Abstract
OBJECTIVE—To create a risk model for predicting major adverse complicating events of percutaneous transluminal coronary angioplasty (PTCA), and to test the accuracy of the model on a prospective cohort of patients SETTING—Tertiary cardiac centre METHODS—Available software can predict probabilities of events using Bayes's theorem. To establish the accuracy of these predictive tools, a Bayes table was created to evaluate major adverse complicating events (MACE)—death, emergency coronary artery bypass grafting (CABG), or Q wave infarct occurring during the in-patient episode—on the first 1500 patients in the department PTCA database (development group); the predictive value of this model was then tested with the subsequent 1000 patients (evaluation group). The following probabilities were assessed to determine their association with MACE: age, sex, left ventricular function, American Heart Association lesion morphology classification, cardiogenic shock, previous CABG, diabetes, hypertension, multivessel PTCA. MAIN OUTCOME MEASURES—To establish the discriminatory ability of the predictive index, calibration plots and receiver operating characteristic (ROC) curves were obtained to compare the development and evaluation groups. RESULTS—The ROC curve plotted to determine the discriminatory value of the Bayesian table created from the development group (n = 1500) in predicting MACE in the evaluation group (n = 1000) showed a moderately predictive area under the curve of 0.76 (SEM 0.07). This predictive accuracy was confirmed with separately constructed calibration plots. CONCLUSIONS—Accurate predictions of MACE can be identified in populations undergoing percutaneous intervention. The database used allows operators to obtain consent from patients appropriately from their own experience rather than from other published data. If a national PTCA database existed along similar lines, individual operators and interventional centres could compare themselves with nationally available data. Keywords: percutaneous transluminal coronary angioplasty; Bayesian risk; outcome prediction
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Figure 1 .
Receiver operating characteristic (ROC) curve plotted to determine the discriminatory value of the Bayesian table created from the development group (n = 1500) in predicting major adverse cardiac events (MACE) in the evaluation group (n = 1000). The area under the ROC curve is a moderately predictive 0.76 (SEM 0.07).
Figure 2 .
Bayes's risk groups were calculated from the development group and plotted against the incidence of major adverse cardiac events (MACE). These were compared against the actual event rate of MACE using the same risk groups created from the evaluation group. This calibration plot shows an accurate assessment of risk in the low risk groups, but it was less accurate for patients with greater risk.
Selected References
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