A systematic review of risk prediction in adult cardiac surgery: considerations for future model development

OBJECTIVES

Risk prediction in adult patients undergoing cardiac surgery remains inaccurate and should be further improved. Therefore, we aimed to identify risk factors that are predictive of mortality, stroke, renal failure and/or length of stay after adult cardiac surgery in contemporary practice.

METHODS

We searched the Medline database for English-language original contributions from January 2000 to December 2011 to identify preoperative independent risk factors of one of the following outcomes after adult cardiac surgery: death, stroke, renal failure and/or length of stay. Two investigators independently screened the studies. Inclusion criteria were (i) the study described an adult cardiac patient population; (ii) the study was an original contribution; (iii) multivariable analyses were performed to identify independent predictors; (iv) ≥ 1 of the predefined outcomes was analysed; (v) at least one variable was an independent predictor, or a variable was included in a risk model that was developed.

RESULTS

The search yielded 5768 studies. After the initial title screening, a second screening of the full texts of 1234 studies was performed. Ultimately, 844 studies were included in the systematic review. In these studies, we identified a large number of independent predictors of mortality, stroke, renal failure and length of stay, which could be categorized into variables related to: disease pathology, planned surgical procedure, patient demographics, patient history, patient comorbidities, patient status, blood values, urine values, medication use and gene mutations. Many of these variables are frequently not considered as predictive of outcomes.

CONCLUSIONS

Risk estimates of mortality, stroke, renal failure and length of stay may be improved by the inclusion of additional (non-traditional) innovative risk factors. Current and future databases should consider collecting these variables.

Almanac 2012: adult cardiac surgery: the national society journals present selected research that has driven recent advances in clinical cardiology

This review covers the important publications in adult cardiac surgery in the last few years, including the current evidence base for surgical revascularisation and the use of off-pump surgery, bilateral internal mammary arteries and endoscopic vein harvesting. The changes in conventional aortic valve surgery are described alongside the outcomes of clinical trials and registries for transcatheter aortic valve implantation, and the introduction of less invasive and novel approaches of conventional aortic valve replacement surgery. Surgery for mitral valve disease is also considered, with particular reference to surgery for asymptomatic degenerative mitral regurgitation.

Almanac 2012 adult cardiac surgery: the National Society Journals present selected research that has driven recent advances in clinical cardiology

This review covers the important publications in adult cardiac surgery in the last few years, including the current evidence base for surgical revascularisation and the use of off-pump surgery, bilateral internal mammary arteries and endoscopic vein harvesting. The changes in conventional aortic valve surgery are described alongside the outcomes of clinical trials and registries for transcatheter aortic valve implantation, and the introduction of less invasive and novel approaches to conventional aortic valve replacement surgery. Surgery for mitral valve disease is also considered, with particular reference to surgery for asymptomatic degenerative mitral regurgitation.

Dynamic trends in cardiac surgery: why the logistic EuroSCORE is no longer suitable for contemporary cardiac surgery and implications for future risk models

OBJECTIVES

Progressive loss of calibration of the original EuroSCORE models has necessitated the introduction of the EuroSCORE II model. Poor model calibration has important implications for clinical decision-making and risk adjustment of governance analyses. The objective of this study was to explore the reasons for the calibration drift of the logistic EuroSCORE.

METHODS

Data from the Society for Cardiothoracic Surgery in Great Britain and Ireland database were analysed for procedures performed at all National Health Service and some private hospitals in England and Wales between April 2001 and March 2011. The primary outcome was in-hospital mortality. EuroSCORE risk factors, overall model calibration and discrimination were assessed over time.

RESULTS

A total of 317 292 procedures were included. Over the study period, mean age at surgery increased from 64.6 to 67.2 years. The proportion of procedures that were isolated coronary artery bypass grafts decreased from 67.5 to 51.2%. In-hospital mortality fell from 4.1 to 2.8%, but the mean logistic EuroSCORE increased from 5.6 to 7.6%. The logistic EuroSCORE remained a good discriminant throughout the study period (area under the receiver-operating characteristic curve between 0.79 and 0.85), but calibration (observed-to-expected mortality ratio) fell from 0.76 to 0.37. Inadequate adjustment for decreasing baseline risk affected calibration considerably.

DISCUSSIONS

Patient risk factors and case-mix in adult cardiac surgery change dynamically over time. Models like the EuroSCORE that are developed using a 'snapshot' of data in time do not account for this and can subsequently lose calibration. It is therefore important to regularly revalidate clinical prediction models.

Almanac 2012--adult cardiac surgery: the national society journals present selected research that has driven recent advances in clinical cardiology

This review covers the important publications in adult cardiac surgery in the last few years, including the current evidence base for surgical revascularisation and the use of off-pump surgery, bilateral internal mammary arteries and endoscopic vein harvesting. The changes in conventional aortic valve surgery are described alongside the outcomes of clinical trials and registries for transcatheter aortic valve implantation, and the introduction of less invasive and novel approaches of conventional aortic valve replacement surgery. Surgery for mitral valve disease is also considered, with particular reference to surgery for asymptomatic degenerative mitral regurgitation.

Prediction of in-hospital death following aortic valve replacement: a new accurate model

OBJECTIVES

Aortic valve replacement (AVR) is accepted as the standard treatment for severe symptomatic aortic valve stenosis and regurgitation. As novel treatments are introduced for patients at high risk for conventional surgery, it is important to have models that accurately predict procedural risk. The aim of this study was to develop and validate a risk-stratification model to predict in-hospital risk of death for patients undergoing AVR and to compare the model with existing algorithms.

METHODS

We reviewed data from the Central Cardiac Adult Database, which holds prospectively collected clinical information on all adult patients undergoing cardiac surgery in National Health Service (NHS) hospitals and some private providers in the UK and Ireland. We included all the patients undergoing AVR with or without coronary artery bypass grafting. The study population consists of 55 157 patients undergoing surgery between 1 April 2001 and 31 March 2009. The model was built using data from April 2001 to March 2008 and validated using data from patients undergoing surgery from April 2008 to March 2009. The model was compared against the additive and logistic EuroSCORE models and a valve-specific risk-prediction model.

RESULTS

The final multivariable model includes items describing cardiovascular risk status and procedural factors. Applying the model to the independent validation dataset provided a c-statistic (index of rank correlation) of 0.791, which was substantially better than that achieved by previously developed risk models in Europe, and significantly improved risk prediction in higher-risk patients.

CONCLUSIONS

We have produced an accurate risk model to predict outcome following AVR surgery. It will be of use for patient selection and informed consent, and of particular interest in defining those patients at high risk who may benefit from novel approaches to AVR.

Long-term outcomes after transcatheter aortic valve implantation in high-risk patients with severe aortic stenosis: the U.K. TAVI (United Kingdom Transcatheter Aortic Valve Implantation) Registry

OBJECTIVES

The objective was to define the characteristics of a real-world patient population treated with transcatheter aortic valve implantation (TAVI), regardless of technology or access route, and to evaluate their clinical outcome over the mid to long term.

BACKGROUND

Although a substantial body of data exists in relation to early clinical outcomes after TAVI, there are few data on outcomes beyond 1 year in any notable number of patients.

METHODS

The U.K. TAVI (United Kingdom Transcatheter Aortic Valve Implantation) Registry was established to report outcomes of all TAVI procedures performed within the United Kingdom. Data were collected prospectively on 870 patients undergoing 877 TAVI procedures up until December 31, 2009. Mortality tracking was achieved in 100% of patients with mortality status reported as of December 2010.

RESULTS

Survival at 30 days was 92.9%, and it was 78.6% and 73.7% at 1 year and 2 years, respectively. There was a marked attrition in survival between 30 days and 1 year. In a univariate model, survival was significantly adversely affected by renal dysfunction, the presence of coronary artery disease, and a nontransfemoral approach; whereas left ventricular function (ejection fraction <30%), the presence of moderate/severe aortic regurgitation, and chronic obstructive pulmonary disease remained the only independent predictors of mortality in the multivariate model.

CONCLUSIONS

Midterm to long-term survival after TAVI was encouraging in this high-risk patient population, although a substantial proportion of patients died within the first year.

What is the impact of providing a transcatheter aortic valve implantation service on conventional aortic valve surgical activity: patient risk factors and outcomes in the first 2 years

OBJECTIVES

To assess the impact of introducing a transcatheter aortic valve implantation (TAVI) service on aortic valve surgical activity and outcomes.

DESIGN

A retrospective analysis of prospectively collected data.

SETTING

University hospital of south Manchester.

PATIENTS

815 consecutive patients undergoing isolated aortic valve replacement (AVR) or coronary artery bypass grafting plus AVR from January 2006 to December 2009. Fifty consecutive patients who underwent TAVI from January 2008 to December 2009.

MAIN OUTCOME MEASURES

Aortic valve surgical activity in the 2years before the introduction of a TAVI service and in the 2years following. Outcomes following conventional aortic valve surgery and TAVI.

RESULTS

In the 2years following the introduction of TAVI at this centre, conventional AVR activity has increased by 37% compared with an 8% increase nationally (p<0.001). Compared with the 2years before TAVI there was no change in the mean logistic EuroSCORE (7.4 vs 7.9 p=0.16) or crude mortality rate (2.9% vs 2.1% p=0.48). Fifty high-risk patients underwent TAVI with a 30-day mortality rate of 0%. The mean logistic EuroSCORE of the TAVI patients was 25.3.

CONCLUSIONS

TAVI is an emerging alternative to AVR in high-risk patients. Since the introduction of a TAVI service at this centre, conventional AVR activity has increased. Despite a trend of increasing mean logistic EuroSCORE indicating that more complex cases are being undertaken, there has been a non-significant reduction in the crude mortality rate. Offering a TAVI service has a positive impact on the volume of conventional AVR surgical activity.

Cardiac registers: the adult cardiac surgery register

AIMS OF THE SCTS ADULT CARDIAC SURGERY DATABASE: To measure the quality of care of adult cardiac surgery in GB and Ireland and provide information for quality improvement and research.

QUALITY OF CARE INTERVENTIONS

Feedback of structured data to hospitals, publication of named hospital and surgeon mortality data, publication of benchmarked activity and risk adjusted clinical outcomes through intermittent comprehensive database reports, annual screening of all hospital and individual surgeon risk adjusted mortality rates by the professional society.

SETTING

All NHS hospitals in England, Scotland and Wales with input from some private providers and hospitals in Ireland.

YEARS

1994-ongoing.

POPULATION

Consecutive patients, unconsented. Current number of records: 400000.

STARTPOINTS

Adult cardiac surgery operations excluding cardiac transplantation and ventricular assist devices.

BASELINE DATA

129 fields covering demographic factors, pre-operative risk factors, operative details and post-operative in-hospital outcomes.

DATA CAPTURE

Entry onto local software systems by direct key board entry or subsequent transcription from paper records, with subsequent electronic upload to the central cardiac audit database. Non-financial incentives at hospital level.

DATA QUALITY

Local validation processes exist in the hospitals. There is currently no external data validation process.

ENDPOINTS AND LINKAGES TO OTHER DATA

All cause mortality is obtained through linkage with Office for National Statistics. No other linkages exist at present.

ACCESS TO DATA

Available for research and audit by application to the SCTS database committee at http://www.scts.org.

Omega-3 fatty acid supplementation does not reduce risk of atrial fibrillation after coronary artery bypass surgery: a randomized, double-blind, placebo-controlled clinical trial

BACKGROUND

Omega-3 polyunsaturated fatty acids (n-3 PUFA) have been reported to reduce the risk of sudden cardiac death presumed to be due to fatal ventricular arrhythmias, but their effect on atrial arrhythmias is unclear.

METHODS AND RESULTS

Patients (n=108) undergoing coronary artery bypass graft surgery were randomly assigned to receive 2 g/d n-3 PUFA or placebo (olive oil) for at least 5 days before surgery (median, 16 days; range, 12 to 21 days). Phospholipid n-3 PUFA were measured in serum at study entry and at surgery and in right atrial appendage tissue at surgery. Echocardiography was used to assess left ventricular function and left atrial dimensions. Postoperative continuous ECG monitoring (Lifecard CF) for 5 days or until discharge, if earlier, was performed with a daily 12-lead ECG and clinical review if patients remained in the hospital beyond 5 days. Lifecard recordings were analyzed for episodes of atrial fibrillation (AF) > or =30 seconds (primary outcome). Clinical AF, AF burden (% time in AF), hospital stay, and intensive care/high dependency care stay were measured as secondary outcomes. One hundred three patients completed the study (51 in the placebo group and 52 in the n-3 PUFA group). There were no clinically relevant differences in baseline characteristics between groups. n-3 PUFA levels were higher in serum and right atrial tissue in the active treatment group. There was no significant difference between groups in the primary outcome of AF (95% confidence interval [CI], -6% to 30%, P=0.28) in any of the secondary outcomes or in AF-free survival.

CONCLUSIONS

Omega-3 PUFA do not reduce the risk of AF after coronary artery bypass graft surgery. Clinical Trial Registration- www.ukcrn.org.uk. Identifier: 4437.

Quality assessment of cardiac surgery in Britain

Data are available for every Cardiac Surgery unit in Britain and in 70 % are identifiable by surgeon. The data are linked to registration of deaths so survival for a range of operations, and associated patient or procedure related factors, can be evaluated. The choice of statistical triggers (outside 99.99 % confidence intervals) and the time frames of reported data (averaged over three years) (See P.285/353 of the report http://www.scts.org/documents/PDF/5thBlueBook2003.pdf) reduces its value as an early warning system but the rigour of data collecting systems and the level of scrutiny required probably ensure that poor performance will be detected.