How does hemoglobin impact the severity of non-ST segment elevation acute coronary syndromes?

Introduction

Non–ST-segment elevation acute coronary syndromes (NSTE-ACS) represent the most common presentation of acute coronary syndrome. Low hemoglobin levels are known to be associated with adverse outcomes in ischemic heart disease and may exacerbate myocardial injury following an acute coronary syndrome.

Objective

We aimed to evaluate whether low hemoglobin values at admission are associated with increased NSTE-ACS severity.

Methods

This retrospective observational study included patients admitted to our center with NSTE-ACS between October 2010 and July 2025, recorded in a national registry. Patients were stratified according to hemoglobin levels at admission using a cutoff of 12 g/dL. Group differences were analyzed using the chi-square test for categorical variables and median-based tests for continuous variables. The association between low hemoglobin levels and NSTE-ACS severity was evaluated using multivariable logistic regression, with a composite endpoint comprising Killip class III–IV at admission, cardiogenic shock during hospitalization, or LVEF <40% at discharge, adjusted for potential confounders.

Results

A total of 709 patients were included, of whom 509 (71.8%) were male, with a median age of 67 years. Ninety-three patients (13.1%) presented hemoglobin levels below 12 g/dL at admission. The median hemoglobin level in the overall population was 14.2 g/dL; patients with hemoglobin levels below 12 g/dL had a median value of 11.1 g/dL, whereas those with levels ≥12 g/dL had a median value of 14.5 g/dL.

Significant differences between groups were observed with respect to sex (p<0.001), age (p<0.001), smoking status (p<0.001), arterial hypertension (p<0.001), dyslipidemia (p=0.03), diabetes mellitus (p<0.001), prior acute myocardial infarction (p=0.025), valvular heart disease (p=0.006), and chronic kidney disease (p<0.001). In addition, significant differences were found in the occurrence of LVEF <40% (p<0.001), cardiogenic shock (p=0.013), and Killip class at admission (p<0.001) (Table 1).

In multivariable logistic regression analysis, hemoglobin levels below 12 g/dL at admission were independently associated with the occurrence of the composite endpoint (OR 3.21, 95% CI 1.51–46.55; p=0.001

Conclusions

In our study, hemoglobin levels below 12 g/dL at admission were associated with greater severity of NSTE-ACS, as reflected by poorer LVEF at discharge, a higher incidence of cardiogenic shock during hospitalization, and a higher Killip class at admission. This association may be explained by the reduced oxygen-carrying capacity in patients with anemia, which further compromises an already hypoxic myocardium. Additionally, the compensatory increase in myocardial workload to overcome impaired oxygen delivery may contribute to more extensive myocardial injury.For image description, please refer to the figure legend and surrounding text.For image description, please refer to the figure legend and surrounding text.