Australian And New Zealand Society Of Cardiac And Thoracic Surgeons Research Articles

Paying attention to cardiac surgical risk: An interpretable machine learning approach using an uncertainty-aware attentive neural network.

Machine learning (ML) is increasingly applied to predict adverse postoperative outcomes in cardiac surgery. Commonly used ML models fail to translate to clinical practice due to absent model explainability, limited uncertainty quantification, and no flexibility to missing data. We aimed to develop and benchmark a novel ML approach, the uncertainty-aware attention network (UAN), to overcome these common limitations. Two Bayesian uncertainty quantification methods were tested, generalized variational inference (GVI) or a posterior network (PN). The UAN models were compared with an ensemble of XGBoost models and a Bayesian logistic regression model (LR) with imputation. The derivation datasets consisted of 153,932 surgery events from the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) Cardiac Surgery Database. An external validation consisted of 7343 surgery events which were extracted from the Medical Information Mart for Intensive Care (MIMIC) III critical care dataset. The highest performing model on the external validation dataset was a UAN-GVI with an area under the receiver operating characteristic curve (AUC) of 0.78 (0.01). Model performance improved on high confidence samples with an AUC of 0.81 (0.01). Confidence calibration for aleatoric uncertainty was excellent for all models. Calibration for epistemic uncertainty was more variable, with an ensemble of XGBoost models performing the best with an AUC of 0.84 (0.08). Epistemic uncertainty was improved using the PN approach, compared to GVI. UAN is able to use an interpretable and flexible deep learning approach to provide estimates of model uncertainty alongside state-of-the-art predictions. The model has been made freely available as an easy-to-use web application demonstrating that by designing uncertainty-aware models with innately explainable predictions deep learning may become more suitable for routine clinical use.

Tree-based survival analysis improves mortality prediction in cardiac surgery.

Machine learning (ML) classification tools are known to accurately predict many cardiac surgical outcomes. A novel approach, ML-based survival analysis, remains unstudied for predicting mortality after cardiac surgery. We aimed to benchmark performance, as measured by the concordance index (C-index), of tree-based survival models against Cox proportional hazards (CPH) modeling and explore risk factors using the best-performing model. 144,536 patients with 147,301 surgery events from the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) national database were used to train and validate models. Univariate analysis was performed using Student's T-test for continuous variables, Chi-squared test for categorical variables, and stratified Kaplan-Meier estimation of the survival function. Three ML models were tested, a decision tree (DT), random forest (RF), and gradient boosting machine (GBM). Hyperparameter tuning was performed using a Bayesian search strategy. Performance was assessed using 2-fold cross-validation repeated 5 times. The highest performing model was the GBM with a C-index of 0.803 (0.002), followed by RF with 0.791 (0.003), DT with 0.729 (0.014), and finally CPH with 0.596 (0.042). The 5 most predictive features were age, type of procedure, length of hospital stay, drain output in the first 4 h (ml), and inotrope use greater than 4 h postoperatively. Tree-based learning for survival analysis is a non-parametric and performant alternative to CPH modeling. GBMs offer interpretable modeling of non-linear relationships, promising to expose the most relevant risk factors and uncover new questions to guide future research.

Clinical Outcomes in Surgical and Transcatheter Aortic Valve Replacement: An ANZSCTS Database Review 2001–2019

Since the last formal publication reporting on the findings of the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) database on surgical aortic valve replacement (SAVR) and transcatheter aortic valve replacement (TAVR) in 2016, transcatheter approaches have become common practice. There has been an increase in use of TAVR following large, randomised control trials that only report short-term outcomes in a selective cohort. This study aimed to report primary outcome measures and identify complications associated with SAVR and TAVR from a large national database.

Brian Fowell Buxton (15/04/1940-20/05/2022)-Outstanding Achievements and Personal Memories.

Brian F. Buxton, one of Australia's greatest cardiac surgeons, died in May 2022, aged 82 years. In June 2022, a memorial celebration of Brian's life was held in Melbourne, Australia, attended by 550 colleagues and friends from many walks of life-not only "medical people" but also friends involved in Brian's sailing and hiking activities. This Special Article includes an introduction from Professor Jayme Bennetts, President of the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS), an abridged version of a memorial address by Professor James Tatoulis and contributions from two other long-term professional colleagues and personal friends of Buxton, Professor Jaishankar Raman and Professor Franklin Rosenfeldt, founding editor of Heart, Lung and Circulation. Buxton was an outstanding and pioneering surgeon, clinical leader, and good friend to many. The Brian F. Buxton Cardiac and Thoracic Aortic Surgery Unit in Melbourne, Australia, is now so named in honour of his outstanding achievements and as a legacy. Vale Brian F. Buxton.

Clinical Outcomes in Surgical and Transcatheter Aortic Valve Replacement: An ANZSCTS Database Review 2001-2019

Since the last formal publication reporting on the findings of the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) database on surgical aortic valve replacement (SAVR) and transcatheter aortic valve replacement (TAVR) in 2016, transcatheter approaches have become common practice. There has been an increase in use of TAVR following large, randomised control trials that only report on short-term outcomes in a selective cohort. This study aims to report on primary outcome measures and identify complications associated with SAVR and TAVR from a large national database. From the ANZSCTS database (2001-19), 14,097 SAVR and 1,194 TAVR patients were identified with clinical details and 30-day follow-up available. The primary endpoint was the composite of all-cause mortality and/or permanent stroke at 30 days. Secondary endpoints were post-procedure complications requiring treatment. Logistical regression followed by propensity score matching was performed. Using logistical regression when all patient factors considered for all patients who had SAVR and TAVR, the only preoperative factors that had an impact on 30-day mortality was cerebrovascular disease, respiratory disease, preoperative dialysis, angina, and hypertension. Primary outcome 30-day mortality rate was 1.83% in the SAVR group, and 1.68% in patients in the TAVR group, p=0.7001, and permanent stroke was seen in 1.07% patients in the SAVR group, and 1.26% patients in the TAVR group. Acute limb ischaemia, aortic dissection, ventricular tachycardia, bradyarrhythmia and heart block were more common following TAVR (p<0.001), while reintubation and atrial arrhythmia were more common following SAVR (p<0.001). In the real world SAVR and TAVR have been used in very different patient groups and it is difficult to compare as different baseline characteristics and complications. The two patient groups maintain similarities in primary and secondary endpoints, but differences in life threatening and life altering morbidity remains significant. Collection of SAVR and TAVR data in a combined database may help to better capture and compare these complications and institute strategies to prevent them.

2021 CSANZ and ANZSCTS Position Statement on the Operator and Institutional Requirements for a Transcatheter Aortic Valve Implantation (TAVI) Program in Australia

This document establishes the minimum standard for accreditation of institutions and operators as endorsed by the Cardiac Society of Australia and New Zealand (CSANZ) and the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS). The original Joint Society Position Statement was ratified in August 2014. This 2021 update replaces the original and serves as a consensus within which the Conjoint Committee for Trancatheter Aortic Valve Implantation (TAVI) Accreditation will function, as recommended by Medical Services Advisory Committee (MSAC) Determination for TAVI. This is not a Guideline Statement but takes into consideration regional, legislative, and health system factors important to establishing requirements for TAVI accreditation in Australia.

Renal Disease Is Associated With Poor Outcomes Following Isolated Coronary Artery Bypass Grafting

BackgroundPeople with renal disease have a markedly higher risk of cardiovascular disease as well as morbidity and mortality after cardiac surgery. Little is known regarding the post-operative adverse outcomes following isolated coronary artery bypass graft (CABG) in the Australian population with renal disease. ObjectivesThe aim of this study was to examine the effect of different stages of renal disease on patients' risk of post-operative mortality and complications following isolated CABG in an Australian cohort. MethodsUsing the ANZSCTS (Australian and New Zealand Society of Cardiac and Thoracic Surgeons) registry, data from 44,968 patients who underwent isolated CABG between 2001 and 2014 were used. The effect of renal disease stages on short- and long-term outcomes were examined using multivariable logistic and Cox's regression methods respectively. ResultsThree of 4 Australian patients (74.6%) who underwent isolated CABG had some degree of renal disease: 50.2% mild; 20.9% moderate; 2.1% severe; and 1.6% dialysis-dependent. Adjusted risk of 30-day mortality increased with deteriorating renal disease from mild (1.6-fold) to dialysis-dependent (4.6-fold). Worsening renal disease was also associated with higher risk of post-operative complications. Hazard ratio for long-term survival shows steady increase of mortality risk with worsening renal disease categories from 1.1-fold for mild to 3.9-fold for patients on dialysis. ConclusionsPre-existing renal disease is significantly associated with 30-day and long-term mortality, length of intensive care unit and hospital stay as well as several other post-operative complications.

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

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. 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. 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. 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.

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

To develop a model for predicting long-term survival following coronary artery bypass graft surgery. 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. 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. 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.

Age and other perioperative risk factors for postoperative systemic inflammatory response syndrome after cardiac surgery

BackgroundThe inflammatory response to surgery varies considerably between individual patients. Age might be a substantial factor in this variability. Our objective was to examine the association of patient age and other potential risk factors with the occurrence of a postoperative systemic inflammatory response syndrome, during the first 24 h after cardiac surgery. MethodsThis was a retrospective cohort study, using linked data from the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) Database and the Australian and New Zealand Intensive Care Society (ANZICS) Adult Patient Database. Data from patients who underwent coronary artery bypass grafting and/or valve surgery were used. The association between age and postoperative SIRS was analysed using Poisson regression, and corrected for other risk factors. Restricted cubic splines were used to determine relevant age categories. Results are expressed as risk ratios (RR) with 95% confidence intervals (CI). ResultsData from 28 513 patients were used. In both univariable and multivariable models, increased patient age was strongly associated with reduced postoperative SIRS prevalence. Using 73–83 yr as the reference category, the RRs (95% CI) for the age categories were 1.38 (1.28–1.49) for ≤43 yr, 1.15 (1.09–1.20) for 44–63 yr, 1.05 (1.00–1.09) for 64–72 yr, and 1.03 (0.94–1.12) for >83 yr, respectively. The predictive value for postoperative SIRS of the final model, however, was moderate (c-statistic: 0.61). ConclusionsWe have demonstrated that advanced patient age is associated with a decreased risk of postoperative SIRS among cardiac surgery patients, where patients aged over 72 yr had the lowest risk.

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

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. 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. 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. 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.

Single Centre Review of Surgically Managed Infective Endocarditis

Purpose: Infective endocarditis (IE) is a life-threatening illness that requires early intervention. We sought to identify the outcomes of all patients who underwent surgical intervention for IE at an Australian tertiary hospital. Methodology: The study institution's Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) database was searched for all patients who underwent valve surgery with active IE between 2000 and 2015. Additional data was obtained by reviewing medical records. Results: There were 133 patients who underwent surgical management of IE. Mean patient age was 54 ± 16 years. A history of IV drug use was present in 23% (31/133) of patients. The commonest infective agents were Staphylococcus aureus in 32% (42/133), of which 14% were MRSA (6/42), Streptococcus viridans in 15% (20/133), and Enterococcus faecalis in 13% (17/133). A single valve procedure was performed in 75% (100/133), while multiple valve procedures were performed in 25% (33/133). The surgical procedures were: aortic valve surgery in 68% (90/133), mitral valve surgery in 47% (63/133) and tricuspid valve surgery in 10% (13/133). Surgical mortality was 15% (20/133). On univariate analysis having emergency surgery (p = 0.003), cross clamp time (p = 0.015) and cardiopulmonary bypass time (p = 0.03) were identified as significant risk factors for mortality. On multivariable analysis emergency surgery (p = 0.021) was identified as a significant risk factor for mortality. Conclusion: Surgery for infective endocarditis is associated with substantial early mortality. Emergency surgery is associated with increased risk of mortality. A multidisciplinary approach with early referral to cardiothoracic surgery is indicated.

Abstract 162: The Impact of Data Quality on Outcomes From The National Cardiac Surgery Registry in Australia - Can Derivable Data Help?

Introduction: The Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) Database Program collects pre-, peri-, and post-operative clinical information on patients undergoing cardiac surgery across Australia. It is a clinical quality registry aimed at improving patient outcome by reporting and benchmarking hospital and surgeon performance. Reports for the Database is dependent on the capturing of accurate and complete data by trained data managers at 28 participating Units. The ANZSCTS Database was audited to determine the adherence of Units to the current data definitions of post-operative New Renal Failure (NRF). Methods: Data between 1st January 2009 and 31st December 2013 (N=45322) from the ANZSCTS Database Program was analysed for reported NRF in patients undergoing cardiac surgery each Unit. To assess the accuracy of the reported data, NRF was also derived using pre- and post-operative renal status variables according to the ANZSCTS Database Data Definitions criteria for NRF. The reported and derived NRF data was then evaluated by procedure type and stratified by Units. Results: Overall, reported NRF was 5.1% (2308/45129) compared to derived NRF of 4.9% (2223/45322) across the 28 Units over the 5 year period. In isolated coronary artery bypass graft, reported NRF was 3.6% (853/24017) compared to derived NRF of 3.4% (824/24081). Unit-specific evaluation showed large variation in reported versus derived NRF across the Units. Out of the 28 Units, 10 Units had under-reported NRF and 18 Units had over-reported NRF post cardiac surgery (see figure). Conclusion: This study demonstrates that Units may not always adhere to the data definitions when collecting and entering data into the Database. As such, derivable data is a good indicator of potential data entry error within Units. In the case of NRF, the overall rates of NRF are similar (both derived and reported), however, large variations exists when NRF rates are evaluated at Unit level. This demonstrates that reporting overall rates of NRF in ANZSCTS Database routine activities may not be as useful as providing Unit-specific data as feedback. Therefore in future, reported NRF rates will be cross-checked against derived NRF, and both overall and Unit-specific rates of NRF should also be included in future Annual Reports.

Procedure-specific Cardiac Surgeon Volume associated with Patient outcome following Valve Surgery, but not Isolated CABG Surgery

Trends towards surgical sub-specialisation to improve patient-outcomes are well-documented and largely supported by evidence. However few studies have examined whether this benefit exists within adult-cardiac surgery. To answer whether sub-specialisation within adult-cardiac surgery improves patient-outcomes, this study assessed the relationship between procedure-specific and total-cardiac surgeon-volume and mortality and morbidity in cardiac-valve and coronary artery bypass grafting (CABG) surgery. Data came from the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) registry from 2001 to 2010 and included 23 hospitals, 109 surgeons, 20,619 patients with isolated-CABG-surgery and 11,536 patients with a valve-procedure. Hierarchical logistic regression using generalised estimating equations was used to analyse outcomes. Measures included operative-mortality and occurrence of a complication (deep sternal wound infection, new stroke, acute kidney injury). Crude operative mortality (and complication rates) were 1.7% (4.9%) and 4% (11%) in the isolated-CABG and valve-surgical populations respectively. A greater procedure-specific surgeon volume was associated with reduced mortality and complication rates in valve-surgery but not isolated-CABG. There was a 33% decrease in odds of dying for every additional 50 valve procedures performed [OR 0.67, p=0.003]. Conversely, greater total-cardiac surgical volume for individual surgeons did not result in improved outcomes, for both isolated-CABG and valve populations. Our finding of an association between increased valve-specific surgeon volumes with improved valve-surgery outcomes, and absence of an association between these outcomes and annual total-cardiac surgical experience supports the case for sub-specialisation specifically within the field of valve surgery.

Percutaneous Retrieval of an Embolised Vascular Stent

© 2014 Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) a Inc. All rights reserved. *Corresponding author at: Cardiovascular Unit, John Hunter Hospital, Newcastle, N Email: Nicholas.Collins@hnehealth.nsw.gov.au ventricular outflow tract (RVOT)(Fig. 1a and1b), with the stent position confirmed on 2D and 3D transoesophageal echocardiography (Fig. 1c and 1d). Percutaneous device retrieval was planned, with stent position confirmed on fluoroscopy (Fig. 2a). A 6 JR4 guide was positioned into the RVOT with a loop snare capturing the embolised stent (Fig. 2b).

Postoperative Mortality Following Lung Cancer Surgery

hypothesise that procedural volume (both surgeon and hospital) is not associated with improved patient outcomes in isolated coronary artery bypass grafting surgery in Australia. Methods: Data from the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) registry including 43,000 patients, 23 hospitals and 122 surgeonhospital combination from 2001 to 2010 was reviewed. 20,619 patients with isolated CABG surgery were included. Two variables of interest were hospital-specific surgeon volume and hospital volume. Hierarchical logistic regression was performed after adjustment for other risk factors. Outcome measures included operative mortality and morbidity (deep sternal wound infection, new stroke, new renal failure). Results: Hospital volumes ranged from 96 to 429 isolated CABG procedures and hospital-specific surgeon volumes ranged from <10 to 129. Both hospital and hospital-specific surgeon volume were not associated with improved mortality or morbidity outcomes to a significance level of p 0.01.

Malignant Solitary Fibrous Tumour of the Pleura: A Case Report and Review of the Literature

Introduction: Infective endocarditis (IE) is a life threatening infection, requiring surgical intervention in around half of all cases. Recommendations regarding surgical management are, however, based on limited data. We aimed to investigate patient and bacterial characteristics as well as outcomes associated with surgically treated aortic valve IE in an Australian tertiary hospital. Methods: The study institution’s Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) database was searched for all patients who underwent aortic valve surgery with active IE between 2001 and 2011. Patients were excluded if other valves were affected. Additional data were obtained by reviewing medical records and investigation results. Results: There were 35 patients in this cohort, all of whom underwent aortic valve replacement. Mean age was 50 18 years, 86% (30/35) were male and 31% (11/35) had a history of IV drug use. There were 12 cases (34%) of Staphylococcus aureus (2/12 were MRSA), seven cases of viridans Streptococci (20%) and six cases of Enterococcus faecalis (17%) IE. Mean time from admission to surgery was 17 31 days. Overall 30-day mortality was 20% (7/35), three deaths occurred in patients with S. aureus infections (25% of S. aureus patients). Twelve operations were performed as an emergency procedure and five of these patients died within 30days of surgery (42%). Discussion: Surgery for active aortic valve IE is associated with substantial mortality, especially when performed as an emergency procedure. Staphylococcus aureus is the commonest causative bacteria in patients requiring surgery at our institution and has a high mortality rate.

The Freestyle Valve as a Right Ventricle to Pulmonary Artery Conduit

Introduction: Infective endocarditis (IE) is a life threatening infection, requiring surgical intervention in around half of all cases. Recommendations regarding surgical management are, however, based on limited data. We aimed to investigate patient and bacterial characteristics as well as outcomes associated with surgically treated aortic valve IE in an Australian tertiary hospital. Methods: The study institution’s Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) database was searched for all patients who underwent aortic valve surgery with active IE between 2001 and 2011. Patients were excluded if other valves were affected. Additional data were obtained by reviewing medical records and investigation results. Results: There were 35 patients in this cohort, all of whom underwent aortic valve replacement. Mean age was 50 18 years, 86% (30/35) were male and 31% (11/35) had a history of IV drug use. There were 12 cases (34%) of Staphylococcus aureus (2/12 were MRSA), seven cases of viridans Streptococci (20%) and six cases of Enterococcus faecalis (17%) IE. Mean time from admission to surgery was 17 31 days. Overall 30-day mortality was 20% (7/35), three deaths occurred in patients with S. aureus infections (25% of S. aureus patients). Twelve operations were performed as an emergency procedure and five of these patients died within 30days of surgery (42%). Discussion: Surgery for active aortic valve IE is associated with substantial mortality, especially when performed as an emergency procedure. Staphylococcus aureus is the commonest causative bacteria in patients requiring surgery at our institution and has a high mortality rate.

Single Centre Review of Surgically Managed Aortic Valve Endocarditis

Introduction: Infective endocarditis (IE) is a life threatening infection, requiring surgical intervention in around half of all cases. Recommendations regarding surgical management are, however, based on limited data. We aimed to investigate patient and bacterial characteristics as well as outcomes associated with surgically treated aortic valve IE in an Australian tertiary hospital. Methods: The study institution’s Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) database was searched for all patients who underwent aortic valve surgery with active IE between 2001 and 2011. Patients were excluded if other valves were affected. Additional data were obtained by reviewing medical records and investigation results. Results: There were 35 patients in this cohort, all of whom underwent aortic valve replacement. Mean age was 50 18 years, 86% (30/35) were male and 31% (11/35) had a history of IV drug use. There were 12 cases (34%) of Staphylococcus aureus (2/12 were MRSA), seven cases of viridans Streptococci (20%) and six cases of Enterococcus faecalis (17%) IE. Mean time from admission to surgery was 17 31 days. Overall 30-day mortality was 20% (7/35), three deaths occurred in patients with S. aureus infections (25% of S. aureus patients). Twelve operations were performed as an emergency procedure and five of these patients died within 30days of surgery (42%). Discussion: Surgery for active aortic valve IE is associated with substantial mortality, especially when performed as an emergency procedure. Staphylococcus aureus is the commonest causative bacteria in patients requiring surgery at our institution and has a high mortality rate.

External validation and updating of a prediction model for nosocomial pneumonia after coronary artery bypass graft surgery.

The generalizability of a prediction model from North America for incident nosocomial pneumonia following coronary artery bypass graft surgery was assessed for 23247 patients on the Australian and New Zealand Society of Cardiac and Thoracic Surgeons (ANZSCTS) registry. The performance of the North American model was evaluated using measures of calibration and discrimination. The model had reasonable discrimination (area under the receiver-operating characteristic curve, AUC=0·69), but unsatisfactory calibration (Hosmer-Lemeshow test, P<0·001) in the ANZSCTS patients. An update of the model coefficients yielded a model with AUC=0·71 and good calibration (P=0·46).