Acute coronary syndromes (ACS) is defined as clinical syndromes characterized by acute myocardial ischemia, including unstable angina pectoris (UAP), ST-segment elevation myocardial infarction (STEMI), and non-ST-segment elevation myocardial infarction (NSTEMI)[1]. ACS is the most severe clinical type of coronary artery disease (CAD)[2]. Most clinical ischemic events result from the rupture of the fibrous cap superimposed on the atherosclerotic plaque[3], [4]. As a chronic inflammatory disease, the immune system plays a key role in atherogenesis [5], [6], [7], [8].

IgM is an antibody that appears in the body's initial immune response and is generally distributed in the human blood, playing an important role in the early response to immune defense[9]. Serum IgM is often used for early diagnosis of the presence of infection in patients[10]. Studies have shown that infection and inflammation are closely related to the formation and development of atherosclerosis, and are also important factors leading to ACS[11]. The immuno-inflammatory response can affect the prognosis of patients with ACS by regulating plaque instability or by influencing the pathological mechanism of plaques[12].

Patients with ACS can improve their prognosis through individualized treatment, which is based on accurate risk stratification of patients. Traditional prognostic scores for ACS, such as the Global Registry of Acute Coronary Event (GRACE), incorporate traditional cardiovascular risk factors to rapidly stratify the risk of ACS patients. However, these scores lack the prognostic impact of immuno-inflammatory markers on patients with ACS. Our study hypothesized that total serum IgM, as a potential therapeutic biomarker for atherosclerosis, may indicate prognosis in patients with ACS.