Introduction: Patients with symptoms indicative of acute myocardial infarction (MI) frequently present to the emergency department and undergo a structured assessment to determine the diagnosis of MI, myocardial injury or other causes of chest pain. Beyond the acute diagnostic evaluation, estimation of long-term risk is crucial to guide preventive strategies. This is particularly relevant for those patients not diagnosed with acute MI. However, long-term outcome data of these patients is largely lacking. 

Purpose: To assess and compare the long-term incidence of all-cause death and cardiovascular events in patients with MI, myocardial injury and other causes of acute chest pain.

Methods: We conducted a prospective, observational cohort study enrolling consecutive patients presenting with suspected MI to the emergency department of a German tertiary hospital. Management was at the discretion of the treating physician. The final diagnosis was adjudicated by two independent cardiologists according to the 4^th Universal Definition of MI. Patients were followed to assess incident events of all-cause death and a secondary composite endpoint including any cardiac revascularization or hospitalization, non-fatal MI, non-fatal stroke, or death. We used Kaplan-Meier plots for crude and cox regression models (providing hazard ratios [95% confidence intervals]) for adjusted (patient characteristics, cardiovascular risk factors, a history of heart failure, renal function) time-to-event analyses, respectively, using patients with other causes of chest pain as reference. Scale variables are presented as median [25^th, 75^th percentile] and categorial variables as count (%). 

Results: Overall, we included 2,714 patients with a median age of 64 [51, 75] years, of whom 1,745 (64.3%) were male. In total, 143 (5.3%) had ST-elevation MI, 128 (4.7%) Non-ST-elevation MI Type 1, 236 (8.7%) Non-ST-elevation MI type 2, 86 (3.2%) acute myocardial injury, 677 (24.9%) chronic myocardial injury, and 1444 (53.2%) other diagnoses not involving hs-cTnI elevation. The median and maximum follow-up times were 4.6 years [4.5, 7.3] and 7.7 years, respectively. Per 1000 patient-years, we observed 82 deaths (95% CI 72, 92) in those diagnosed with acute or chronic myocardial injury, 56 events (95% CI 46, 67) in those with any type of MI and 12 (95% CI 10, 15) in the remaining patients. Unadjusted events are shown in Figure 1. Upon adjustment, all patients with MI or myocardial injury were significantly at higher risk for all-cause death: adj-HR for STEMI 3.16 (1.82, 5.49); NSTEMI Type 1 2.81 (1.83, 4.30); Type 2 2.49 (1.63, 3.80); acute myocardial injury 3.29 (2.09, 5.18); chronic myocardial injury 2.23 (1.63, 3.03). Additionally, the risk for the secondary composite endpoint was significantly increased in those with chronic myocardial injury (1.37 [1.12, 1.68], p = 0.0026) and Non-ST-elevation MI Type 1 (1.50 [1.11, 2.03], p = 0.0089), yet not in other diagnoses. 

Conclusion: Patients with acute and chronic myocardial injury are at high long-term cardiovascular risk, which is comparable to patients with acute MI. Further studies need to determine appropriate management strategies for these patients.