To assess whether a simple echocardiographic grading system reflecting the severity and stage of myocardial injury can stratify long-term mortality risk among patients with first-time ST-segment elevation myocardial infarction (STEMI).

Multicentre prospective registry-based cohort study.

Eight hospitals in China.

Consecutive patients with first-time STEMI between June 2016 and June 2024 who survived to hospital discharge and underwent echocardiography were included. A total of 2708 patients were enrolled and followed up for a median of 5.5 years (IQR: 5.3–6.4).

The primary outcome was long-term all-cause mortality.

Patients were stratified into four grades: 1392 (51.4%) were classified as Grade 1; 905 (33.4%) as Grade 2; 350 (12.9%) as Grade 3; and 61 (2.3%) as Grade 4. During follow-up, long-term all-cause mortality increased stepwise across increasing echocardiographic grades. In multivariable Cox regression analysis, the baseline grading remained an independent predictor of long-term mortality after adjustment (adjusted HR for Grade 4 vs Grade 1: 3.35, 95% CI 1.34 to 8.38, p

Patient grade from the echocardiographic grading system was associated with long-term mortality after first-time STEMI, with the highest risk observed in patients classified as Grade 4. As a simple and objective classification, this grading system may provide a practical way to describe and communicate infarct severity among clinicians and others involved in patient care, as the term ‘myocardial infarction’ alone may inadequately reflect disease severity.