The Society of Thoracic Surgeons 2018 Adult Cardiac Surgery Risk Models: Part 2—Statistical Methods and Results

doi:10.1016/j.athoracsur.2018.03.003

The Annals of Thoracic Surgery

Volume 105, Issue 5, May 2018, Pages 1419-1428

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https://doi.org/10.1016/j.athoracsur.2018.03.003 Get rights and content

Background

The Society of Thoracic Surgeons (STS) uses statistical models to create risk-adjusted performance metrics for Adult Cardiac Surgery Database (ACSD) participants. Because of temporal changes in patient characteristics and outcomes, evolution of surgical practice, and additional risk factors available in recent ACSD versions, completely new risk models have been developed.

Methods

Using July 2011 to June 2014 ACSD data, risk models were developed for operative mortality, stroke, renal failure, prolonged ventilation, mediastinitis/deep sternal wound infection, reoperation, major morbidity or mortality composite, prolonged postoperative length of stay, and short postoperative length of stay among patients who underwent isolated coronary artery bypass grafting surgery (n = 439,092), aortic or mitral valve surgery (n = 150,150), or combined valve plus coronary artery bypass grafting surgery (n = 81,588). Separate models were developed for each procedure and endpoint except mediastinitis/deep sternal wound infection, which was analyzed in a combined model because of its infrequency. A surgeon panel selected predictors by assessing model performance and clinical face validity of full and progressively more parsimonious models. The ACSD data (July 2014 to December 2016) were used to assess model calibration and to compare discrimination with previous STS risk models.

Results

Calibration in the validation sample was excellent for all models except mediastinitis/deep sternal wound infection, which slightly underestimated risk and will be recalibrated in feedback reports. The c-indices of new models exceeded those of the last published STS models for all populations and endpoints except stroke in valve patients.

Conclusions

New STS ACSD risk models have generally excellent calibration and discrimination and are well suited for risk adjustment of STS performance metrics.

Section snippets

Endpoints

Risk models were developed for the following nine endpoints chosen for consistency with prior STS risk models and current performance metrics (eg, STS composite scores): (1) operative mortality, defined in all STS databases as all deaths, regardless of cause, occurring during the hospitalization in which the operation was performed even if after 30 days (includes patients transferred to other acute care facilities), and all deaths, regardless of cause, occurring after discharge from the

Results

A total of 670,830 records met study inclusion criteria and were included in the development samples for CABG (n = 439,092), valve (n = 150,150), and valve plus CABG (n = 81,588). The number of endpoint events in the development sample ranged from 1,875 for DSWI to 286,362 for short PLOS (Table 2). As discussed above, the relatively small number of DSWI endpoints in valve (n = 244) and valve plus CABG (n = 285) populations raised concerns about potential overfitting in these populations, and

Comment

We have described the development and validation of a comprehensive set of new STS adult cardiac surgical risk models that will be used to adjust for case mix in the STS participant feedback report and the STS voluntary public reporting program. Our approach to model development incorporated several novel features including the use of simulations to assess the feasible number of predictors in relation to sample size, and the combined use of bootstrapping and cross validation to estimate model

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: The STS Executive Committee approved this document.

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Report of the STS quality measurement task forceThe Society of Thoracic Surgeons 2018 Adult Cardiac Surgery Risk Models: Part 2—Statistical Methods and Results

Background

Methods

Results

Conclusions

Section snippets

Endpoints

Results

Comment

Ann Thorac Surg

Ann Thorac Surg

Ann Thorac Surg

Ann Thorac Surg

J Clin Epidemiol

Report of the STS quality measurement task force
The Society of Thoracic Surgeons 2018 Adult Cardiac Surgery Risk Models: Part 2—Statistical Methods and Results