Original Articles
Risk stratification for cardiac valve replacement. National Cardiac Surgery Database

Presented in part at the Thirty-third Annual Meeting of The Society of Thoracic Surgeons, San Diego, CA, Feb 3–5, 1997.
https://doi.org/10.1016/S0003-4975(99)00175-7Get rights and content

Abstract

Background. The Society of Thoracic Surgeons National Database Committee is committed to risk stratification and assessment as integral elements in the practice of cardiac operations. The National Cardiac Surgery Database was created to analyze data from subscribing institutions across the country. We analyzed the database for valve replacement procedures with and without coronary artery bypass grafting to determine trends in risk stratification.

Methods. The database contains complete records of 86,580 patients who had valve replacement procedures at the participating institutions between 1986 and 1995, inclusive. The 1995 harvest of data was conducted in late 1996 and available for evaluation in 1997. These records were used to conduct an in-depth analysis of risk factors associated with valve replacement and to provide prediction of operative death by using regression analysis. Regression models were made for six subgroups.

Results. Adverse patient risk factors, including diabetes, hypertension and reoperation, but not ventricular function, increased over time. There were trends with regard to increasing age of the various population subsets. The types of prostheses used remained similar over time, with more mechanical prostheses than bioprostheses used for both aortic and mitral valve replacement. There was a trend toward increased use of bioprostheses in aortic replacements and decreased use in mitral replacements between 1991 and 1995 than between 1986 and 1990. The mortality rate was determined by patient subset for primary operation and reoperation and by urgency status. The modeling showed that the predicted and observed mortality correlated for all age groups and within patient subsets.

Conclusions. Risk modeling is a valuable tool for predicting the probability of operative death in any individual patient. This large, multiinstitutional database is capable of determining modern operative risk and should provide standards for acceptable care. The study illustrates the importance of risk stratification for early death both for the patient and the surgeon.

Section snippets

Material and methods

All patients registered in the database who had valve replacement operations between 1986 and 1995, incorporating the 1996 harvest, were considered for inclusion in the study. Patient records that had obviously conflicting information or insufficient information were excluded from the study. The resultant population contained clinical information on 86,580 patients. The definition of each risk factor was consistent with the published guidelines in the STS National Cardiac Surgery Database

Patient characteristics

The patient populations grouped by subset model and the respective early mortality rates are given in Table 1. The total database encompassed 86,580 patients and the overall mortality was 7.5%. There were 26,317 patients with isolated aortic valve replacement (AVR) and 13,936 patients with isolated mitral valve replacement (MVR), with respective operative mortality rates of 4.3% and 6.4%. There were 3,840 patients with multiple valve replacement and the early or operative mortality rate was

Comment

The STS National Cardiac Surgery Database contains information from many institutions, both nonacademic and academic centers, on cardiac valve replacement operations in 86,580 patients during a 10-year period. The database provides a benchmark for quality assurance, because institutions can enter their patient population data and obtain direct risk-adjusted comparisons of their results with the national standard.

The patient population that had valve replacement operations has evolved during the

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