Limitations of the MIRACLE₂ score in coronary cardiac arrest: Findings from a French interventional cohort

In patients resuscitated from out-of-hospital cardiac arrest caused by acute coronary syndrome, interventional cardiologists must rapidly assess neurological prognosis to guide immediate decisions regarding revascularization and advanced life support strategies.

To evaluate the performance of the MIRACLE₂ score for predicting poor neurological outcome in this specific population.

We retrospectively included 77 consecutive patients admitted between 2015 and 2023 to the catheterization laboratory of a tertiary cardiac arrest centre with final confirmation of acute coronary syndrome on coronary angiography. The primary outcome was neurological status at hospital discharge. The MIRACLE₂ score was evaluated for discrimination, calibration and predictive values at the recommended threshold. Patients misclassified as high risk despite favourable outcomes were compared with correctly classified patients.

The study population was predominantly male (75.3%), with a median age of 60 (52-68) years. Poor neurological outcomes occurred in 40 of the 77 patients (51.9%). The MIRACLE₂ score showed good discrimination (area under the curve 0.81) and acceptable calibration. However, at the threshold of 5, the positive predictive value was only 79.3%, with 20.7% of high-risk patients ultimately discharged with favourable neurological outcomes. Most misclassified cases involved cardiac arrests occurring after the arrival of advanced prehospital teams. Excluding these cases increased the score's specificity to 90.3%, and its positive predictive value to 87.5%.

In acute coronary syndrome-related cardiac arrest, early advanced care may alter the prognostic accuracy of the MIRACLE₂ score. Until prospectively validated in this context, it should not be used as a standalone decision tool to guide treatment intensity.