Background: We hypothesize that the discriminative performance of GRACE, ACHTUNG-Rule, CHADS₂ or CHA₂DS₂-VASc may be lower in patients with a Myocardial Infarction (MI) and concurrent atrial fibrillation (AF), as none of these scores seem able to fully capture both atherothrombotic/thromboembolic risks. This study aims to evaluate the mid-term prognostic performance of these algorithms in patients with these two conditions and to analyze the utility of a score combining GRACE and CHA₂DS₂-VASc.

Methods: Observational retrospective single-centre cohort study including 1852 patients admitted with a MI. We tested the prognostic performance of the aforementioned risk stratification schemes in patients with vs. without AF at admission or during hospitalization.  Primary endpoints: a) total all-cause mortality, comprising intrahospital and post-discharge all-cause mortality; b) intrahospital all-cause mortality and c) all-cause mortality during follow-up. Furthermore, all three versions of the ACHTUNG-Rule were directly compared to their equivalent GRACE score versions, and a new score, entitled GRACE-CHA₂DS₂-VASc, was developed and compared with GRACE.

Results: The mid-term prognostic performance of all scores was considerably lower in patients with AF, corroborating our hypothesis. The ACHTUNG-Rule seemed superior to GRACE in the prediction of post-discharge (AUC 0.790±0.032 vs. 0.685±0.038, p=0.079; integrated discrimination improvement index [IDI] of 0.166 and relative IDI of 83.7%) and total mortality (0.762±0.031 vs. 0.712±0.033, p=0.144; IDI of 0.042, relative IDI of 11.7%), but its performance decreased in those with AF as well. GRACE-CHA₂DS₂-VASc was only marginally superior to GRACE in discriminative performance, but detected truly low- (CHA₂DS₂-VASc <2; total mortality 0%) and high-risk patients (GRACE high-risk stratum, and CHA₂DS₂-VASc >4; total mortality 44.3%) with considerable efficacy.

Conclusions: In patients with MI and concurrent AF, the GRACE, CHADS₂ and CHA₂DS₂-VASc scores seemed less accurate in the prediction of all-cause mortality. A hypothetic GRACE-CHA₂DS₂-VASc score or the recently developed ACHTUNG-Rule may eventually provide a more rigorous approach to risk stratification in this high-risk setting.