Background: Only a few reports have analyzed low-risk patient outcomes and in every case, the risk was based on a logistic EuroSCORE ≤ 2. Since this original EuroSCORE overestimates surgical risk, we developed this study to prospectively evaluate the immediate results of cardiac surgery in patients with an expected mortality risk ≤ 2% according to the EuroSCORE II as a new gold standard. We also examined the cause of death and whether it could be considered preventable.

Methods: A prospective risk stratification of all cardiac surgical patients treated at the Bue­nos Aires University Hospital of Argentina was performed between 2012 and 2014 using the EuroSCORE II. Causes of death were classified as preventable or not preventable.

Results: From a total of 990 patients, 63.2% had EuroSCORE II ≤ 2 (low-risk group) and 32.5% EuroSCORE II < 1 (very low-risk group). In the low-risk group, in-hospital mortal­ity was 1.8%, whereas predicted mortality was 1.04% (AUC 0.765). The observed/expected ratio was 1.73 (95% CI 0.68–4.43) and the observed-expected difference was 0.76 (95% CI –0.68–2.10). Fifty-four percent of deaths were considered preventable.

Conclusions: We propose to use and further validate the EuroSCORE II as a new standard for assessing low-risk patients. This model proved to be useful in evaluating the quality standards of local cardiac surgery. The review of cause of death in low-risk patients provided valuable information, which revealed potentially correctable issues. Adoption of a more demanding standard, as the EuroSCORE II to identify low-risk patients, avoids the sense of safety offered by previous versions of the score.