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Mortality prediction in adult cardiac surgery
patients: comparison of two risk stratification
models
WK Au, MP Sun, KT Lam, LC Cheng, SW Chiu, SR Das
Division of Cardiothoracic Surgery, The Grantham Hospital, Aberdeen, Hong
Kong
OBJECTIVE. To assess and compare the two commonly applied models—
EuroSCORE and Parsonnet—in our local adult cardiac surgery
patients, according to risk factor quantification related to
mortality using a risk stratification protocol to assess the quality
of cardiac surgical care.
DESIGN. Prospective study.
SETTING. Cardiac surgery centre in a regional hospital in Hong Kong.
PATIENTS. All adult patients undergoing coronary artery bypass graft and
heart valve surgery at the Grantham Hospital were evaluated
prospectively from November 1999 to July 2005.
MAIN OUTCOME MEASURES. In-hospital mortality was the defined end-point. Statistical
analyses consisted of observed against expected mortality,
Hosmer-Lemeshow goodness-of-fit test for calibration accuracy,
and receiver operating characteristic curve for discrimination
performance.
RESULTS. During the study period, 1247 patients underwent coronary artery
bypass graft surgery and 1406 underwent heart valve surgery.
Observed mortality rates in these two patient groups were 2.9%
and 4.8% respectively. The expected mortality rates as predicted
by the EuroSCORE were (mean±standard deviation) 4.0±3.3%
and 5.2±3.0% respectively, and by the Parsonnet model were
5.9±4.2% and 7.3±4.4% respectively. EuroSCORE performed
better than the Parsonnet model at predicting in-hospital
mortality assessed by the Hosmer-Lemeshow goodness-of-fit
test. The areas under the receiver operating characteristic curves
in coronary artery bypass graft surgery were 0.76 for EuroSCORE
and 0.74 for Parsonnet. The receiver operating characteristic
curve areas in valve surgery were 0.77 for EuroSCORE and 0.79 for
Parsonnet.
CONCLUSION. Despite significant geographic and demographic differences
between European and Asian patients, in our local adult cardiac
surgery patients, the EuroSCORE performed well with good
calibration and discrimination in predicting mortality. There
was a tendency for both models to over predict. However, the
EuroSCORE can serve as a baseline for the development of a
local risk model.
Hong Kong Med J 2007;13:293-7
Key words: Heart diseases; Hospital mortality;
Prospective studies; Risk assessment;
Risk factors
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