Letter by Miceli et al Regarding Article, “Risk of Assessing Mortality Risk in Elective Cardiac Operations: Age, Creatinine, Ejection Fraction, and the Law of Parsimony”
To the Editor:
We read with interest the article by Ranucci et al that suggests a simple mortality risk score in patients undergoing elective cardiac surgery based on age, left ventricular ejection fraction, and serum creatinine.1
Operative mortality is a good indicator of the quality of cardiac surgical care, and preoperative risk assessment needs to be the most accurate possible. Risk factors such as gender, chronic pulmonary disease, previous cardiac operations, and major cardiac procedures other than or in addition to coronary artery bypass graftare well-established independent predictors for adverse events in cardiac surgery and, in our opinion, must be accounted for in a mortality risk model.2–4
Among 33 variables tested in the developmental subset, Ranucci and colleagues identified age, body surface area, left ventricular ejection fraction, congestive heart failure, serum creatinine, chronic obstructive pulmonary disease, hematocrit, recent myocardial infarction, long-term dialysis, cardiac procedures other than isolated coronary artery bypass graft, and combined operations to be predictors of mortality in the univariate analysis. However, only 3 variables with the best area under curve value were used and tested in a subsequent multivariate analysis for prediction of mortality. Although the other risk factors had lower accuracy, these could contribute to the magnitude of the risk if statistically significant in the multivariate analysis. Furthermore, serum creatinine value was dichotomized according to a cutoff value of 2 mg/dL and was associated with a relative risk of mortality of 5.3. This cutoff identifies patients with advanced renal disease. Recent data demonstrate that mild preoperative renal dysfunction (serum creatinine 1.47 mg/dL to 2.25 mg/dL) is associated with an increased risk of in-hospital mortality and should be weighted in the risk stratification algorithms for mortality.5 We think it would be of interest to show how the model may be more calibrated and accurate by including these factors in a multivariate analysis.
Ranucci M, Castelvecchio S, Menicanti L, Frigiola A, Pelissero G. Risk of assessing mortality risk in elective cardiac operations: age, creatinine, ejection fraction, and the law of parsimony. Circulation. 2009; 119: 3053–3061.
Roques F, Nashef SAM, Micheal P, Gauducheau E, de Vincentiis C, Baudet E, Cortina J, David M, Faichney A, Gabrielle F, Gams E, Harjula A, Jones NT, Pinna Pintor P, Salamon R, Thulin L. Risk factors and outcome in European cardiac surgery: analysis of the EuroSCORE multinational database of 19 030 patients. Eur J Cardiothorac Surg. 1999; 15: 816–823.
Albert MA, Halevy N, Antman EM. Preoperative evaluation for cardiac surgery. In: Cohn LM, ed. Cardiac Surgery in the Adult. 3rd ed. New York: McGraw-Hill; 2007: 261–280.
Zakeri R, Freemantle N, Barnett V, Lipkin GW, Bonser RS, Graham TR, Rooney SJ, Wilson IC, Cramb R, Keogh BE, Pagano D. Relation between mild renal dysfunction and outcomes after coronary artery bypass grafting. Circulation. 2005; 112: I-270–I-275.