Risk of assessing mortality risk in elective cardiac operations: age, creatinine, ejection fraction, and the law of parsimony.
BACKGROUND
Several mortality risk scores exist in cardiac surgery. All include a considerable number of independent risk factors. In elective cardiac surgery patients, the operative mortality is low, the number of events recorded per year is limited, and the risk model may be overfitted. The present study aims to develop and validate an operative mortality risk score for elective patients based on a limited number of factors.


RESULTS
The development series included 4557 adult patients who had undergone an elective cardiac operation at our institution from 2001 to 2003; the validation series includes the 4091 patients who subsequently underwent an operation. Three independent factors were included in the mortality risk model: age, creatinine, and left ventricular ejection fraction (ACEF). The ACEF score was computed as follows: age (years)/ejection fraction (%)+1 (if serum creatinine value was >2 mg/dL). The ACEF score was compared with 5 other risk scores in the validation series. Discriminatory power (accuracy) was defined with a receiver-operating characteristics analysis. The best accuracy was achieved by the Cleveland Clinic score (0.812), with ACEF score just below it (0.808). In coronary operations, the 2 scores performed equally well (0.815 versus 0.813), and in isolated coronary operations, the best accuracy was achieved by ACEF (0.826), with the Cleveland Clinic score at 0.806.


CONCLUSIONS
A risk model limited to 3 independent predictors has similar or better accuracy and calibration compared with more complex risk scores if applied to elective cardiac operations.
Ranucci
Marco
M
Director of Clinical Research in the Department of Anesthesia and Intensive Care, IRCCS Policlinico S. Donato, Via Morandi 30, 20097 San Donato Milanese, Milan, Italy. cardioanestesia@virgilio.it
Castelvecchio
Serenella
S
Menicanti
Lorenzo
L
Frigiola
Alessandro
A
Pelissero
Gabriele
G
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D006348:Cardiac Surgical Procedures / Q000401:mortality*; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood*; D017558:Elective Surgical Procedures / Q000401:mortality*; D005260:Female; D006331:Heart Diseases / Q000097:blood / Q000401:mortality / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D011237:Predictive Value of Tests; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors; D013318:Stroke Volume
D003404:Creatinine