Unravelling the Difference Between Men and Women in Post-CABG Survival.

Objectives: Women have a worse prognosis after coronary artery bypass grafting (CABG) surgery compared to men. We sought to quantify to what extent this difference in post-CABG survival could be attributed to sex itself, or whether this was mediated by difference between men and women at the time of intervention. Additionally, we explored to what extent these effects were homogenous across patient subgroups. Methods: Time to all-cause mortality was available for 102,263 CABG patients, including 20,988 (21%) women, sourced through an individual participant data meta-analysis of five cohort studies. Difference between men and women in survival duration was assessed using Kaplan-Meier estimates, and Cox's proportional hazards model. Results: During a median follow-up of 5 years, 13,598 (13%) patients died, with women more likely to die than men: female HR 1.20 (95%CI 1.16; 1.25). We found that differences in patient characteristics at the time of CABG procedure mediated this sex effect, and accounting for these resulted in a neutral female HR 0.98 (95%CI 0.94; 1.02). Next we performed a priori defined subgroup analyses of the five most prominent mediators: age, creatinine, peripheral vascular disease, type 2 diabetes, and heart failure. We found that women without peripheral vascular disease (PVD) or women aged 70+, survived longer than men (interaction p-values 0.04 and 6 × 10-5, respectively), with an effect reversal in younger women. Conclusion: Sex differences in post-CABG survival were readily explained by difference in patient characteristics and comorbidities. Pre-planned analyses revealed patient subgroups (aged 70+, or without PVD) of women that survived longer than men, and a subgroup of younger women with comparatively poorer survival.

Economic Evaluation of National Patient Blood Management Clinical Guidelines in Cardiac Surgery.

OBJECTIVES: To the best of our knowledge, no published clinical guidelines have ever undergone an economic evaluation to determine whether their implementation represented an efficient allocation of resources. Here, we perform an economic evaluation of national clinical guidelines designed to reduce unnecessary blood transfusions before, during, and after surgery published in 2012 by Australia's sole public blood provider, the National Blood Authority (NBA). METHODS: We performed a cost analysis from the government perspective, comparing the NBA's cost of implementing their perioperative patient blood management guidelines with the estimated resource savings in the years after publication. The impact on blood products, patient outcomes, and medication use were estimated for cardiac surgeries only using a large national registry. We adopted conservative counterfactual positions over a base-case 3-year time horizon with outcomes predicted from an interrupted time-series model controlling for differences in patient characteristics and hospitals. RESULTS: The estimated indexed cost of implementing the guidelines of A$1.5 million (2018-2019 financial year prices) was outweighed by the predicted blood products resource saving alone of A$5.1 million (95% confidence interval A$1.4 million-A$8.8 million) including savings of A$2.4 million, A$1.6 million, and A$1.2 million from reduced red blood cell, platelet, and fresh frozen plasma use, respectively. Estimated differences in patient outcomes were highly uncertain and estimated differences in medication were financially insignificant. CONCLUSIONS: Insofar as they led to a reduction in red blood cell, platelet, and fresh frozen plasma use during cardiac surgery, implementing the perioperative patient blood management guidelines represented an efficient use of the NBA's resources.

Preoperative identification of cardiac surgery patients at risk of receiving a platelet transfusion: The Australian Cardiac Surgery Platelet Transfusion (ACSePT) risk prediction tool.

Platelet (PLT) transfusions are limited and costly resources. Accurately predicting clinical demand while limiting product wastage remains difficult. A PLT transfusion prediction score was developed for use in cardiac surgery patients who commonly require PLT transfusions. STUDY DESIGN AND METHODS: Using the Australian and New Zealand Society of Cardiac and Thoracic Surgeons National Cardiac Surgery Database, significant predictors for PLT transfusion were identified by multivariate logistic regression. Using a development data set containing 2005 to 2016 data, the Australian Cardiac Surgery Platelet Transfusion (ACSePT) risk prediction tool was developed by assigning weights to each significant predictor that corresponded to a probability of PLT transfusion. The predicted probability for each score was compared to actual PLT transfusion occurrence in a validation (2017) data set. RESULTS: The development data set contained 38 independent variables and 91 521 observations. The validation data set contained 12 529 observations. The optimal model contained 23 variables significant at P < .001 and an area under the receiver operating characteristic (ROC) curve of 0.69 (95% confidence interval [CI], 0.68-0.69). ACSePT contained nine variables and had an area under the ROC curve of 0.66 (95% CI, 0.65-0.66) and overall predicted probability of PLT transfusion of 19.8% for the validation data set compared to an observed risk of 20.3%. CONCLUSION: The ACSePT risk prediction tool is the first scoring system to predict a cardiac surgery patient's risk of receiving a PLT transfusion. It can be used to identify patients at higher risk of receiving PLT transfusions for inclusion in clinical trials and by PLT inventory managers to predict PLT demand.

Prophylactic Intra-Aortic Balloon Counterpulsation in High Risk Cardiac Surgery: The PINBALL Pilot Multicentre, Registry-Linked, Randomised, Controlled Feasibility Trial.

BACKGROUND: Prophylactic intra-aortic balloon counterpulsation (IABC) is commonly used in selected patients undergoing coronary artery bypass graft (CABG) surgery, but definitive evidence is lacking. The aim of the multicentre PINBALL Pilot randomised controlled trial (RCT) was to assess the feasibility of performing a definitive trial to address this question. METHODS: Patients listed for CABG surgery with impaired left ventricular function and at least one additional risk factor for postoperative low cardiac output syndrome were eligible for inclusion if the treating surgical team was uncertain as to the benefit of prophylactic IABC. The primary outcome of feasibility was based on exceeding a pre-specified recruitment rate, protocol compliance and follow-up. RESULTS: The recruitment rate of 0.5 participants per site per month did not meet the feasibility threshold of two participants per site per month and the study was stopped early after enrolment of 24 out of the planned sample size of 40 participants. For 20/24 (83%) participants, preoperative IABC use occurred according to study assignment. Six (6)-month follow-up was available for all enrolled participants, [IABC 1 death (8%) vs. control 1 death (9%), p = 0.95]. CONCLUSION: The PINBALL Pilot recruitment rate was insufficient to demonstrate feasibility of a multicentre RCT of prophylactic IABC in high risk patients undergoing CABG surgery.

Surgical aortic valve replacement in Australia, 2002-2015: temporal changes in clinical practice, patient profiles and outcomes.

BACKGROUND: This study describes the temporal changes in risk profiles and outcomes among patients with aortic stenosis (AS) undergoing surgical aortic valve replacement (SAVR) in Australia between 2002 and 2015. METHODS: Using the Australian and New Zealand Society of Cardiac and Thoracic Surgeons database, we identified first-recorded SAVR for AS over 14 years. Patients' surgical risk profiles, procedures, 30-day and 12-month outcomes were summarized before and after the introduction of transcatheter aortic valve implantation in Australia, in 2008. We applied multivariable regression models to investigate the changes over time on risk-adjusted 30-day mortality, re-hospitalization and 12-month mortality. RESULTS: We identify a total of 18 147 patients with AS who underwent SAVR; mostly men (64%) with a mean age of 72 years. The proportion of major cardiac surgeries devoted to SAVR increased from 14% in 2002 to 20% in 2015. More SAVRs were performed electively (80% in 2002 versus 86% in 2015), and the recipients were at lower surgical risk (mean multi-risk score 3.9% in 2002 versus 3.0% in 2015). The use of bioprosthetic aortic valves increased over time (67% in 2002 to 88% in 2015). We found no significant changes in 30-day mortality, a significant decrease in 30-day readmission and minor fluctuations in 12-month mortality over the study period. CONCLUSION: SAVR comprises an increasingly larger proportion of all adult cardiac surgeries in Australia. There has been a greater use of bioprosthetic aortic valves, a fall in 30-day readmission but no significant changes in mortality.

The Australian and New Zealand Society of Cardiac and Thoracic Surgeons Database Program - Two Decades of Quality Assurance Data.

Over two decades, the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) cardiac surgery database program has evolved from a single state-based database to a national clinical quality registry program and is now the most comprehensive cardiac surgical registry in Australia. We report the current structure and governance of the program and its key activities.

On-Pump Beating Heart Versus Conventional Coronary Artery Bypass Grafting Early After Myocardial Infarction: A Propensity-Score Matched Analysis From the ANZSCTS Database.

BACKGROUND: Coronary artery bypass grafting (CABG) performed early after acute myocardial infarction (AMI) carries a high risk of mortality. By avoiding cardioplegic arrest and aortic cross-clamping, on-pump beating heart CABG (ONBEAT) may benefit patients requiring urgent or emergency revascularisation in the setting of AMI. We evaluated the early and long-term outcomes of ONBEAT versus conventional CABG (ONSTOP) utilising the ANZSCTS National Cardiac Surgery Database. METHODS: Between 2001 and 2015, 5,851 patients underwent non-elective on-pump CABG within 7 days of AMI. Of these, 77 patients (1.3%) underwent ONBEAT and 5774 (98.7%) underwent ONSTOP surgery. Propensity-score matching (with a 1:2 matching ratio) was performed for risk adjustment. Survival data were obtained from the National Death Index. RESULTS: Before matching, the unadjusted 30-day mortality was ONBEAT: 9/77 (11.7%) vs. ONSTOP: 256/5,774 (4.4%), p<0.001. Preoperative factors independently associated with the ONBEAT were: septuagenarian age, peripheral vascular disease, redo surgery, cardiogenic shock, emergency surgery and single-vessel disease. After propensity-score matching, 30-day mortality was similar (ONBEAT: 9/77 (11.7%) vs. ONSTOP: 16/154 (10.4%), p=0.85), as was the rate of major adverse cardiac and cerebrovascular events (ONBEAT: 17/77 (22.1%) vs. ONSTOP: 38/154 (24.7%), p=0.84). ONBEAT patients received fewer distal anastomoses and were more likely to have incomplete revascularisation (ONBEAT: 15/77 (19.5%) vs. ONSTOP: 15/154, (9.7%), p=0.03). Despite this, 12-year survival was comparable (ONBEAT: 64.8% (95% CI 39.4-82.4%) vs. ONSTOP: 63.6% (95% CI 50.5, 74.3%), p=0.89). CONCLUSIONS: ONBEAT can be performed safely in high-risk patients requiring CABG early after AMI with similar short and long-term survival compared to ONSTOP.

Structured Feedback: Acceptability and Feasibility of a Strategy to Enhance the Role of a Clinical Quality Registry to Drive Change in Cardiac Surgical Practice.

BACKGROUND: The Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) Database collects and monitors preoperative, operative, and 30-day outcome data on patients undergoing cardiac surgery, and delivers regular performance feedback reports to key personnel with intent to drive quality improvement. The current feedback approach appears to be ineffective in driving change to minimise Unit performance variation. We sought to determine the acceptability and feasibility of providing structured feedback in addition. METHODS: Cardiac surgeons were surveyed to assess their evaluation of the current feedback reports and assist in developing the content of structured feedback. We then assessed acceptability and performance outcomes of control Units receiving current feedback reports via email, versus intervention Units that in addition received structured feedback. RESULTS: Survey respondents assessing the current feedback report agreed that the content is relevant (95%), key performance indicators (KPIs) are useful (85%), and that it would be beneficial to compare surgeons' KPIs (75%). Survey respondents rating method of feedback, requested structured feedback sessions one to two times annually (67%; control Units), and future structured feedback (83%; intervention Units). With combined report and structured feedback, improved performance was noted for an under-performing Unit. Limitations of feedback in driving quality improvement was high performance of Units at baseline, low surgeon participation, and scheduling challenges for structured feedback. CONCLUSIONS: In this pilot study, compared to the control method, structured feedback did not significantly improve communication. To maximise quality improvement efforts, a collaborative feedback approach that fosters a climate of continuous performance improvement, is recommended.

The Real-World Cost-Effectiveness of Coronary Artery Bypass Surgery Versus Stenting in High-Risk Patients: Propensity Score-Matched Analysis of a Single-Centre Experience.

BACKGROUND: There are limited economic evaluations comparing coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI) for multi-vessel coronary artery disease (MVCAD) in contemporary, routine clinical practice. OBJECTIVE: The aim was to perform a cost-effectiveness analysis comparing CABG and PCI in patients with MVCAD, from the perspective of the Australian public hospital payer, using observational data sources. METHODS: Clinical data from the Melbourne Interventional Group (MIG) and the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) registries were analysed for 1022 CABG (treatment) and 978 PCI (comparator) procedures performed between June 2009 and December 2013. Clinical records were linked to same-hospital admissions and national death index (NDI) data. The incremental cost-effectiveness ratios (ICERs) per major adverse cardiac and cerebrovascular event (MACCE) avoided were evaluated. The propensity score bin bootstrap (PSBB) approach was used to validate base-case results. RESULTS: At mean follow-up of 2.7 years, CABG compared with PCI was associated with increased costs and greater all-cause mortality, but a significantly lower rate of MACCE. An ICER of $55,255 (Australian dollars)/MACCE avoided was observed for the overall cohort. The ICER varied across comparisons against bare metal stents (ICER $25,815/MACCE avoided), all drug-eluting stents (DES) ($56,861), second-generation DES ($42,925), and third-generation of DES ($88,535). Moderate-to-low ICERs were apparent for high-risk subgroups, including those with chronic kidney disease ($62,299), diabetes ($42,819), history of myocardial infarction ($30,431), left main coronary artery disease ($38,864), and heart failure ($36,966). CONCLUSIONS: At early follow-up, high-risk subgroups had lower ICERs than the overall cohort when CABG was compared with PCI. A personalised, multidisciplinary approach to treatment of patients may enhance cost containment, as well as improving clinical outcomes following revascularisation strategies.

Medical Management of Rheumatic Heart Disease: A Systematic Review of the Evidence.

Rheumatic heart disease (RHD) is an important cause of heart disease globally. Its management can encompass medical and procedural (catheter and surgical) interventions. Literature pertaining to the medical management of RHD from PubMed 1990-2016 and via selected article reference lists was reviewed. Areas included symptom management, left ventricular dysfunction, rate control in mitral stenosis, atrial fibrillation, anticoagulation, infective endocarditis prophylaxis, and management in pregnancy. Diuretics, angiotensin blockade and beta-blockers for left ventricular dysfunction, and beta-blockers and If inhibitors for rate control in mitral stenosis reduced symptoms and improved left ventricular function, but did not alter disease progression. Rhythm control for atrial fibrillation was preferred, and where this was not possible, rate control with beta-blockers was recommended. Anticoagulation was indicated where there was a history of cardioembolism, atrial fibrillation, spontaneous left atrial contrast, and mechanical prosthetic valves. While warfarin remained the agent of choice for mechanical valve implantation, non-vitamin K antagonist oral anticoagulants may have a role in RHD-related AF, particularly with valvular regurgitation. Evidence for anticoagulation after bioprosthetic valve implantation or mitral valve repair was limited. RHD patients are at increased risk of endocarditis, but the evidence supporting antibiotic prophylaxis before procedures that may induce bacteremia is limited and recommendations vary. The management of RHD in pregnancy presents particular challenges, especially regarding decompensation of previously stable disease, the choice of anticoagulation, and the safety of medications in both pregnancy and breast feeding.

Thirty-day outcomes in Indigenous Australians following coronary artery bypass grafting.

BACKGROUND: Indigenous Australians have higher rates of cardiovascular disease and comorbidities compared to their non-indigenous counterparts. AIMS: We sought to evaluate whether indigenous status per se portends a worse prognosis following isolated coronary artery bypass grafting (CABG). METHODS: The outcomes of 778 Indigenous Australians (55 ± 10 years; 32% female) enrolled in the Australian and New Zealand Society of Cardiac and Thoracic Surgeons registry were compared to 36 124 non-Indigenous Australians (66 ± 10 years; 21% female) following isolated CABG. In a secondary analysis, patients were propensity-matched by age, sex, renal function, diabetes and ejection fraction (778 individuals in each group). RESULTS: Indigenous Australians were younger and more likely to be female and current smokers and to have diabetes, hypertension, renal impairment, heart failure and previous CABG (all P < 0.04). Indigenous patients had fewer bypasses with arterial conduits (including less internal mammary artery use) and a higher number of distal vein anastomoses (P < 0.001). Postoperative bleeding rates were higher in indigenous patients (P = 0.001). However, in-hospital and 30-day all-cause mortality and rates of 30-day readmission were similar between both groups, although cardiac mortality was higher in the indigenous cohort (1.5% vs 0.8%, P = 0.02). With propensity-matching, rates of postoperative complications were similar among the two groups, with the exception of bleeding, which remained higher in Indigenous Australians (P = 0.03). CONCLUSIONS: Despite procedural differences and higher rates of baseline comorbidities, Indigenous Australians do not have worse short-term outcomes following isolated CABG. Given the higher rates of baseline comorbidities and lower rates of arterial conduit use, it will be essential to determine long-term outcomes.

Impact of Discontinuation of Antiplatelet Therapy Prior to Isolated Valve and Combined Coronary Artery Bypass Graft and Valve Procedures on Short and Intermediate Term Outcomes.

BACKGROUND: A change in cardiac surgery practice over the past decade has seen an increase in urgent or inpatient referrals for surgery, with antiplatelet therapy often continued up until surgery. This study aims to identify the optimal timing for administration of aspirin to minimise risk of perioperative morbidity and mortality. METHODS: From a prospectively compiled database collected by the Australian and New Zealand Society of Cardiac and Thoracic Surgeons, we identified 8294 patients undertaking combined CABG and valve or isolated valve procedures while discontinuing aspirin. Time points for cessation of antiplatelet therapy were categorised as follows: <2 days, 3-7 days or >7 days preoperatively. We evaluated the association of adverse in-hospital events and intermediate term survival in each time category. RESULTS: Discontinuing aspirin 3 to 7 days from surgery decreased rates of perioperative MI (HR=0.300, p=0.027), return to theatre (HR=0.560, p=0.002) reduced drain output (HR=0.757, p=0.000) and red blood cell and platelet transfusions (HR=0.719, p=0.000 and HR=0.604, p=0.000 respectively) compared to patients continuing aspirin until <2 days from the procedure. Stopping aspirin <2 days from the date of surgery increased risk of perioperative MI (HR=5.919, p=0.000), reoperation for bleeding (HR=2.076, p=0.001), returning to theatre (HR=1.781, p=0.000), ICC drain losses (HR=1.337, p=0.000) and transfusion demands for red blood cells (HR=1.381, p=0.000) and platelets (HR=1.450, p=0.000) when compared to those discontinuing aspirin >7 days from surgery. CONCLUSION: Late discontinuation of aspirin before combined coronary artery bypass graft and valve procedures results in greater rates of bleeding and transfusion requirements. Earlier discontinuation of aspirin results in no benefit in intermediate term survival.

Two Long-Term Mortality Risk Models For Coronary Artery Bypass Graft Surgery Produced in American Populations Validated in an Australian Population.

BACKGROUND: Short-term mortality prediction models have an important role in current cardiac surgical practice. There has been much less attention paid to prediction of long-term outcomes which are probably an equal marker both of surgeon performance and appropriateness of surgical treatment. The aim of this study was to assess the performance of the New York State Cardiac Surgery Reporting System (NYSCSRS) risk model and the Northern New England Cardiovascular Disease Study Group (NNECDSG) risk model on the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) patient database. METHODS: The NYSCSRS and the NNECDSG risk models were applied to all patients undergoing isolated coronary artery bypass graft (CABG) surgery that had complete data, were over the age of 18 and had a body mass index between 12 and 78 kg/m2. Predicted mortality was calculated using the published risk model formulae and compared with observed mortality, obtained via linkage with the National Death Index, at four time-points (one, three, five and seven years following surgery). Model discrimination and model calibration were tested at all four time points by determining the C-statistics for receiver operator characteristic (ROC) curves, and studying the Hosmer-Lemeshow chi-square tests, respectively. RESULTS: The NYSCSRS and NNECDSG risk models were applied to 34,961 and 34,998 patients, respectively. The NYSCSRS risk model over-predicted mortality by between 130% and 216% at all four time-points while the NNECDSG risk model under-predicted mortality at one year by 4.3% but over-predicted mortality at three, five and seven years by between 42.5% and 145.7%. The C-statistics obtained fell between 0.779 and 0.741 for the NYSCSRS risk model and between 0.785 and 0.752 for the NNECDSG risk model at all four time-points. Hosmer-Lemeshow chi-square tests returned p-values <0.001 at all four time-points for both risk models. CONCLUSION: The NYSCSRS and NNECDSG risk models do not accurately predict long-term mortality following isolated CABG surgery in the ANZSCTS patient population. The use of either of these risk models is not appropriate in Australia.

Predicting long-term survival after coronary artery bypass graft surgery.

OBJECTIVES: To develop a model for predicting long-term survival following coronary artery bypass graft surgery. METHODS: This study included 46 573 patients from the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZCTS) registry, who underwent isolated coronary artery bypass graft surgery between 2001 and 2014. Data were randomly split into development (23 282) and validation (23 291) samples. Cox regression models were fitted separately, using the important preoperative variables, for 4 'time intervals' (31-90 days, 91-365 days, 1-3 years and >3 years), with optimal predictors selected using the bootstrap bagging technique. Model performance was assessed both in validation data and in combined data (development and validation samples). Coefficients of all 4 final models were estimated on the combined data adjusting for hospital-level clustering. RESULTS: The Kaplan-Meier mortality rates estimated in the sample were 1.7% at 90 days, 2.8% at 1 year, 4.4% at 2 years and 6.1% at 3 years. Age, peripheral vascular disease, respiratory disease, reduced ejection fraction, renal dysfunction, arrhythmia, diabetes, hypercholesterolaemia, cerebrovascular disease, hypertension, congestive heart failure, steroid use and smoking were included in all 4 models. However, their magnitude of effect varied across the time intervals. Harrell's C-statistics was 0.83, 0.78, 0.75 and 0.74 for 31-90 days, 91-365 days, 1-3 years and >3 years models, respectively. Models showed excellent discrimination and calibration in validation data. CONCLUSIONS: Models were developed for predicting long-term survival at 4 time intervals after isolated coronary artery bypass graft surgery. These models can be used in conjunction with the existing 30-day mortality prediction model.

Mortality risk prediction models for coronary artery bypass graft surgery: current scenario and future direction.

INTRODUCTION: Many risk prediction models are currently in use for predicting short-term mortality following coronary artery bypass graft (CABG) surgery. This review critically appraised the methods that were used for developing these models to assess their applicability in current practice setting as well as for the necessity of up-gradation. EVIDENCE ACQUISITION: Medline via Ovid was searched for articles published between 1946 and 2016 and EMBASE via Ovid between 1974 and 2016 to identify risk prediction models for CABG. Article selection and data extraction was conducted using the CHARMS checklist for review of prediction model studies. Association between model development methods and model's discrimination was assessed using Kruskal-Wallis one-way analysis of variance and Mann-Whitney U-test. EVIDENCE SYNTHESIS: A total of 53 risk prediction models for short-term mortality following CABG were identified. The review found a wide variation in development methodology of risk prediction models in the field. Ambiguous predictor and outcome definition, sub-optimum sample size, inappropriate handling of missing data and inefficient predictor selection technique are major issues identified in the review. Quantitative synthesis in the review showed "missing value imputation" and "adopting machine learning algorithms" may result in better discrimination power of the models. CONCLUSIONS: There are aspects in current risk modeling, where there is room for improvement to reflect current clinical practice. Future risk modelling needs to adopt a standardized approach to defining both outcome and predictor variables, rational treatment of missing data and robust statistical techniques to enhance performance of the mortality risk prediction.

Missing Value Imputation Improves Mortality Risk Prediction Following Cardiac Surgery: An Investigation of an Australian Patient Cohort.

BACKGROUND: The aim of this study was to evaluate the impact of missing values on the prediction performance of the model predicting 30-day mortality following cardiac surgery as an example. METHODS: Information from 83,309 eligible patients, who underwent cardiac surgery, recorded in the Australia and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) database registry between 2001 and 2014, was used. An existing 30-day mortality risk prediction model developed from ANZSCTS database was re-estimated using the complete cases (CC) analysis and using multiple imputation (MI) analysis. Agreement between the risks generated by the CC and MI analysis approaches was assessed by the Bland-Altman method. Performances of the two models were compared. RESULTS: One or more missing predictor variables were present in 15.8% of the patients in the dataset. The Bland-Altman plot demonstrated significant disagreement between the risk scores (p<0.0001) generated by MI and CC analysis approaches and showed a trend of increasing disagreement for patients with higher risk of mortality. Compared to CC analysis, MI analysis resulted in an average of 8.5% decrease in standard error, a measure of uncertainty. The MI model provided better prediction of mortality risk (observed: 2.69%; MI: 2.63% versus CC: 2.37%, P<0.001). CONCLUSION: 'Multiple imputation' of missing values improved the 30-day mortality risk prediction following cardiac surgery.

The burden and implications of preoperative atrial fibrillation in Australian heart valve surgery patients.

BACKGROUND: Atrial fibrillation (AF) is the most common preoperative arrhythmia in heart valve surgery patients and its prevalence is rising. This study aims to investigate the impact of AF on valve surgery early complications and survival and on valve disease of different aetiologies and populations with particular reference to Indigenous Australians with rheumatic heart disease (RHD). METHODS: The Australian and New Zealand Society of Cardiac and Thoracic Surgeons Cardiac Surgery Database was analysed to determine the association between preoperative AF and valve surgery outcome. Its association with demographics, co-morbidities, preoperative status and short and long term outcome was assessed. RESULTS: Outcome of 1594 RHD and 19,029 non-RHD-related surgical procedures was analysed. Patients with preoperative AF were more likely to be older, female, Indigenous, to have RHD and to bear a greater burden of comorbidities. Patients with RHD and preoperative AF had a longer hospital stay and were more likely to require reoperation. Adjusted short (OR 1.4, 95% CI 1.2-1.7) and long term (HR 1.5, 95% CI 1.3-1.7) survival was inferior for patients with non-RHD preoperative AF but was no different for Indigenous and non-Indigenous Australians with RHD. CONCLUSIONS: In this prospective Australian study, patients with valve disease and preoperative AF had inferior short and long term survival. This was particularly the case for patients with non-RHD valve disease. Earlier intervention or more aggressive AF management should be investigated as mechanisms for enhancing postoperative outcomes. This may influence treatment choice and the need for ongoing anticoagulation.

Variable selection methods for multiple regressions influence the parsimony of risk prediction models for cardiac surgery.

OBJECTIVE: To compare the impact of different variable selection methods in multiple regression to develop a parsimonious model for predicting postoperative outcomes of patients undergoing cardiac surgery. METHODS: Data from 84,135 patients in the Australian and New Zealand Society of Cardiac and Thoracic Surgeons registry between 2001 and 2014 were analyzed. Primary outcome was 30-day-mortality. Mixed-effect logistic regressions were used to build the model. Missing values were imputed by the use of multiple imputations. The following 5 variable selection methods were compared: bootstrap receiver-operative characteristic (ROC), bootstrap Akaike information criteria, bootstrap Bayesian information criteria, and stepwise forward and stepwise backward methods. The final model's prediction performance was evaluated by the use of Frank Harrell's calibration curve and using a multifold cross-validation approach. RESULTS: Stepwise forward and backward methods selected same set of 21 variables into the model with the area under the ROC (AUC) of 0.8490. The bootstrap ROC method selected 13 variables with AUC of 0.8450. Bootstrap Bayesian information criteria and Akaike information criteria respectively selected 16 (AUC: 0.8470) and 23 (AUC: 0.8491) variables. Bootstrap ROC model was selected as the final model which showed very good discrimination and calibration power. CONCLUSIONS: Clinical suitability in terms of parsimony and prediction performance can be achieved substantially by using the bootstrap ROC method for the development of risk prediction models.

Outcomes after mitral valve surgery for rheumatic heart disease.

OBJECTIVE: To further the understanding of the factors influencing outcome following rheumatic heart disease (RHD) related mitral valve surgery, which globally remains an important cause of heart disease and a particular problem in Indigenous Australians. METHODS: The Australian Cardiac Surgery Database was utilised to assess outcomes following mitral valve repair and replacement for RHD and non-RHD valve disease. The association with aetiology, demographics, comorbidities, preoperative status and operative procedure was evaluated. RESULTS: Mitral valve repairs and replacements undertaken in Australia were analysed from 119 and 1078 RHD surgical procedures and 3279 and 2400 non-RHD procedures, respectively. RHD mitral valve repair, compared with replacement, resulted in a slightly shorter hospital stay and more reoperation for valve dysfunction, but no difference in 30-day survival. In unadjusted survival analysis to 5 years, RHD mitral valve repair and replacement were no different (HR 0.86, 95% CI 0.4 to 1.7), non-RHD repair was superior to replacement (HR 1.7, 95% CI 1.4 to 2.0), RHD and non-RHD repair were no different (HR 0.9, 95% CI 0.5 to 1.7), and RHD replacement was superior to non-RHD (HR 1.5, 95% CI 1.2 to 1.9). None of these differences persisted in adjusted analyses and there was no difference in long-term survival for Indigenous Australians. CONCLUSION: In this large prospective cohort study we have demonstrated that adjusted long-term survival following RHD mitral valve repair surgery in Australia is no different to replacement and no different to non-RHD. Interpretation of valve surgery outcome requires careful consideration of patient factors that may also influence survival.