Abstract
Patients with a history of myocardial infarction (MI) and lower admission hemoglobin (aHb) levels have a worse outcome than patients with higher aHb, but lower or similar peaks in enzymatic infarct size. Hemoglobin levels are positively correlated with body surface area (BSA), which is positively correlated with cardiac mass. We hypothesized that patients with lower aHb suffer comparatively greater myocardial injury. We examined the relationships between aHb, and troponin (Tn) normalized to BSA (Tn/BSA) and its association with 30-day mortality. Data from 6055 patients, who were divided into seven groups based on their aHb at 10g/L intervals, were analyzed, and the groups were compared. The relationships between aHb and Tn/BSA and between Tn/BSA and 30-day mortality were assessed. Patients with higher aHb levels had greater BSA (p<0.0001). A negative relationship between aHb and log10Tn/BSA was observed in the entire group, and in men and women separately (p<0.0001, p<0.0001, and p=0.013, respectively). The log10Tn/BSA value was associated with 30-day mortality in the entire group, and in men and women separately (p<0.0001, p=0.014, and p<0.0001, respectively). Our finding suggests that a similar peak Tn value in patients with lower aHb means comparatively greater myocardial injury relative to cardiac mass. This hypothesis helps to explain the worse outcomes in patients with lower aHb. According to our findings, Tn should be indexed to BSA to provide comparable information on cardiac injury relative to cardiac mass. Whether this relationship is causal remains to be clarified.
Highlights
Substantial evidence from previous studies suggests that low admission hemoglobin levels in patients with myocardial infarction (MI) are a predictor of poor outcome [1,2,3,4,5]
We investigated the association between admission hemoglobin (aHb) levels in patients with MI treated with percutaneous coronary intervention (PCI) and their possible association with Tn/body surface area (BSA), as well as the association between Tn/BSA and 30-day mortality
The main results of our study are that the Tn/BSA was independently associated with 30-day mortality and that a gradual increase in aHb levels was associated with a decrease in the peak Tn/BSA
Summary
Substantial evidence from previous studies suggests that low admission hemoglobin (aHb) levels in patients with myocardial infarction (MI) are a predictor of poor outcome [1,2,3,4,5]. Some studies have found similar peaks in enzymatic infarct size in different aHb classes [5], while others found even lower peaks in enzymatic infarct size in patients with lower aHb levels, these patients had significantly higher mortality rates [4,6]. Available data suggest that lower aHb levels are associated with a similar or lower enzymatic infarct size but higher mortality rates after MI than higher aHb levels [4,5,6]. This contradicts the fact that higher troponin (Tn) levels are associated with larger myocardial injuries and poorer outcomes [7,8]. If two patients have similar peak Tn values but different cardiac mass, they would have different infarct sizes relative to cardiac mass, and these similar Tn values would be expected to have different clinical consequences in these patients
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