Invited Commentary

Abstract

Algarni and colleagues [1Algarni K.D. Maganti M. Yau T.M. Predictors of low cardiac output syndrome after isolated coronary artery bypass surgery: trends over 20 years.Ann Thorac Surg. 2011; 92: 1678-1685Abstract Full Text Full Text PDF PubMed Scopus (92) Google Scholar] present a 20-year analysis of a large cohort of patients undergoing coronary artery bypass grafting, in which they document a decrease in the prevalence of low cardiac output syndrome, improved in-hospital mortality, and a reduction in major postoperative complications over this 20-year span. Two unexpected findings in the current era were an increase in mortality among patients suffering low cardiac output syndrome and an increase in the likelihood of low cardiac output syndrome among patients with an ejection fraction less than 20%. A major conclusion of this analysis suggests caution in the evaluation of suitability for coronary bypass surgery among patients with a low ejection fraction and emphasizes the persistent imperfections of current methods of myocardial preservation. Is the reader to conclude that surgeons and physicians are experiencing degradation in their punctilious management of low cardiac output or preservation of the myocardium in patients with low ejection fraction in the current era? Although possible, it seems highly unlikely. A more plausible explanation acknowledges the inimical effect of accepting “sicker” patients for surgery with depressed ejection fraction in the current era, and that other variables describing the severity of advanced heart failure are not identified in this multivariable analysis. It is well known, for example, that ejection fraction is a poor discriminator of overall cardiac reserves. The same likely applies to the increased mortality among patients who develop low cardiac output syndrome, in that other unidentified patient-specific risk factors likely account for the increased mortality in the current era. All this speaks to the challenges of multivariate analyses that examine “era effects” and the inferences based on such analyses. Patients that are actually sicker in the current era may evade the detection of higher risk related to the panoply of additional comorbidities and other subtleties of the risk profile that are not always elucidated by variables entered into a statistical model. This conundrum confounds performance reports in many areas of cardiothoracic surgery when recent outcomes appear worse compared with the more distant past. This missive is not intended to deprecate the value of such research, but rather to underscore the challenge for the outcomes for researchers who strive to identify variables that connote true risk when depicting severity of illness and risk of mortality for individual patients undergoing increasingly complex cardiac operations. Predictors of Low Cardiac Output Syndrome After Isolated Coronary Artery Bypass Surgery: Trends Over 20 YearsThe Annals of Thoracic SurgeryVol. 92Issue 5PreviewPostoperative low cardiac output syndrome (LCOS) is associated with high morbidity and mortality after coronary artery bypass grafting (CABG). We sought to examine trends in predictors of LCOS after isolated CABG. Full-Text PDF