Date Published: July 27, 2017
Publisher: Public Library of Science
Author(s): Wei-Chieh Lee, Hsiu-Yu Fang, Huang-Chung Chen, Chien-Jen Chen, Cheng-Hsu Yang, Chi-Ling Hang, Chiung-Jen Wu, Chih-Yuan Fang, Chiara Lazzeri.
The effect of anemia on patients with ST-segment elevation myocardial infarction (STEMI) remains a controversial issue. The aim of this study was to explore the effect of anemia on STEMI patients.
From January 2005 to December 2014, 1751 patients experienced STEMI checked serum hemoglobin initially before any administration of fluids or IV medications. 1751 patients then received primary percutaneous intervention immediately. A total of 1388 patients were enrolled in the non-anemia group because their serum hemoglobin level was more than 13 g/L in males, and 12 g/L in females. A total of 363 patients were enrolled in the anemia group because their serum hemoglobin level was less than 13 g/L in males, and 12 g/L in females. Higher incidences of major adverse cerebral cardiac events (22.9% vs. 33.8%; p<0.001) were also noted in the anemia group, and these were related to higher incidence of cardiovascular mortality (6.5% vs. 20.4%; p<0.001). A higher incidence of all-cause mortality (8.6% vs. 27.7%; p<0.001) was also noted in the anemia group. A Kaplan-Meier curve of one-year cardiovascular mortality showed significant differences between the non-anemia and anemia group in all patients (P<0.001), and the patients with hypertension (P<0.001), and chronic kidney disease (CKD) (P = 0.011). Anemia is a marker of an increased risk in one-year cardiovascular mortality in patients with STEMI. If the patients have comorbidities such as hypertension, or CKD, the effect of anemia is very significant.
According to previous reports, a high prevalence (16.9%) of patients with ST-segment elevation myocardial infarction (STEMI) had some degree of anemia at presentation.  Anemia is associated with a significantly increased prevalence of baseline comorbidities, and a lower use of guidelines-based therapies, and is associated with increasing odds of in-hospital mortality.  The anemic patients have a high prevalence of hypertension,  diabetes mellitus,  chronic kidney disease (CKD),  and heart failure.  Many studies already have explored the poor prognosis of anemic STEMI patients. [7, 8] Anemia also influences the incidence of acute kidney injury (AKI) after percutaneous coronary intervention (PCI).  Anemia has the potential to worsen myocardial ischemic insult by decreasing the oxygen content of the blood supplied to the jeopardized myocardium  and by increasing myocardial oxygen demand through necessitating a higher cardiac output to maintain adequate systemic oxygen delivery.  Mixed comorbidities in anemic patients may influence their short-term and long-term mortality. There are few studies that focus on which specific comorbidity could be influenced by anemia in STEMI patients. Anemia seems to be a significant factor related to improving the long-term survival of STEMI patients.
Anemia has been shown high prevalence (around 15%) in the patients with acute MI, and especially in elderly patients (up to 43%).  Hemoglobin plays an important role in supplying oxygen to tissues. Shacham et al had indicated that anemia may begin before the patient seeks medical attention, and a longer duration from symptom onset to emergency admission results in a lower admission hemoglobin. They also documented a longer time lag from symptom onset to emergency admission results in a higher level of inflammatory marker. Inflammation was the key in hemoglobin decline during the evolution of STEMI and it emerges before the patient undergoing invasive procedures or IV fluid hemodilution.  When hemoglobin decreases, the body may increase cardiac output in order to maintain the normal metabolic demands of tissues. This increases the work load of the heart, and results in myocardial damage.  The pathophysiological link between anemia and prolonged QT intervals and increased risk of ventricular arrhythmia is, probably, hypoxia and decreased myocardial oxygen supply.  Left ventricular systolic and diastolic dysfunction, increased QTc intervals and QT dispersions and late ventricular potentials were found in patients with beta-thalassemia. [19, 20]
This was a retrospective cohort study, and we did not randomize our patients to decrease bias. In addition, we only provided and analyzed data from a single center. However, we shared the precious view and results of the clinical outcomes in anemic STEMI patients, especially in the patients with hypertension, diabetes mellitus, CKD stage ≧ 3, or advanced heart failure. Our research also provides insight into possible improvements in healthcare policies for anemic STEMI patients in the future.
Anemia is a marker of an increased risk in one-year cardiovascular mortality in patients with STEMI. If the patients have comorbidities such as hypertension, or CKD, the effect of anemia becomes very significant.