Haemoglobin concentration on admission influences the rate of inhospital 30-day mortality and complications in patients with acute myocardial infarction: a retrospective analysis of 637 Chinese patients

Objective

To determine the association between haemoglobin concentrations on admission and inhospital 30-day cardiac mortality and complications among patients with acute myocardial infarction during their hospital course.

Methods

We conducted a retrospective study of data on 637 Chinese patients who were hospitalized with acute myocardial infarction. Patients were categorized according to the haemoglobin concentration on admission (<12 g/dl, mean ± standard deviation 10.5 ± 1.4 g/dl; 12–13.9 g/dl, mean ± standard deviation 13 ± 0.6 g/dl; 14 g/dl or greater, mean ± standard deviation 15.2 ± 0.9 g/dl), and data were evaluated to determine whether there was an association between the haemoglobin concentrations on admission and inhospital 30-day mortality and complications. Complications were defined as cardiogenic shock, congestive heart failure, arrhythmia, ventricular tachycardial or fibrillation and pneumonia.

Results

Patients with lower haemoglobin concentrations on admission had higher inhospital 30-day mortality rates (P < 0.001). Inhospital 30-day mortality was 21.4% in patients with haemoglobin concentrations <12 g/dl, 11.6% in patients with haemoglobin concentrations of 12–13.9 g/dl, and 5.3% in patients with haemoglobin concentrations 14 g/dl or greater. The increase in risk of complications associated with a low haemoglobin concentration was more pronounced in patients with anaemia than in patients without. Compared with patients with haemoglobin concentrations 14 g/dl or greater, those with haemoglobin concentrations <12 g/dl and 12–13.9 g/dl had more inhospital complications, including arrhythmia, congestive heart failure and pneumonia (40.5% versus 33.8% versus 23.1%, P = 0.001; 28.2% versus 20.0% versus 8.2%, P < 0.001; and 26.7% versus 8.4% versus 2.8%, P < 0.001, respectively). As expected, a significant inverse correlation between haemoglobin concentrations and ages was observed in the patients with acute myocardial infarction (r = -0.51; P < 0.001).

Conclusions

The traditional belief is that anaemic patients with coronary artery disease are at high risk for myocardial ischaemia or infarction because they cannot increase oxygen extraction or augment coronary arterial flow. It is demonstrated in this study that a low haemoglobin concentration on admission increases the risk of death or serious complications in the patients with acute myocardial infarction. There is a greater incidence of patients with a low haemoglobin concentration on admission in the elderly patient than that in the younger one.