In general, patients with anemia were older, more likely to be female, to have a DNR order, history of aspirin use, and additional comorbid conditions present compared to patients without anemia (). These differences were mostly larger for patients with moderate-to-severe anemia versus those with mild anemia, with the exception of the likelihood of being a female or having a history of angina, myocardial infarction, hypertension, or aspirin use, which were higher for patients with mild anemia. In contrast, patients without anemia were more likely to be current smokers and have hyperlipidemia than patients with moderate-to-severe anemia (). At the time of AMI presentation, patients with anemia had, on average, lower systolic blood pressure, higher serum creatinine levels and platelet counts, a higher frequency of either major or minor bleeding episodes, and were more likely to have heart failure than patients without anemia; trends were stronger among patients with moderate-to-severe anemia (; p < 0.05).
The use of cardiac catheterization during hospitalization for NSTEMI was significantly higher in patients without anemia (58.9%) compared to those with mild anemia (39.5%) and moderate-to-severe anemia (25.6%; p <0.01 for difference and trend). After risk adjustment using forward stepwise regression modeling, differences in cardiac catheterization usage remained significantly lower in patients with anemia; patients with mild anemia had a 20% lower odds (adjusted OR = 0.79; 95% CI: 0.67–0.95) and patients with moderate-to-severe anemia had a 55% lower odds (adjusted OR = 0.45; 95% CI: 0.42–0.49) of receiving cardiac catheterization compared to patients without anemia. Among patients who underwent cardiac catheterization, rates of PCI were unrelated to the severity of anemia (p = 0.18); whereas the rates of CABG were significantly higher in patients with moderate-to-severe anemia compared to patients with mild or no anemia (p = 0.02, ).
Figure 1 Frequency of coronary revascularization (PCI or CABG) among patients who underwent cardiac catheterization according to severity of anemia. Among patients who underwent cardiac catheterization, the rates of PCI (lighter grey bars) were unrelated to the (more ...)
Patients who underwent cardiac catheterization were younger, more likely to be male, a current smoker, and to have a history of angina, PCI, aspirin use, and hyperlipidemia (). On admission, they had, on average, lower resting heart rate and creatinine levels and higher systolic blood pressure and hematocrit levels. Patients who underwent cardiac catheterization were also more likely to have received aspirin, clopidogrel, and heparin during their hospital stay. In contrast, patients who did not undergo cardiac catheterization were more likely to have a do-not-resuscitate order and comorbidities that included myocardial infarction, diabetes, stroke, bleeding, and peptic ulcer disease. They were also more likely to have a higher white count, heart failure, and major and minor bleeding on the day of admission ().
Characteristics of Patients With NSTEMI in Relation to Cardiac Catheterization During Hospitalization for AMI Before Propensity Match
The logistic regression model to generate the propensity score for cardiac catheterization had excellent predictive discrimination with a c-index of 0.85. Based on the propensity score, 44% of catheterization patients (n = 549) were matched with non-catheterization controls (n = 549). Examination of this matched cohort () showed successful matching, with balance of the baseline characteristics between patients who underwent cardiac catheterization and those who did not, with the exception of hospital use of aspirin, clopidogrel, and heparin. After adjusting for hospital use of aspirin, clopidogrel, and heparin with conditional logistic regression modeling, cardiac catheterization was associated with a 52% reduction in 6-month mortality in the full matched sample (n = 1098; adjusted OR = 0.48; 95%CI: 0.32–0.71). The effect of cardiac catheterization differed according to severity of anemia. Cardiac catheterization was associated with reductions in 6-month mortality only in patients without anemia (n=525, adjusted OR = 0.26; 95%CI: 0.09–0.79) but not among patients with mild anemia (n = 503, adjusted OR = 0.55; 95%CI: 0.25–1.23). Small sample size (n = 70) rendered data inconclusive for patients with moderate-to-severe anemia.
Characteristics of Patients With NSTEMI in Relation to Cardiac Catheterization While in Hospital After Propensity Match