The significance of anaemia in patients with acute ST-elevation myocardial infarction undergoing primary percutaneous coronary intervention

Abstract

Background: The effects of pre-existing anaemia on the occurrence and course of an acute coronary syndrome has recently become a topic of extensive research. The data on the significance of anaemia in patients with ST-elevation myocardial infarction (STEMI) undergoing percutaneous coronary intervention (PCI) are less abundant and the conclusions equivocal.
Aim: To evaluate the incidence of anaemia and its impact on early outcomes in patients undergoing primary PCI for STEMI.
Methods: Based on a retrospective review of the medical records of hospitalised patients we selected a study group comprising 551 consecutive patients with STEMI, including 164 females, mean age 63.4 ± 12 years, undergoing primary PCI within the first 12 hours after the onset of chest pain. Anaemia was diagnosed according to the World Health Organisation criteria based on haemoglobin (Hb) values on admission (< 12 g/dL for females, < 13 g/dL for males).
Results: Anaemia was diagnosed in 61 (11%) patients (in 13% of females and 10% of males). The anaemic patients were older (71 vs 63 years, p < 0.001), had a lower body mass (70 vs 80 kg, p < 0.003) and a higher TIMI risk score for STEMI (5 vs 3, p < 0.0001). Their laboratory results showed a greater renal impairment (GFR 66.8 vs 75.8 mL/min, p < 0.008) and higher C-reactive protein levels (24.8 vs 14.4 mg/L, p < 0.001). There were no significant differences in post-infarction myocardial damage as estimated on the basis of ejection fraction and the baseline and peak CK-MB levels. During treatment, in both groups, there was a significant decrease in Hb levels from 11.9 to 11.0 g/dL in the anaemic patients (p < 0.0004) and from 14.3 to 13.3 g/dL in the non-anaemic patients (p < 0.001). While GFR did not change significantly in the anaemic patients, there was a significant increase in the non-anaemic patients from 75.8 to 80.9 mL/min (p < 0.001). The in-hospital mortality was low with a total of 8 (1.3%) patients dying: 5 (8.2%) in the anaemic group and 3 (0.6%) in the non-anaemic group (p < 0.001). The anaemic patients were also characterised by a higher incidence of cardiovascular complications (33% vs 17%, p = 0.003). In the multivariate analysis, older age, systolic blood pressure on admission and elevated white blood count were independently associated with a higher risk of death and cardiovascular complications, whereas baseline Hb level was a significant prognostic factor only in the univariate analysis.
Conclusions: Patients with anaemia who develop STEMI are, right from the admission, a separate, higher-risk population of patients with considerably increased risk of death and in-hospital cardiovascular complications. The unfavourable impact of anaemia on outcomes in patients with acute MI undergoing PCI is complex and cannot be explained by the increased extend of post-infarction myocardial damage. In patients with STEMI, anaemia on admission should be treated as an additional risk factor.
Kardiol Pol 2011; 69, 1: 33-39