Background: Anemia and acute blood loss occur often in patients hospitalized with acute ST-segment elevation myocardial infarction (STEMI). A lack of oxygen carriers may additionally worsen the myocardial ischemia. In-hospital hemoglobin drop is associated with 1-year mortality in patients with acute coronary syndrome. However, data on the effect of in-hospital hemoglobin reduction on myocardial salvage and long-term outcomes in patients with STEMI are scarce.

Objective: The objective of this study was to investigate the impact of in-hospital hemoglobin drop on myocardial salvage and 5-year mortality in patients with STEMI treated with primary percutaneous coronary intervention (PPCI).

Methods: This study included patients with STEMI treated with PPCI between 2002-2007. Hemoglobin drop was defined as a positive difference between hemoglobin values on admission and nadir during hospitalisation. Patients were categorized into four groups: no hemoglobin drop (no drop), <3 g/dL hemoglobin drop (minimal drop), 3 to <5 g/dL hemoglobin drop (minor drop) and ≥5 g/dL hemoglobin drop (major drop). The myocardial area at risk and myocardial infarct size were measured using serial single-photon emission computed tomography imaging on admission and 7 to 14 days after PCI, respectively. Co-primary outcomes were relative myocardial salvage and five-year all-cause mortality.

Results: Of 1,204 patients, 1,169 (97.1%) showed a drop of hemoglobin during hospitalization: minimal, minor and major hemoglobin drop occurred in 894 (74.3%), 214 (17.8%), and 61 (5.1%) patients, respectively. Relative myocardial salvage (median [interquartile range]) was reduced in patients with minimal (0.53 [0.27-0.83]), minor (0.40 [0.18-0.62]) and major (0.40 [0.14-0.77]) drop compared to patients with no drop (0.70 [0.44-1.0], P<0.001). After adjusting for covariates, hemoglobin drop remained an independent correlate of relative myocardial salvage (beta -0.069, 95% confidence interval -0.108 – -0.03, P<0.001 for 1 g/dL hemoglobin drop). A hemoglobin drop of ≥3 g/dL was associated with reduced left ventricular function at 6 months and with increased mortality at 5-year follow-up after STEMI (Hazard Ratio 1.92, 95% CI 1.22-3.00, P<0.01 for mortality).

Conclusion: In patients with STEMI undergoing PPCI, in-hospital hemoglobin drop was associated with reduced myocardial salvage, reduced left ventricular function and increased long-term (5-year) mortality. Whether minimizing in-hospital hemoglobin drop may improve myocardial salvage and long-term outcomes remains to be investigated.