Background: The 4th Universal Definition of Myocardial Infarction (UDMI) recommends the use of sex-specific troponin cut-offs for the diagnosis of myocardial injury and infarction. Data on their impact on the diagnosis and prognosis of patients with suspected myocardial infarction (MI) is limited.

Methods: Patients with symptoms suggestive of MI presenting in the emergency department were prospectively enrolled and followed up to assess the combined endpoint of mortality, cardiac rehospitalization, incident MI and revascularization. The final diagnosis was adjudicated by three physicians in a blinded fashion according to the 3^rd and 4^th UDMI. For adjudication of the latter, sex-specific cut-offs of a high-sensitive troponin T assay were used (9ng/L for female patients, 15.5ng/L for male patients). Changes of diagnoses after re-adjudication were analysed for both sexes separately.

Results: We included 2302 patients, of which 35.9% were female with a median age of 68 years [54;77] while male patients were 63 years [50;74] old. Hypertension (68.3% vs. 64.7%), dyslipoproteinemia (38.8% vs. 30.4%), diabetes (14.4% vs. 10.4%), smoking (26.8% vs. 17.3%) and history of MI (18.6% vs. 11.3%) were more common in male patients in comparison to female patients. Coronary angiography (33.5% vs. 21.8%) and revascularization (20.5% vs. 10.2%) were performed more frequently in male patients. In male patients with type 1 MI angiography was performed in 97.1% vs. 88.3% in female patients. Intake of antiplatelet medication (41.3% vs. 32.1%) and statin therapy (34.9% vs. 27.4%) were substantially more frequent in male patients, while beta blockers (40.6% vs. 40.2%) and ACE-inhibitors (47.1% vs. 45.1%) were prescribed to both sexes equally often. After re-adjudication, the number of MIs decreased in both sexes (male patients 23.6% to 20.9%, female patients 18.5% to 15.1%) mostly due to reclassification to the categories acute and chronic myocardial injury. Acute myocardial injury was equally frequent in both sexes (3.1% vs. 3.9%), while chronic injury was significantly more frequent in female patients (32.4% vs. 21.5%). Out of 112 female patients with troponin concentrations between the common (14ng/L) and the sex-specific (9ng/L) threshold, 102 patients (91.1%) were reclassified mostly to the category of chronic myocardial injury. The combined endpoint occurred similarly often in male and female patients, but patients that got reclassified during re-adjudication had a significantly worse outcome compared to non-reclassified patients in both sexes (p<0.001).

Conclusion: Female patients presenting with suspected MI were older but had less cardiovascular risk factors than male patients. The use of sex-specific cut-offs led to identification of substantially more female patients with poor outcome, especially due to the new category of chronic myocardial injury.

Table 1: Reclassification of female patients with high-sensitive troponin T concentrations between the sex-specific (9ng/L) and the common (14ng/L) cut-off. MI = myocardial infarction, UAP = unstable angina pectoris, SAP = stable angina pectoris, CNCCP = cardiac non-coronary chest pain, NCCP = non-cardiac chest pain