The Relationship between Hematocrit Levels and Major Adverse Cardiovascular Events in Patients with Acute Myocardial Infarction

Background: The relationship between hematocrit (HCT) levels and the occurrence of major adverse cardiovascular events (MACEs) in patients with acute myocardial infarction (AMI) remains unexplored. A better understanding of this interplay may enhance the prognosis and management of AMI patients. Methods: Between January 2021 and August 2022, clinical data were collected from patients diagnosed with AMI at 10 tertiary healthcare institutions in China. A total of 1946 eligible participants were included and divided into three groups based on sex- specific tertiles of HCT levels upon admission: 648 patients with low HCT levels, 649 patients with intermediate HCT levels, and 649 patients with high HCT levels. Follow-up approaches included hospital outpatient visits, inpatient stays, and telephone calls for 180 days. The primary endpoint was the occurrence of MACEs. Influential factors, including general information, admission status, and supplementary examination results that differed across the cohorts, were analyzed. Cox regression analysis was employed to evaluate the 180-day MACE rates and HCT levels in patients with AMI. To assess the reliability of the findings, three sensitivity analyses and subgroup analyses were performed. Results: During this time, 136 individuals in the low HCT group, 77 in the intermediate HCT group, and 73 in the high HCT group experienced endpoint events. With all covariates controlled, the Cox regression analysis indicated that the low HCT group had a higher risk of MACEs compared to the intermediate HCT group [hazard ratio (HR) = 1.44, 95% confidence interval (CI) = 1.07-1.95, p = 0.017]. The low HCT group also presented a higher risk of acute coronary syndrome (HR = 1.57, 95% CI = 1.06-2.32, p = 0.024). However, the high and intermediate HCT groups exhibited comparable prognoses for AMI. The limited cubic spline plot revealed that HCT values between 41.58% and 45.36% implied a protective effect against MACEs. These results were further verified by sensitivity analysis, and the subgroup analysis showed no variable interaction. Conclusions: Our findings indicate that low HCT levels in patients with AMI increase the incidence of MACEs within 180 days, offering new insights into the prognosis and management of AMI patients.