Algorithm allows paramedics to predict brain damage risk after cardiac arrest

Results from the RAPID-MIRACLE trial have found, for the first time, that the widely used MIRACLE₂ risk score can be applied outside a hospital setting to accurately predict brain injury following a cardiac arrest. This could inform the type of immediate care patients receive, helping to ensure they have the best treatment available while saving crucial resources.

An out-of-hospital cardiac arrest (OHCA) carries a high risk of death, with fewer than 10% of patients surviving. Even when a patient’s heart is successfully restarted through CPR and circulation is restored, known as return of spontaneous circulation (ROSC), clinicians often face uncertainty about the extent of brain injury.

Despite current UK and European guidelines recommending that patients who experience an out-of-hospital cardiac arrest are sent to a specialist cardiac center, the majority of patients are still conveyed to local emergency departments. The MIRACLE₂ score, when applied in the pre-hospital setting, may now open up the possibility of identifying patients earlier and enabling direct transfer to specialist centers, allowing faster access to expert care and advanced treatments for patients who might otherwise have been conveyed to a local hospital.

Created by Dr. Nilesh Pareek, Adjunct Senior Lecturer and Consultant Interventional Cardiologist, the MIRACLE2 score accurately predicts the extent of brain damage after 30 days following an OHCA. Until now, it has only been applied once a patient reaches hospital.

Dr. Pareek and his team worked with the London Ambulance Service and Heart Research UK to evaluate whether the score could be calculated immediately after ROSC in the community.

The study followed patients from paramedic care through to hospital treatment across multiple London sites, providing real-world evidence of how the score performs outside a hospital environment.

The researchers tested two new versions of the score—one which included a blood test and one which didn’t. While the version with the blood test was highly accurate, paramedics frequently found it impractical due to technical failures and time pressure. The version without the blood test, known as Pre-MIRACLE2, was almost identical in terms of accuracy.

“While MIRACLE² has supported early in-hospital risk stratification following out-of-hospital cardiac arrest, RAPID-MIRACLE extends this work into the pre-hospital setting, enabling paramedics to assess risk earlier in a patient’s care pathway. By validating the model in the field, we have taken an important step towards integrating earlier risk assessment into routine emergency care,” says Dr. Nilesh Pareek, senior author of the study and Adjunct Senior Lecturer, King’s College London and Consultant Interventional Cardiologist, King’s College Hospital.

Alongside the study, the MIRACLE₂ app, led by Dr. Pareek, has been updated to incorporate the newly validated pre-hospital model. The app, developed by Ensono Digital, uses the MIRACLE₂ algorithm and is designed as a practical tool to help clinicians calculate the score quickly and accurately, without needing to recall each variable from memory.

By entering patient information such as age, initial heart rhythm, and other markers, paramedics and hospital clinicians can generate an immediate estimate of a patient’s risk of poor neurological outcome following out-of-hospital cardiac arrest.

The research team is now in discussion with emergency medical services regarding a potential service evaluation to explore how the updated tool could be implemented in routine practice.

The research findings were presented in Washington at the CRT 2026 conference and the full study was published in European Heart Journal: Acute Cardiovascular Care.