average postoperative length of stay ranged from 6.3 days in category 1 to 34.0 days in category 5. CONCLUSIONS Complication rates and postoperative length of stay provide related but not redundant information about morbidity. The Morbidity Scores and Categories provide an objective assessment of risk associated with operations for congenital heart disease, which should facilitate comparison of outcomes across cohorts with differing case mixes.

Linking clinical registry data with administrative data using indirect identifiers: Implementation and validation in the congenital heart surgery population

BACKGROUND The use of clinical registries and administrative data sets in pediatric cardiovascular research has become increasingly common. However, this approach is limited by relatively few existing datasets, each of which contain limited data, and do not communicate with one another. We describe the implementation and validation of methodology using indirect patient identifiers to link The Society of Thoracic Surgeons Congenital Heart Surgery (STS-CHS) Database to The Pediatric Health Information Systems (PHIS) Database (a pediatric administrative database). METHODS Centers submitting data to STS-CHS and PHIS during 2004 to 2008 were included (n=30). Both data sets were limited to patients 0 to 18 years old undergoing cardiac surgery. An exact match was defined as an exact match on each of the following: date of birth, date of admission, date of discharge, sex, and center. Likely matches were defined as an exact match for all variables except ±1 day for one of the date variables. RESULTS Of 45,830 STS-CHS records, 87.4% matched to PHIS using the exact match criteria and 90.3% using the exact or likely match criteria. Validation in a subset of patients revealed that 100% of exact and likely matches were true matches. CONCLUSIONS This analysis demonstrates that indirect identifiers can be used to create high-quality link between a clinical registry and administrative data set in the congenital heart surgery population. This methodology, which can also be applied to other data sets, allows researchers to capitalize on the strengths of both types of data and expands the pool of data available to answer important clinical questions.

The Influence of Surgeon Specialty on Outcomes in General Thoracic Surgery: A National Sample 1996 to 2005

BACKGROUND While general thoracic surgical procedures are performed by several different surgical subspecialties, debate remains as to whether surgeon specialty impacts outcomes. METHODS The Nationwide Inpatient Sample (NIS) was queried for procedure codes for pneumonectomy, lobectomy, limited lung resection, and decortication. We constructed multivariate logistic regression models to calculate odds of hospital mortality or length-of-stay (LOS) greater than 14 days (a marker of morbidity), adjusted for age, sex, patient comorbidities, hospital setting, and surgeon specialty. A surgeon was considered general thoracic if they performed greater than 75% general thoracic operations and less than 10% cardiac operations, Cardiac if greater than 10% cardiac operations, and general surgeon if less than 75% general thoracic and less than 10% cardiac operations. A second set of models additionally adjusted for procedure-specific hospital and surgeon volume. RESULTS From 1996 to 2005, the NIS estimates 41,808 pneumonectomies, 321,767 lobectomies, 75,200 limited lung resections, and 149,318 decortications were performed in the United States. For all procedures studied, general thoracic surgeons had significantly decreased odds-of-death and LOS greater than 14 days compared with general surgeons. Cardiac surgeons had significantly decreased LOS greater than 14 days for all operations and decreased odds-of-death for decortications, lobectomy, and limited lung resection compared with general surgeons. When further adjusted for surgeon volume, most differences in odds-of-death were no longer present; however, significantly decreased LOS greater than 14 days largely persisted for both general thoracic and cardiac surgeons. CONCLUSIONS The majority of general thoracic surgical operations in the United States are performed by surgeons not specializing in thoracic surgery. Both general thoracic surgeons and cardiac surgeons achieve better outcomes than general surgeons. Differences in mortality may be more dependent on surgeon volume than subspecialty. Differences in morbidity are significantly impacted by surgeon specialty and volume.

Congenital Heart Surgery Outcomes in Down Syndrome: Analysis of a National Clinical Database

OBJECTIVE: We describe patient characteristics and postoperative morbidity and mortality rates for patients with Down syndrome undergoing congenital heart disease surgery. METHODS: This retrospective cohort study used the Society of Thoracic Surgeons Congenital Heart Surgery Database to compare patient characteristics and postoperative outcomes for patients (0–18 years) with or without Down syndrome who underwent surgery in 2000–2008. RESULTS: A total of 45 579 patients (4350 patients with Down syndrome and 41 229 without Down syndrome) were included (median age: 7 months [interquartile range [IQR]: 47 days to 4 years]; 56% male). Patients with Down syndrome were younger at surgery, with the exception of those undergoing tetralogy of Fallot repair or atrioventricular septal defect repair. Mortality rates for patients with or without Down syndrome did not differ significantly. Lengths of stay were prolonged for patients with Down syndrome undergoing atrial septal defect closure (median: 4 days [IQR: 3–5 days] vs 3 days [IQR: 2–4 days]; P < .0001), ventricular septal defect closure (median: 5 days [IQR: 4–8 days] vs 4 days [IQR: 3–6 days]; P < .0001), or tetralogy of Fallot repair (7 days [IQR: 5–10 days] vs 6 days [IQR: 5–9 days]; P < .001) and were associated with postoperative respiratory and infectious complications. Patients with Down syndrome undergoing ventricular septal defect closure had a higher rate of heart block requiring pacemaker placement (2.9% vs 0.8%; P < .0001). CONCLUSION: In this large, contemporary cohort, Down syndrome did not confer a significant mortality risk for the most common operations; however, postoperative morbidity remained common.