MSTCVS Quality Collaborative Publications
Association Between Medicaid Expansion and
Cardiovascular Interventions in Michigan
Michigan is one of several states that expanded Medicaid coverage under the Affordable Care Act. The “Healthy Michigan Plan,” implemented in April 2014, provides coverage through Medicaid to adults with incomes up to 138% of the federal poverty level and requires a health risk assessment and cost sharing by enrollees.
Early results suggest that the Michigan Plan has been successful. Within 1 year of expansion, 600,000 new adults had enrolled (1). Primary care service utilization increased 6% following expansion, and participation in health risk assessments are more than double that of private health insurance plans (2). Less well known is the association between Medicaid expansion and the use and outcomes of cardiovascular revascularization.
Development of a Risk Prediction Model and
Clinical Risk Score for Isolated Tricuspid Valve Surgery
Background: While tricuspid valve (TV) operations remain associated with high mortality (∼8-10%), no robust prediction models exist to support clinical decision-making. We developed a preoperative clinical risk model with an easily calculable clinical risk score (CRS) to predict mortality and major morbidity after isolated TV surgery.
Methods: Multi-state Society of Thoracic Surgeons database records were evaluated for 2,050 isolated TV repair and replacement operations for any etiology performed at 50 hospitals (2002-2014). Parsimonious preoperative risk prediction models were developed using multi-level mixed effects regression to estimate mortality and composite major morbidity risk. Model results were utilized to establish a novel CRS for patients undergoing TV operations. Models were evaluated for discrimination and calibration..
Results: Operative mortality and composite major morbidity rates were 9% and 42%, respectively. Final regression models performed well (both P<0.001, AUC = 0.74 and 0.76) and included preoperative factors: age, gender, stroke, hemodialysis, ejection fraction, lung disease, NYHA class, reoperation and urgent or emergency status (all P<0.05). A simple CRS from 0-10+ was highly associated (P<0.001) with incremental increases in predicted mortality and major morbidity. Predicted mortality risk ranged from 2%-34% across CRS categories, while predicted major morbidity risk ranged from 13%-71%.
Conclusions: Mortality and major morbidity after isolated TV surgery can be predicted using preoperative patient data from the STS Adult Cardiac Database. A simple clinical risk score predicts mortality and major morbidity after isolated TV surgery. This score may facilitate perioperative counseling and identification of suitable patients for TV surgery.
Drivers of Payment Variation in 90-Day Coronary Artery Bypass Grafting Episodes
Importance: Coronary artery bypass grafting (CABG) is scheduled to become a mandatory Medicare bundled payment program in January 2018. A contemporary understanding of 90-day CABG episode payments and their drivers is necessary to inform health policy, hospital strategy, and clinical quality improvement activities. Furthermore, insight into current CABG payments and their variation is important for understanding the potential effects of bundled payment models in cardiac care.
Objective To examine CABG payment variation and its drivers.
Design, Setting, and Participants This retrospective cohort study used Medicare and private payer claims to identify patients who underwent nonemergent CABG surgery from January 1, 2012, through October 31, 2015. Ninety-day price-standardized, risk-adjusted, total episode payments were calculated for each patient, and hospitals were divided into quartiles based on the mean total episode payments of their patients. Payments were then subdivided into 4 components (index hospitalization, professional, postacute care, and readmission payments) and compared across hospital quartiles. Seventy-six hospitals in Michigan representing a diverse set of geographies and practice environments were included.
Main Outcomes and Measures Ninety-day CABG episode payments.
Results: A total of 5910 patients undergoing nonemergent CABG surgery were identified at 33 of the 76 hospitals; of these, 4344 (73.5%) were men and mean (SD) age was 68.0 (9.3) years. At the patient level, risk-adjusted, 90-day total episode payments for CABG varied from $11 723 to $356 850. At the hospital level, the highest payment quartile of hospitals had a mean total episode payment of $54 399 compared with $45 487 for the lowest payment quartile (16.4% difference, P < .001). The highest payment quartile hospitals compared with the lowest payment quartile hospitals had 14.6% higher index hospitalization payments ($34 992 vs $30 531, P < .001), 33.9% higher professional payments ($8060 vs $6021, P < .001), 29.6% higher postacute care payments ($7663 vs $5912, P < .001), and 35.1% higher readmission payments ($3576 vs $2646, P = .06). The drivers of this variation are diagnosis related group distribution, increased inpatient evaluation and management services, higher utilization of inpatient rehabilitation, and patients with multiple readmissions.
Conclusions and Relevance Wide variation exists in 90-day CABG episode payments for Medicare and private payer patients in Michigan. Hospitals and clinicians entering bundled payment programs for CABG should work to understand local sources of variation, with a focus on patients with multiple readmissions, inpatient evaluation and management services, and postdischarge outpatient rehabilitation care.
Impact of Medicaid Expansion on Cardiac Surgery Volume and Outcomes
Background: Thirty-one states approved Medicaid expansion after implementation of the Affordable Care Act. The objective of this study was to evaluate the effect of Medicaid expansion on cardiac surgery volume and outcomes comparing one state that expanded to one that did not.
Methods: Data from the Virginia (nonexpansion state) Cardiac Services Quality Initiative and the Michigan (expanded Medicaid, April 2014) Society of Thoracic and Cardiovascular Surgeons Quality Collaborative were analyzed to identify uninsured and Medicaid patients undergoing coronary bypass graft or valve operations, or both. Demographics, operative details, predicted risk scores, and morbidity and mortality rates, stratified by state and compared across era (preexpansion: 18 months before vs postexpansion: 18 months after), were analyzed.
Results: In Virginia, there were no differences in volume between eras, whereas in Michigan, there was a significant increase in Medicaid volume (54.4% [558 of 1,026] vs 84.1% [954 of 1,135], p < 0.001) and a corresponding decrease in uninsured volume. In Virginia Medicaid patients, there were no differences in predicted risk of morbidity or mortality or postoperative major morbidities. In Michigan Medicaid patients, a significant decrease in predicted risk of morbidity or mortality (11.9% [8.1% to 20.0%] vs 11.1% [7.7% to 17.9%], p = 0.02) and morbidities (18.3% [102 of 558] vs 13.2% [126 of 954], p = 0.008) was identified. Postexpansion was associated with a decreased risk-adjusted rate of major morbidity (odds ratio, 0.69; 95% confidence interval, 0.51 to 0.91; p = 0.01) in Michigan Medicaid patients.
Conclusions: Medicaid expansion was associated with fewer uninsured cardiac surgery patients and improved predicted risk scores and morbidity rates. In addition to improving health care financing, Medicaid expansion may positively affect patient care and outcomes.
Organizational Contributors to the Variation in Red Blood Cell Transfusion Practices in Cardiac Surgery: Survey Results From the State of Michigan
Background: While large volumes of red blood cell transfusions are given to preserve life for cardiac surgical patients, indications for lower volume transfusions (1–2 units) are less well understood. We evaluated the relationship between center-level organizational blood management practices and center-level variability in low volume transfusion rates.
Methods: All 33 nonfederal, Michigan cardiac surgical programs were surveyed about their blood management practices for isolated, nonemergent coronary bypass procedures, including: (1) presence and structure of a patient blood management program, (2) policies and procedures, and (3) audit and feedback practices. Practices were compared across low (N = 14, rate: 0.8%–10.1%) and high (N = 18, rate: 11.0%–26.3%) transfusion rate centers.
Results: Thirty-two (97.0%) of 33 institutions participated in this study. No statistical differences in organizational practices were identified between low- and high-rate groups, including: (1) the membership composition of patient blood management programs among those reporting having a blood management committee (P= .27–1.0), (2) the presence of available red blood cell units within the operating room (4 of 14 low-rate versus 2 of 18 high-rate centers report that they store no units per surgical case, P= .36), and (3) the frequency of internal benchmarking reporting about blood management audit and feedback practices (low rate: 8 of 14 versus high rate: 9 of 18; P= .43).
Conclusions: We did not identify meaningful differences in organizational practices between low- and high-rate intraoperative transfusion centers. While a larger sample size may have been able to identify differences in organizational practices, efforts to reduce variation in 1- to 2-unit, intraoperative transfusions may benefit from evaluating other determinants, including organizational culture and provider transfusion practices.
For a more on this article, please go to Anesthesia & Analgesia
Prediction of Transfusions After Isolated Coronary Artery Bypass Grafting Surgical Procedures
Background: Although blood transfusions are common and have been associated with adverse sequelae after cardiac surgical procedures, few contemporaneous models exist to support clinical decision making. This study developed a preoperative clinical decision support tool to predict perioperative red blood cell transfusions in the setting of isolated coronary artery bypass grafting.
Methods: We performed a multicenter, observational study of 20,377 patients undergoing isolated coronary artery bypass grafting among patients at 39 hospitals participating in the Michigan Society of Thoracic and Cardiovascular Surgeons Quality Collaborative’s PERFusion measures and outcomes (PERForm) registry between 2011 and 2015. Candidates’ preoperative risk factors were identified based on previous work and clinical input. The study population was randomly divided into a 70% development sample and a 30% validation sample. A generalized linear mixed-effect model was developed to predict perioperative red blood cell transfusion. The model’s performance was assessed for calibration and discrimination. Sensitivity analysis was performed to assess the robustness of the model in different clinical subgroups.
Results: Transfusions occurred in 36.8% of patients. The final regression model included 16 preoperative variables. The correlation between the observed and expected transfusions was 1.0. The risk prediction model discriminated well (receiver operator characteristic [ROC]development, 0.81; ROCvalidation, 0.82) and had satisfactory calibration (correlation between observed and expected rates was r = 1.00). The model performance was confirmed across medical centers and clinical subgroups.
Conclusions: Our risk prediction model uses 16 readily obtainable preoperative variables. This model, which provides a patient-specific estimate of the need for transfusion, offers clinicians a guide for decision making and evaluating the effectiveness of blood management strategies.
The Relationship between Intra-Operative Transfusions and Nadir Hematocrit on Post-Operative Outcomes after Cardiac Surgery
Abstract: Uncertainty exists regarding the optimal strategy for the management of anemia in the setting of cardiac surgery. We sought to improve our understanding of the role of intra-operative hematocrit (HCT) and transfusions on peri-operative outcomes following cardiac surgery. A total of 18,886 patients undergoing on-pump cardiac surgery were identified from a multi-institutional registry including surgical and perfusion data. Patients were divided into four groups based on their intra-operative nadir HCT (<21 or ≥21) and whether or not they received intra-operative red blood cell (+RBC or −RBC) transfusions. Outcomes were adjusted for the Society of Thoracic Surgeons predicted risk of mortality (PROM), pre-operative HCT, and medical center. Regardless of nadir HCT cohort, those who received a transfusion had higher PROM relative to patients who did not receive a transfusion. The mean PROM was significantly higher among those HCT ≥21 + RBC (5.3%) vs. HCT ≥ 21 − RBC (1.9%), p < .001. Similarly, the PROM was significantly higher among HCT <21 + RBC (5.1%) vs. those HCT <21 − RBC (3.1%), p < .001. Adjusted outcomes demonstrated an increased impact of RBC transfusions on adverse outcomes irrespective of nadir HCT including stroke (p < .001), renal failure (p < .001), prolonged ventilation (p < .001), and mortality (p< .001). This study demonstrates that transfusions have a more profound effect on post-operative cardiac surgery outcomes than anemia.
Aortic Valve Replacement in the Moderately Elevated Risk Patient: A Population-Based Analysis of Outcomes
Background: As transcatheter aortic valve replacement (TAVR) therapy transitions from inoperable or high-risk patients to those considered moderate risk, a contemporary evaluation of AVR in this latter group is warranted
Methods: Using the Michigan Cardiothoracic Surgical Quality Collaborative Database, we analyzed outcomes and identified predictors of a composite end point (30-day death, stroke, and dialysis) for 2,979 patients (2007 to 2015) undergoing AVR (n = 1,196) or AVR and coronary artery bypass grafting (n = 1,783) with a preoperative The Society of Thoracic Surgeons predicted risk of mortality (PROM) of 4% to 8% (mean, 5.5%; interquartile range, 4.5% to 6.3%).
Results: The 30-day mortality was 3.9%. Independent predictors of death included stage 4 chronic kidney disease and the presence of pulmonary hypertension (both p < 0.05), but not year of procedure, despite a significant trend in decreased PROM during the study period (p = 0.003). Morbidity included stroke in 2.3%, and renal failure, defined as Acute Kidney Injury Network stage 1 to 3, in 43.7%, although only 5.4% required dialysis. Prolonged ventilator support was required by 21.0%. After a mean length of stay of 10 days (interquartile range 6 to 11 days), 36.4% were discharged to extended care facilities. Independent predictors of the composite outcome included the Society of Thoracic Surgeons PROM (p < 0.001 for trend) and pulmonary hypertension (p < 0.001). Compared with those presenting with pure aortic stenosis, mixed aortic stenosis and aortic insufficiency was independently protective of the composite outcome (odds ratio, 0.58; p < 0.001), whereas pure aortic insufficiency was not (odds ratio, 0.87; p = 0.58). The composite end point frequency was not significantly different in the 17 hospitals developing TAVR programs (TAVR 9.6% vs non-TAVR 9.6%, p = 0.98).
Conclusions: This population-based contemporary assessment suggests moderate-risk patients undergoing AVR experience favorable outcomes. Although increasing PROM is important in preoperative evaluation of risk, preexisting pulmonary hypertension and indication for operation are among other factors that should be considered as TAVR expands into this group of patients.
A Preoperative Risk Model for Postoperative Pneumonia After Coronary Artery Bypass Grafting
Background: Postoperative pneumonia is the most prevalent of all hospital-acquired infections after isolated coronary artery bypass graft surgery (CABG). Accurate prediction of a patient’s risk of this morbid complication is hindered by its low relative incidence. In an effort to support clinical decision making and quality improvement, we developed a preoperative prediction model for postoperative pneumonia after CABG.
Methods: We undertook an observational study of 16,084 patients undergoing CABG between the third quarter of 2011 and the second quarter of 2014 across 33 institutions participating in the Michigan Society of Thoracic and Cardiovascular Surgeons Quality Collaborative. Variables related to patient demographics, medical history, admission status, comorbid disease, cardiac anatomy, and the institution performing the procedure were investigated. Logistic regression through forward stepwise selection (p < 0.05 threshold) was utilized to develop a risk prediction model for estimating the occurrence of pneumonia. Traditional methods were used to assess the model’s performance.
Results: Postoperative pneumonia occurred in 3.30% of patients. Multivariable analysis identified 17 preoperative factors, including demographics, laboratory values, comorbid disease, pulmonary and cardiac function, and operative status. The final model significantly predicted the occurrence of pneumonia, and performed well (C-statistic: 0.74). These findings were confirmed through sensitivity analyses by center and clinically important subgroups.
Conclusions: We identified 17 readily obtainable preoperative variables associated with postoperative pneumonia. This model may be used to provide individualized risk estimation and to identify opportunities to reduce a patient’s preoperative risk of pneumonia through prehabilitation.
The Midterm Impact of Transcatheter Aortic Valve Replacement on Surgical Aortic Valve Replacement in Michigan
Methods: We analyzed data obtained after SAVR (n =15,288) and TAVR (n= 1,783) using the Michigan Society of Thoracic and Cardiovascular Surgery Quality Collaborative from 2006 to 2015. During this period, 17 of 33 hospitals developed TAVR programs.
Results: Annual SAVR volume increased by 38.1% at TAVR hospitals and by 20.4% at non-TAVR hospitals, (ptrend < 0.001). In TAVR hospitals, the Society of Thoracic Surgeons (STS) Predicted Risk of Mortality (PROM) decreased before (4.7% 5.1%) and after (3.5% 3.6%) initiation of TAVR (p < 0.001). Rates of 30-day mortality (pre-TAVR, 3.9% vs post-TAVR, 2.7%; p < 0.001) and renal failure (pre-TAVR, 5.2% vs post-TAVR, 3.3%; p < 0.001) butnot stroke (pre-TAVR, 1.9% vs post-TAVR, 1.7%; p= 0.47) were lower after TAVR implementation. Length of stay decreased from 9.0 to 8.5 days (p < 0.001). When analyzing high-risk patients undergoing SAVR (ie, PROM >8%), neither mortality, stroke, nor renal failure was different (all p > 0.15). Despite a reduction in the STS-PROM, non-TAVR hospitals did not display changes in mortality, stroke, or renal failure for either the entire or the high-risk SAVR cohorts after initiation of TAVR in Michigan.
Conclusions: TAVR implementation in Michigan has dramatically increased overall SAVR volume. This phenomenon has occurred with a concomitant decrease in preoperative risk profile and has improved early SAVR outcomes, particularly at TAVR hospitals, but surprisingly not in patients considered at high preoperative risk. As TAVR use increases, these issues may be further clarified and elucidated.
Impact of institutional culture on rates of transfusions during cardiovascular procedures: The Michigan experience
Background: Red blood cell (RBC) transfusions have been associated with morbidity and mortality in both coronary artery bypass grafting (CABG) and percutaneous coronary interventions (PCI). As a mechanism for identifying determinants of RBC practice, we quantified the relationship between a center’s PCI and CABG transfusion rate.
Methods: We identified all patients undergoing CABG (n = 16,568) or PCI (n = 94,634) at each of 33 centers from
2010 through 2012 in the state of Michigan and compared perioperative RBC transfusion rates for CABG and PCI at each center. Crude and adjusted transfusion rates were modeled separately. We adjusted for common preprocedural risk factors (12 for CABG and 23 for PCI) and reported Pearson correlation coefficients based on the crude and risk-adjusted rates.
Results: As expected, RBC transfusion was more common after CABG (mean 46.5%) than PCI (mean 3.3%), with wide variation across centers for both (CABG min:max 26.5:71.3, PCI min:max 1.6:6.0). However, RBC transfusion rates were significantly correlated between CABG and PCI in both crude, 0.48 (P = .005), and adjusted, 0.53 (P = .001), analyses. These findings were consistent when restricting to nonemergent cases (radj = 0.44, P = .001).
Conclusions: Red blood cell transfusion rates were significantly correlated between the CABG and PCI at individual hospitals in Michigan, independent of patient case mix. Future work should explore institutional practice patterns philosophies, and guidelines for RBC transfusions.
Greater Volume of Acute Normovolemic Hemodilution May Aid in Reducing Blood Transfusions After Cardiac Surgery
Background: Perioperative red blood cell transfusions (RBC) are associated with increased morbidity and mortality after cardiac surgery. Acute normovolemic hemodilution (ANH) is recommended to reduce perioperative transfusions; however, supporting data are limited and conflicting. We describe the relationship between ANH and RBC transfusions after cardiac surgery using a multi-center registry.
Methods: We analyzed 13,534 patients undergoing cardiac surgery between 2010 and 2014 at any of the 26 hospitals participating in a prospective cardiovascular perfusion database. The volume of ANH (no ANH, <400 mL, 400 to 799 mL, ≥800 mL) was recorded and linked to each center’s surgical data. We report adjusted relative risks reflecting the association between the use and amount of ANH and the risk of perioperative RBC transfusion. Results were adjusted for preoperative risk factors, procedure, body surface area, preoperative hematocrit, and center.
Results: The ANH was used in 17% of the patients. ANH was associated with a reduction in RBC transfusions (RRadj [adjusted risk ratio] 0.74, p < 0.001). Patients having 800 mL or greater of ANH had the most profound reduction in RBC transfusions (RRadj 0.57, p < 0.001). Platelet and plasma transfusions were also significantly lower with ANH. The ANH population had superior postoperative morbidity and mortality compared with the no ANH population.
Conclusions: There is a significant association between ANH and reduced perioperative RBC transfusion in cardiac surgery. Transfusion reduction is most profound with larger volumes of ANH. Our findings suggest the volume of ANH, rather than just its use, may be an important feature of a center’s blood conservation strategy.
Sources of Variation in Hospital-Level Infection Rates After Coronary Artery Bypass Grafting: An Analysis of The Society of Thoracic Surgeons Adult Heart Surgery Database
Background: Patients undergoing coronary artery bypass grafting (CABG) are at risk for a variety of infections. Investigators have focused on predictors of these adverse sequelae, but less attention has been focused on characterizing hospital-level variability in these outcomes.
Methods: Between July 2011 and December 2013, The Society of Thoracic Surgeons Adult Cardiac Surgery Database shows 365,686 patients underwent isolated CABG in 1,084 hospitals. Hospital-acquired infections (HAIs) were defined as pneumonia, sepsis/septicemia, deep sternal wound infection/mediastinitis, vein harvest/cannulation site infection, or thoracotomy infection. Hospitals were ranked by their HAI rate as low (10th percentile), medium (10th to 90th percentile), and high (>90th percentile). Differences in perioperative factors and composite morbidity and mortality end points across these groups were determined using the Wilcoxon rank sum and tests.
Results: HAIs occurred among 3.97% of patients overall, but rates varied across hospital groups (low: <0.84%, medium: 0.84% to 8.41%, high: >8.41%). Pneumonia (2.98%) was the most common HAI, followed by sepsis/septicemia (0.84%). Patients at high-rate hospitals more often smoked, had diabetes, chronic lung disease, New York Heart Association Functional Classification III to IV, and received blood products (p < 0.001); however, they less often were prescribed the appropriate antibiotics (p < 0.001). Major morbidity and mortality occurred among 12.3% of patients, although this varied by hospital group (low: 8.6%, medium: 12.3%, high: 17.9%; p < 0.001).
Conclusions: Substantial hospital-level variation exists in postoperative HAIs among patients undergoing CABG, driven predominantly by pneumonia. Given the relatively small absolute differences in comorbidities across hospital groups, our findings suggest factors other than case mix may explain the observed variation in HAI rates.
Nadir Hematocrit on Bypass and Rates of Acute Kidney Injury: Does Sex Matter?
Background: Reports have associated nadir hematocrit (Hct) on cardiopulmonary bypass with the occurrence of renal dysfunction. Recent literature has suggested that women, although more often exposed to lower nadir Hct, have a lower risk of postoperative renal dysfunction. We assessed whether this relationship held across a large multicenter registry.
Methods: We undertook a prospective, observational study of 15,221 nondialysis-dependent patients (10,376 male, 68.2%; 4,845 female, 31.8%) undergoing cardiac surgery between 2010 and 2014 across 26 institutions in Michigan. We calculated crude and adjusted OR between nadir Hct during cardiopulmonary bypass and stage 2 or 3 acute kidney injury (AKI), and tested the interaction of sex and nadir Hct. The predicted probability of AKI was plotted separately for men and women.
Results: Nadir Hct less than 21% occurred among 16.6% of patients, although less commonly among men (9.5%) than women (31.9%; p < 0.001). Acute kidney injury occurred among 2.7% of patients, with small absolute differences between men and women (2.6% versus 3.0%, p = 0.20). There was a significant interaction between sex and nadir Hct (p = 0.009). The effect of nadir Hct on AKI was stronger among male patients (adjusted odds ratio per 1 unit decrease in nadir Hct 1.10, 95% confidence interval: 1.05 to 1.13) than female patients (adjusted odds ratio 1.01, 95% CI: 0.96, 1.06).
Conclusions: Lower nadir Hct was associated with an increased risk of AKI, and the effect appears to be stronger among men than women. Understanding of the mechanism underlying this association remains uncertain, although these results suggest the need to limit exposure to lower nadir Hct, especially for male patients.
Impact of Ultrafiltration on Kidney Injury After Cardiac Surgery: The Michigan Experience
Background: This study examines the relationship between the use and volume of conventional ultrafiltration (CUF) and the risk of acute kidney injury (AKI) after isolated on-pump coronary artery bypass graft surgery.
Methods: A total of 6,407 consecutive patients underwent isolated on-pump coronary artery bypass graft surgery between 2010 and 2013 at 21 medical centers participating in the PERFusion Measures and Outcomes (PERForm) registry. We assessed the effect of CUF use on AKI and other postoperative sequelae using a generalized linear mixed-effect model with a logit link. We also modeled the effect of increasing volume of CUF per weight on AKI, and tested for any modification by a patient’s preoperative kidney function.
Results: Patients having CUF were more likely to have diabetes, vascular disease, chronic obstructive pulmonary disease, congestive heart failure, history of a myocardial infarction, or an intraaortic balloon pump (p < 0.05). They had lower preoperative and nadir hematocrits, creatinine clearance, and ejection fraction (p < 0.05). Patients exposed to CUF had higher adjusted risk of AKI (adjusted odds ratio, 1.36; p = 0.002), although similar rates of death, stroke, and reoperation for bleeding (p > 0.05). The risk of AKI was modified by a patient’s preoperative kidney function (p < 0.0004). Among patients with a creatinine clearance of less than 99.6 mL/min (95% confidence interval, 67.6 to 137.5), increasing volume of CUF was associated with a higher risk of AKI.
Conclusions: Patients exposed to CUF had a higher adjusted risk of AKI. Clinical teams should consider lower volumes of CUF among patients with low creatinine clearance to minimize the risk of AKI.
Red Blood Cell Transfusions Impact Pneumonia Rates After Coronary Artery Bypass Grafting
Background: Pneumonia, a known complication of coronary artery bypass grafting (CABG), significantly increases a patient’s risk of morbidity and mortality. Although not well characterized, red blood cell (RBC) transfusions may increase a patient’s risk of pneumonia. We describe the relationship between RBC transfusion and postoperative pneumonia after CABG.
Methods: A total of 16,182 consecutive patients underwent isolated CABG between 2011 and 2013 at 1 of 33 hospitals in the state of Michigan. We used multivariable logistic regression to estimate the relative odds of pneumonia associated with the use or number of RBC units (0, 1, 2, 3, 4, 5, and ≥ 6). We adjusted for predicted risk of mortality, preoperative hematocrit values, history of pneumonia, cardiopulmonary bypass duration, and medical center. We confirmed the strength and direction of these relationships among selected clinical subgroups in a secondary analysis.
Results: Five hundred seventy-six (3.6%) patients had pneumonia and 6,451 (39.9%) received RBC transfusions. There was a significant association between any RBC transfusion and pneumonia (adjusted odds ratio [ORadj], 3.4; p < 0.001). There was a dose response between number of units and odds of pneumonia, with a ptrend less than 0.001. Patients receiving only 2 units of RBCs had a 2-fold (ORadj, 2.1; p < 0.001) increased odds of developing pneumonia. These findings were consistent across clinical subgroups.
Conclusions: We found a significant volume-dependent association between an increasing number of RBCs and the odds of pneumonia, which persisted after risk adjustment. Clinical teams should explore opportunities for preventing a patient’s risk of RBC transfusions, including reducing hemodilution or adopting a lower transfusion threshold in a stable patient.
The Society of Thoracic Surgeons Adult Cardiac Surgery Database Version 2.73: More Is Better
Background:With the introduction of version 2.73, several new patient risk factors are now captured in The Society of Thoracic Surgeons’ (STS) Adult Cardiac Surgery Database. We sought to evaluate the potential association of these risk factors with mortality.
Methods:We reviewed all patients with an STS predicted risk of mortality in our statewide quality collaborative database from July 2011 to September 2013 (N = 19,743). Univariate analyses were used to determine significant associations between mortality and the new risk factors in version 2.73. We then performed multivariable analysis, incorporating the STS predicted risk of mortality into our regression.
Results:In the univariate model, patients with illicit drug use, syncope, unresponsive neurologic state, cancer within the last 5 years, current smoking history, other tobacco use, or sleep apnea had no significant difference in mortality (p > 0.05). Patients with liver disease, elevated Model for End-Stage Liver Disease score, mediastinal radiation, prolonged 5-meter walk test, home oxygen use, inhaled medications or bronchodilator therapy, decreased forced expiratory volume, and history of recent pneumonia had significant increases in operative mortality (p < 0.05). In multivariable analysis incorporating the STS predicted risk models, liver disease, elevated Model for End-Stage Liver Disease score, prolonged 5-meter walk test, home oxygen use, bronchodilator therapy, and abnormal pulmonary function tests were independently predictive of mortality.
Conclusion:Several of the new STS data variables were significantly associated with operative mortality after cardiac surgery. The addition of these patient factors improves our understanding of evolving patient demographics and comorbid conditions and their impact on perioperative risk. This will improve both shared decision making and assessments of provider performance.
Red Blood Cells and Mortality After Coronary Artery Bypass Graft Surgery: An Analysis of 672 Operative Deaths
Background: Prior studies have implicated transfusion as a risk factor for mortality in coronary artery bypass graft surgery (CABG). To further our understanding of the true association between transfusion and outcome, we specifically analyzed the subgroup of patients who died after undergoing CABG.
Methods: A total of 34,362 patients underwent isolated CABG between January 2008 and September 2013 and were entered into a statewide collaborative database; 672 patients (2.0%) died and form the basis for this study. Univariate analysis compared preoperative and intraoperative variables, as well as postoperative outcomes, between those with and without transfusion in both unadjusted cohorts and those matched by predicted risk of mortality (PROM). Mortality was further evaluated with phase of care analysis.
Results: Of the 672 deaths, 566 patients (84.2%) received a transfusion of red blood cells. The PROM was 7.5% for the transfused patients versus 4.3% for those not transfused (p < 0.001). Transfused patients were older, more often female, had more emergency, on-pump, and redo procedures, and had a lower preoperative and on-bypass nadir hematocrit. Most other demographics were similar between the groups. Postoperatively, transfused patients were ventilated longer, had more renal and multisystem organ failure, and were more likely to die of infectious and pulmonary causes after longer intensive care unit and overall lengths of stay.
Conclusion: Significant differences in PROM and the postoperative course leading to death between those with and without transfusion suggest the role of transfusion may be secondary to other patient-related factors. Recognizing that the relationship between transfusion and outcome after CABG remains incompletely understood, these findings are suggestive of a complex interaction of many variables.
Center-level Variation in Infection Rates after Coronary Artery Bypass Grafting
Background: Health-care-acquired infections (HAIs) are a leading cause of morbidity and mortality after cardiac surgery. Prior work has identified several patient-related risk factors associated with HAIs. We hypothesized that rates of HAIs would differ across institutions, in part attributed to differences in case mix.
Methods and Results: We analyzed 20 896 patients undergoing isolated coronary artery bypass grafting surgery at 33 medical centers in Michigan between January 1, 2009, and June 30, 2012. Overall HAIs included pneumonia, sepsis/septicemia, and surgical site infections, including deep sternal wound, thoracotomy, and harvest/cannulation site infections. We excluded patients presenting with endocarditis. Predicted rates of HAIs were estimated using multivariable logistic regression. Overall rate of HAI was 5.1% (1071 of 20 896; isolated pneumonia, 3.1% [n=644]; isolated sepsis/septicemia, 0.5% [n=99]; isolated deep sternal wound infection, 0.5% [n=96]; isolated harvest/cannulation site, 0.5% [n=97]; isolated thoracotomy, 0.02% [n=5]; multiple infections, 0.6% [n=130]). HAI subtypes differed across strata of center-level HAI rates. Although predicted risk of HAI differed in absolute terms by 2.8% across centers (3.9-6.7%; min:max), observed rates varied by 18.2% (0.9-19.1%).
Conclusion: There was a 18.2% difference in observed HAI rates across medical centers among patients undergoing isolated coronary artery bypass grafting surgery. This variability could not be explained by patient case mix. Future work should focus on the impact of other factors (eg, organizational and systems of clinical care) on risk of HAIs.
Morbidity But Not Mortality Is Decreased After Off-Pump Coronary Artery Bypass Surgery
Background: Off-pump coronary bypass surgery (CABG) has been advocated to avoid the physiologic perturbations related to cardiopulmonary bypass and improve outcomes compared with on-pump CABG. Previous reports have been inconsistent, and thus its benefits remain uncertain. This retrospective study compared outcomes between on-pump and off-pump CABG from a large multicenter cohort of propensity-matched patients.
Methods: The study consisted of 21,640 patients (19,639 [90.8%] on-pump, 2,001 [9.2%] off-pump) who underwent isolated CABG between January 1, 2008, and June 30, 2011, and were entered into a statewide collaborative database. Univariate analysis compared 37 baseline characteristics between on-pump and off-pump procedures. Patients were matched 1:1 based on similarities in propensity scores derived from statistically significant baseline characteristics. Propensity scores and surgery type were used in conditional logistic regression models for predicting each of 14 postoperative outcomes using the sample of 3,898 matched procedures.
Results: Patients undergoing off-pump CABG had significantly fewer complications overall, including decreased red blood cell transfusion, stroke, intensive care unit and ventilator time, reoperation for bleeding, and length of stay. There was no difference in renal failure, wound infection, discharge location, or 30-day readmission rate. Although off-pump patients received fewer bypass grafts per patient (2.5 1.2 versus 3.0 1.1; p < 0.001), operative mortality was similar for the two groups (1.8% on-pump versus 2.3% off-pump; p = 0.30).
Transfusion of 1 and 2 Units of Red Blood Cells Is Associated With Increased Morbidity and Mortality
Background: This study examined the relationship between transfusion of 1 or 2 units of red blood cells (RBCs) and the risk of morbidity and mortality after isolated onpump coronary artery bypass grafting (CABG). Methods. A total of 22,785 consecutive patients underwent isolated on-pump CABG between January 1, 2008, and December 31, 2011 in Michigan. We excluded 5,950 patients who received three or more RBC units. Twenty-one preoperative variables significantly associated with transfusion by univariate analysis were included in a logistic regression model predicting transfusion, and propensity scores were calculated. Transfusion and the propensity score covariate were included in additional logistic regression models predicting mortality and each of 11 postoperative outcomes.
Results: Operative mortality for the study cohort of 16,835 patients was 0.8% overall, 0.5% for the 10,884 patients with no transfusion, and 1.3% for the 5,951 patients who received transfusion of 1 or 2 units (odds ratio 2.44; confidence interval 1.74 to 3.42; p < 0.0001). The association between transfusion and mortality lessened after propensity adjustment but remained highly significant (odds ratio 1.86; confidence interval 1.21 to 2.87; p = 0.005). Of the 11 postoperative outcomes studied, all but sternal wound infection and need for dialysis were also significantly associated with transfusion.
Conclusions: Transfusion of as little as 1 or 2 units of RBCs is common and is significantly associated with increased morbidity and mortality after on-pump CABG. The relationship persists after adjustment for preoperative risk factors. These results suggest that aggressive attempts at blood conservation and avoidance of even small amounts of RBC transfusion may improve outcomes after CABG.
Aortic Valve Replacement: Using a Statewide Cardiac Surgical Database Identifies a Procedural Volume Hinge Point
Background: Expanding therapies for aortic stenosis have focused on high-risk and inoperable patients, suggesting that an evaluation of outcomes of conventional aortic valve replacement (AVR) or AVR and coronary artery bypass grafting (CABG) is timely and warranted.
Methods: Outcomes for 6,270 AVR (3,487) or AVR/CABG (2,783) procedures performed in Michigan (2008-2011) were analyzed using a statewide cardiothoracic surgical database. Hospital and surgeon volumeoutcome relationships were assessed.
Results: Independent predictors of early mortality (all p < 0.05) included age, female sex, predicted risk of mortality, and hospital volume, with a hinge point of a 4-year volume of 390 procedures (high-volume hospital [HVH], 2.41% versus low-volume hospital [LVH], 4.34%; p < 0.001). At this hinge point, observed to expected ratio (O/E) for operative mortality after AVR was lower inHVHs for patients with a predicted risk of mortality (PRoM) greater than 4.7%. In contrast, no surgeon-volume outcome relationship was identified, even when stratified by preoperative patient-risk profile. With respect to other measures, HVHs reported lower rates of prolonged ventilation (24.9% versus LVH, 30.9%; p < 0.001), postoperative transfusion (46.1% versus LVH, 59.0%; p < 0.001), pneumonia (6.6% versus LVH, 9.0%; p=0.01), and multisystem organ failure (0.7% versus LVH, 1.8%; p =0.012).
Transfusion Rate as a Quality Metric: Is Blood Conservation a Learnable Skill?
Background: Between January 2008 and December 2012, a multicenter quality collaborative initiated a focus on blood conservation as a quality metric, with educational presentations and quarterly reporting of institutional-level perioperative transfusion rates and outcomes. This prospective cohort study was undertaken to determine the effect of that initiative on transfusion rates after isolated coronary artery bypass grafting (CABG).
Methods: Between January 1, 2008, and December 31, 2012, 30,271 patients underwent isolated CABG in Michigan. Evaluated were annual crude and adjusted trends in overall transfusion rates for red blood cells (RBCs), fresh frozen plasma (FFP), and platelets, and in operative death.
Results: Transfusion rates continuously decreased for all blood products. RBC use decreased from 56.4% in 2008 (baseline) to 38.3% in 2012, FFP use decreased from 14.8% to 9.1%, and platelet use decreased from 20.5% to 13.4% (ptrend < 0.001 for all). A significant reduction occurred in deep sternal wound infection, reoperation for bleeding, renal failure, prolonged ventilation, initial ventilator time, and intensive care unit duration. The percentage ofpatients discharged home significantly increased (ptrend<0.001). Mortality rates did not differ significantly (ptrend= 0.11).
Analyzing “Failure to Rescue”: Is This an Opportunity for Outcome Improvement in Cardiac Surgery?
Background: In the setting of a statewide quality collaborative approach to the review of cardiac surgical mortalities in intensive care units (ICUs), variations in complication-related outcomes became apparent.Utilizing “failure to rescue”methodology (FTR; the probability of death after a complication), we compared FTR rates after adult cardiac surgery in low, medium, and high mortality centers from a voluntary, 33-center quality collaborative.
Methods: We identified 45,904 patients with a Society of Thoracic Surgeons predicted risk of mortality who underwent cardiac surgery between 2006 and 2010. The 33 centers were ranked according to observedto-expected ratios for mortality and were categorized into 3 equal groups. We then compared rates of complications and FTR.
Results: Overall unadjusted mortality was 2.6%, ranging from 1.5% in the low-mortality group to 3.6% in the high group. The rate of 17 complications ranged from 19.1% in the low group to 22.9% in the high group while FTR rates were 6.6% in the low group, 10.4% in the medium group, and 13.5% in the high group (p < 0.001). The FTR rate was significantly better in the low mortality group for the majority of complications (11 of 17) with the most significant findings for cardiac arrest, dialysis, prolonged ventilation, and pneumonia.
Validation of a Perfusion Registry: Methodological Approach and Initial Findings
Abstract: Although regional and national registries exist to measure and report performance of cardiac surgical programs, few registries exist dedicated to the practice of cardiopulmonary bypass (CPB). We developed and implemented a cardiovascular perfusion registry (Perfusion Measures and outcomes [PERForm] Registry) within the structure of the Michigan Society of Thoracic and Cardiovascular Surgeons (MSTCVS) to improve our understanding of the practice of CPB. The PERForm Registry comprises data elements describing the practice of CPB. Fourteen medical centers within MSTCVS have voluntarily reported these data on procedures in which CPB is used. We validated the case count among procedures performed between January 1, 2011 to December 31, 2011, and validated the values among 20 fields at three medical centers. We queried database managers at all 14 medical centers to identify the infrastructure that contributed to best overall data collection performance. We found that 98% of all records submitted to the PERForm and 95% of those submitted to the Society of Thoracic Surgeons (STS) matched. We found quite favorable agreement in our audit of select fields (95.8%). Those centers with the most favorable performance in this validation study were more likely to use electronic data capture, have a perfusionist as the STS database manager, and have involvement of the STS database manager in the PERForm or STS databases. We successfully and accurately collected data concerning cardiovascular perfusion among 14 institutions in conjunction with the MSTCVS. Future efforts will focus on expanding data collection to all MSTCVS participating institutions as well as more broadly outside of Michigan.
Preoperative predicted risk does not fully explain the association between red blood cell transfusion and mortality in coronary artery bypass grafting
Objective: Perioperative red blood cell transfusion is associated with increased morbidity and mortality after coronary artery bypass grafting (CABG). Whether transfusion is a cause of these outcomes or serves as a surrogate for a high-risk patient population remains uncertain. This retrospective study tested the hypothesis that increased preoperative risk profile of patients receiving transfusion would explain the relationship between red blood cell transfusion and operative mortality in isolated CABG.
Methods: A total of 31,818 patients undergoing isolated CABG were entered into a statewide collaborative database between January 2006 and June 2010. With the Society of Thoracic Surgeons risk calculator, patient cohorts were stratified into 4 groups by predicted risk of mortality (PROM) of less than 2%, 2% to 5%, more than 5% to 10% and more than 10%. The association between blood transfusion and mortality was tested at each stratum with a x2 test. A Breslow-Day test for homogeneity of odds ratios was used to test whether the 4 odds ratios of the strata were similar, and a Cochran-Mantel-Haenszel test was used to test the association between blood transfusion and mortality while controlling for predicted risk mortality strata.
Results: In all, 17,720 (55.7%) of all patients were transfused during the hospitalization. Incidence of transfusion increased stepwise with risk level; 93.3% of patients with PROM greater than 10% received blood. Operative mortality was 2.1% overall, 0.6% among the 44.3% of patients who were not transfused, and 3.3% in the transfused group (odds ratio, 6.19; P<.0001). The association between blood transfusion and mortality was significant within each predicted risk stratum. Increased mortality associated with transfusion was statistically equivalent across all predicted risk strata (P =.1778). The association between blood transfusion and mortality for all patients lessened somewhat when controlling for PROM (odds ratio, 2.99 vs 6.19), yet remained highly significant (P<.0001).
A Method to Evaluate Cardiac Surgery Mortality: Phase of Care Mortality Analysis
Background: This is a study of a method of mortality review, adopted by the Michigan Society of Thoracic and Cardiovascular Surgeons, to enhance understanding of mortality and potentially avoidable deaths after cardiac surgery, utilizing a voluntary statewide database.
Methods: A system to categorize mortality was developed utilizing a phase of care mortality analysis approach as well as providing criteria to classify mortality as potentially “avoidable.” For each mortality, the operating surgeon categorized a cardiac surgery mortality trigger into 1 of 5 time frames: preoperative, intraoperative, intensive care unit (ICU), postoperative, and discharge.
Results: A total of 53,674 adult cardiac operations were performed from January 1, 2006 to June 30, 2010 with a crude mortality of 3.5% (1,905 of 53,674). Of the mortalitiesanalyzed, 35% (618 of 1,780) were preoperative, 25% (451 of 1,780) were ICU, 19% (333 of 1,780) were intraoperative, 11% (198 of 1,780) were floor, and 10% (180 of 1,780) were discharge phase. “Avoidable” mortality triggers occurred in 53% (174 of 333) of the intraoperative, 41% (253 of 618) and (184 of 451) of the preoperative and ICU phases, 42% (83 of 198) of the floor, and 19% (35 of 180) of the discharge phase. Overall potentially avoidable mortality was 41% (729 of 1780). Thirty-six percent (644 of 1,780) of the mortalities were coronary artery bypass grafting patients and 29% (188 of 644) of these were in the preoperative phase, with a mean predicted risk of 16%.
How A Regional Collaborative Of Hospitals And Physicians In Michigan Cut Costs And Improved The Quality Of Care
Abstract: There is evidence that collaborations between hospitals and physicians in particular regions of the country have led to improvements in the quality of care. Even so, there have not been many of these collaborations. We review one, the Michigan regional collaborative improvement program, which was paid for by a large private insurer, has yielded improvements for a range of clinical conditions, and has reduced costs in several important areas. In general and vascular surgery alone, complications from surgery dropped almost 2.6 percent among participating Michigan hospitals—a change that translates into 2,500 fewer Michigan patients with surgical complications each year. Estimated annual savings from this one collaborative are approximately $20 million, far exceeding the cost of administering the program. Regional collaborative improvement programs should become increasingly attractive to hospitals and physicians, as well as to national policy makers, as they seek to improve health care quality and reduce costs.
Statewide Quality Collaborative for Process Improvement: Internal Mammary Artery Utilization
Background: The Michigan Society of Thoracic and Cardiovascular Surgeons (MSTCVS) Quality Collaborative is a voluntary, surgeon-directed quality initiative involving all cardiac surgery programs in Michigan. Understanding that internal mammary artery (IMA) use during coronary artery bypass grafting is an important process measure associated with improved outcomes, this analysis reviews our methodology to understand IMA use and increase appropriate IMA use statewide.
Methods: Adult cardiac Society of Thoracic Surgeons data were collected at each Michigan site and submitted quarterly to the Duke Clinical Research Institute and the MSTCVS. Seven cardiac surgery programs with IMA use less than 90% in isolated coronary artery bypass grafting were identified as low IMA users. An improvement plan was adopted at the state level and included quarterly monitoring of IMA use, documenting the rationale for IMA exclusion, evidence-based lectures, feedback letters to sites, and physician-led site visits if no improvement was noted.
Results: From 2005 through 2008, 29,114 patients underwent coronary artery bypass grafting in Michigan. Internal mammary artery utilization varied widely at the beginning of this investigation, ranging from 66.2% to 98.4%. Seven Michigan programs were identified as low IMA users. Using the MSTCVS Quality Collaborative’s process-improvement plan, collectively the seven low IMA users increased IMA grafting from 82.0% to 92.7% (p < 0.0001). Michigan IMA use increased from 91.9% to 95.8% (p < 0.0001) and is now higher than The Society of Thoracic Surgeon’s average.
Cardiac Surgeons and the Quality Movement: the Michigan Experience
The Michigan Society of Thoracic and Cardiovascular Surgeons (MSTCVS) was founded in 1965 during an era when many national, regional, and state speciality societies were beginning. The first meeting of what was initially called the Michigan Society of Thoracic Surgeons was held on September 21, 1965 in Detroit in conjunction with the Michigan State Medical Society (personal communication, Allen Silbergleit, MD, PhD, Historian, Michigan Society of Thoracic and Cardiovascular Surgeons, August 2008). The initial meeting was attended by 17 of the 60 board certified thoracic surgeons in Michigan. Dr Cameron Haight, Head of the Section of Thoracic Surgery at the University of Michigan in Ann Arbor, was the President of the society.
As one of the first state thoracic organizations, plans were implemented for an annual meeting, which in the initial years often occurred in conjunction with the American College of Surgeons Michigan Chapter meeting. In the mid-1980s the Michigan Society of Thoracic Surgeons created its own meeting time and moved the annual meeting to resort areas in northern Michigan in late summer. Recognizing the evolution of the speciality of Thoracic Surgery, in 1988 the name of the organization was changed from the Michigan Society of Thoracic Surgeons to the Michigan Society of Thoracic and Cardiovascular Surgeons. Today, the Society has over 100 board-certified thoracic surgeon members, as well as associate members, including data managers, physician assistants, and perfusionists.
Since its inception in 1965 the society has had yearly meetings with the initial focus of these meetings on case presentations, as well as providing an opportunity for house officers from Michigan programs in general surgery, and the two thoracic surgical residency programs to present scientific papers. Presentations from invited cardiac and thoracic surgeon guests with expertise in various areas have become a part of the meeting programs in recent years.
Partnering with payers to improve surgical quality: The Michigan plan
With growing recognition that surgical outcomes vary widely across providers, employers and payers are becoming more actively involved in strategies for improving the quality of surgical care.Employers have obvious interests in minimizing productivity losses from employees undergoing surgical procedures. With ever-rising health care costs, purchasers and payers are also increasingly aware of the financial implications of surgical complications. According to one recent analysis, major complications add over $11,000 to the baseline cost of a surgical procedure.
Payers are using a variety of tactics to improve surgical outcomes. Some are focusing on selective referral strategies. For example, the Leapfrog Group is using public reporting, selective contracting, and a variety of financial incentives to steer patients to hospitals or surgeons likely to have the best results. However, many payers are shifting their focus to “pay-for-performance”(P4P) strategies, using direct financial incentives to motivate quality improvement. With P4P, hospitals are rewarded for meeting specific performance benchmarks, as determined by process of care or direct outcome measures. For example, in a new P4P initiative launched by the Center for Medicare and Medicaid Services, hospitals scoring in the top decile of performance (based on a composite of quality indicators) for coronary artery bypass will receive a 2% bonus on their Medicare payments for this procedure. Similarly, both Centers for Medicare & Medicaid Services (CMS) and many private payers are implementing P4P plans focused on the appropriate use of perioperative antibiotics.
Literature Related to Quality and Cardiac Surgery
Shahian D, Normand S. Low-volume coronary artery bypass surgery: Measuring and optimizing performance. J Thor Cardiovasc Surg. 2008;135:1202-1209.
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Recent Journal Publications
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